JP3844326B2 - Mounting method of integrated optical module - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical waveguide device in which a planar optical waveguide is formed (planar optical waveguide device), and in particular, a planar optical semiconductor device in which an alignment key that is a mark for alignment is formed with high positional accuracy. About. Furthermore, the present invention relates to a configuration and a mounting method of an integrated optical module configured by mounting the above planar optical waveguide device and a semiconductor laser on a submount.
[0002]
[Prior art]
In the optical communication field, development of a compact and low-cost integrated optical module in which a semiconductor laser, an electronic device, an optical fiber, and the like are hybrid-integrated on a silica-based lightwave circuit platform is regarded as important.
[0003]
What is important in the formation of such an integrated optical module is to fix each element with high positional accuracy and minimize transmission loss. For this purpose, a surface-mount type optical module that directly couples a semiconductor laser and a single mode fiber using a Si-V groove substrate has been realized (for example, 1997 IEICE General Conference, C -3-63).
[0004]
FIG. 9 is a perspective view schematically showing a configuration of an optical module obtained by the above technique.
[0005]
In this configuration, an alignment key (positioning marker) 126 having a predetermined shape (pattern) is formed in the chip mounting area 125 of the Si submount 26, and also the semiconductor laser 27 to be mounted in the chip mounting area 125. Then, an alignment key (positioning marker) 127 having a predetermined shape (pattern) is formed. Then, by recognizing these alignment keys 126 and 127 and calculating their position information by an image processing process, the center of the V groove 28 formed in the Si submount 26 with high precision by anisotropic etching of Si. The active layer of the semiconductor laser 27 is aligned and adjusted with high accuracy on the axis. On the other hand, an optical fiber 29 is mounted in the V-groove 28. This mounting is performed with high accuracy using the shapes of the V-groove 28 and the optical fiber 29, and the optical axis of the optical fiber 29 is The center axis is aligned and adjusted with high accuracy.
[0006]
In this way, in the configuration of FIG. 9, the optical axis of the optical fiber 29 and the light emitting point (active layer) of the semiconductor laser 27 are aligned and adjusted with high accuracy, and the mounting variation is about ± 0.61 μm in the x direction, The suppression to about ± 1 μm in the z direction is realized.
[0007]
On the other hand, in the field of optical information processing, a small short-wavelength light source is required in order to realize high density optical discs and high-definition displays. As a technique for realizing a shorter wavelength, second harmonic generation using a semiconductor laser and a quasi phase matching (hereinafter referred to as “QPM”) type wavelength conversion device using a planar optical waveguide ( Hereinafter, there is a method using a technique (referred to as “SHG”) (see, for example, Yamamoto et al .: Optics Letters, Vol. 16, No. 15, p. 1156 (1991)).
[0008]
FIG. 10 shows a schematic configuration diagram of a blue light source including a wavelength conversion device having a planar optical waveguide.
[0009]
In the configuration of FIG. 10, a tunable semiconductor laser 30 having a distributed Bragg reflection (hereinafter referred to as “DBR”) region 32 is used as the semiconductor laser 30. In the following, a wavelength tunable semiconductor laser having a DBR region is referred to as a “DBR semiconductor laser” or “DBR laser”. The DBR semiconductor laser 30 is a 100 mW class AlGaAs-based DBR semiconductor laser 30 having a 0.85 μm band, for example, and includes an active layer region 31 and a DBR region 32. By varying the amount of injection current injected into the DBR region 32 via the wiring 39 and the bonding wire 40, the oscillation wavelength of the DBR semiconductor laser 30 can be varied. On the other hand, the wavelength conversion device 33 using a planar optical waveguide as a wavelength conversion element is an X plate MgO-doped LiNbO._ThreeA planar optical waveguide 34 formed on the substrate 36 and a periodic domain-inverted region 35 are included. The DBR semiconductor laser 30 and the wavelength conversion device 33 are fixed on the submounts 37 and 38 by junction-up, respectively. The submounts 37 and 38 are fixed on the same support member 41.
[0010]
Laser light obtained from the light emitting end face of the DBR semiconductor laser 30 is directly coupled to the planar optical waveguide 34 of the wavelength conversion device 33 without using a coupling optical system such as a lens. Specifically, by adjusting the positional relationship between the DBR semiconductor laser 30 and the wavelength conversion device 33 on the submounts 37 and 38, the laser light of about 60 mW with respect to the laser output of about 100 mW from the semiconductor laser 30 is obtained. Is coupled to the planar optical waveguide 34 of the wavelength conversion device 33. Further, by controlling the amount of current injected into the DBR region 32 of the DBR semiconductor laser 30, the oscillation wavelength is fixed within the phase matching wavelength tolerance of the wavelength conversion device 33. With such a configuration, blue light having a wavelength of 425 nm can be obtained at an output of about 10 mW at present.
[0011]
[Problems to be solved by the invention]
In the optical module in which the semiconductor laser 27 and the optical fiber 29 shown in FIG. 9 are integrated, the optical fiber 29 is mounted in a V-groove 28 formed on the Si submount 26, and the semiconductor is formed with the V-groove 28 as a reference position. A laser 27 is mounted. The optical fiber 29 has a cylindrical shape, and its core portion (light propagation region) is formed at the center of the optical fiber 29. In addition, the diameter of the optical fiber 29 is also controlled with high accuracy. Further, the V-groove 28 formed on the Si submount 26 is also formed with high accuracy by using Si anisotropic etching. As a result, the core that is the center of the optical fiber 29 is mounted with high alignment accuracy on the Si submount 26. Also, the semiconductor laser 27 can be mounted on the Si submount 26 with high alignment accuracy because the alignment keys 126 and 127 formed for the alignment are formed with reference to the V groove 28. .
[0012]
On the other hand, in the wavelength conversion device 33 using the planar optical waveguide in the configuration of FIG._ThreeA planar (two-dimensional) planar optical waveguide 34 is formed on the substrate 36 by a method such as proton exchange. In the present specification, a planar (two-dimensional) planar optical waveguide (so-called “planar optical waveguide”) using a thin film or the like other than an optical waveguide device having an optical waveguide layer in the center of a coaxial line such as an optical fiber. The optical waveguide device in which the “waveguide”) is formed is also referred to as “planar optical waveguide device”.
[0013]
In this planar optical waveguide device, the position of the planar optical waveguide in the height direction from the substrate surface can be controlled with high accuracy during its formation. However, the position of the planar optical waveguide in the lateral direction of the device is greatly affected by processes such as cutting and polishing when manufacturing individual devices, and it is difficult to control the position with high accuracy. On the other hand, it is possible to mount a planar optical waveguide device by forming an alignment key or the like and detecting the position of the planar optical waveguide by a method similar to that for mounting a semiconductor laser. Then, since each of the semiconductor laser and the planar optical waveguide device is mounted on the alignment key, a mounting error becomes large.
[0014]
In particular, in a wavelength conversion device using a planar optical waveguide and utilizing second harmonic generation (SHG), the wavelength conversion efficiency is proportional to the incident power of the fundamental wave into the planar optical waveguide of the wavelength conversion device, The obtained harmonic optical power is proportional to the square of the incident power of the fundamental wave. For this reason, in order to obtain a wavelength conversion device exhibiting excellent operating characteristics, it is essential to improve the coupling efficiency of the device to the planar optical waveguide and to reduce the variation between samples.
[0015]
The present invention has been made in order to solve the above-mentioned problems, and an object thereof is to provide (1) an optical waveguide device having a planar optical waveguide in which an alignment key for mounting is formed with high accuracy. (2) Providing an integrated optical module configured by combining a semiconductor laser and the planar optical waveguide as described above, and (3) Optical light having the semiconductor laser and the planar optical waveguide as described above. It is to provide an integrated optical module mounting method in which an integrated optical module is configured by highly accurately aligning and adjusting the mounting position with a waveguide device.
