JP5385674B2 - Laser module - Google Patents

Description

  The present invention relates to a laser module, and more particularly to a laser module for optical communication provided with an electronic cooling element.

  A laser module in which a semiconductor laser is incorporated in a package is widely used as a light source for transmission in an optical communication system. On the other hand, in order to increase the capacity of optical communication systems, a wavelength division multiplexing system (WDM system) is adopted, and a wavelength tunable laser module capable of controlling the wavelength of laser light is an indispensable component. It has become.

  FIG. 9 is a schematic diagram showing the configuration of the wavelength tunable laser module 70. A Peltier cooler 8 and a mount stage 1 are mounted in a semiconductor laser package 51. On the upper surface of the mount stage 1, a semiconductor optical amplifier 14 (SOA: Semiconductor Optical Amplifier), a wavelength tunable reflector 17, and a fabric are provided. A wavelength tunable laser is configured by arranging a Perot etalon 16 (FP etalon), an optical isolator 15, and the like.

  The SOA 14 has an end surface 14a coated with a light reflecting film and an end surface 14b coated with a non-reflective coating (see FIG. 10), and the end surface 14a coated with the light reflecting film and a wavelength tunable reflector. A laser resonator L is formed between the two. Further, in the laser resonator L, light is amplified by the SOA 14 to cause laser oscillation, and laser light is emitted to the outside of the laser resonator L. In the laser module 70 shown in FIG. 9, the laser light emitted from the wavelength tunable laser is emitted to the outside through the sapphire window 53 provided in the package 51, and the laser light condensed by the condenser lens 56 is It is coupled to the optical fiber held by the fiber holding unit 54 and propagates through the optical fiber network.

  The wavelength of the laser beam used in the optical network employing the WDM system needs to conform to the ITU grid (International Telecommunication Union grid) which is an international standard. For this reason, the wavelength of the laser beam emitted from the wavelength tunable laser needs to be controlled precisely. In the laser module 70 of FIG. 9, the light narrowed down to a predetermined wavelength range by the wavelength tunable reflector 17 is further precisely selected by the FP etalon 16, and laser light having a wavelength suitable for the ITU grid is emitted. Further, the temperature of the mount stage is controlled to be constant by the Peltier cooler 8, and the oscillation state of the wavelength tunable laser is stably maintained.

  On the other hand, the Peltier cooler 8 indispensable for controlling the temperature of the laser module is a device having a Peltier element sandwiched between two plates. The temperature of one plate 12 is kept constant, and the other plate 11 Dissipate or absorb heat. Therefore, when the Peltier cooler is operating effectively, a temperature difference occurs between the two plates, which inevitably causes thermal deformation.

  FIG. 10 is an explanatory view schematically showing deformation of the mount stage 1 caused by thermal deformation of the Peltier cooler 8. The upper plate 12 of the Peltier cooler 8 to which the mount stage 1 is joined is a plate on the side that keeps the temperature constant, while the lower plate 11 that is joined to the base 7 of the package 51 passes through the base 7. To dissipate or absorb heat.

  As shown in FIG. 10A, when the temperature difference between the upper plate 12 and the lower plate 11 is small, the Peltier cooler 8 does not undergo thermal deformation, and the mount stage 1 is kept flat. . However, when the temperature difference between the upper plate 12 and the lower plate 11 becomes large, the Peltier cooler is thermally deformed as shown in FIG. 10B, and the mount stage 1 connected to the upper plate 12 is deformed. . In the drawing, the upper plate 12 is cooled and heat is dissipated from the lower plate 11. That is, as a result of the temperature of the upper plate 12 becoming lower than the temperature of the lower plate 11, the Peltier cooler 8 is thermally deformed, and the mount stage 1 is warped upward.

  As shown in FIG. 10B, when the mount stage 1 is deformed, the interval of the resonator L of the wavelength tunable laser disposed on the mount stage changes from L1 to L2 shown in FIG. The wavelength range of light selected by the tunable reflector is shifted. As a result, there may be a problem that the wavelength of the laser light that is precisely controlled by the FP etalon 16 deviates from the ITU grid. For example, if the optical path difference between L1 and L2 is different by several microns, the laser wavelength may deviate from the ITU grid standard. As means for solving this problem, Patent Literature 1 describes a technique for reducing deformation of the mount stage caused by thermal deformation of the Peltier cooler by inserting an intermediate plate between the Peltier cooler and the mount stage. .

