JP5187507B2 - Surface emitting laser element, surface emitting laser array, optical scanning device, image forming apparatus, optical transmission module, and optical transmission system - Google Patents

Description

  The present invention relates to a surface emitting laser element, a surface emitting laser array, an optical scanning device, an image forming apparatus, an optical transmission module, and an optical transmission system, and more specifically, a surface emitting laser that emits light in a direction perpendicular to a substrate. Element, surface emitting laser array in which surface emitting laser elements are integrated, optical scanning device having surface emitting laser element or surface emitting laser array, image forming apparatus including the optical scanning device, and surface emitting laser array The present invention relates to an optical transmission module and an optical transmission system.

  BACKGROUND ART A vertical cavity surface emitting laser (VCSEL) is a semiconductor laser element that emits light in a direction perpendicular to a substrate, and is an edge emitting that emits light in a direction parallel to the substrate. Compared with conventional semiconductor laser devices, it has the following features: (1) low price, (2) low power consumption, (3) small size and high performance, and (4) easy two-dimensional integration. Yes.

  The surface emitting laser element has a constricted structure in order to increase current inflow efficiency. As this constriction structure, a constriction structure obtained by selective oxidation of an Al (aluminum) As (arsenic) layer (hereinafter, also referred to as “oxidized constriction structure” for convenience. For example, see Patent Document 1) is often used. . In this oxidized constriction structure, after a mesa having a predetermined size with a selective oxidation layer made of p-AlAs exposed on the side surface is formed, the mesa is selectively placed from the side surface of the mesa by placing it in a high-temperature steam atmosphere. In this case, an unoxidized region in the selective oxidation layer remains in the vicinity of the center of the mesa. This non-oxidized region becomes a driving current passing region (current injection region) of the surface emitting laser element. Thus, current constriction can be easily achieved.

The refractive index of a layer oxidized with Al (Al _x O _y ) (hereinafter abbreviated as “oxidized layer”) in the oxidized constriction structure is about 1.6, which is lower than that of the semiconductor layer. Thereby, a refractive index difference in the lateral direction is generated in the resonator structure, and light is confined in the center of the mesa, so that the light emission efficiency can be improved. As a result, excellent characteristics such as low threshold current and high efficiency can be realized.

  By the way, when the surface emitting laser element promptly dissipates heat generated in the active layer, an increase in junction temperature (active layer temperature) can be suppressed, a decrease in gain can be suppressed, and a high output can be obtained. In addition, so-called temperature characteristics are good and the life is long.

  In general, an AlGaAs-based material is used for the semiconductor multilayer mirror. The AlGaAs-based material greatly varies in thermal conductivity depending on the Al composition, and AlAs has the highest thermal conductivity (see FIG. 23).

  Therefore, in the semiconductor multilayer reflector on the heat dissipation path side, it has been proposed to increase the optical thickness of the low refractive index layer made of AlAs close to the resonator structure than usual (for example, Patent Documents 2 to 2). 4).

US Pat. No. 5,493,577 Japanese Patent Laid-Open No. 2005-354061 JP 2007-299897 A US Pat. No. 6,720,585

  By the way, in the semiconductor multilayer mirror, when the optical thickness of the low refractive index layer is changed from λ / 4 (λ is an oscillation wavelength) to 3λ / 4, light absorption (hereinafter also simply referred to as “absorption” for convenience) is achieved. Tripled. In the semiconductor multilayer mirror, the closer to the resonator structure, the stronger the electric field strength, so the influence of absorption is large. With the methods disclosed in Patent Documents 2 to 4, the slope efficiency is lowered and the threshold current is raised. There was an inconvenience of inviting.

  The present invention has been made under such circumstances, and a first object thereof is to provide a surface-emitting laser element and a surface-emitting laser array having a long lifetime, high light emission efficiency, and excellent temperature characteristics. .

  A second object of the present invention is to provide an optical scanning device capable of performing stable optical scanning.

  A third object of the present invention is to provide an image forming apparatus capable of forming a high quality image.

  A fourth object of the present invention is to provide an optical transmission module capable of generating a stable optical signal.

  A fifth object of the present invention is to provide an optical transmission system capable of performing high-quality optical transmission.

  In a first aspect, the present invention is a surface emitting laser element that emits light in a direction perpendicular to a substrate, and includes a resonator structure including an active layer; and the resonator structure interposed therebetween And a semiconductor multilayer film reflecting mirror composed of a plurality of pairs in which a first layer and a second layer having different refractive indexes are paired, and the second layer is more thermally conductive than the first layer. The semiconductor multilayer mirror has at least one pair, and the second layer has a thicker optical thickness than the first layer, and the first partial reflector Provided between a mirror and the resonator structure, the optical thickness of each of the first and second layers is at least one pair and is thinner than the second layer of the first partial reflection mirror A surface-emitting laser element having a second partial reflection mirror.

  In addition, when the composition inclination layer which changed the composition gradually from one composition toward the other composition is provided between each refractive index layer, the optical thickness of each refractive index layer is all. Further, it may include a half of the adjacent composition gradient layer.

  According to this, heat dissipation efficiency can be improved while suppressing an increase in absorption loss. And it becomes possible to have a long lifetime, high luminous efficiency, and excellent temperature characteristics.

  From a second viewpoint, the present invention is a surface emitting laser array in which the surface emitting laser elements of the present invention are integrated.

  According to this, since the surface emitting laser element of the present invention is integrated, it is possible to have a long life, high luminous efficiency and excellent temperature characteristics.

  From a third aspect, the present invention is an optical scanning device that scans a surface to be scanned with light, a light source having the surface emitting laser element of the present invention; a deflector that deflects light from the light source; A first optical scanning device comprising: a scanning optical system that condenses the light deflected by the deflector onto the surface to be scanned.

  According to a fourth aspect of the present invention, there is provided an optical scanning device that scans a surface to be scanned with light, the light source having the surface emitting laser array of the present invention; a deflector that deflects the light from the light source; And a scanning optical system that condenses the light deflected by the deflector onto the surface to be scanned.

  According to each of the above optical scanning devices, since the light source has the surface-emitting laser element of the present invention or the surface-emitting laser array of the present invention, stable optical scanning can be performed.

  According to a fifth aspect of the present invention, there is provided at least one image carrier; and at least one optical scanning device according to the invention that scans light including image information on the at least one image carrier. An image forming apparatus provided.

  According to this, since at least one optical scanning device of the present invention is provided, a high-quality image can be formed.

  According to a sixth aspect of the present invention, there is provided an optical transmission module for generating an optical signal corresponding to an input electric signal, the surface emitting laser array of the present invention; An optical transmission module comprising: a driving device that is driven according to an electrical signal.

  According to this, since the surface emitting laser array of the present invention is provided, a stable optical signal can be generated.

  According to a seventh aspect of the present invention, an optical transmission module of the present invention; an optical transmission medium that transmits an optical signal generated by the optical transmission module; and an optical signal that passes through the optical transmission medium as an electrical signal. An optical transmission system comprising: a converter for converting.

  According to this, since the optical transmission module of the present invention is provided, high-quality optical transmission can be performed.

  Hereinafter, an embodiment of the present invention will be described.

  FIG. 1 shows a schematic configuration of a laser printer 1000 according to an embodiment of the present invention.