[0022]
[Means for Solving the Problems]
Of the present inventionHow to mount an integrated optical moduleAnd mounting method of integrated optical module configured by mounting at least a semiconductor laser and an optical waveguide device on which a planar optical waveguide is formed on a submountBecauseAn edge portion of the light emitting end face of the semiconductor laser and an edge portion of the light incident end face of the optical waveguide deviceBased on images recognized in the same field of view by irradiating infrared light from the back surface of the submountAnd detecting the positions of the semiconductor laser and the optical waveguide device within the surface of the submount using the detection results of the respective edge portions, and the normal direction of the light emitting end face of the semiconductor laser. Adjusting the alignment in a direction substantially along the axis, thereby achieving the above object.
[0023]
[Means for Solving the Problems]
  The integrated optical module mounting method according to the present invention is used when a semiconductor laser having a first alignment key and a planar optical waveguide are formed on a ferroelectric substrate and the planar optical waveguide is formed. A method of mounting an integrated optical module comprising: an optical waveguide device in which a second alignment key is formed on a ferroelectric substrate using a photomask to be mounted; and at least a submount. AndThe planar optical waveguide is formed by proton exchange processing through the opening, using the photomask in which the second alignment key is previously formed at a predetermined position with respect to the opening for forming the planar optical waveguide. Forming the second alignment key by etching, andSemiconductor laser andSaidEither one of the optical waveguide devicesSaidSubmountSurface ofA step to fix to,SaidSemiconductor laserSaidWith the first alignment keySaidOptical waveguide deviceSaidWith the second alignment keySaidIrradiating infrared light from the back surface of the submount and detecting based on an image recognized in the same field of view;SaidWithin the surface of the submount,SaidUsing either one of the detected first and second alignment keys as a reference position,SaidThe detected position of the other alignment keySaidAdjusting the alignment in a direction substantially parallel to the light incident end face of the optical waveguide device, thereby achieving the above object.
[0024]
For example, the position of the first alignment key may be used as a reference position, and the position of the second alignment key may be adjusted in a direction substantially parallel to the light incident end face of the optical waveguide device. Alternatively, the position of the first alignment key may be adjusted in a direction substantially parallel to the light incident end face of the optical waveguide device, with the position of the second alignment key as a reference position.
[0025]
  The integrated optical module mounting method of the present invention includes a first mounting step of mounting the semiconductor laser on which the first alignment key is formed on the submount, and a planar optical waveguide on the ferroelectric substrate. An optical waveguide device having a second alignment key formed on the ferroelectric substrate is mounted on the submount using a photomask formed and used in forming the planar optical waveguide. A second implementation step, the second implementation step comprising:The planar optical waveguide is formed by proton exchange processing through the opening, using the photomask in which the second alignment key is previously formed at a predetermined position with respect to the opening for forming the planar optical waveguide. Forming the second alignment key by etching, andOn the semiconductor laserSaidWith the first alignment keySaidAbove the optical waveguide deviceSaidWith the second alignment keySaidIrradiate infrared light from the back of the submount and detect it based on the image recognized in the same field of view.SaidWithin the surface of the submount,SaidUsing the detected position of the first alignment key as a reference position,SaidThe position of the detected second alignment key isSaidAdjusting the alignment in a direction substantially parallel to the light incident end face of the optical waveguide device;SaidThe edge of the light emitting end face above the semiconductor laser;SaidAn edge portion of the light incident end face of the optical waveguide device;SaidIrradiate infrared light from the back of the submount and detect it based on the image recognized in the same field of view.SaidUsing the detection results of each edge,SaidWithin the surface of the submount,SaidSemiconductor laser andSaidThe position of the optical waveguide deviceSaidSemiconductor laserSaidAdjusting the alignment in a direction substantially along the normal direction of the light emitting end face, thereby achieving the above object.
[0026]
In the integrated optical module mounting method according to the present invention as described above, the planar optical waveguide and the second alignment key may be formed using the same photomask.
[0027]
Preferably, the second alignment key is located at a position away from the planar optical waveguide by 10 μm or more.
[0028]
Further, for example, the planar optical waveguide may be a proton exchange planar optical waveguide formed by a proton exchange method.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
As described above, in an integrated optical module in which a semiconductor laser and an optical waveguide device having a planar optical waveguide (planar optical waveguide device) are integrated, the emitted light from the semiconductor laser is transferred to the planar optical waveguide. It is important to improve the coupling efficiency of the sample and to reduce the variation in the coupling efficiency between samples. In particular, an integrated optical module of a short wavelength light source using second harmonic generation (SHG) composed of a semiconductor laser and a wavelength conversion device using a planar optical waveguide as a planar optical waveguide device is obtained. Since the generated harmonic optical power is proportional to the square of the incident power of the fundamental wave coupled to the planar optical waveguide, the improvement of the coupling efficiency and the reduction of the variation between samples are particularly important factors.
[0030]
In the following, in a planar optical waveguide device having an alignment key formed with high accuracy, and an integrated optical module composed of the same and a semiconductor laser, an optical device that enables alignment adjustment for realizing high-precision optical coupling. Several specific embodiments of the present invention will be described regarding the configuration of the waveguide device and the method of mounting the optical module using the waveguide device.
[0031]
(First embodiment)
Conventionally, in order to form an alignment key, a buffer layer is formed on the planar optical waveguide and an alignment key is formed thereon in order to avoid waveguide loss of the planar optical waveguide. However, in this method, since an alignment error of the photomask occurs when forming the alignment key, it is difficult to form the alignment key with high accuracy.
[0032]
Therefore, in this embodiment, in order to solve the above-described problem, a planar optical waveguide device 100 in which a planar optical waveguide and an alignment key for alignment are formed on a ferroelectric substrate using the same photomask. Will be described.
[0033]
FIG. 1 is a perspective view showing a configuration of a planar optical waveguide device 100 in the present embodiment.
[0034]
In this configuration, a substrate made of a ferroelectric material, for example, Mg-doped LiNbO_ThreeA planar optical waveguide 3 is formed along the center line M2 of the substrate 1. A pair of alignment keys 4 made of, for example, a Ta film and a pair of additional patterns 4A are formed at positions symmetrical with respect to the planar optical waveguide 3. Furthermore, for example, SiO₂A protective film 5 is formed on the surface of the substrate 1 so as to cover the planar optical waveguide 3, the alignment key 4, and the additional pattern 4A. However, the numbers of the alignment keys 4 and the additional patterns 4A are not limited to a pair, and any number (the number of pairs) can be formed. Further, the shapes of the alignment key 4 and the additional pattern 4A are not limited to those shown in the figure, and may be any appropriate shape.
[0035]
In forming the planar optical waveguide device 100 having such a configuration, first, as shown in FIG. 2, Mg-doped LiNbO_ThreeA stripe having an opening 2A (for example, a width of about 5 μm) for forming a planar optical waveguide 3 is formed by depositing a Ta film on the substrate 1 and performing a general photolithography process and a dry etching process on the Ta film. A mask 2 is formed. In this mask formation process (photolithographic process and dry etching process), a pair of alignment keys 4 are simultaneously formed at positions symmetrical to the center line M2 of the opening 2A.
[0036]
Next, proton exchange treatment through the opening 2A of the mask 2 is performed in pyrophosphoric acid (temperature of about 200 ° C.) for about 7 minutes, followed by annealing (temperature of about 330 ° C. for about 200 minutes). ) To form the planar optical waveguide 3. Thereafter, the portion corresponding to the formation position of the formed alignment key 4 and the pair of additional patterns 4A shown in FIG. 1 is masked with a resist, and the Ta film is removed by wet etching. By this wet etching, an additional pattern 4A is formed. After that, the surface of the substrate 1 is covered with SiO2 so as to cover the planar optical waveguide 3, the alignment key 4, and the additional pattern 4A.₂A protective film 5 is formed.