WO2008 / 006387A1 Publication

  In order to prevent deformation of the mount stage, a method of increasing the strength of the mount stage itself can be considered. That is, it is conceivable to increase the thickness of the mount stage or select a material that is difficult to deform.

  However, there is a solution for increasing the thickness of a laser module package disposed between boards in a transmission apparatus in a situation where the optical communication system is becoming multi-wavelength and the transmission apparatus is required to be downsized. It is difficult to choose. Also, if the mount stage is thickened and the volume is increased, a larger Peltier cooler is required, which may increase the package size. In addition, from the viewpoint of stably maintaining the temperature of the mount stage, it is essential to use a material having high thermal conductivity, and there is also a problem that there is little room for selecting a material that has high strength and does not deform.

  Further, the prior art described in Patent Document 1 also has a problem that the connection surface between the Peltier cooler and the mount stage is increased because of the structure in which the intermediate plate is newly inserted. That is, the problem of solder creep on the connection surface is likely to occur, and the optical axis may fluctuate and the laser beam output may not be stable. In addition, an adverse effect can be considered in that the number of assembly steps increases due to an increase in the number of parts.

  In view of the above problems, an object of the present invention is to provide a laser module that suppresses deformation of a mount stage due to thermal deformation of an electronic cooling element and operates stably without wavelength variation.

In order to solve the above problems, a laser module according to the present invention includes a mount stage on which a wavelength tunable laser having an optical amplifying element and a laser resonator is disposed, and a temperature of the mount stage that is joined to the mount stage. An electronic cooling element that is controlled to a certain level,
The mount stage includes a first main surface on which the wavelength tunable laser is disposed, a second main surface joined to the electronic cooling element, and a strength reinforcing portion integrally formed on the second main surface, the a, portion where the reinforcement part is provided, Ru thickness der than the other portions. The strength reinforcing portion is a raised portion having a projecting surface joined to the electronic cooling element, and a wall-shaped rib connected to the raised portion, the direction being parallel to the second main surface from the raised portion And a rib extending to the surface.

  According to the present invention, the strength reinforcing portion is provided on the mount stage on which the wavelength tunable laser is disposed. Thereby, deformation of the mount stage due to thermal deformation of the electronic cooling element can be suppressed, and a laser module with less fluctuation of the oscillation wavelength can be realized.

It is a schematic diagram which shows the mount stage of the laser module which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows the structure of the laser module which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows the mount stage which concerns on the 2nd Embodiment of this invention. It is a schematic diagram which shows another mount stage which concerns on the 2nd Embodiment of this invention. It is a schematic diagram which shows the structure of the laser module which concerns on the 2nd Embodiment of this invention. It is a schematic diagram which shows the mount stage which concerns on the 3rd Embodiment of this invention. It is a schematic diagram which shows the mount stage which concerns on the 4th Embodiment of this invention. It is a schematic diagram which shows another mount stage which concerns on the 4th Embodiment of this invention. It is a schematic diagram which shows the structure of the laser module which concerns on a prior art. It is explanatory drawing which shows the laser module which concerns on a prior art.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the drawings.

  In the laser module according to the present embodiment, a wavelength tunable laser having an SOA 14 that is an optical amplifying element and a laser resonator L that is configured between one end face 14a of the SOA 14 and the wavelength tunable reflector 17 is disposed. And a Peltier cooler 8 that is an electronic cooling element that is bonded to the mount stage 10 and controls the temperature of the mount stage 10 to be constant. (See Figure 2)

  Further, the mount stage 10 includes a first main surface A on which the wavelength tunable laser is arranged, a second main surface B joined to the Peltier cooler 8, and a strength reinforcement integrally formed on the second main surface B. Part 3. Moreover, the part in which the strength reinforcement part 3 was provided is thicker than the other part. (See Figure 2)

  FIG. 1 is a schematic diagram showing a mount stage 10 according to the first embodiment of the present invention. FIG. 1A is a front view of the mount stage 10, and FIG. 1B shows a top view. The strength reinforcing portion 3 is a protruding portion having a protruding surface 4 protruding from the second main surface B, and the protruding surface 4 and the upper plate 12 of the Peltier cooler 8 are soldered and joined (see FIG. 2). ).