  The laser printer 1000 includes an optical scanning device 1010, a photosensitive drum 1030, a charging charger 1031, a developing roller 1032, a transfer charger 1033, a charge eliminating unit 1034, a cleaning unit 1035, a toner cartridge 1036, a paper feeding roller 1037, a paper feeding tray 1038, A registration roller pair 1039, a fixing roller 1041, a paper discharge roller 1042, a paper discharge tray 1043, a communication control device 1050, a printer control device 1060 that comprehensively controls the above-described units, and the like are provided. These are housed in predetermined positions in the printer housing 1044.

  The communication control device 1050 controls bidirectional communication with a host device (for example, a personal computer) via a network or the like.

  The photosensitive drum 1030 is a cylindrical member, and a photosensitive layer is formed on the surface thereof. That is, the surface of the photoconductor drum 1030 is a scanned surface. The photosensitive drum 1030 rotates in the direction of the arrow in FIG.

  The charging charger 1031, the developing roller 1032, the transfer charger 1033, the charge removal unit 1034, and the cleaning unit 1035 are each disposed in the vicinity of the surface of the photosensitive drum 1030. Then, along the rotation direction of the photosensitive drum 1030, the charging charger 1031 → the developing roller 1032 → the transfer charger 1033 → the discharging unit 1034 → the cleaning unit 1035 are arranged in this order.

  The charging charger 1031 uniformly charges the surface of the photosensitive drum 1030.

  The optical scanning device 1010 irradiates the surface of the photosensitive drum 1030 charged by the charging charger 1031 with a light beam modulated based on image information from the host device. As a result, a latent image corresponding to the image information is formed on the surface of the photosensitive drum 1030. The latent image formed here moves in the direction of the developing roller 1032 as the photosensitive drum 1030 rotates. The configuration of the optical scanning device 1010 will be described later.

  The toner cartridge 1036 stores toner, and the toner is supplied to the developing roller 1032.

  The developing roller 1032 causes the toner supplied from the toner cartridge 1036 to adhere to the latent image formed on the surface of the photosensitive drum 1030 to visualize the image information. Here, the latent image to which the toner is attached (hereinafter also referred to as “toner image” for the sake of convenience) moves in the direction of the transfer charger 1033 as the photosensitive drum 1030 rotates.

  Recording paper 1040 is stored in the paper feed tray 1038. A paper feed roller 1037 is disposed in the vicinity of the paper feed tray 1038, and the paper feed roller 1037 takes out the recording paper 1040 one by one from the paper feed tray 1038 and conveys it to the registration roller pair 1039. The registration roller pair 1039 temporarily holds the recording paper 1040 taken out by the paper supply roller 1037, and in the gap between the photosensitive drum 1030 and the transfer charger 1033 according to the rotation of the photosensitive drum 1030. Send it out.

  A voltage having a polarity opposite to that of the toner is applied to the transfer charger 1033 in order to electrically attract the toner on the surface of the photosensitive drum 1030 to the recording paper 1040. With this voltage, the toner image on the surface of the photosensitive drum 1030 is transferred to the recording paper 1040. The recording sheet 1040 transferred here is sent to the fixing roller 1041.

  In the fixing roller 1041, heat and pressure are applied to the recording paper 1040, whereby the toner is fixed on the recording paper 1040. The recording paper 1040 fixed here is sent to the paper discharge tray 1043 via the paper discharge roller 1042 and is sequentially stacked on the paper discharge tray 1043.

  The neutralization unit 1034 neutralizes the surface of the photosensitive drum 1030.

  The cleaning unit 1035 removes the toner remaining on the surface of the photosensitive drum 1030 (residual toner). The surface of the photosensitive drum 1030 from which the residual toner has been removed returns to the position facing the charging charger 1031 again.

  Next, the configuration of the optical scanning device 1010 will be described.

  As shown in FIG. 2 as an example, the optical scanning device 1010 includes a deflector-side scanning lens 11a, an image plane-side scanning lens 11b, a polygon mirror 13, a light source 14, a coupling lens 15, an aperture plate 16, an anamorphic. A lens 17, a reflection mirror 18, a scanning control device (not shown), and the like are provided. These are assembled at predetermined positions in the housing 30.

  In the following, for convenience, the direction corresponding to the main scanning direction is abbreviated as “main scanning corresponding direction”, and the direction corresponding to the sub scanning direction is abbreviated as “sub scanning corresponding direction”.

  The coupling lens 15 converts the light beam emitted from the light source 14 into substantially parallel light. The light source 14 and the coupling lens 15 are fixed to one holding member made of aluminum and unitized.

  The aperture plate 16 has an aperture and defines the beam diameter of the light beam through the coupling lens 15.

  The anamorphic lens 17 forms an image of the light beam that has passed through the opening of the aperture plate 16 in the sub-scanning corresponding direction in the vicinity of the deflection reflection surface of the polygon mirror 13 via the reflection mirror 18.

  The optical system arranged on the optical path between the light source 14 and the polygon mirror 13 is also called a pre-deflector optical system. In the present embodiment, the pre-deflector optical system includes a coupling lens 15, an aperture plate 16, an anamorphic lens 17, and a reflection mirror 18.

  As an example, the polygon mirror 13 has a hexahedral mirror having an inscribed circle radius of 18 mm, and each mirror serves as a deflecting reflection surface. The polygon mirror 13 deflects the light flux from the reflection mirror 18 while rotating at a constant speed around an axis parallel to the sub-scanning corresponding direction.

  The deflector-side scanning lens 11 a is disposed on the optical path of the light beam deflected by the polygon mirror 13.

  The image plane side scanning lens 11b is disposed on the optical path of the light beam via the deflector side scanning lens 11a. Then, the light beam that has passed through the image plane side scanning lens 11b is irradiated onto the surface of the photosensitive drum 1030, and a light spot is formed. This light spot moves in the longitudinal direction of the photosensitive drum 1030 as the polygon mirror 13 rotates. That is, the photoconductor drum 1030 is scanned. The moving direction of the light spot at this time is the “main scanning direction”. The rotation direction of the photosensitive drum 1030 is the “sub-scanning direction”.

  The optical system arranged on the optical path between the polygon mirror 13 and the photosensitive drum 1030 is also called a scanning optical system. In the present embodiment, the scanning optical system includes a deflector side scanning lens 11a and an image plane side scanning lens 11b. At least one folding mirror is disposed on at least one of the optical path between the deflector side scanning lens 11a and the image plane side scanning lens 11b and the optical path between the image plane side scanning lens 11b and the photosensitive drum 1030. May be.

  As an example, the light source 14 includes a surface emitting laser element 100 as illustrated in FIG. 3. In this specification, the laser oscillation direction is defined as the Z-axis direction, and two directions orthogonal to each other in a plane perpendicular to the Z-axis direction are described as the X-axis direction and the Y-axis direction.

  The surface emitting laser element 100 is a surface emitting laser having a design oscillation wavelength of 780 nm band, and includes a substrate 101, a lower semiconductor DBR 103, a lower spacer layer 104, an active layer 105, an upper spacer layer 106, an upper semiconductor DBR 107, and a contact layer 109. Etc.

  The substrate 101 is an n-GaAs single crystal substrate.

The lower semiconductor DBR 103, as shown in FIG. 4 as an example, has a first lower semiconductor DBR 103 _1, the second lower semiconductor DBR 103 _2, and a third lower semiconductor DBR 103 _3.