[0037]
As described above, the planar optical waveguide device 100 having the configuration shown in FIG. 1 is manufactured.
[0038]
SiO₂The protective film 5 is a planar when the planar optical waveguide device 100 is mounted on the submount in a junction-down manner (that is, in a direction in which the optical waveguide formation surface faces the submount) to form an integrated optical module. It is also used to adjust the height of the mold optical waveguide 3 from the submount. That is, the thickness of the protective film 5 (SiO₂In order to construct an integrated optical module, the thickness of the semiconductor laser is similarly mounted on the submount in a junction-down manner and coupled to the planar optical waveguide device 100 from the submount surface to the active layer. Control is based on distance. Specifically, for example, in this embodiment, the protective film 5 having a thickness of about 1000 nm is formed.
[0039]
On the other hand, the film thickness of the Ta film (metal film) formed to constitute the mask 2, the alignment key 4, and the additional pattern 4A is, for example, about 100 nm. Here, the additional pattern 4A is formed in order to uniformly maintain the height of the planar optical waveguide 3 from the submount when the planar optical waveguide device 100 is mounted on the submount in a junction-down manner. Is. If only the alignment key 4 is formed without forming this additional pattern 4A, the planar type optical waveguide 3 may be formed with respect to the submount depending on the thickness of the metal film (Ta film) constituting the alignment key 4. It will be located diagonally in the longitudinal direction, which is not preferable. On the other hand, by forming the additional pattern 4A made of a film having the same thickness as the alignment key 4, the above problem does not occur.
[0040]
As in the prior art, when an alignment key is formed by alignment of a photomask, the accuracy is usually about ± 0.3 μm. On the other hand, as in this embodiment, for the proton exchange planar optical waveguide 3, the alignment key 4 can be formed using the same photomask when the Ta mask 2 for proton exchange processing is formed. . For this reason, since the position of the alignment key 4 can be controlled with the photomask fabrication accuracy, a high positional accuracy can be obtained with respect to the alignment key 4. Specifically, for example, the alignment is performed with an accuracy of about ± 0.1 μm. Key 4 can be formed.
[0041]
Further, by forming the alignment key 4 between the protective film 5 and the substrate 1, the alignment key 4 can be mounted even if the planar optical waveguide device 100 is mounted on the submount at the junction down in the configuration of the integrated optical module. Does not come into contact with the submount. As a result, the alignment key 4 is not damaged, and a clear shape of the edge portion is maintained and image recognition is reliably performed, so that the practical effect is great.
[0042]
By the way, in the proton exchange planar optical waveguide 3 as described above, the alignment key 4 can be formed with the same photomask when forming the Ta mask 2 at the time of proton exchange for forming the planar optical waveguide 3. On the other hand, in the Ti diffusion planar type optical waveguide, in forming the planar type optical waveguide, it is necessary to perform a heat treatment at 1000 ° C. or more for 6 hours in order to diffuse Ti. For this reason, when the alignment key is formed with the same photomask at the time of forming the planar optical waveguide as described above, the formed Ti alignment key is deformed and deteriorated by the heat treatment for diffusing Ti. Therefore, it is difficult to form an alignment key for a Ti diffusion planar optical waveguide by using a photomask when forming the planar optical waveguide as in this embodiment.
[0043]
As described above, the formation of the alignment key as in this embodiment is particularly effective for a planar optical waveguide device manufactured by proton exchange, and a high-precision alignment key can be easily formed.
[0044]
In the configuration of the present embodiment, the alignment key 4 is typically formed at a position away from the planar optical waveguide 3, for example, at a position separated by at least about 10 μm. This is due to the following reason.
[0045]
If the alignment key 4 is formed on or near the planar optical waveguide 3, the effective refractive index, that is, the phase state of the planar optical waveguide 3 changes. Further, since the alignment key 4 is formed of a metal film (for example, a Ta film), if the alignment key 4 is too close to the planar optical waveguide 3, the waveguide loss is increased. These points become a serious problem in a wavelength conversion device using a planar optical waveguide in which a periodically poled structure is formed. Therefore, in order to avoid such a problem, it is preferable that the alignment key 4 is formed at a position apart from the planar optical waveguide 3 and separated by at least about 10 μm or more based on the result of examination by the present inventors.
[0046]
The above point is the same for the additional pattern 4A formed from the same metal film (for example, Ta film) as the alignment key 4. For the same reason as described above, the additional pattern 4A is formed as a planar optical waveguide. Preferably, it is formed at a distance of at least about 10 μm from 3.
[0047]
Further, hereinafter, a wavelength conversion device 200 using a planar optical waveguide will be described as a more specific configuration example of the planar optical waveguide device having the characteristics described above.
[0048]
FIG. 3 is a perspective view showing the configuration of the wavelength conversion device 200 formed according to the present embodiment.
[0049]
In this configuration, the X plate Mg-doped LiNbO_ThreeA proton exchange planar optical waveguide 3 is formed along the center line M2 of the substrate 1. A periodic domain-inverted region 7 with a period of 3.2 μm is formed on the surface of the substrate 1 in a direction orthogonal to the proton exchange planar optical waveguide 3. A pair of alignment keys 4 made of a Ta film and a pair of additional patterns 4A are formed at positions symmetrical with respect to the planar optical waveguide 3. Furthermore, SiO₂A protective film 5 is formed on the surface of the substrate 1 so as to cover the planar optical waveguide 3, the alignment key 4, and the additional pattern 4A.
[0050]
The method of forming the alignment key 4 and the additional pattern 4A is as described above. Further, the numbers of the alignment keys 4 and the additional patterns 4A are not limited to a pair, and any number (the number of pairs) can be formed. Furthermore, those shapes are not limited to those shown in the figure, and can be set appropriately. The functions of the protective film 5 and the additional pattern 4A are also as described above.
[0051]
In this wavelength conversion device 200, the periodic polarization inversion region 7 compensates for the difference in propagation speed generated between the fundamental wave incident on the planar optical waveguide 3 and the second harmonic generated by converting the fundamental wave. The Therefore, when a phase change is given to the planar optical waveguide 3, the wavelength conversion characteristics deteriorate, such as a decrease in wavelength conversion efficiency and a change in the second harmonic generation curve with respect to the wavelength. Here, as described above, when the alignment key is formed on or near the planar optical waveguide, the effective refractive index, that is, the phase state of the planar optical waveguide changes.
[0052]
Therefore, the waveguide loss characteristics of the wavelength conversion device when the three pairs of alignment keys 4 are formed adjacent to the proton exchange planar optical waveguide 3 in the configuration of FIG. As a result, when the alignment key 4 is not formed, the waveguide loss of the planar optical waveguide is 0.5 dB / cm, whereas the alignment key 4 is close to the planar optical waveguide 3. When formed (specifically, when formed at a distance of about 5 μm), the waveguide loss is 0.8 dB / cm, and the formation of the alignment key 4 increases the waveguide loss. It was.
[0053]
In the configuration of the wavelength conversion device 200 of the present embodiment, the alignment key 4 is formed at a distance of about 10 μm or more from the planar optical waveguide 3 in order to avoid the increase in waveguide loss as described above. This point is the same for the additional pattern 4A formed from the same metal film (Ta film) as the alignment key 4. For the same reason as described above, the additional pattern 4A is a planar optical waveguide. It is preferable to form it at a distance of about 10 μm or more from 3.
