JP2001196684A - Semiconductor laser module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent misalignment between elements caused by the thermal expansion difference of members at both sides (semiconductor laser element and light wavelength conversion element) of an adhesive layer, and peeling of the adhesive layer in a semiconductor laser module consisting of the semiconductor laser and light wavelength conversion elements being bonded each other for fixing. SOLUTION: In this semiconductor laser module, a semiconductor laser element 10 of a light source for generating a fundamental wave is optically and directly connected to a light wavelength conversion element 12 that has a light waveguide 17. The fundamental wave from the semiconductor laser element 10 enters by allowing the light emission end of the semiconductor laser element and the light incidence one of the light wavelength conversion element to approach each other, and the semiconductor laser element 10 and the light wavelength conversion element 12 are fixed with an adhesive 15. The adhesive 15 with hardness less than 80 should be used. The harness should be measured by type D of a durometer hardness test according to JIS standard number K6253 at the operating temperature of the semiconductor laser module.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser comprising a semiconductor laser device as a light source for generating a fundamental wave and an optical wavelength conversion device having an optical waveguide into which the fundamental wave from the semiconductor laser device is incident. Regarding the laser module,
More particularly, the present invention relates to a semiconductor laser module having a structure in which these two elements are fixed to each other with an adhesive.

[0002]

2. Description of the Related Art Conventionally, a laser beam generated from a fundamental wave light source is made incident on an optical wavelength conversion element made of a nonlinear optical material, and the optical wavelength conversion element converts the wavelength into a second harmonic or the like (to shorten the wavelength). ) Is known.

When a semiconductor laser device is used as a fundamental wave light source and an optical waveguide type device is used as an optical wavelength conversion device, for example, Japanese Patent Application No. 11-9 filed by the present applicant.
As shown in the specification of Japanese Patent No. 3845, the light emitting end face of the semiconductor laser element and the light incident end face of the light wavelength conversion element are in close proximity to each other, and the two elements are directly optically coupled to each other to form a module. It is also widely practiced.

When a semiconductor laser module and an optical wavelength conversion element are directly coupled to each other to form a semiconductor laser module, a method of fixing both elements using an adhesive is often used. In that case, the end faces of both elements may be directly bonded and fixed, or, as disclosed in the above specification, the semiconductor laser element and the optical wavelength conversion element may be separated into separate first and second elements. Two holders may be mounted and the holders may be fixed to each other with an adhesive.

[0005]

As described above, in a semiconductor laser module in which a semiconductor laser device and an optical wavelength conversion device are bonded and fixed (including a case where their holders are bonded and fixed), both of these are used. The bonding position of the element is in the so-called submicron order,
It has been recognized that the optical coupling efficiency is degraded even if the distance deviates from 0.1 μm by less than 1 μm.

Therefore, when the two elements are combined, a step of aligning the two so that a laser beam as a fundamental wave emitted from the semiconductor laser element is accurately incident on the end face of the optical waveguide of the optical wavelength conversion element; In addition to the step of fixing the two elements in that state, it is required to take measures to prevent the two elements from being displaced by the subsequent transportation, storage environment, use environment, and even over time.

In particular, since both elements are likely to be displaced due to the thermal expansion of the module components due to a change in the use temperature, the members bonded and fixed to each other as described above are made of a material having the same thermal expansion coefficient (linear expansion coefficient). It is desired to form. However, it is sometimes necessary to configure each member using a material having a different coefficient of linear expansion from other circumstances. May move. When the bonded portion moves in this way, a position shift occurs between the semiconductor laser device and the optical wavelength conversion device.

[0008] Further, when the relative position fluctuates due to the difference in linear expansion coefficient between the members bonded by the adhesive, there is a possibility that the adhesive layer is peeled off due to concentration of stress on the adhesive layer. There is also.

The present invention has been made in view of the above circumstances, and in a semiconductor laser module including a semiconductor laser element and an optical wavelength conversion element that are bonded and fixed to each other, both sides of the adhesive layer (that is, the semiconductor laser element side). It is an object of the present invention to prevent a displacement between the two elements due to a difference in thermal expansion between members of the optical wavelength conversion element and the optical wavelength conversion element, and also to prevent the adhesive layer from peeling off.