The first lower semiconductor DBR 103 ₁ is stacked on the + Z side of the substrate 101 via a buffer layer (not shown), and a low refractive index layer 103a made of _{n-AlAs, n-Al 0.3} Ga 0. 76.5 pairs of high refractive index layers 103b made of ₇ As are provided. The low refractive index layer 103a has a higher thermal conductivity than the high refractive index layer 103b (see FIG. 23). Between each refractive index layer, in order to reduce electrical resistance, a composition gradient layer (not shown) in which the composition is gradually changed from one composition to the other composition is provided. Each refractive index layer includes 1/2 of the adjacent composition gradient layer, and is set to have an optical thickness of λ / 4 when the oscillation wavelength is λ.

The second lower semiconductor DBR 103 ₂ is stacked on the first lower semiconductor DBR 103 ₁ + Z side, and has a pair of the low refractive index layer 103a and the high refractive index layer 103b 3 pairs. Between each refractive index layer, in order to reduce electrical resistance, a composition gradient layer (not shown) in which the composition is gradually changed from one composition to the other composition is provided. The low refractive index layer 103a is set to have an optical thickness of 3λ / 4 including 1/2 of the adjacent composition gradient layer, and the high refractive index layer 103b is 1 / of the adjacent composition gradient layer. 2 so that the optical thickness is λ / 4. The second lower semiconductor DBR 103 ₂ is, so-called "heat dissipation structure". Further, the second low refractive index layer 103a in the lower semiconductor DBR 103 ₂ is, so-called "radiation layer".

The third lower semiconductor DBR 103 ₃ of is stacked on the + Z side of the second lower semiconductor DBR 103 _2, and a pair of the low refractive index layer 103a and the high refractive index layer 103b has one pair. Between each refractive index layer, in order to reduce electrical resistance, a composition gradient layer (not shown) in which the composition is gradually changed from one composition to the other composition is provided. Each refractive index layer is set to have an optical thickness of λ / 4 including 1/2 of the adjacent composition gradient layer.

  Thus, the lower semiconductor DBR 103 has 40.5 pairs of a low refractive index layer and a high refractive index layer.

The lower spacer layer 104 is laminated on the + Z side of the _third lower semiconductor DBR 1033, and is a layer made of non-doped (Al _0.1 Ga _0.9 ) _0.5 In _0.5 P.

The active layer 105 is stacked on the + Z side of the lower spacer layer 104, and includes, as an example, as shown in FIG. 5, three quantum well layers 105a and four barrier layers 105b. Each quantum well layer 105a is made of GaInPAs, which has a composition that induces compressive strain, and has a band gap wavelength of about 780 nm. Each barrier layer 105b is made of Ga _0.6 In _0.4 P, which is a composition that induces tensile strain.

The upper spacer layer 106 is laminated on the active layer 105 on the + Z side, and is a layer made of non-doped (Al _0.1 Ga _0.9 ) _0.5 In _0.5 P.

  A portion composed of the lower spacer layer 104, the active layer 105, and the upper spacer layer 106 is also called a resonator structure, and the thickness thereof is set to be an optical thickness of one wavelength. The active layer 105 is provided at the center of the resonator structure at a position corresponding to the antinode in the standing wave distribution of the electric field so that a high stimulated emission probability can be obtained.

  Further, heat generated in the active layer 105 is radiated to the substrate 101 mainly through the lower semiconductor DBR 103. The back surface of the substrate 101 is attached to the package using a conductive adhesive or the like, and heat is radiated from the substrate 101 to the package.

The upper semiconductor DBR 107 is stacked on the + Z side of the upper spacer layer 106, and includes a low refractive index layer 107a made of p-Al _0.9 Ga _0.1 As and a high refractive index layer made of p-Al _0.3 Ga _0.7 As. There are 24 pairs of refractive index layers 107b. And between each refractive index layer, in order to reduce an electrical resistance, the composition inclination layer (illustration omitted) which changed the composition gradually toward the other composition from one composition is provided. Each refractive index layer is set to have an optical thickness of λ / 4 including 1/2 of the adjacent composition gradient layer.

  In one of the low refractive index layers in the upper semiconductor DBR 107, a selective oxidation layer made of p-AlAs is inserted with a thickness of 30 nm. This selective oxidation layer is inserted at a position optically separated from the upper spacer layer 106 by 5λ / 4, and is in the third pair of low refractive index layers from the upper spacer layer 106.

  The contact layer 109 is stacked on the + Z side of the upper semiconductor DBR 107 and is a layer made of p-GaAs.

  Note that a structure in which a plurality of semiconductor layers are stacked on the substrate 101 is also referred to as a “stacked body” for convenience in the following.

  Next, a method for manufacturing the surface emitting laser element 100 will be briefly described.

(1) The laminate is formed by crystal growth by metal organic vapor phase epitaxy (MOCVD) or molecular beam epitaxy (MBE).

Here, trimethylaluminum (TMA), trimethylgallium (TMG), and trimethylindium (TMI) are used as Group III materials, and arsine (AsH ₃ ) gas and phosphine (PH ₃ ) gas are used as Group V materials. Used. Further, carbon tetrabromide (CBr ₄ ) is used as a p-type dopant material, and hydrogen selenide (H ₂ Se) is used as an n-type dopant material.

(2) A square resist pattern having a side of 20 μm is formed on the surface of the laminate.

(3) A square columnar mesa is formed by using an ECR etching method using Cl ₂ gas and a square resist pattern as a photomask. Here, the bottom surface of the etching is positioned in the lower spacer layer 104 (see FIG. 3). The mesa size (length of one side) is preferably 10 μm or more. This is because if it is too small, heat will be accumulated during operation and the characteristics may be deteriorated.

(4) The photomask is removed.

(5) The laminated body is heat-treated in water vapor. Here, Al in the selective oxidation layer is selectively oxidized from the outer periphery of the mesa. Then, an unoxidized region 108b surrounded by the Al oxide layer 108a is left in the center of the mesa (see FIG. 3). As a result, an oxidized constriction structure is formed that restricts the drive current path of the light emitting part to only the central part of the mesa. The non-oxidized region 108b is a current passage region (current injection region). Here, based on the results of various preliminary experiments, the heat treatment conditions (holding temperature, holding time, etc.) are appropriately selected so that the current passing region 108b has a desired size.

(6) A protective layer 111 made of SiN or SiO ₂ is formed by vapor phase chemical deposition (CVD) (see FIG. 3).

(7) Flatten with polyimide 112 (see FIG. 3).

(8) Open the window of the P-side electrode contact on the top of the mesa. Here, after masking with a photoresist, the opening at the top of the mesa is exposed to remove the photoresist at that portion, and then the polyimide 112 and the protective layer 111 are etched and opened with BHF.

(9) A square resist pattern having a side of 10 μm is formed in a region to be a light emitting portion on the top of the mesa, and a p-side electrode material is deposited. As the electrode material on the p side, a multilayer film made of Cr / AuZn / Au or a multilayer film made of Ti / Pt / Au is used.

(10) Lift off the electrode material of the light emitting portion to form the p-side electrode 113 (see FIG. 3).

(11) After polishing the back side of the substrate 101 to a predetermined thickness (for example, about 100 μm), an n-side electrode 114 is formed (see FIG. 3). Here, the n-side electrode 114 is a multilayer film made of AuGe / Ni / Au.

(12) Ohmic conduction is established between the p-side electrode 113 and the n-side electrode 114 by annealing. Thereby, the mesa becomes a light emitting part.

(13) Cut for each chip.