[0054]
On the other hand, FIG. 4 shows that a portion near the top of the second harmonic generation curve with respect to the wavelength is flattened by further providing a phase change portion in the periodic polarization inversion region included in the wavelength conversion device using the planar optical waveguide. Thus, the wavelength tolerance for wavelength conversion is increased (see, for example, Optical Letter, Vol. 23, No. 24, pp. 1880-1882, 1998). As described above, when the characteristics of the second harmonic generation curve are adjusted by the installation of the phase change unit, if a phase change or a change in waveguide loss is given, the influence on the second harmonic generation curve is as follows. growing. For example, FIG. 5 shows a structure of a wavelength conversion device using a planar optical waveguide having the characteristics shown in FIG. 4 (a configuration in which a phase change portion is further provided in a periodic polarization inversion region). A second harmonic generation curve obtained when an alignment key is further formed at a distant position is shown. In this case, as compared with the characteristics shown in FIG. 4, the flat portion near the top of the curve is inclined and the characteristics are deteriorated. On the other hand, if the alignment key is formed at a position at least 10 μm away from the planar optical waveguide, a second harmonic generation curve similar to that in FIG. 4 is observed, and no characteristic deterioration is observed.
[0055]
As in this embodiment, in a wavelength conversion device using a planar optical waveguide, the alignment key 4 is formed on the planar optical waveguide 3 so as to avoid the vicinity thereof, whereby the planar accompanying the installation of the alignment key 4 The influence on the waveguide loss and phase state of the optical waveguide 3 can be reduced. In particular, in the wavelength conversion device using the second harmonic generation of the quasi-phase matching method, the reduction in wavelength conversion efficiency and the deterioration of the second harmonic generation curve can be reduced by the above, and the practical effect is great.
[0056]
Furthermore, in this embodiment, since the additional pattern 4A made of a film having the same thickness as the alignment key 4 is formed on both sides of the planar optical waveguide 3, a wavelength conversion device using the planar optical waveguide is junctioned. Even when mounted on the submount in a down state, the height of the planar optical waveguide 3 from the submount is kept uniform, and a stable optical coupling characteristic is realized.
[0057]
(Second Embodiment)
In the present embodiment, in the integrated optical module 300 in which the semiconductor laser and the planar optical waveguide device are integrated on the submount, the alignment key formed on each of the semiconductor laser and the planar optical waveguide device is recognized, A mounting method for realizing highly efficient optical coupling between the semiconductor laser and the planar optical waveguide device by adjusting the positional relationship between the alignment keys will be described.
[0058]
FIGS. 6A and 6B are a side view and a plan view showing the configuration of the integrated optical module 300 configured according to the present embodiment.
[0059]
In the optical module 300 of this embodiment, the semiconductor laser 11 and the planar optical waveguide device are mounted on the Si submount 13. As the planar optical waveguide device, the Mg-doped LiNbO described in the first embodiment is used._ThreeA wavelength conversion device 200 in which a periodic domain-inverted region (not shown in FIG. 6) and a proton exchange planar optical waveguide 3 are formed on a substrate 1 is used. On the substrate 1 of the wavelength conversion device 200, the alignment key 4 is formed at a position 10 μm away from the planar optical waveguide 3 by the method shown in the first embodiment. An additional pattern 4A is further formed on both sides of the planar optical waveguide 3 by a film (for example, a Ta film) having the same material and thickness as the alignment key 4. In addition, after the alignment key 4 and the additional pattern 4A are formed, in order to adjust the position of the planar type optical waveguide 3 and the laser light emitting portion 19 of the semiconductor laser 11 at the time of junction down mounting in the height direction, SiO₂The protective film 5 is formed in the same manner as in the first embodiment. Further, a metal film 21 made of Ta, for example, is deposited on the protective film 5. Then, the wavelength conversion device 200 is fixed to the Si submount 13 by fixing the Ta metal film 21 to the solder layer 15 deposited on the Si submount 13 via the metal film 14 functioning as an electrode.
[0060]
On the other hand, an electrode 23 and an alignment key 17 are also formed on the surface of the semiconductor laser 11. The semiconductor laser 11 is fixed to the Si submount 13 by fixing the electrode 23 to the solder layer 15 deposited on the Si submount 13 via the metal film 14.
[0061]
When the semiconductor laser 11 is a DBR semiconductor laser, the electrode 23 of the semiconductor laser 11 and the metal film 14 and the solder layer 15 formed on the Si submount 13 corresponding to the semiconductor laser 11 include the semiconductor laser 11. Each of the 11 active layer regions and the DBR region (not shown) is divided and provided as shown. Alternatively, in the case where the semiconductor laser 11 is a general semiconductor laser that is not a DBR type, the electrode 23, the metal film 14, and the solder layer 15 need to be provided separately as illustrated in consideration of the structure. There is no.
[0062]
In FIG. 6B, for convenience, the alignment key 17 formed on the surface of the semiconductor laser 11 on the submount side, and the alignment key 4 formed on the surface of the wavelength conversion device 200 on the submount side, The additional pattern 4A and the position of the planar optical waveguide 3 are depicted in the figure.
[0063]
Both the semiconductor laser 11 and the wavelength conversion device 200 are mounted on the Si submount 13 by junction-down so that the active layer (junction) surface or the planar optical waveguide forming surface is in contact with the Si submount 13. In mounting, the semiconductor laser 11 and the wavelength conversion device 200 are held in parallel to the Si submount 13 by separate chip hands 161 and 162, respectively. The position of the laser light emitting portion 19 of the semiconductor laser 11 and the position of the planar optical waveguide 3 of the wavelength conversion device 200 using the planar optical waveguide are 10 μm high from the surface of the Si submount 13 after mounting. It has been adjusted to be.
[0064]
The detection device 136 used for image recognition of the alignment keys 4 and 17 at the time of mounting is a halogen lamp that emits infrared light, an infrared light camera for detecting infrared light, and a process for processing the detected image. Including computers. Specifically, the infrared light of the halogen lamp is irradiated from the back surface of the Si submount 13, and the alignment key 17 formed on the semiconductor laser 11 and the alignment formed on the wavelength conversion device 200 with an infrared camera. Each key 4 is detected. The alignment keys 17 and 4 on the semiconductor laser 11 and the wavelength conversion device 200 are formed at positions that are centrally symmetric with respect to the portions where the light is guided (the laser light emitting unit 19 and the planar optical waveguide 3). Therefore, the images of the alignment keys 17 and 4 detected by the infrared light camera of the detection device 136 are subjected to image processing by a computer, and the center lines M1 and M2 of the respective alignment keys 17 and 4 are obtained.
[0065]
With reference to FIGS. 11A and 11B, the calculation process of the center lines M1 and M2 of the alignment keys 17 and 4 will be described in detail. FIGS. 11A and 11B are diagrams schematically showing recognition images of the alignment keys 17 and 4 on the semiconductor laser 11 and the wavelength conversion device 200 obtained by the detection device 136, respectively. Each of the alignment keys 17 and 4 is actually composed of two pairs, which are referred to as 17-1 and 17-2, and 4-1 and 4-2.
[0066]
First, the centroids A1 and A2 of the alignment keys 17-1 and 17-2 on the semiconductor laser 11 shown in FIG. 11A are obtained by image processing with a computer based on the recognized image. Next, the center line M1 of the calculated centroids A1 and A2 is obtained. Similarly, the centroids B1 and B2 of the alignment keys 4-1 and 4-2 on the wavelength conversion device 200 shown in FIG. 11B are obtained by image processing with a computer based on the recognized image. Next, the center line M2 of the calculated centroids B1 and B2 is obtained. In actual processing, four alignment keys 17-1 and 17-2 and 4-1 and 4-2 are recognized on one screen. First, only one side of the screen is image-processed, and then the screen By processing only the other side, the respective centerlines M1 and M2 are recognized.