  The dimensions of each part are illustrated below. First, in the mount stage 10 shown in FIG. 1, the thickness d1 of the region 2 excluding the strength reinforcing portion 3 is 0.5 to 1.0 mm. On the other hand, the thickness d2 of the strength reinforcing portion 3 is formed to be 0.5 to 1.0 mm. The length W1 of the mount stage 10 in the optical axis direction is 15 to 18 mm, and the lateral width W2 is 7 to 8 mm. Furthermore, the length W3 of the strength reinforcing portion 3 is 3 to 5 mm, and the lateral width W4 is 6 to 7 mm.

  FIG. 2 is a schematic diagram showing a configuration inside the package of the laser module using the mount stage 10. On the first main surface A of the mount stage 10, the SOA 14, the FP etalon 16 and the wavelength tunable reflector 17 constituting the wavelength tunable laser are arranged along the optical axis P. A reflection film is coated on the end face 14 a of the SOA 14, and a laser resonator is formed between the reflection face of the variable wavelength reflector 17. In addition, an optical isolator 15 and a plurality of optical lenses 19 that block the return of laser light from the outside are disposed. Further, the protruding surface 4 of the strength reinforcing portion 3 provided on the second main surface B is joined to the upper plate 12 of the Peltier cooler 8 via the solder layer 13. The optical isolator may be connected to an optical fiber inside or outside the package.

  On the other hand, the lower plate 11 of the Peltier cooler 8 is soldered and fixed to the base 7 of the package, and performs heat exchange with the outside through the base 7. Thereby, the Peltier cooler 8 controls the temperature of the mount stage 10 to be constant, and stabilizes the output of the wavelength variable laser and the wavelength of the laser beam.

  In the above configuration, the temperature of the mount stage 10 was controlled to 25 ° C., the ambient temperature of the laser module was changed from 5 ° C. to 75 ° C., and the fluctuations in the wavelength and output of the laser light were confirmed. During this time, the temperature difference between the upper plate 12 and the lower plate of the Peltier cooler 8 increased to about 50 ° C., but the laser output fluctuation was 5% or less, and the wavelength fluctuation was 2 GHz or less. This result shows that the deformation of the mount stage 10 is suppressed by the strength reinforcing portion 3 provided on the second main surface B. Further, in the above embodiment, the strength reinforcing portion 3 is provided at the center portion of the mount stage 10, but is not limited to this form, and the formation position is shifted in the direction along the optical axis P. Also good. In particular, there are cases where the temperature of the mount stage 10 can be controlled more stably by providing it in a portion facing the position where the SOA 14 generating a large amount of heat is disposed.

  FIG. 3 is a schematic view showing a mount stage 20 according to the second embodiment of the present invention. In the present embodiment, a raised portion 23 is provided on the first main surface A of the mount stage 20 across a region where the wavelength tunable laser is disposed. That is, the strength reinforcing portion in the present embodiment is a raised portion 23 that is integrally formed on the first main surface A and is formed substantially parallel to the optical axis of the wavelength tunable laser.

  For example, the length W1 of the mount stage 20 in the optical axis direction is 15 to 18 mm, and the lateral width W2 is 8 to 10 mm. The width W5 of the region where the wavelength tunable laser is disposed is about 6 mm, and the thickness d3 is 0.5 to 0.8 mm. Moreover, the thickness d4 of the raised portion 23 is 1 to 2 mm.

  FIG. 4 is a schematic diagram showing another mount stage 30 according to the second embodiment of the present invention. In the mount stage 30 according to the present embodiment, the wall-like ribs 25 provided along the end sides of the first main surface A function as strength reinforcing portions, and the deformation of the mount stage 30 is suppressed. Further, as compared with the mount stage 20 described above, since the area of the region 26 where the wavelength tunable laser is disposed can be increased, there is an advantage in that it can be applied to amplifying elements and optical parts of various sizes.

  For example, the length W1 of the mount stage 30 in the optical axis direction is 15 to 18 mm, and the lateral width W2 is 8 to 10 mm. The thickness d5 is 0.5 to 0.8 mm. The width W6 of the rib 25 is 0.5 to 0.7 mm, and the height d6 is 1 to 2 mm.

  FIG. 5 is a schematic diagram showing a state in which a wavelength tunable laser is arranged on the mount stage 20 and is joined to the Peltier cooler 8. Obviously, the same configuration is obtained in the case of the mount stage 30. On the first main surface A of the mount stage 20 shown in the figure, the SOA 14 and the FP etalon 16, the wavelength tunable reflector 17, the optical isolator 15, and the plurality of optical lenses 19 constituting the wavelength tunable laser are provided on the optical axis. It is arranged along P. On the other hand, the second main surface B is directly soldered to the upper plate 12 of the Peltier cooler 8 via the solder layer 13.