[0010]

As described above, a semiconductor laser module according to the present invention has a semiconductor laser device as a light source for generating a fundamental wave and an optical waveguide on which the fundamental wave from the semiconductor laser device is incident. In a semiconductor laser module in which an optical wavelength conversion element is optically directly coupled with the former light emitting end face and the latter light incident end face in close proximity, the semiconductor laser element and the light wavelength converting element are bonded with an adhesive. It is fixed, and the adhesive is JIS standard number K at the operating temperature of the semiconductor laser module.
A hardness of less than 80 as measured by a durometer hardness test type D according to 6253 is used.

In the semiconductor laser module of the present invention having the above structure, the semiconductor laser element is mounted on the first holder, and the optical wavelength conversion element is formed separately from the first holder. It is preferable that one surface mounted on the holder and facing the same side as the light emitting end surface of the first holder and one surface facing the same side as the light incident end surface of the second holder be fixed with an adhesive.

The thickness of the adhesive is preferably 8 μm or less. As this adhesive, an acrylic adhesive or an epoxy adhesive is preferably used.

On the other hand, the semiconductor laser module according to the present invention preferably has a storage or use temperature range of -45 to 80 ° C.

[0014]

In the semiconductor laser module according to the present invention, a durometer hardness test type D according to JIS standard number K6253 at the operating temperature of the semiconductor laser module is used as an adhesive for bonding the semiconductor laser element and the optical wavelength conversion element. By using a relatively flexible adhesive having a measured hardness of less than 80, when a stress due to a difference in linear expansion coefficient between the semiconductor laser device side and the light wavelength conversion device side acts on the bonded portion, This stress is sufficiently absorbed by the deformation of the adhesive. Therefore, the relative position does not fluctuate between both side portions of the adhesive layer, that is, between the semiconductor laser device side portion and the optical wavelength conversion device side portion, the displacement between the two devices is prevented, and the adhesive layer is separated. Is also prevented.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a perspective view and a partially broken side view, respectively, of a semiconductor laser module according to one embodiment of the present invention. As shown, the semiconductor laser module of the present embodiment is
The semiconductor laser 10 is a light source that generates a fundamental wave and an optical wavelength conversion element 12 that converts a fundamental wave incident from the semiconductor laser 10 into a second harmonic. The semiconductor laser 10 and the light wavelength conversion element 12 are optically directly coupled with the former light emitting end face 10a and the latter light incident end face 12a in close proximity.

The semiconductor laser 10 is mounted on a first holder 13 having a U-shaped cross section, and the optical wavelength conversion element 12 is formed separately from the first holder 13 and a second holder 14 having the same U-shaped cross section.
It is installed in. And one surface 13a of the first holder 13 facing the same side as the light emitting end face 10a,
14 is fixed to the same side 14a facing the same side as the light incident end face 12a by an adhesive 15, so that the semiconductor laser
10 and the light wavelength conversion element 12 are coupled as described above.

The light wavelength conversion element 12 is made of, for example, 5 m of MgO.
ol% doped LiNbO ₃ (hereinafter, MgO-LN
) Formed on a crystal substrate 16 by proton exchange, for example, and a periodic domain inversion structure 18. The periodic domain inversion structure 18 is made of MgO-LN
A domain inversion portion obtained by inverting the spontaneous polarization (domain) of the substrate 16 is repeatedly formed at a predetermined period along a direction in which the optical waveguide 17 extends. A laser beam as a fundamental wave having a wavelength of 950 nm, for example, emitted from the semiconductor laser 10 is incident on the optical waveguide 17. This laser beam is guided through the optical waveguide 17 and phase-matched (so-called quasi-phase matching) by the periodic domain inversion structure 18 so that the wavelength becomes 1 /
2 is converted to the second harmonic.

In this embodiment, since the TE mode waveguide type optical wavelength conversion element 12 and the TE mode waveguide type semiconductor laser 10 are also directly coupled, both substrates can be made parallel to each other. The core and fixing are easy. Further, as the semiconductor laser 10, a distributed Bragg reflection type (DBR: distributed Brag
g reflector), the oscillation wavelength can be adjusted to the phase matching wavelength of the optical wavelength conversion element 12. Thereby, the wavelength conversion efficiency can be maximized, and the second harmonic output can be maximized.

Hereinafter, the coupling between the semiconductor laser 10 and the optical wavelength conversion element 12 will be described in detail with reference to FIGS. Semiconductor laser 10 and optical wavelength conversion element 12
When both faces upward, the respective optical waveguides can be well observed with a microscope, so that mutual position adjustment is easy.

