JP2004014820A - Laser module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain superior characteristics and reliability by eliminating contaminants in a vessel, in a laser module wherein a semiconductor laser element is installed in the hermetically closed vessel. <P>SOLUTION: In the vessel 2, a heat sink 4 wherein the semiconductor laser element 6 is stuck on a submount 5, an electrode terminal 8 which is connected with the semiconductor laser element 6 by using a wire 9, a photodiode 10 for monitoring which is connected with an electrode terminal 12 by using a wire 13, and columnar zeolite sorbent 11 whose diameter is 1.5 mm and height is 1.5 mm are fixed on a stem 1, and a glass window 3 which is subjected to reflection free coating is installed. Ring-weld sealing is performed by using the vessel 2 in a dried air (N<SB>2</SB>=80%, O<SB>2</SB>=20%) atmosphere. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser module in which a semiconductor laser element is installed in a sealed container.
[0002]
[Prior art]
A laser module in which a semiconductor laser element, a collimator lens, a condensing lens, an optical fiber, and the like are sealed in a sealed container is known. In this laser module, contaminants remaining in the sealed container are semiconductor lasers. There is a problem in that it adheres to optical components such as the emission end face of the element, lens and optical fiber, and deteriorates laser characteristics. Examples of the pollutant include hydrocarbon compounds mixed in from the atmosphere of the manufacturing process, and it is known that the hydrocarbon compounds are polymerized or decomposed by laser light and adhered.
[0003]
In order to solve this problem, various methods have been proposed as described below. For example, in JP-A-11-167132, it is effective to reduce the amount of hydrocarbon compound in the container to 0.1% or less in order to prevent a decrease in the output of laser light of 400 nm or less. It is described that deposition on an optical component or the like due to photodecomposition of a hydrogen compound can be prevented. It has also been proposed that the sealed atmosphere be dry air, and a deposit removal effect is expected by a photochemical reaction between oxygen in the atmosphere and the deposited hydrocarbon compound.
[0004]
Further, in US Pat. No. 5,392,305, in order to prevent the hydrocarbon compound from adhering to the end face of the semiconductor laser element due to the photolysis of the hydrocarbon gas, 100 ppm or more of oxygen intended to decompose this gas is sealed. It is described that it is mixed into the stop gas.
[0005]
Japanese Patent Application Laid-Open No. 11-87814 describes that long-term reliability can be ensured by degreasing and washing away contaminants such as oil.
[0006]
On the other hand, in Japanese Patent Application No. 2000-336850, the present applicant has proposed a laser module using a GaN-based semiconductor laser element having an oscillation wavelength of 350 to 450 nm, but short-wavelength laser light has high energy. Therefore, there is a high probability that the hydrocarbon gas present in the module is polymerized or decomposed and adheres to the end face of the semiconductor laser element or the optical component, which is a particular problem.
[0007]
[Problems to be solved by the invention]
As shown in the above-mentioned US Pat. No. 5,392,305, the hydrocarbon-based deposit produced by the reaction between the laser beam and the hydrocarbon compound is converted into CO ₂ and H ₂ O in a gas atmosphere containing a certain amount or more of oxygen. It is solved by disassembling.
[0008]
However, in this type of deposit, not only hydrocarbon compounds but also silicon compounds have been confirmed, and it is understood that this type of deposit cannot be decomposed and removed only by containing oxygen in the atmosphere. ing. The deposited silicon compound is generated by a photochemical reaction between an organic compound gas containing Si such as a siloxane bond (Si—O—Si) and a silanol group (—Si—OH) (hereinafter referred to as an organosilicon compound) and laser light. Moreover, the presence of oxygen in the atmosphere has the effect of increasing the reaction rate. Since the deposits of hydrocarbon compounds and silicon compounds generate optical absorption, there is a problem that the reliability over time in continuous oscillation is significantly impaired.
[0009]
The silicon compound here refers to a compound having any structure including silicon regardless of organic or inorganic, and includes inorganic SiOx and an organic silicon compound.
[0010]
The generation source is a gas emitted mainly from a silicone-based material used in an arbitrary place in the laser module manufacturing process. This may be adhered to the surface of each component in the laser module, and when the module is used in a sealed state, it is contained in a small amount in the sealing gas. Examples of the method for removing gas components in these steps include normal clean room operation and installation of a sealing gas purifier, but even these methods cannot be completely removed, Capital investment is required. Even through a degreasing process of oil or the like as disclosed in JP-A-11-87814, it is unavoidable that the compound is mixed from the manufacturing process atmosphere.