[0067]
In the configuration after mounting the optical module 300 in this embodiment, the laser light emitting unit 19 of the semiconductor laser 11 and the planar optical waveguide 3 of the wavelength conversion device 200 using the planar optical waveguide are respectively 10 μm from the Si submount 13. It is adjusted to be located at the height. On the other hand, when the center line M1 in the semiconductor laser 11 is calculated, the wavelength conversion device 200 is intentionally held at a height different from that of the semiconductor laser 11, for example, 50 μm from the Si submount 13. Only the alignment keys 17-1 and 17-2 on the laser 11 are detected.
[0068]
When the respective center lines M1 and M2 are obtained as described above, the light of the wavelength conversion device 200 is then set so that the center line M1 of the semiconductor laser coincides with the center line M2 of the wavelength conversion device 200 as a reference. The position of the semiconductor laser 11 is adjusted in a direction parallel to the incident end face (in this case, a direction perpendicular to the light propagation direction). The center line M1 of the semiconductor laser may be used as a reference and the center line M2 of the wavelength conversion device 200 may be adjusted with respect to the center line M1, but the semiconductor laser 11 is smaller than the wavelength conversion device 200 and Since it is light, it is desirable to adjust the alignment by moving the semiconductor laser 11.
[0069]
Next, based on the detection results of the edge part of the light emitting end face of the semiconductor laser 11 and the edge part of the light incident end face of the wavelength conversion device 200, the distance between these end faces is 3 μm. The position in the direction along the normal direction of the light emitting end face (in this case, the light propagation direction) is adjusted. When the distance between the semiconductor laser 11 and the wavelength conversion device 200 is 10 μm, compared to the case where this distance is 0 μm (that is, when the semiconductor laser 11 and the wavelength conversion device 200 are in direct contact), The coupling efficiency between the two is reduced by half. However, if the semiconductor laser 11 and the wavelength conversion device 200 are too close, there is a risk of destroying the end face of the semiconductor laser 11. Therefore, in the present embodiment, the distance between the semiconductor laser 11 and the wavelength conversion device 200 (between the light emitting end surface and the light incident end surface) is set to 3 μm.
[0070]
When the alignment is completed as described above, the semiconductor laser 11 and the wavelength conversion device 200 are respectively placed on the Si submount 13, the Si submount 13 is heated to 300 ° C., and the solder layer 15 is melted. To do. Subsequently, N to avoid solder oxidation₂Cool with gas flow to solidify the solder again. As a result, the semiconductor laser 11 and the wavelength conversion device 200 are fixed on the Si submount 13.
[0071]
In the configuration of the integrated optical module 300 of the present embodiment, the laser light obtained from the light emitting end face of the semiconductor laser 11 is coupled to the planar optical waveguide 3 of the wavelength conversion device 200. Specifically, for a laser output of 100 mW from the semiconductor laser 11, 50 mW of laser light was coupled to the planar optical waveguide 3 of the wavelength conversion device 200 (coupling efficiency 50%). By fixing the oscillation wavelength of the semiconductor laser 11 within the phase matching wavelength tolerance of the wavelength conversion device 200, about 5 mW of harmonic light having a wavelength of 425 nm was obtained, and high-efficiency optical coupling and wavelength conversion were realized.
[0072]
In the present invention, an alignment key for alignment is not formed on the Si submount 13. This is because if the alignment adjustment is performed on the alignment key on the Si submount 13 as in the prior art, an error occurs during each mounting, resulting in a large mounting error. For example, when an alignment key is provided on the Si submount 13 according to the prior art and alignment adjustment is performed on the alignment key, the positional accuracy during mounting is about ± 0.6 μm. On the other hand, if the alignment key 17 of the semiconductor laser 11 is aligned and adjusted with respect to the alignment key 4 on the wavelength conversion device 200 as in this embodiment, the relative positional relationship is directly adjusted. Therefore, high-precision alignment adjustment is possible, and it was possible to mount with alignment adjustment accuracy of typically about ± 0.3 μm or less. In the optical coupling characteristics between the semiconductor laser and the wavelength conversion device, the alignment adjustment accuracy at which the optical coupling efficiency is halved is generally about ± 0.5 μm, so about ± 0.3 μm or less as described above By realizing the above alignment adjustment accuracy, a coupling efficiency of 45% or more can be obtained in a sample of 90% or more. Moreover, since mounting is possible by one alignment adjustment, the time required for mounting is short. Therefore, the alignment adjustment and mounting method of the present embodiment is a practical method suitable for mass productivity and has a great effect.
[0073]
In the present embodiment, since the positional relationship between the semiconductor laser 11 and the wavelength conversion device 200 can be directly adjusted, the alignment adjustment and mounting accuracy depend on errors in manufacturing the alignment keys 17 and 4. As described in relation to the first embodiment, in the proton exchange planar optical waveguide 3, the alignment key 4 is formed with the same photomask when forming the Ta mask during proton exchange for forming the planar optical waveguide. can do. On the other hand, in the Ti diffusion planar type optical waveguide, in forming the planar type optical waveguide, it is necessary to perform a heat treatment at 1000 ° C. or more for 6 hours in order to diffuse Ti. For this reason, when the alignment key is formed with the same photomask at the time of forming the planar optical waveguide as described above, the formed Ti alignment key is deformed and deteriorated by the heat treatment for diffusing Ti. Therefore, it is difficult to form an alignment key for a Ti diffusion planar optical waveguide by using a photomask when forming the planar optical waveguide as in this embodiment. As a result, also in the alignment adjustment method of the integrated optical module according to the present embodiment, it is easier to form a high-precision alignment key in the case of a planar optical waveguide device manufactured by proton exchange. Alignment adjustment and mounting are possible, which is more effective.
[0074]
In the above description of the present embodiment, the configuration using the wavelength conversion device 200 using the planar optical waveguide described in the first embodiment as an example of the wavelength conversion device is described. According to the present embodiment, by directly adjusting the positional relationship between the semiconductor laser 11 and the wavelength conversion device 200 using the planar optical waveguide, high-precision alignment adjustment is possible. Efficient optical coupling can be realized. In particular, in an integrated optical module of a short wavelength light source using second harmonic generation (SHG) composed of a semiconductor laser and a wavelength conversion device using a planar optical waveguide, the obtained harmonic optical power has a planar optical power. Since it is proportional to the square of the incident power of the fundamental wave coupled to the optical waveguide, improvement of the coupling efficiency is a particularly important factor. Therefore, the method for adjusting the alignment of the integrated optical module according to the present embodiment is particularly effective for the planar optical waveguide device that is the second harmonic generation device.
[0075]
In this embodiment, a heat treatment for melting the solder layer 15 is performed at the time of mounting and fixing to the Si submount 13. At this time, the wavelength conversion device 200 is heated to 300 ° C., and the proton exchange planar type is used. The optical waveguide 3 is annealed. Therefore, the wavelength conversion device 200 is designed and formed in advance in consideration of the annealing effect on the proton exchange planar optical waveguide 3. Thereby, even if the semiconductor laser 11 and the wavelength conversion device 200 are mounted and fixed to the Si submount 13 by heating and melting the solder layer 15, highly efficient wavelength conversion characteristics can be obtained.
[0076]
(Third embodiment)
In this embodiment, in an optical module 400 in which a semiconductor laser and a planar optical waveguide device are integrated, an alignment key formed on each of the semiconductor laser and the planar optical waveguide device is recognized from the device side. By adjusting the positional relationship, a semiconductor laser and a planar optical waveguide device are mounted with high accuracy on an AlN submount that has higher thermal conductivity than Si, and high-efficiency optical coupling between the two is achieved. An optical module mounting method to be realized will be described. In the present embodiment, by using a submount made of a material with high thermal conductivity (AlN), the life of the semiconductor laser can be extended, and distortion of the submount caused by heat distribution can be reduced.