The semiconductor laser 10 is shown in FIG.
An LD chip 20 as a semiconductor laser body is fixed on a heat sink 21 as shown in a plan view and a front view in FIG. 4A and FIG.
Is fixed on the bottom surface of the concave portion of the first holder 13. The first holder 13 has a reference plate whose end face 13a is polished with high precision.
22 is formed so as to be in close contact with one reference surface 22a. Therefore, when fixing the heat sink 21 on which the LD chip 20 is mounted to the first holder 13, the respective end surfaces of the LD chip 20, the heat sink 21 and the first holder 13 are aligned with the reference surface 22 a of the reference plate 22. To That is, with the end surface 20a of the LD chip 20, the end surface 21a of the heat sink 21 and the end surface 13a of the first holder 13 in contact with the reference surface 22a of the reference plate 22, the LD chip 20 is placed on the heat sink 21.
Then, the heat sink 21 is fixed to the first holder 13.

Similarly, the light wavelength conversion element 12 is fixed on the bottom surface of the concave portion of the second holder 14, as shown in the plan view and the front view in FIGS. 3B and 4B, respectively. Second
The end surface 14a of the holder 14 is also polished with high precision, and is formed so as to be able to adhere to the other reference surface 22b of the reference plate 22. Therefore, when the light wavelength conversion element 12 is fixed to the second holder 14, the end faces of the light wavelength conversion element 12 and the second holder 14 are arranged on the same plane with respect to the reference surface 22b of the reference plate 22. That is, the end surface 12a of the light wavelength conversion element 12 and the end surface of the second holder 14 are placed on the reference surface 22b of the reference plate 22.
The optical wavelength conversion element 12 is fixed to the second holder 14 in a state where the light wavelength conversion element 14a is in contact with the second holder 14.

Thereafter, the first holder 13 and the second holder 14 are opposed to each other so that the respective end faces 13a and 14a face each other, and the beam emission position of the semiconductor laser 10 and the optical waveguide 17 of the optical wavelength conversion element 12 are determined. (See FIGS. 5A and 5B). Then, after adjusting the position in the joining surface, the holders 13 and 14 are fixed to each other with the adhesive 15. The LD chip 20 and the optical wavelength conversion element 12 are firstly respectively set using the reference plate 22 in advance as described above.
Since the position is adjusted so as not to protrude from the end face 13a of the holder and the end face 14a of the second holder, it is possible to obtain an optical coupling efficiency of 50% or more without hitting and breaking each other.

The first holder 13 and the second holder
The depth of each recess of 14 is the lower surface 13b of the first holder 13.
It is preferable to set the distance from the beam emission position of the semiconductor laser 10 to the distance from the lower surface 14b of the second holder 14 to the beam incidence position of the optical waveguide 17 (see FIG. 4). By doing so, by adjusting the first holder 13 and the second holder 14 only in the horizontal direction (the direction of arrow A in FIG. 4), it is possible to easily match the above-mentioned beam emission position with the incident position.

Next, the collimator lens 25 is adjusted and fixed to the semiconductor laser module including the semiconductor laser 10 and the optical wavelength conversion element 12 formed as described above, as shown in FIG. Specifically, an assembly of the semiconductor laser 10 mounted on the first holder 13 and the optical wavelength conversion element 12 mounted on the second holder 14 is firstly mounted on a pedestal 26.
Fixed to. A collimator lens 25 is attached to the pedestal 26. When the assembly is fixed, the collimator lens 25 is adjusted and fixed so that the second harmonic 27 emitted from the collimator lens 25 becomes parallel light. And D
Optical amplification region injection current I _L for the semiconductor laser 10 is BR _lasers, and by adjusting the DBR region injection current I _T, adjusts the oscillation wavelength of the semiconductor laser 10 to the phase matching wavelength of the optical wavelength conversion element 12. Thereby, the maximum second harmonic output can be obtained.

In addition to the two-electrode type DBR laser used in the present embodiment, the three-electrode type DBR laser and the distributed feedback type (DFB: distributed feedback) ) A laser or the like can also be used.

Next, the adhesive 15 for fixing the first holder 13 and the second holder 14 will be described in detail. In this embodiment, the thickness of the adhesive 15 is 1 μm as an example. An acrylic adhesive and an epoxy-based adhesive are used as the adhesive 15 in order to examine the displacement between the semiconductor laser 10 and the light wavelength conversion element 12 and the occurrence of peeling of the adhesive layer for each type and hardness of the adhesive 15. Using an adhesive, the hardness of each of the adhesives 15 measured by a durometer hardness test type D according to JIS Standard No. K6253 was 30,
50, 75, 78, 80 and 85 were set.