Here, in the first case (see FIG. 6) where the lower semiconductor DBR 103 is composed only of the first lower semiconductor DBR 103 ₁ composed of 40.5 pairs, the first lower semiconductor DBR 103 composed of 37.5 pairs. ₁ and the second case composed of the second lower semiconductor DBR 103 ₂ consisting of three pairs (see FIG. 7), the first consisting Similarly 36.5 pairs and the embodiment of the lower semiconductor DBR 103 ₁ and 3 the absorption loss for the third case consists of the second lower semiconductor DBR 103 ₂ consisting of a pair and the third lower semiconductor DBR 103 ₃ consisting of a pair was calculated. When the increase amount of the absorption loss in the second case with respect to the first case is 100%, the increase amount of the absorption loss in the third case with respect to the first case is about 77%. That is, the third lower semiconductor DBR 103 _3, it was found that it is possible to reduce approximately 23% of the increase in absorption loss. When the number of pairs in the third lower semiconductor DBR 1033 was ₃ (see FIG. 8), the increase in absorption loss with respect to the first case was about 46%.

Even when the impurity concentration (impurity doping concentration) was 3 × 10 ¹⁸ (cm ⁻³ ) and 5 × 10 ¹⁸ (cm ⁻³ ), the effect of reducing absorption loss was the same. Further, the effect of reducing the absorption loss was the same even when the wavelength was changed. Furthermore, the number of pairs as 5 pair in the second lower semiconductor DBR 103 _2, the effect of reducing the absorption loss were similar.

The thermal resistance of the lower semiconductor DBR 103 in this embodiment was calculated to be 2720 (K / W). On the other hand, the thermal resistance in the first case (see FIG. 6) and the second case (see FIG. 7) was calculated to be 3050 (K / W) and 2670 (K / W), respectively. Therefore, with respect to the thermal resistance of the lower semiconductor DBR 103, the third lower semiconductor DBR 103 ₃ of, it can be seen that substantially no adverse effect.

FIG. 9 shows the relationship between the number of pairs of the _third lower semiconductor DBR 1033 and the thermal resistance of the lower semiconductor DBR 103. According to this, the number of pairs of the third lower semiconductor DBR 103 ₃ exceeds 5 pairs, the heat dissipation effect of the second lower semiconductor DBR 103 ₂ becomes half or less. Therefore, the number of pairs of the third lower semiconductor DBR 103 ₃ is preferably 1 to 5 pairs.

By the way, the heat dissipation layer not only increases absorption loss, but also may cause a decrease in crystallinity of a layer laminated thereon. When the crystallinity of the active layer laminated on the upper side (here, + Z side) of the heat dissipation layer is lowered, the light emission efficiency is lowered. If, heat radiation effect and the second lower semiconductor DBR 103 ₂ comprising the entire lower semiconductor DBR 103 from 40.5 pairs is high but it is difficult to maintain the crystallinity of the active layer. Therefore, the number of pairs of the second lower semiconductor DBR 103 ₂ is preferably 1 to 5 pairs. The third lower semiconductor DBR 103 ₃ of, to restore the crystallinity of the layer to be laminated thereon, an effect of reducing an adverse effect on the active layer.

  In addition, a surface emitting laser having an oxide confinement structure is etched in a mesa shape or the like in order to be electrically or spatially separated from the surroundings in the manufacturing process. At this time, it is necessary to etch deeper than the selective oxidation layer so that Al can be selectively oxidized. The selective oxidation layer is close to the active layer of the p-side semiconductor DBR (the upper semiconductor DBR provided above the active layer) for the purpose of suppressing the spread of current, and is active in the standing wave distribution of the electric field of the laser beam. Generally, it is provided at a position corresponding to the first to fifth nodes from the layer. However, it is difficult to control the etching bottom so that it is deeper than the selective oxidation layer and does not reach the lower semiconductor DBR due to the problem of controllability of the etching depth. In particular, in order to control the etching depth in the whole wafer surface, in addition to controlling the etching time, it is necessary to make the etching uniform in the wafer surface and also make the thickness of the crystal growth layer uniform. In addition, it is extremely difficult in production to perform etching so that the bottom surface of the etching does not reach the lower semiconductor DBR.

  For this reason, it has been proposed that the lower semiconductor DBR has a two-stage configuration (for example, see Japanese Patent Application Laid-Open No. 2003-347670). In this proposal, AlAs having a much higher thermal conductivity than AlGaAs is used for most of the low refractive index layers on the substrate side in the lower semiconductor DBR. Conventional AlGaAs is used for the low refractive index layer on the active layer side of the lower semiconductor DBR. In this case, it is difficult to increase the thermal conductivity of the low refractive index layer close to the resonator structure.

  In the surface emitting laser element 100 according to the present embodiment, the main material of the semiconductor DBR is an AlGaAs material, and the resonator structure material is an AlGaInPAs material containing In. In this case, the etching rate of the resonator structure can be made smaller than the etching rate of the semiconductor DBR. Thereby, it can be easily detected by the etching monitor that the etching bottom surface has reached the resonator structure, and the etching can be accurately performed to the vicinity of the center of the resonator structure, and the carrier can be expanded. It is possible to reduce carriers that do not contribute to oscillation.

As is clear from the above description, in the surface emitting laser element 100 according to the present embodiment, the lower semiconductor DBR 103 constitutes a first semiconductor multilayer reflector, and the upper semiconductor DBR 107 constitutes a second semiconductor multilayer reflector. It is configured. The first partial reflection mirror by the second lower semiconductor DBR 103 ₂ is configured and second partially reflective mirror by the third lower semiconductor DBR 103 ₃ is formed.

  The high refractive index layer 103b constitutes a first layer, and the low refractive index layer 103a constitutes a second layer.

As described above, according to the surface-emitting laser device 100 according to the present embodiment, the resonator structure including the active layer 105 and the low-refractive index layer and the high-refractive index layer provided between the resonator structures are provided. And a lower semiconductor DBR 103 and an upper semiconductor DBR 107, which are a plurality of pairs. The lower semiconductor DBR 103 includes a low refractive index layer 103a made of n-AlAs having a high thermal conductivity and a high refractive index layer 103b made of n-Al _0.3 Ga _0.7 As having a lower thermal conductivity. A pair includes a _first lower semiconductor DBR 103 ₁ having 36.5 pairs, a second lower semiconductor DBR 103 ₂ having 3 pairs, and a third lower semiconductor DBR 103 ₃ having one pair.

In the second lower semiconductor DBR 103 _2, the low refractive index layer 103a includes a half of the adjacent gradient composition layer is set to have an optical thickness of 3 [lambda] / 4, the high refractive index layer 103b is adjacent The optical thickness is set to λ / 4 including 1/2 of the composition gradient layer.

The third lower semiconductor DBR 103 ₃ of is provided between the resonator structure and the second lower semiconductor DBR 103 _2, any refractive index layers includes a half of the adjacent gradient composition layer, lambda The optical thickness is set to / 4.

  Thereby, since heat dissipation efficiency can be improved while suppressing an increase in absorption loss, it is possible to have a long lifetime, high luminous efficiency, and excellent temperature characteristics.

  According to the optical scanning device 1010 according to the present embodiment, since the light source 14 includes the surface emitting laser element 100, stable optical scanning can be performed.

  Since the laser printer 1000 according to the present embodiment includes the optical scanning device 1010, a high-quality image can be formed.

  Further, since the lifetime of the surface emitting laser element is remarkably improved, the writing unit or the light source unit can be reused.