[0077]
FIGS. 7A and 7B are a side view and a plan view showing the configuration of the integrated optical module 400 configured according to the present embodiment.
[0078]
In the optical module 300 of this embodiment, the semiconductor laser 11 and the planar optical waveguide device are mounted on the AlN submount 24. As the planar optical waveguide device, the Mg-doped LiNbO described in the first embodiment is used._ThreeA wavelength conversion device 200 in which a periodic domain-inverted region (not shown in FIG. 7) and a proton exchange planar optical waveguide 3 are formed on a substrate 1 is used. On the substrate 1 of the wavelength conversion device 200, the alignment key 4 is formed at a position 10 μm away from the planar optical waveguide 3 by the method shown in the first embodiment. An additional pattern 4A is further formed on both sides of the planar optical waveguide 3 by a film (for example, a Ta film) having the same material and thickness as the alignment key 4. In addition, after forming the alignment key 4 and the additional pattern 4A, in order to adjust the alignment of the planar optical waveguide 3 and the laser light emitting portion 19 of the semiconductor laser 11 in the height direction, SiO 2₂The protective film 5 is formed in the same manner as in the first embodiment. Further, a metal film 21 made of Ta, for example, is deposited on the protective film 5. Then, the wavelength conversion device 200 is fixed to the AlN submount 24 by fixing the Ta metal film 21 to the solder layer 15 deposited via the metal film 14 functioning as an electrode on the AlN submount 24.
[0079]
On the other hand, an electrode 23 and an alignment key 17 are also formed on the surface of the semiconductor laser 11. The semiconductor laser 11 is fixed to the AlN submount 24 by fixing the electrode 23 to the solder layer 15 deposited on the AlN submount 24 via the metal film 14.
[0080]
When the semiconductor laser 11 is a DBR semiconductor laser, the electrode 23 of the semiconductor laser 11 and the metal film 14 and the solder layer 15 formed on the AlN submount 24 corresponding to the semiconductor laser 11 include the semiconductor laser 11. Each of the 11 active layer regions and the DBR region (not shown) is divided and provided as shown. Alternatively, in the case where the semiconductor laser 11 is a general semiconductor laser that is not a DBR type, the electrode 23, the metal film 14, and the solder layer 15 need to be provided separately as illustrated in consideration of the structure. There is no.
[0081]
7B, for convenience, the alignment key 17 formed on the surface of the semiconductor laser 11 on the submount side, and the alignment key 4 formed on the surface of the wavelength conversion device 200 on the submount side, The additional pattern 4A and the position of the planar optical waveguide 3 are depicted in the figure.
[0082]
Both the semiconductor laser 11 and the wavelength conversion device 200 are mounted on the AlN submount 24 by junction-down so that the active layer (junction) surface or the planar optical waveguide forming surface is in contact with the AlN submount 24. In mounting, the semiconductor laser 11 and the wavelength conversion device 200 are held in parallel with the AlN submount 24 by separate chip hands 161 and 162, respectively. The position of the laser light emitting portion 19 of the semiconductor laser 11 and the position of the planar optical waveguide 3 of the wavelength conversion device 200 using the planar optical waveguide are 10 μm high from the surface of the Si submount 13 after mounting. It has been adjusted to be.
[0083]
The detection device 136 used for image recognition of the alignment keys 4 and 17 at the time of mounting is a halogen lamp that emits infrared light, an infrared light camera for detecting infrared light, and a process for processing the detected image. Including computers. Specifically, in the configuration of the optical module of the present embodiment, since the AlN submount 24 does not transmit infrared light, the infrared light from the halogen lamp is irradiated from the device mounting surface side of the submount 24, and infrared light is transmitted. The optical camera detects the alignment key 17 formed on the semiconductor laser 11 and the alignment key 4 formed on the wavelength conversion device 200, respectively. The alignment keys 17 and 4 on the semiconductor laser 11 and the wavelength conversion device 200 are formed at positions that are centrally symmetric with respect to the portions where the light is guided (the laser light emitting unit 19 and the planar optical waveguide 3). Therefore, the images of the alignment keys 17 and 4 detected by the infrared camera of the detection device 136 are obtained by the method described with reference to FIGS. 11A and 11B in relation to the second embodiment. Image processing is performed by a computer, and center lines M1 and M2 of the respective alignment keys 17 and 4 are obtained.
[0084]
When the respective center lines M1 and M2 are obtained, next, the center line M2 of the wavelength conversion device 200 is used as a reference, and the center line M1 of the semiconductor laser coincides with the center line M1 of the wavelength conversion device 200. The position of the semiconductor laser 11 is adjusted in such a direction (in this case, a direction perpendicular to the light propagation direction). The center line M1 of the semiconductor laser may be used as a reference and the center line M2 of the wavelength conversion device 200 may be adjusted with respect to the center line M1, but the semiconductor laser 11 is smaller than the wavelength conversion device 200 and Since it is light, it is desirable to adjust the alignment by moving the semiconductor laser 11.
[0085]
Next, in the same manner as in the second embodiment, the positions of the two are set so that the distance between the edge portion of the light emitting end face of the semiconductor laser 11 and the edge portion of the light incident end face of the wavelength conversion device 200 is 3 μm. Is adjusted to a direction along the normal direction of the light emitting end face of the semiconductor laser 11 (in this case, the light propagation direction). When the alignment is completed, the semiconductor laser 11 and the wavelength conversion device 200 are respectively placed on the AlN submount 24, the AlN submount 24 is heated to 300 ° C., and the solder layer 15 is melted. Subsequently, N to avoid solder oxidation₂The solder is solidified again by cooling with flowing gas. As a result, the semiconductor laser 11 and the wavelength conversion device 200 are fixed on the AlN submount 24.
[0086]
In the configuration of the integrated optical module 400 of this embodiment, laser light obtained from the light emitting end face of the semiconductor laser 11 is coupled to the planar optical waveguide 3 of the wavelength conversion device 200. Specifically, for a laser output of 100 mW from the semiconductor laser 11, 50 mW of laser light was coupled to the planar optical waveguide 3 of the wavelength conversion device 200 (coupling efficiency 50%). By fixing the oscillation wavelength of the semiconductor laser 11 within the phase matching wavelength tolerance of the wavelength conversion device 200, about 5 mW of harmonic light having a wavelength of 425 nm was obtained, and high-efficiency optical coupling and wavelength conversion were realized. The AlN submount 24 has a high thermal conductivity, and its thermal expansion coefficient is close to that of GaAs typically used as a constituent material of a semiconductor laser substrate. On the other hand, a more stable optical coupling than that of the Si submount can be obtained. Specifically, the variation in coupling efficiency was about ± 5% or less with respect to a temperature change of about ± 20 ° C.
[0087]
Also in this embodiment, as in the second embodiment, an alignment key for alignment is not formed on the AlN submount 24. As described with reference to the second embodiment, if the alignment adjustment is performed with respect to the alignment key on the submount, an error occurs during each mounting, resulting in a large mounting error. Because. According to the present embodiment, by adjusting the positional relationship between the semiconductor laser 11 and the wavelength conversion device 200 directly, high-precision alignment adjustment is possible. Moreover, since mounting is possible by one alignment adjustment, the time required for mounting is short. Therefore, the alignment adjustment and mounting method of the present embodiment is a practical method suitable for mass productivity and has a great effect.
[0088]
Also in this embodiment, since the positional relationship between the semiconductor laser 11 and the wavelength conversion device 200 can be directly adjusted, as in the second embodiment, the alignment adjustment and mounting accuracy are the same as the production of the alignment keys 17 and 4. Depends on time error. As already described, in the proton exchange planar optical waveguide 3, the alignment key 4 can be formed with high accuracy using the same photomask when forming the Ta mask during proton exchange for forming the planar optical waveguide. As a result, in the integrated optical module alignment adjustment method of the present embodiment, it is easier to form a high-precision alignment key in the planar optical waveguide device manufactured by proton exchange. Adjustment and implementation are possible and more effective.