When the coupling efficiency between the laser beam and the guided light in the semiconductor laser modules of these 12 samples was measured, they were all 50%. After this measurement, for each semiconductor laser module, -45 to 80C
The temperature cycle was applied 100 times, and then the second harmonic output was measured, and the peeling state of the adhesive 15 was examined.

The results are shown in (Table 1). In Table 1 below, ○, Δ, and × indicate (1) no change in the output of the second harmonic after the addition of the temperature cycle, (2) the output of the second harmonic after the addition of the temperature cycle, 3) The three situations of the peeling of the adhesive 15 and the second harmonic output lowering are shown.

[0029]

[Table 1] As shown in (Table 1), when the hardness of the adhesive 15 measured by the durometer hardness test type D according to JIS standard number K6253 is 78 or less, the output of the second harmonic is different from that before the temperature cycle is added. On the other hand, when the hardness of the adhesive 15 is 80 or more, the second harmonic output after the addition of the temperature cycle decreases. This is a semiconductor laser 10
It is considered that a position shift has occurred between the optical wavelength conversion element 12 and the optical wavelength conversion element 12. In particular, when the hardness is 85, peeling of the adhesive 15 also occurs. In view of the above, in the present invention, the hardness of the adhesive measured by the durometer hardness test type D according to JIS standard number K6253 is 8
It should be less than 0.

Although the embodiment in which the thickness of the adhesive layer is 1 μm has been described above, the thickness of the adhesive layer is not limited to this value, and the adhesive is an acrylic or epoxy adhesive. In the case, the thickness of the adhesive layer is 8
If it is less than μm, basically the effects of the present invention can be obtained.

Specifically, the adhesive 15 in the above embodiment is used.
Instead, a semiconductor laser module in which the first holder 13 and the second holder 14 are fixed with an adhesive having a layer thickness of 4 μm and 8 μm is manufactured, and a temperature cycle similar to that described above is added thereto, and thereafter, The second harmonic output and the occurrence of peeling of the adhesive were examined, and the results were exactly the same as in (Table 1).

On the other hand, if the thickness of the adhesive layer exceeds 8 μm, deformation of the adhesive layer itself due to a change in temperature becomes remarkable, causing a positional shift between the semiconductor laser device and the optical wavelength conversion device. It will be easier. Considering only suppressing the deformation of the adhesive layer itself, the smaller the thickness of the adhesive layer is, the more preferable. However, in order to secure sufficient adhesive strength, the lower limit of the thickness is practically in the submicron order, that is, It is about 0.1 μm to less than 1 μm.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a semiconductor laser module according to an embodiment of the present invention.

FIG. 2 is a partially cutaway side view of the semiconductor laser module.

FIG. 3 is a plan view illustrating an assembly process of the semiconductor laser module.

FIG. 4 is a front view illustrating an assembly process of the semiconductor laser module.

FIG. 5 is a schematic view illustrating an assembling process of the semiconductor laser module.

FIG. 6 is a plan view showing a use state of the semiconductor laser module.

[Explanation of symbols]

 10 Semiconductor laser 12 Optical wavelength conversion element 13 First holder 14 Second holder 15 Adhesive 16 MgO-LN crystal substrate 17 Optical waveguide 18 Periodic domain inversion structure

Claims (5)

[Claims] 1. A semiconductor laser device, which is a light source for generating a fundamental wave, and an optical wavelength conversion device having an optical waveguide into which the fundamental wave from the semiconductor laser device enters, the former light emitting end face and the latter light incident surface. In a semiconductor laser module that is optically directly coupled with an end face close to each other, the semiconductor laser element and the light wavelength conversion element are fixed with an adhesive, and the adhesive is used at the operating temperature of the semiconductor laser module. A semiconductor laser module having a hardness measured by a durometer hardness test type D according to JIS standard number K6253 of less than 80 is used. 2. The semiconductor laser device is mounted on a first holder, and the optical wavelength conversion device is mounted on a second holder formed separately from the first holder. 2. The semiconductor according to claim 1, wherein one surface facing the same side as the light emitting end surface and one surface facing the same side as the light incident end surface of the second holder are fixed by the adhesive. Laser module. 3. The semiconductor laser module according to claim 1, wherein said adhesive has a thickness of 8 μm or less. 4. The semiconductor laser module according to claim 1, wherein said adhesive is one of an acrylic adhesive and an epoxy adhesive. 5. The storage or use temperature range is -45 to 80.
The semiconductor laser module according to any one of claims 1 to 4, wherein the temperature is ° C.