[0011]
The hydrocarbon compound and silicon compound gas adhering to the components in the laser module can be removed by decomposition and evaporation by heat treatment at a temperature of 200 ° C. or higher, preferably 300 ° C. or higher. However, heat treatment requires several to several tens of hours of processing time, and when fixing the components in the module with an organic adhesive, the mechanical properties due to the thermal deterioration of the adhesive deteriorate, so this method should be used. I can't.
[0012]
In view of the above circumstances, an object of the present invention is to provide a highly reliable laser module in which contaminants are well removed in a laser module in which a semiconductor laser element is disposed in a sealed container. .
[0013]
[Means for Solving the Problems]
The laser module of the present invention is a laser module in which a semiconductor laser element is installed in a sealed container, wherein a substance having a gas adsorption function is arranged in the sealed container.
[0014]
The substance having a gas adsorption function arranged in the container is desirably at least one of a zeolite adsorbent and activated carbon.
[0015]
Further, the sealed container may include an optical fiber and an optical system for inputting laser light from the semiconductor laser element into the fiber.
[0016]
The oscillation wavelength of the semiconductor laser element is desirably 450 nm or less.
[0017]
【The invention's effect】
According to the laser module of the present invention, a laser module in which a semiconductor laser element is installed in an airtight container, and a substance having a gas adsorption function is disposed in the airtight container. Since silicon compounds and the like are favorably adsorbed, these compounds are not deposited on the emission end face of the semiconductor laser element, and laser characteristics and reliability can be improved. In addition, since it is not necessary to perform heat treatment, a highly reliable semiconductor laser element can be efficiently manufactured.
[0018]
Further, unlike the prior art, there is no need to adjust the atmosphere of the sealed space or to perform degreasing and cleaning treatment, and the module manufacturing process can be simplified.
[0019]
By using at least one of a zeolite adsorbent and activated carbon as a substance having a gas adsorption function, it is possible to favorably adsorb hydrocarbon compounds and the like, so that laser characteristics and reliability are improved. it can.
[0020]
Further, in a laser module having an optical fiber, it is effective to apply the present invention because it is possible to satisfactorily prevent contamination from being deposited on the surface of the optical system member and the input end of the optical fiber. is there.
[0021]
In particular, in the case of a semiconductor laser element having an oscillation wavelength of 450 nm or less, the deposition rate and the deposition amount of hydrocarbon compounds by these short wavelength laser beams are larger than those in the case of long wavelength laser beams, so the present invention is applied. That is effective.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0023]
A can-type sealed laser module according to the first embodiment of the present invention will be described. FIG. 1 shows a schematic configuration diagram of the laser module, FIG. 2 (a) shows a schematic plan view, and FIG. 2 (b) shows a schematic side view.
[0024]
As shown in FIG. 1, the laser module according to the present embodiment includes a heat sink 4 in which a semiconductor laser element 6 is bonded on a submount 5, an electrode terminal 8 connected from the semiconductor laser element 6 by a wire 9, and an electrode. A monitoring photodiode 10 connected to the terminal 12 by a wire 13 is fixed on the stem 1, and further, one zeolite adsorbent 11 is fixed by an inorganic adhesive, Ring-weld sealing is performed in a dry air (N ₂ = 80%, O ₂ = 20%) atmosphere by a container 2 having a glass window 3 with a reflective coating. The internal volume of the container 2 is 67.5 mm ³ .
[0025]
The zeolite adsorbent 11 is installed on the stem 1 between the wall surface of the container 2 and the heat block 4 as shown in FIGS. 2 (a) and 2 (b). Moreover, as shown in FIG.2 (c), the zeolite adsorbent 11 used what was shape | molded in the column shape of diameter (x) 1.5mm and height (y) 1.5mm. The installation location of the zeolite adsorbent is not limited to the above location, and may be any location in the container as long as it does not interfere with laser oscillation.
[0026]
As the zeolite adsorbent 11, “Zeoram F9HA” manufactured by Tosoh Corporation is preferable. This “Zeolam F9HA” is an alkali metal or alkaline earth metal crystalline hydrous aluminosilicate (Me / x · Al ₂ O). ₃ · mSiO ₂ · nH ₂ O: Me is an x-valent metal ion). The amount of the zeolite adsorbent 11 is desirably determined in consideration of the internal volume of the container, the estimated amount of contaminants, the adsorption capacity of the adsorbent 11, and the like.