[0089]
In the above description of the present embodiment, the configuration using the wavelength conversion device 200 using the planar optical waveguide described in the first embodiment as an example of the wavelength conversion device is described. According to the present embodiment, by directly adjusting the positional relationship between the semiconductor laser 11 and the wavelength conversion device 200, highly accurate alignment adjustment is possible, and highly efficient optical coupling can be realized between the two. . In particular, in an integrated optical module of a short wavelength light source using second harmonic generation (SHG) composed of a semiconductor laser and a wavelength conversion device using a planar optical waveguide, the obtained harmonic optical power has a planar optical power. Since it is proportional to the square of the incident power of the fundamental wave coupled to the optical waveguide, improvement of the coupling efficiency is a particularly important factor. Therefore, the method for adjusting the alignment of the integrated optical module according to the present embodiment is particularly effective for the planar optical waveguide device that is the second harmonic generation device.
[0090]
In this embodiment, a heat treatment for melting the solder layer 15 is performed at the time of mounting and fixing to the AlN submount 24. At this time, the wavelength conversion device 200 is heated to 300 ° C., and the proton exchange planarization is performed. The mold optical waveguide 3 is annealed. Therefore, the wavelength conversion device 200 is designed and formed in advance in consideration of the annealing effect on the proton exchange planar optical waveguide 3. Thereby, even if the semiconductor laser 11 and the wavelength conversion device 200 are mounted and fixed to the AlN submount 24 by heating and melting the solder layer 15, highly efficient wavelength conversion characteristics can be obtained.
[0091]
(Fourth embodiment)
In the present embodiment, in an optical module 500 in which a semiconductor laser and a planar optical waveguide device are integrated, the alignment keys formed on each of the semiconductor laser and the planar optical waveguide device are recognized, and the positional relationship between the alignment keys. A mounting method for realizing highly efficient optical coupling between the semiconductor laser and the planar optical waveguide device by adjusting the above will be described.
[0092]
FIGS. 8A to 8E are diagrams for explaining each step of the mounting method of the integrated optical module 500 in the present embodiment.
[0093]
In the optical module 500 of this embodiment, the semiconductor laser 11 and the planar optical waveguide device are mounted on the Si submount 13. As the planar optical waveguide device, the Mg-doped LiNbO described in the first embodiment is used._ThreeA wavelength conversion device 200 in which a periodic domain-inverted region (not shown in FIG. 8) and a proton exchange planar optical waveguide 3 are formed on a substrate 1 is used. On the substrate 1 of the wavelength conversion device 200, the alignment key 4 is formed at a position 10 μm away from the planar optical waveguide 3 by the method shown in the first embodiment. An additional pattern 4A is further formed on both sides of the planar optical waveguide 3 by a film (for example, a Ta film) having the same material and thickness as the alignment key 4. In addition, after forming the alignment key 4 and the additional pattern 4A, in order to adjust the alignment of the planar optical waveguide 3 and the laser light emitting portion 19 of the semiconductor laser 11 in the height direction, SiO 2₂The protective film 5 is formed in the same manner as in the first embodiment. In this embodiment, the wavelength conversion device 200 having such a configuration is fixed to the metal film 14 functioning as an electrode formed on the Si submount 13 with an ultraviolet curable resin (UV curable resin). .
[0094]
On the other hand, an electrode 23 and an alignment key 17 are formed on the surface of the semiconductor laser 11 by, for example, an Au film. A solder layer 15 is formed on a metal film 14 functioning as an electrode at a position corresponding to the mounting position of the semiconductor laser 11 on the Si submount 13, and the electrode 23 is fixed to the solder layer 15. Thus, the semiconductor laser 11 is fixed to the Si submount 13.
[0095]
When the semiconductor laser 11 is a DBR semiconductor laser, the electrode 23 of the semiconductor laser 11 and the metal film 14 and the solder layer 15 formed on the Si submount 13 corresponding to the semiconductor laser 11 include the semiconductor laser 11. Each of the 11 active layer regions and the DBR region (not shown) is divided and provided as shown. Alternatively, in the case where the semiconductor laser 11 is a general semiconductor laser that is not a DBR type, the electrode 23, the metal film 14, and the solder layer 15 need to be provided separately as illustrated in consideration of the structure. There is no.
[0096]
Next, with reference to FIGS. 8A to 8E, a method of mounting the optical module 500 in the present embodiment will be described again.
[0097]
Also in this embodiment, the semiconductor laser 11 and the wavelength conversion device 200 are both mounted on the Si submount 13 by junction-down so that the active layer (junction) surface or the planar optical waveguide formation surface is in contact with the Si submount 13. The In mounting, first, as shown in FIG. 8A, the semiconductor laser 11 and the wavelength conversion device 200 are held parallel to the Si submount 13 by separate chip hands 161 and 162, respectively. It is positioned above each mounting location on the submount 13. Next, after placing the semiconductor laser 11 on the solder layer 15 of the Si submount 13, the Si submount 13 is heated to 300 ° C. to melt the solder layer 15. Subsequently, N to avoid solder oxidation₂The solder is solidified again by cooling with flowing gas, and the semiconductor laser 11 is fixed on the Si submount 13 as shown in FIG.
[0098]
Next, alignment adjustment of the wavelength conversion device 200 is performed using the alignment key 17 formed on the semiconductor laser 11, and the planar optical waveguide surface is formed on the Si submount 13 on the Si submount 13. Implement to touch.
[0099]
Specifically, as shown in FIG. 8C, first, the wavelength conversion device 200 is held by the chip hand 162, and the position is adjusted so as to be parallel to the Si submount 13.
[0100]
Next, the rear surface of the Si submount 13 was irradiated with a halogen lamp (not shown) that emits infrared light, and formed on the semiconductor laser 11 and the wavelength conversion device 200 with an infrared camera (not shown). Alignment keys 17 and 4 are detected. Then, the center of gravity of the alignment key 17 is first obtained by image processing by a computer based on the detected image, and the center line M1 of the alignment key 17 is obtained based on the center of gravity. Next, similarly, the center of gravity of each alignment key 4 on the wavelength conversion device 200 is obtained, and the center line M2 is further obtained. In actual processing, both alignment keys 17 and 4 are recognized on one screen. First, image processing is performed only on one side of the screen, and then only the other side of the screen is processed. Centerlines M1 and M2 are recognized.
[0101]
The alignment keys 17 and 4 on the semiconductor laser 11 and the wavelength conversion device 200 are formed at positions that are centrally symmetric with respect to the portions where the light is guided (the laser light emitting unit 19 and the planar optical waveguide 3). When the respective center lines M1 and M2 are obtained as described above, the wavelength conversion device 200 is then set so that the center line M2 of the wavelength conversion device 200 coincides with the center line M1 of the semiconductor laser 11 as a reference. Is adjusted in a direction perpendicular to the light propagation direction, that is, a direction parallel to the light incident end face of the wavelength conversion device 200 (the direction of the arrow 62 in FIG. 8D).
[0102]
Next, as in the second embodiment, based on the detection results of the respective edge portions so that the distance between the light emitting end surface of the semiconductor laser 11 and the light incident end surface of the wavelength conversion device 200 is 3 μm. Position adjustment is performed in the light propagation direction, that is, the direction along the normal direction of the light emitting end face of the semiconductor laser 11 (the direction of the arrow 64 in FIG. 8D). When the alignment is completed, a UV curable resin is applied between the wavelength conversion device 200 and the Si submount 13 by a dispenser (not shown), and further irradiated with UV light to cure the applied resin. As a result, as shown in FIG. 8E, the wavelength conversion device 200 is fixed on the Si submount 13, and the optical module 500 is configured.