In the case, in the above embodiment, in the second lower semiconductor DBR 103 _2, the low refractive index layer 103a is, by including 1/2 of the adjacent composition gradient layer is set to have an optical thickness of 3 [lambda] / 4 However, the present invention is not limited to this, and the low refractive index layer 103a includes 1/2 of the adjacent composition gradient layer, and uses an integer n of 1 or more to set (2n + 1) λ / 4. Any optical thickness that satisfies the requirement is acceptable.

In the above embodiment, the case has been described where the second lower semiconductor DBR 103 ₂ has three pairs pairs of the low refractive index layer 103a and the high refractive index layer 103b, but is not limited thereto.

Further, in the above embodiment, the third lower semiconductor DBR 103 ₃ has been described having one pair pairs of the low refractive index layer 103a and the high refractive index layer 103b, but is not limited thereto. The third lower semiconductor DBR 103 ₃ of, need only a pair of the low refractive index layer 103a and the high refractive index layer 103b has one pair 5 pairs.

  In the above embodiment, the case where the mesa shape in the cross section perpendicular to the laser oscillation direction is square has been described. However, the present invention is not limited to this, and may be any shape such as a circle, an ellipse, or a rectangle. Can do.

Moreover, in the said embodiment, you may make the impurity concentration of the part close | similar to the resonator structure of lower semiconductor DBR103 relatively lower than another part. Since the amount of absorption increases as the impurity concentration increases, the thickness of the low refractive index layer can be reduced by making the impurity concentration in the portion where the influence of absorption is large lower than the impurity concentration in the portion where the influence of absorption is small. An increase in the amount of absorption due to the increase in thickness can be suppressed. For example, the impurity concentration of four pairs adjacent to the resonator structure of the lower semiconductor DBR 103 may be 5 × 10 ¹⁷ (cm ⁻³ ), and the other impurity concentration may be 1 × 10 ¹⁸ (cm ⁻³ ).

  Moreover, although the said embodiment demonstrated the case where the oscillation wavelength of a light emission part was a 780 nm band, it is not limited to this. The oscillation wavelength of the light emitting unit may be changed according to the characteristics of the photoreceptor.

  Further, the surface emitting laser element 100 can be used for applications other than the image forming apparatus. In that case, the oscillation wavelength may be a wavelength band such as a 650 nm band, an 850 nm band, a 980 nm band, a 1.3 μm band, and a 1.5 μm band depending on the application.

  As an example, FIG. 10 shows a surface emitting laser element 100A having a design oscillation wavelength of 850 nm.

  The surface emitting laser element 100A includes a substrate 201, a lower semiconductor DBR 203, a lower spacer layer 204, an active layer 205, an upper spacer layer 206, an upper semiconductor DBR 207, a contact layer 209, and the like.

  The substrate 201 is an n-GaAs single crystal substrate.

The lower semiconductor DBR 203, as shown in FIG. 11 as an example, the first lower semiconductor DBR 203 _1, the second lower semiconductor DBR 203 _2, which is a third lower semiconductor DBR 203 ₃ Prefecture.

The first lower semiconductor DBR 203 ₁ is stacked on the + Z side surface of the substrate 201 via a buffer layer (not shown), and includes a low refractive index layer 203a made of n-AlAs and n-Al _0.1 Ga _0.9. There are 30.5 pairs of high refractive index layers 203b made of As. The low refractive index layer 203a has a higher thermal conductivity than the high refractive index layer 203b (see FIG. 23). Between each refractive index layer, in order to reduce electrical resistance, a composition gradient layer (not shown) in which the composition is gradually changed from one composition to the other composition is provided. Each refractive index layer includes 1/2 of the adjacent composition gradient layer, and is set to have an optical thickness of λ / 4 when the oscillation wavelength is λ.

The second lower semiconductor DBR 203 ₂ is stacked on the first lower semiconductor DBR 203 ₁ of the + Z side, and a pair of the low refractive index layer 203a and the high refractive index layer 203b has 5 pairs. Between each refractive index layer, in order to reduce electrical resistance, a composition gradient layer (not shown) in which the composition is gradually changed from one composition to the other composition is provided. The low refractive index layer 203a is set to have an optical thickness of 3λ / 4 including 1/2 of the adjacent composition gradient layer, and the high refractive index layer 203b is 1 / of the adjacent composition gradient layer. 2 so that the optical thickness is λ / 4.

The third lower semiconductor DBR 203 ₃ of is stacked on the + Z side of the second lower semiconductor DBR 203 _2, and a pair of the low refractive index layer 203a and the high refractive index layer 203b has one pair. Between each refractive index layer, in order to reduce electrical resistance, a composition gradient layer (not shown) in which the composition is gradually changed from one composition to the other composition is provided. Each refractive index layer is set to have an optical thickness of λ / 4 including 1/2 of the adjacent composition gradient layer.

The lower spacer layer 204 is laminated on the + Z side of the _third lower semiconductor DBR 2033 and is a layer made of non-doped Al _0.4 Ga _0.6 As.

The active layer 205 is stacked on the + Z side of the lower spacer layer 204, and as shown in FIG. 12, for example, includes three quantum well layers 205a and four barrier layers 205b. Each quantum well layer 205a is made of Al _0.12 Ga _0.88 As, and each barrier layer 205b is made of Al _0.3 Ga _0.7 As.

The upper spacer layer 206 is laminated on the + Z side of the active layer 205 and is a layer made of non-doped Al _0.4 Ga _0.6 As.

  A portion composed of the lower spacer layer 204, the active layer 205, and the upper spacer layer 206 is also called a resonator structure, and the thickness thereof is set to be an optical thickness of one wavelength. The active layer 205 is provided at the center of the resonator structure, which is a position corresponding to the antinode in the standing wave distribution of the electric field, so that a high stimulated emission probability can be obtained. The heat generated in the active layer 205 is radiated to the substrate 201 mainly through the lower semiconductor DBR 203.

The upper semiconductor DBR 207 is stacked on the + Z side of the upper spacer layer 206, and includes a low refractive index layer 207a made of p-Al _0.9 Ga _0.1 As and a high refractive index layer made of p-Al _0.1 Ga _0.9 As. There are 24 pairs of refractive index layers 207b. And between each refractive index layer, in order to reduce an electrical resistance, the composition inclination layer (illustration omitted) which changed the composition gradually toward the other composition from one composition is provided. Each refractive index layer is set to have an optical thickness of λ / 4 including 1/2 of the adjacent composition gradient layer.

  In one of the low refractive index layers in the upper semiconductor DBR 207, a selective oxidation layer made of p-AlAs is inserted with a thickness of 30 nm. The insertion position of the selective oxidation layer is a position optically separated from the upper spacer layer 206 by λ / 4.

  The contact layer 209 is stacked on the + Z side of the upper semiconductor DBR 207 and is a layer made of p-GaAs.

  The surface emitting laser element 100A can be manufactured in the same manner as the surface emitting laser element 100. In FIG. 10, reference numeral 211 denotes a protective layer, reference numeral 212 denotes polyimide, reference numeral 213 denotes a p-side electrode, reference numeral 214 denotes an n-side electrode, reference numeral 208a denotes an oxide layer, and reference numeral 208b denotes a current passing region. Even in this case, the same effect as the surface emitting laser element 100 can be obtained.

  In the above embodiment, the light source 14 may include the surface emitting laser array 500 shown in FIG. 13 as an example instead of the surface emitting laser element 100.