[0027]
In the present embodiment, an inorganic adhesive is used as an adhesive for adhering the zeolite adsorbent 11, but either an organic adhesive or an inorganic adhesive may be used.
[0028]
Further, FIG. 1 does not describe the front half of the cylindrical container 2 in order to facilitate understanding of the component configuration in the container.
[0029]
The can-type sealed laser module according to the present embodiment emits the laser light 7 that is the front emission light of the semiconductor laser element 6 from the window glass 3 that is coated without reflection, and the rear emission light of the semiconductor laser element 6. The monitor photodiode 10 senses the amount of light emission, and the current is automatically controlled so that the output of the laser beam 7 is constant.
[0030]
Next, the temporal reliability of the laser module according to the present invention and the conventional laser module was evaluated. FIG. 3 shows a graph of change over time in the drive current in the conventional laser module, and FIG. 4 shows a graph of change in drive current over time in the laser module of the present invention. The vertical axis of the graph is a value obtained by normalizing the drive current with the initial drive current.
[0031]
As the laser module according to the present invention, the laser module according to the first embodiment, in which the oscillation wavelength of the semiconductor laser element 6 is 405 nm, is used. As the conventional laser module, the same laser module as in the first embodiment was used except that the zeolite adsorbent 11 was not provided. Both the conventional example and the sealing atmosphere in the laser module of the present invention are dry air (N ₂ = 80%, O ₂ = 20%). Evaluation was performed by adjusting the drive current so that the optical output was 30 mW at an environmental temperature of 25 ° C.
[0032]
In the laser module of the conventional example, as shown in FIG. 3, a change in driving current is seen over time, but in the laser module of the present invention, as shown in FIG. 4, no increase in driving current is seen and stable over time. doing. Therefore, by incorporating the adsorbent in the module, it is possible to satisfactorily prevent contaminants such as hydrocarbon compounds from adhering to the end face of the semiconductor laser element or optical components, and to obtain stable laser characteristics. I understood that I could do it.
[0033]
Next, a laser module according to the second embodiment of the present invention will be described. A schematic side view and top view of the laser module are shown in FIG.
[0034]
In the laser module according to the present embodiment, as shown in FIG. 5, a base plate 42 is fixed to the bottom surface of the container 40, and seven GaN-based semiconductor laser elements LD 21 to LD 27 are bonded onto the base plate 42. The heat block 20, the collimator lenses 31 to 37 held by the collimator lens holder 44 attached to the heat block 20, the condenser lens 43 held by the condenser lens holder 45, and the fiber holder 46. The multimode optical fiber 30 is fixed. An opening is formed in the wall surface of the container 40, and a wiring 47 for supplying a driving current to the GaN-based semiconductor laser elements LD21 to LD27 is drawn out of the container through the opening.
[0035]
In addition, the container 40 includes a lid 41 prepared so as to close the opening thereof, and a columnar zeolite adsorbent 50 having a diameter of 1.5 mm and a height of 1.5 mm is 120 in a region 51 on the back surface of the lid 41. It is fixed with an inorganic adhesive in an array of 10 pieces × 10 pieces. After the semiconductor laser element and the optical member are arranged in the container, the container 40 is sealed with a lid 41 adhered in a dry air (N ₂ = 80%, O ₂ = 20%) atmosphere. The internal volume of the container 40 was 8160 mm ³ , and “Zeolam F9HA” manufactured by Tosoh Corporation was used as the zeolite adsorbent 50 as in the first embodiment.
[0036]
In addition, each of the collimator lenses 31 to 37 is formed in a shape in which a region including the optical axis of a circular lens having an aspherical surface is cut out in a parallel plane. This elongated collimator lens can be formed, for example, by molding resin or optical glass. The collimator lenses 31 to 37 are closely arranged in the arrangement direction of the light emitting points so that the length direction is orthogonal to the arrangement direction of the light emitting points of the GaN-based semiconductor laser elements LD21 to LD27.
[0037]
In FIG. 5A, in order to avoid complication of the figure. Of the plurality of GaN-based semiconductor laser elements, only the semiconductor laser elements LD21 and LD27 are denoted by reference numerals, and only the collimator lenses 31 and 37 among the plurality of collimator lenses are denoted by numerals.