  In the above configuration, the deformation of the mount stage 20 is suppressed by the raised portion 23 that is a strength reinforcing portion, while the stress due to the thermal deformation of the Peltier cooler 8 is caused by the upper plate 12 and the second main surface of the mount stage 20. B is absorbed by the solder layer 13 interposed between the metal and B.

  FIG. 6 is a schematic diagram showing a mount stage 40 according to the third embodiment of the present invention. 6A shows a front view, FIG. 6B shows a top view, and FIG. 6C shows a side view.

  As shown in the figure, the mount stage 40 has a wall-like rib 25 provided in parallel to the optical axis of the wavelength tunable laser disposed on the first main surface A, and has a protruding surface 4. The raised portion 3 is provided on the second main surface B. In other words, the strength reinforcing portion according to the first embodiment and the strength reinforcing portion according to the second embodiment are provided together, and the deformation of the mount stage 40 is further reduced. .

  FIG. 7 is a schematic view showing a mount stage 50 according to the fourth embodiment of the present invention. 7A shows a front view, FIG. 7B shows a top view, and FIG. 7C shows a side view.

  In the mount stage 50 according to the present embodiment, the raised portion 3 having the projecting surface 4 and the wall-shaped rib 35 are both provided on the second main surface B. The upper plate 12 of the Peltier cooler 8 (not shown) is joined to the protruding surface 4. As a result, the first main surface A, which is the arrangement surface of the wavelength tunable laser, is kept flat, so that the assembly of the optical amplifying element and the optical component is facilitated. Moreover, the intensity | strength which resists the deformation | transformation of the mount stage 50 against the thermal deformation of the Peltier cooler 8 is ensured similarly to said Embodiment 3. FIG.

  FIG. 8 is a schematic view showing another mount stage 60 according to the fourth embodiment of the present invention. As in the previous figure, (a) shows a front view, (b) shows a top view, and (c) shows a side view. In the mount stage 60 according to this embodiment, the raised portion 3 having the protruding surface 4 and the wall-like rib 45 are both provided on the second main surface B. Further, the rib 45 is different from the mount stage 50 shown in FIG. 7 in that the rib 45 is provided obliquely with respect to the optical axis of the wavelength tunable laser disposed on the first main surface A. By forming the ribs 45 in the arrangement shown in the figure, the strength against deformation in the direction perpendicular to the optical axis can be increased at both ends where the thickness is small. That is, it is possible to suppress deformation even with respect to a stress acting in a direction that twists the mount stage 60 at both ends.

  The mount stages according to the first to fourth embodiments are integrally formed using a copper tungsten alloy (CuW alloy). Further, as a material other than the CuW alloy, a material such as aluminum nitride (AlN) or silicon carbide (SiC) can be used.

  The preferred embodiment of the present invention has been described in detail above, but the laser module according to the present invention is not limited to the above-described embodiment, and is within the scope of the gist of the present invention described in the claims. Various modifications and changes are possible.

3 Strength reinforcement 4 Projection surface
8 Peltier Cooler 10 Mount Stage 14 Optical Amplifier 16 FP Etalon 17 Wavelength Tunable Reflector
A 1st main surface
B 2nd main surface
P Optical axis
L Laser resonator

Claims (3)

A mount stage in which a wavelength tunable laser having an optical amplification element and a laser resonator is disposed;
An electronic cooling element that is bonded to the mount stage and controls the temperature of the mount stage to be constant;
With
The mount stage is
A first main surface on which the wavelength tunable laser is disposed;
A second main surface joined to the electronic cooling element;
A strength reinforcing portion integrally formed on the second main surface;
Have
The portion provided with the strength reinforcing portion is thicker than other portions ,
The strength reinforcing portion is
A raised portion having a protruding surface joined to the electronic cooling element;
A wall-shaped rib connected to the raised portion, the rib extending in a direction parallel to the second main surface from the raised portion;
A laser module comprising: The laser module according to claim 1, wherein the rib is provided obliquely with respect to the optical axis of the wavelength tunable laser. 3. The laser module according to claim 1, wherein a portion of the mount stage provided with the rib extends outward from the electronic cooling element.

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