  In the surface emitting laser array 500, a plurality (32 in this case) of light emitting units are arranged on the same substrate. Here, the M direction in FIG. 13 is a main scanning corresponding direction, and the S direction is a sub scanning corresponding direction. Note that the number of light emitting units is not limited to 32.

  As shown in FIG. 14, the surface emitting laser array 500 includes four light emitting unit rows in which eight light emitting units are arranged at equal intervals along the T direction which is a direction inclined from the M direction toward the S direction. Has a row. These four light emitting section rows are arranged at equal intervals d in the S direction so that they are equally spaced c when all the light emitting sections are orthogonally projected onto a virtual line extending in the S direction. That is, the 32 light emitting units are two-dimensionally arranged. In this specification, the “light emitting portion interval” refers to the distance between the centers of two light emitting portions.

  Here, the interval c is 3 μm, the interval d is 24 μm, and the light emitting portion interval X in the M direction (see FIG. 14) is 30 μm.

  Each light emitting portion has the same structure as the surface emitting laser element 100 described above, as shown in FIG. The surface emitting laser array 500 can be manufactured by a method similar to that of the surface emitting laser element 100 described above.

  By the way, usually, the desired etching depth differs for each light emitting portion due to variations in the thickness of the crystal growth layer and variations in the etching rate within the substrate (wafer) plane. However, the etching depth is controlled so that the bottom surface of the etching is deeper than the selective oxidation layer and does not reach the low refractive index layer of the lower semiconductor DBR having the same Al composition as the selective oxidation layer for all the light emitting portions. It is difficult to do.

  In particular, in the surface emitting laser array, the etching rate changes when the etching width varies due to the difference in the light emitting portion interval. In this case, even if there is no such variation, the etching depth differs for each light emitting portion.

  In the surface emitting laser array 500, the main material of the semiconductor DBR is an AlGaAs material, and the resonator structure material is an AlGaInPAs material containing In. Therefore, the etching rate in the resonator structure is set to the etching rate in the semiconductor DBR. Can be made smaller. Thereby, in the wafer surface and in the array chip, it is possible to control the etching bottom surface to remain in the resonator structure without etching to the lower semiconductor DBR.

  In this way, in the surface emitting laser array 500, the etching bottom is not provided at a predetermined position, but the etching rate is slow, so that the etching bottom reaches the resonator structure by the etching monitor. Can be easily controlled. Further, the etching to the vicinity of the center of the resonator structure can reduce the spread of carriers, and the number of carriers that do not contribute to oscillation can be reduced.

  When a layer for stopping etching is provided at a predetermined position, the etching can be prevented from proceeding in the depth direction (here, -Z direction), but the lateral direction (here, parallel to the XY plane). Since the etching proceeds in the direction (direction), inconveniences such as fluctuation of the mesa size between lots occur.

  The surface emitting laser array 500 is a 32ch (channel) multi-beam light source. However, since heat radiation measures are taken, thermal interference with surrounding light emitting parts is suppressed, and a plurality of light emitting parts are driven simultaneously. The change in characteristics was small and the service life was long.

  Further, in the surface emitting laser array 500, since the intervals between the light emitting portions when the respective light emitting portions are orthogonally projected onto a virtual line extending in the sub-scanning corresponding direction are equal intervals c, the photosensitive drum 1030 is adjusted by adjusting the lighting timing. In the above, it can be considered that the configuration is the same as the case where the light emitting units are arranged at equal intervals in the sub-scanning direction.

  Since the distance c is 3 μm, if the magnification of the optical system of the optical scanning device 1010 is about 1.8, high-density writing of 4800 dpi (dot / inch) can be performed. Of course, it is possible to increase the density by increasing the number of light emitting portions in the main scanning direction, making the array arrangement in which the distance d is narrowed and the distance c is further reduced, or by reducing the magnification of the optical system. Quality printing is possible. Note that the writing interval in the main scanning direction can be easily controlled by the lighting timing of the light emitting unit.

  In this case, the laser printer 1000 can perform printing without decreasing the printing speed even if the writing dot density increases. Further, when the writing dot density is the same, the printing speed can be further increased.

  By the way, it is preferable that the groove | channel between two light emission parts shall be 5 micrometers or more for the electrical and spatial separation of each light emission part. This is because if it is too narrow, it becomes difficult to control etching during production.

  In the above embodiment, the laser printer 1000 is described as the image forming apparatus. However, the present invention is not limited to this.

  For example, an image forming apparatus that directly irradiates laser light onto a medium (for example, paper) that develops color with laser light may be used.

  Further, an image forming apparatus using a silver salt film as the image carrier may be used. In this case, a latent image is formed on the silver salt film by optical scanning, and this latent image can be visualized by a process equivalent to a developing process in a normal silver salt photographic process. Then, it can be transferred to photographic paper by a process equivalent to a printing process in a normal silver salt photographic process. Such an image forming apparatus can be implemented as an optical plate making apparatus or an optical drawing apparatus that draws a CT scan image or the like.

  As an example, as shown in FIG. 16, a color printer 2000 including a plurality of photosensitive drums may be used.

  The color printer 2000 is a tandem multicolor printer that forms a full-color image by superimposing four colors (black, cyan, magenta, and yellow). The black “photosensitive drum K1, charging device K2, "Developing device K4, cleaning unit K5, and transfer device K6", cyan "photosensitive drum C1, charging device C2, developing device C4, cleaning unit C5, and transfer device C6", and magenta "photosensitive drum" M1, charging device M2, developing device M4, cleaning unit M5, and transfer device M6 ”,“ photosensitive drum Y1, charging device Y2, developing device Y4, cleaning unit Y5, and transfer device Y6 ”for yellow, and light A scanning device 2010, a transfer belt 2080, a fixing unit 2030, and the like are provided.

  Each photosensitive drum rotates in the direction of an arrow in FIG. 16, and a charging device, a developing device, a transfer device, and a cleaning unit are arranged around each photosensitive drum in the order of rotation. Each charging device uniformly charges the surface of the corresponding photosensitive drum. The surface of each photoconductive drum charged by the charging device is irradiated with light by the optical scanning device 2010, and a latent image is formed on each photoconductive drum. Then, a toner image is formed on the surface of each photosensitive drum by a corresponding developing device. Further, the toner image of each color is transferred onto the recording paper on the transfer belt 2080 by the corresponding transfer device, and finally the image is fixed on the recording paper by the fixing unit 2030.

  The optical scanning device 2010 has a light source for each color including either a surface emitting laser element similar to the surface emitting laser element 100 or a surface emitting laser array similar to the surface emitting laser array 500. Therefore, the same effect as that of the optical scanning device 1010 can be obtained. In addition, since the color printer 2000 includes the optical scanning device 2010, the same effect as the laser printer 1000 can be obtained.

  By the way, in the color printer 2000, color misregistration may occur due to manufacturing error or position error of each component. Even in such a case, if each light source of the optical scanning device 2010 has a surface-emitting laser array similar to the surface-emitting laser array 500, color misregistration is reduced by selecting a light-emitting unit to be lit. can do.

  FIG. 17 shows a schematic configuration of an optical transmission system 3000 according to an embodiment of the present invention. In this optical transmission system 3000, an optical transmission module 3001 and an optical reception module 3005 are connected by an optical fiber cable 3004, and one-way optical communication from the optical transmission module 3001 to the optical reception module 3005 is possible.