[0038]
On the other hand, each of the GaN-based semiconductor laser elements LD21 to LD27 includes an active layer having a light emission width of 2 μm, and each laser has a divergence angle in a direction parallel to and perpendicular to the active layer, for example, 10 ° and 30 °, respectively. A laser that emits beams B21 to B27 is used. These semiconductor laser elements LD21 to LD27 are arranged so that the light emitting points are aligned in a direction parallel to the active layer.
[0039]
Therefore, in the laser beams B21 to B27 emitted from the respective light emitting points, the direction in which the divergence angle is large with respect to the elongated collimator lenses 31 to 37 coincides with the length direction as described above, and the direction in which the divergence angle is small. Is incident in a state that coincides with the width direction (direction orthogonal to the length direction). That is, the collimator lenses 31 to 37 have a width of 1.1 mm and a length of 4.6 mm, and the laser beams B21 to B27 incident on the collimator lenses 31 to 37 have a horizontal and vertical beam diameters of 0.9 mm and 2, respectively. 6 mm. Each of the collimator lenses 31 to 37 has a focal length f ₁ = 3 mm, NA = 0.6, and a lens arrangement pitch = 1.25 mm.
[0040]
The condensing lens 43 is formed by cutting a region including the optical axis of a circular lens having an aspherical surface into a long and narrow shape in parallel planes, and is long in the arrangement direction of the collimator lenses 31 to 37, that is, in the horizontal direction and short in the direction perpendicular thereto. Is formed. The condenser lens 43 has a focal length f ₂ = 12.5 mm and NA = 0.3. This condensing lens 43 is also formed by molding resin or optical glass, for example.
[0041]
The multimode optical fiber 30 may be any of a step index type optical fiber, a graded index type optical fiber, and a composite type optical fiber. For example, a graded index optical fiber manufactured by Mitsubishi Cable Industries, Ltd. can be used. This optical fiber has a graded index at the center of the core and a step index at the outer periphery, the core diameter = 25 μm, NA = 0.3, and the transmittance of the end coat = 99.5% or more.
[0042]
Also in the second embodiment, as in the first embodiment, it is confirmed that the drive current does not increase with time and is stable.
[0043]
When an organic adhesive is used for adhering the adsorbent, an organic gas component generated from the adhesive is present in the module. In the laser module according to the second embodiment, Japanese Patent Application No. 2002-101714 It is proposed to remove organic gases and the like by deaeration treatment, but if 150 cylindrical zeolite adsorbents 11 having a diameter of 1.5 mm and a height of 1.5 mm are incorporated, the degassing is performed. Even if sealing is performed without performing gas treatment, the organic gas and the like are favorably adsorbed by the adsorbent. Therefore, good laser characteristics and reliability over time can be obtained without increasing the manufacturing process and manufacturing cost.
[0044]
In the first and second embodiments, the zeolite adsorbent is used as the adsorbent. However, activated carbon or both zeolite adsorbent and activated carbon may be used, and the same as in the case of the zeolite adsorbent. An effect can be obtained. Even when activated carbon is used, it may be fixed in the container using an inorganic or organic adhesive. You may use the adsorption agent which consists of another compound as a substance which has a gas adsorption function.
[0045]
According to the present invention, contaminants such as a hydrocarbon compound existing in a container in which a semiconductor laser element is sealed can be satisfactorily removed, so that a highly reliable laser module can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a laser module according to a first embodiment of the present invention. FIG. 2 is a plan view and a side view showing the laser module according to the first embodiment of the present invention. FIG. 4 is a graph showing the change over time of the drive current in the laser module according to FIG. 4 is a graph showing the change over time in the drive current in the laser module according to the first embodiment of the invention. Schematic configuration diagram showing a laser module according to configuration
1 Stem 2 Lid 3 Window Glass 4 Heat Sink 5 Submount 6 Semiconductor Laser Element 7 Laser Light 8 Electrode Terminal 9 Wire 10 Monitor Photodiode 11 Zeolite Adsorbent 12 Electrode Terminal 13 Wire

Claims (4)

In a laser module in which a semiconductor laser element is installed in a sealed container,
A laser module, wherein a substance having a gas adsorption function is disposed in the sealed container. 2. The laser module according to claim 1, wherein the substance having a gas adsorption function is at least one of a zeolite adsorbent and activated carbon. 3. The laser module according to claim 1, further comprising: an optical fiber and an optical system for inputting laser light from the semiconductor laser element into the sealed container. 4. The laser module according to claim 1, wherein an oscillation wavelength of the semiconductor laser element is 450 nm or less.

Images