  The optical transmission module 3001 includes a light source 3002 and a drive circuit 3003 that modulates the light intensity of the laser light output from the light source 3002 in accordance with an electrical signal input from the outside.

  As an example, the light source 3002 includes a surface emitting laser array 600 as shown in FIG.

  In the surface emitting laser array 600, a plurality of (here, ten) light emitting units are one-dimensionally arranged on the same substrate. Note that the number of light emitting units is not limited to ten.

  Each light emitting portion of the surface emitting laser array 600 is a surface emitting laser having a design oscillation wavelength of 1.3 μm band. As shown in FIG. 19 which is a cross-sectional view taken along the line AA of FIG. A semiconductor DBR 303, a lower spacer layer 304, an active layer 305, an upper spacer layer 306, an upper semiconductor DBR 307, a contact layer 309, and the like are included.

  The substrate 301 is an n-GaAs single crystal substrate.

The lower semiconductor DBR 303, as shown in FIG. 20 as an example, has a first lower semiconductor DBR 303 _1, the second lower semiconductor DBR 303 _2, and a third lower semiconductor DBR 303 _3.

The first lower semiconductor DBR 303 ₁ is stacked on the + Z side of the substrate 301 via a buffer layer (not shown), and a low refractive index layer 303a made of n-AlAs, high refractive index layer made of n-GaAs There are 30.5 pairs of 103b. The low refractive index layer 303a has a higher thermal conductivity than the high refractive index layer 303b. Between each refractive index layer, in order to reduce electrical resistance, a composition gradient layer (not shown) in which the composition is gradually changed from one composition to the other composition is provided. Each refractive index layer includes 1/2 of the adjacent composition gradient layer, and is set to have an optical thickness of λ / 4 when the oscillation wavelength is λ.

The second lower semiconductor DBR 303 ₂ is stacked on the first lower semiconductor DBR 303 ₁ of the + Z side, and a pair of the low refractive index layer 303a and the high refractive index layer 303b has 5 pairs. Between each refractive index layer, in order to reduce electrical resistance, a composition gradient layer (not shown) in which the composition is gradually changed from one composition to the other composition is provided. The low refractive index layer 303a is set to have an optical thickness of 3λ / 4, including 1/2 of the adjacent composition gradient layer, and the high refractive index layer 303b is 1 / of the adjacent composition gradient layer. 2 so that the optical thickness is λ / 4.

The third lower semiconductor DBR 303 ₃ of is stacked on the + Z side of the second lower semiconductor DBR 303 _2, and a pair of the low refractive index layer 303a and the high refractive index layer 303b has one pair. Between each refractive index layer, in order to reduce electrical resistance, a composition gradient layer (not shown) in which the composition is gradually changed from one composition to the other composition is provided. Each refractive index layer is set to have an optical thickness of λ / 4 including 1/2 of the adjacent composition gradient layer.

The lower spacer layer 304 is laminated on the + Z side of the _third lower semiconductor DBR 3033 and is a layer made of non-doped GaAs.

  The active layer 305 is stacked on the + Z side of the lower spacer layer 304, and includes, as an example, as shown in FIG. 21, three quantum well layers 305a and four barrier layers 305b. Each quantum well layer 305a is a layer made of GaInNAs, and each barrier layer 305b is a layer made of GaAs.

  The upper spacer layer 306 is stacked on the + Z side of the active layer 305 and is a layer made of non-doped GaAs.

  A portion composed of the lower spacer layer 304, the active layer 305, and the upper spacer layer 306 is also called a resonator structure, and the thickness thereof is set to an optical thickness of one wavelength. The active layer 305 is provided at the center of the resonator structure, which is a position corresponding to the antinode in the standing wave distribution of the electric field, so that a high stimulated emission probability can be obtained. Further, the heat generated in the active layer 305 is radiated mainly through the lower semiconductor DBR 303.

  The upper semiconductor DBR 307 is stacked on the + Z side of the upper spacer layer 306, and has 26 pairs of a low refractive index layer 307a and a high refractive index layer 307b made of p-GaAs. Between each refractive index layer, in order to reduce electrical resistance, a composition gradient layer (not shown) in which the composition is gradually changed from one composition to the other composition is provided. Each refractive index layer is set to have an optical thickness of λ / 4 including 1/2 of the adjacent composition gradient layer.

  In one of the low refractive index layers in the upper semiconductor DBR 307, a selective oxidation layer made of p-AlAs is inserted with a thickness of 20 nm. The insertion position of this selective oxidation layer is optically separated from the upper spacer layer 306 by 5λ / 4.

The low refractive index layer including the selective oxidation layer is a layer made of p-Al _0.6 Ga _0.4 As, and the other low refractive index layers are p-Al _0.9 Ga _0.1. It is a layer made of As. In the low refractive index layer including the selective oxidation layer, an intermediate layer (not shown) made of p-Al _0.8 Ga _0.2 As having a thickness of 35 nm is provided adjacent to the selective oxidation layer. Yes.

  The surface emitting laser array 600 can be manufactured in the same manner as the surface emitting laser element 100. In FIG. 19, reference numeral 311 is a protective layer, reference numeral 312 is polyimide, reference numeral 313 is a p-side electrode, reference numeral 314 is an n-side electrode, reference numeral 308a is an oxide layer, and reference numeral 308b is a current passing region.

  This surface emitting laser array 600 has the same effects as the surface emitting laser array 500 because the lower semiconductor DBR 303 of each light emitting unit has the same configuration as the lower semiconductor DBR 103 of the surface emitting laser element 100. be able to.

  In order to stop etching in the resonator structure when forming the mesa, a layer made of GaInP containing In (indium) may be used as the spacer layer instead of the layer made of GaAs.

  The optical signal output from the light source 3002 is coupled to the optical fiber cable 3004, guided through the optical fiber cable 3004, and input to the optical receiving module 3005. Note that the optical fiber cable 3004 includes a plurality of optical fibers respectively corresponding to the plurality of light emitting units of the surface emitting laser array 600, as shown in FIG. 22 as an example.

  The optical receiving module 3005 includes a light receiving element 3006 that converts an optical signal into an electric signal, and a receiving circuit 3007 that performs signal amplification, waveform shaping, and the like on the electric signal output from the light receiving element 3006.

  According to the optical transmission module 3001 according to the present embodiment, since the light source 3002 includes the surface emitting laser array 600, it is possible to generate a stable optical signal. As a result, the optical transmission system 3000 can perform high-quality optical transmission.

  Therefore, the optical transmission system 3000 is also effective for short-distance data communication such as home use, office indoor use, and device use.

  In addition, since a plurality of light emitting portions having uniform characteristics are integrated on the same substrate, data transmission by a large number of beams can be easily performed simultaneously, and high-speed communication can be performed.

  Further, since the surface emitting laser operates with low power consumption, the temperature rise can be reduced particularly when incorporated in an apparatus.

  Here, the case where the light emitting section and the optical fiber are made to correspond one-to-one has been described. However, a plurality of surface emitting laser elements having different oscillation wavelengths are arranged in a one-dimensional or two-dimensional array to perform wavelength multiplexing. It is also possible to further increase the transmission rate by transmitting.

  In addition, although a configuration example of one-way communication is shown here, a configuration of two-way communication can also be taken.

  As described above, the surface-emitting laser element and the surface-emitting laser array of the present invention are suitable for realizing a long lifetime, high emission efficiency, and excellent temperature characteristics. Further, the optical scanning device of the present invention is suitable for performing stable optical scanning. The image forming apparatus of the present invention is suitable for forming a high quality image. The optical transmission module of the present invention is suitable for generating a stable optical signal. The optical transmission system of the present invention is suitable for performing high-quality optical transmission.

It is a figure for demonstrating schematic structure of the laser printer which concerns on one Embodiment of this invention. It is the schematic which shows the optical scanning device in FIG. It is a figure for demonstrating the surface emitting laser element contained in the light source in FIG. It is the figure which expanded a part of lower semiconductor DBR in FIG. It is the figure which expanded the active layer vicinity in FIG. It is a figure for demonstrating lower semiconductor DBR in the 1st case. It is a figure for demonstrating lower semiconductor DBR in the 2nd case. It is a figure for demonstrating lower semiconductor DBR which 3rd lower semiconductor DBR consists of 3 pairs. It is a figure for demonstrating the calculation result of thermal resistance. It is a figure for demonstrating the modification of a surface emitting laser element. It is the figure which expanded a part of lower semiconductor DBR in FIG. It is the figure which expanded the active layer vicinity in FIG. It is a figure for demonstrating a surface emitting laser array. It is a figure for demonstrating the two-dimensional arrangement | sequence of the light emission part in FIG. It is AA sectional drawing of FIG. It is a figure for demonstrating schematic structure of a color printer. It is a figure for demonstrating schematic structure of the optical transmission module and optical transmission system which concern on one Embodiment of this invention. It is a figure for demonstrating the surface emitting laser array contained in the light source in FIG. It is AA sectional drawing of FIG. It is the figure which expanded a part of lower semiconductor DBR in FIG. It is the figure which expanded the active layer vicinity in FIG. It is a figure for demonstrating the optical fiber cable in FIG. It is a figure for demonstrating the relationship between the composition of Al in a AlGaAs type material, and thermal conductivity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11a ... Deflector side scanning lens (a part of scanning optical system), 11b ... Image surface side scanning lens (a part of scanning optical system), 13 ... Polygon mirror (deflector), 14 ... Light source, 100 ... Surface emitting laser Element 100A ... Surface emitting laser element 103 ... Lower semiconductor DBR (first semiconductor multilayer reflector), 103 ₂ ... Second lower semiconductor DBR (first partial reflector), 103 ₃ ... Third lower part Semiconductor DBR (second partial reflector), 103a... Low refractive index layer (second layer), 103b... High refractive index layer (first layer), 104... Lower spacer layer (part of resonator structure) , 105 ... Active layer, 106 ... Upper spacer layer (part of resonator structure), 107 ... Upper semiconductor DBR (second semiconductor multilayer reflector), 203 ... Lower semiconductor DBR (first semiconductor multilayer film) reflector), 203 2 _... second lower semiconductor DBR (first partially reflective mirror), 203 3 _... third lower semiconductor DBR (second partially reflective mirror), 203a ... low-refractive index layer (second layer), 203b ... high refractive index layer (first , 204 ... lower spacer layer (part of the resonator structure), 205 ... active layer, 206 ... upper spacer layer (part of the resonator structure), 207 ... upper semiconductor DBR (second semiconductor multilayer) Film reflector), 303 ... lower semiconductor DBR (first semiconductor multilayer reflector), 303 ₂ ... second lower semiconductor DBR (first partial reflector), 303 ₃ ... third lower semiconductor DBR (first mirror) 2, 303 a... Low refractive index layer (second layer), 303 b... High refractive index layer (first layer), 304... Lower spacer layer (part of the resonator structure), 305. Active layer, 306... Upper spacer layer (part of resonator structure), 307. Semiconductor DBR (second semiconductor multilayer mirror), 500... Surface emitting laser array, 600... Surface emitting laser array, 1000... Laser printer (image forming apparatus), 1010. (Supporting body), 2000 ... color printer (image forming apparatus), 2010 ... optical scanning device, 3000 ... optical transmission system, 3001 ... optical transmission module (optical transmission module), 3002 ... light source, 3003 ... drive circuit (drive apparatus), 3004 ... Optical fiber cable (light transmission medium), 3006 ... Light receiving element (part of converter), 3007 ... Receiver circuit (part of converter), K1, C1, M1, Y1 ... Photosensitive drum (image carrier) ).

Claims (15)

A surface emitting laser element that emits light in a direction perpendicular to a substrate,
A resonator structure including an active layer;
A semiconductor multilayer film reflecting mirror that is provided across the resonator structure and includes a plurality of pairs in which a first layer and a second layer having different refractive indexes are paired;
The second layer has a higher thermal conductivity than the first layer,
The semiconductor multilayer film reflecting mirror includes at least one pair, a first partial reflecting mirror having a thicker optical thickness than the first layer, and the first partial reflecting mirror and the resonance A second portion provided between the first and second layers, wherein the first and second layers have an optical thickness that is less than the second layer of the first partial reflector. A surface-emitting laser element comprising a reflecting mirror.   2. The surface emitting laser element according to claim 1, wherein the optical thicknesses of the first and second layers in the second partial reflecting mirror are both ¼ of the oscillation wavelength.   3. The surface emitting laser element according to claim 1, wherein the second partial reflection mirror includes one pair or more and five pairs or less. 4.   In the first partial reflecting mirror, the optical thickness of the first layer is ¼ of the oscillation wavelength, and the optical thickness of the second layer is an oscillation wavelength λ using an integer n of 1 or more. The surface emitting laser element according to claim 1, wherein the surface emitting laser element is (2n + 1) λ / 4.   The surface emitting laser element according to claim 1, wherein the first layer is a layer made of AlAs. The semiconductor multilayer film reflector includes a first semiconductor multilayer film reflector that is stacked on one side of the resonator structure and a second semiconductor multilayer film mirror that is stacked on the other side of the resonator structure. And
The heat generated in the active layer is mainly dissipated through the first semiconductor multilayer mirror,
The surface emitting laser element according to claim 1, wherein the first and second partial reflecting mirrors are included in the first semiconductor multilayer film reflecting mirror.   The surface emitting laser element according to claim 6, wherein a doping concentration of impurities in the first semiconductor multilayer mirror is relatively low on the resonator structure side.   The surface emitting laser element according to claim 1, wherein the resonator structure is made of a material containing indium.   A surface emitting laser array in which the surface emitting laser elements according to any one of claims 1 to 8 are integrated. An optical scanning device that scans a surface to be scanned with light,
A light source comprising the surface emitting laser element according to claim 1;
A deflector for deflecting light from the light source;
A scanning optical system for condensing the light deflected by the deflector onto the surface to be scanned. An optical scanning device that scans a surface to be scanned with light,
A light source comprising the surface emitting laser array according to claim 9;
A deflector for deflecting light from the light source;
A scanning optical system for condensing the light deflected by the deflector onto the surface to be scanned. At least one image carrier;
An image forming apparatus comprising: at least one optical scanning device according to claim 10 or 11 that scans the at least one image carrier with light including image information.   The image forming apparatus according to claim 12, wherein the image information is multicolor color image information. An optical transmission module that generates an optical signal according to an input electrical signal,
A surface emitting laser array according to claim 9;
An optical transmission module comprising: a driving device that drives the surface-emitting laser array in accordance with the input electric signal. An optical transmission module according to claim 14;
An optical transmission medium for transmitting an optical signal generated by the optical transmission module;
A converter for converting an optical signal through the optical transmission medium into an electric signal;

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