[0103]
In the configuration of the integrated optical module 500 of the present embodiment, the laser light obtained from the light emitting end face of the semiconductor laser 11 is coupled to the planar optical waveguide 3 of the wavelength conversion device 200. Specifically, for a laser output of 100 mW from the semiconductor laser 11, 50 mW of laser light was coupled to the planar optical waveguide 3 of the wavelength conversion device 200 (coupling efficiency 50%). Further, as in the second embodiment, an alignment adjustment accuracy of about ± 0.3 μm or less is realized, and as a result, a coupling efficiency of 45% or more is obtained for 90% or more of samples. By fixing the oscillation wavelength of the semiconductor laser 11 within the phase matching wavelength tolerance of the wavelength conversion device 200, about 5 mW of harmonic light having a wavelength of 425 nm was obtained, and high-efficiency optical coupling and wavelength conversion were realized. In the present embodiment, since the wavelength conversion device 200 is mounted without heat treatment, more efficient wavelength conversion characteristics are realized.
[0104]
Also in this embodiment, as in the second embodiment, an alignment key for alignment is not formed on the Si submount 13. As described in relation to the second embodiment, if the alignment adjustment is performed on the alignment key on the submount, an error occurs during each mounting, resulting in a large mounting error. . According to the present embodiment, by adjusting the positional relationship between the semiconductor laser 11 and the wavelength conversion device 200 directly, high-precision alignment adjustment is possible. Moreover, since mounting is possible by one alignment adjustment, the time required for mounting is short. Therefore, the alignment adjustment and mounting method of the present embodiment is a practical method suitable for mass productivity and has a great effect.
[0105]
Also in this embodiment, since the positional relationship between the semiconductor laser 11 and the wavelength conversion device 200 can be directly adjusted, as in the second embodiment, the alignment adjustment and mounting accuracy are the same as the production of the alignment keys 17 and 4. Depends on time error. As already described, in the proton exchange planar optical waveguide 3, the alignment key 4 can be formed with high accuracy using the same photomask when forming the Ta mask during proton exchange for forming the planar optical waveguide. As a result, in the integrated optical module alignment adjustment method of the present embodiment, it is easier to form a high-precision alignment key in the planar optical waveguide device manufactured by proton exchange. Adjustment and implementation are possible and more effective.
[0106]
In the above description of the present embodiment, the configuration using the wavelength conversion device 200 using the planar optical waveguide described in the first embodiment as an example of the wavelength conversion device is described. According to the present embodiment, by directly adjusting the positional relationship between the semiconductor laser 11 and the wavelength conversion device 200, highly accurate alignment adjustment is possible, and highly efficient optical coupling can be realized between the two. . In particular, in an integrated optical module of a short wavelength light source using second harmonic generation (SHG) composed of a semiconductor laser and a wavelength conversion device, a fundamental wave in which the obtained harmonic optical power is coupled to a planar optical waveguide. Since this is proportional to the square of the incident power, the improvement of the coupling efficiency is a particularly important factor. Therefore, the method for adjusting the alignment of the integrated optical module according to the present embodiment is particularly effective for the planar optical waveguide device that is the second harmonic generation device.
[0107]
In this embodiment, since the wavelength conversion device 200 is fixed by the UV curable resin, it can be mounted without performing a heat treatment. As a result, it can be implemented without considering the change in operating characteristics, and the effect is great.
[0108]
When the integrated optical module of the present invention is used as a light source or the like in an optical disc apparatus, it is required to align the light emitting point in the semiconductor laser with a positional accuracy of about 100 μm. In that case, apart from the alignment key according to the present invention, a conventional general alignment key is formed on the semiconductor laser and the submount, and the semiconductor laser is mounted on the submount using these. Then, according to the method of the present embodiment, the same effect can be obtained even if the wavelength conversion device 200 is aligned and adjusted with respect to the mounted semiconductor laser 11 so that the center lines M1 and M2 coincide with each other. can get.
[0109]
In the description of each of the above embodiments, the light incident end face of the planar optical waveguide device included in the integrated optical module is formed perpendicular to the planar optical waveguide. However, the application of the present invention is not limited to such a case, and even in the mounting of an integrated optical module using a planar optical waveguide device whose end face is formed obliquely with respect to the planar optical waveguide. The present invention can achieve the same effect.
[0110]
FIG. 12 schematically shows an example of the configuration of an integrated optical module using a planar optical waveguide device having an oblique end surface.
[0111]
In this integrated optical module, a semiconductor laser 50 and an optical waveguide device 51 having a planar optical waveguide 52 are provided on a submount 53. Implemented to be opposite. Here, the end face of the optical waveguide device 51 is formed to be inclined by about 4 degrees from the direction orthogonal to the optical waveguide 52. In this case, the optical waveguide device 51 is LiNbO._ThreeIf formed using a substrate (refractive index = about 2.1), the incident angle of light to the optical waveguide 52 is about 8.4 degrees according to Snell's law (that is, the light of the optical waveguide 52). The axis is inclined by about 8.4 degrees with respect to the optical axis of the light emitted from the semiconductor laser 50). For this reason, the optical axis of the semiconductor laser 50 and the light propagation direction in the optical waveguide 52 of the optical waveguide device 51 are not parallel to each other.
[0112]
Even in such a case, in order to perform the optical coupling adjustment while keeping the distance between the light emitting end face of the semiconductor laser 50 and the light incident end face of the optical waveguide device 51 constant, it has been described in the above embodiments. According to the method of the present invention, alignment adjustment is performed by moving the optical waveguide device 51 in the direction indicated by the arrow 72 in FIG. 12, that is, in the direction parallel to the light incident end face of the optical waveguide device 51.
[0113]
Note that the alignment adjustment in the direction indicated by the arrow 74 in FIG. 12, that is, the direction along the normal direction of the light emitting end face of the semiconductor laser 50 is performed by the light of the semiconductor laser 50 as described in the previous embodiments. This can be performed based on the detection result of the edge portion of the emission end face and the edge portion of the light incident end face of the optical waveguide device 51.
[0114]
In the description of each of the above embodiments, a configuration using a wavelength conversion device as an optical waveguide device having a planar optical waveguide is specifically described. However, the application of the present invention is not limited to this, and for example, 3 dB The same effect can be obtained in a modulation device having a planar optical waveguide using a coupler, a Mach-Cender interferometer, or the like. Even in the configuration using these, the position of the alignment key on the semiconductor laser and the alignment key on the planar optical waveguide device are positioned on the submount of the semiconductor laser and the planar optical waveguide device. By adjusting the distance between the two end faces so as to coincide with each other to a desired value and mounting each of them, high-efficiency optical coupling can be realized, and light utilization efficiency can be improved. As a result, the output of the semiconductor laser is reduced, and its practical effect is great.
[0115]
In the optical waveguide device having the planar optical waveguide 3, as the substrate 1 on which the planar optical waveguide 3 is formed, the Mg-doped LiNbO as described in the above embodiments is used._ThreeThe substrate is not limited to the substrate, and may be another appropriate ferroelectric substrate used in the art. Specifically, LiTaO_ThreeCrystal, KTiOPO_FourCrystal or KNbO_ThreeThe use of a substrate made of a crystal having a large nonlinear optical constant, such as a crystal, is possible.
[0116]
Further, in each of the above embodiments, the Ta film is used as the constituent material of the alignment key 4 and the additional pattern 4A formed from the same material as the stripe mask for forming the planar optical waveguide 3. However, the present invention is not limited to this, and may be a film made of another appropriate material used in the technical field. Specifically, from the metal film such as Al, Cr, or Ti / Au, in particular, from the metal film having a sufficiently large reflectance with respect to the light used for the detection of the alignment key 4, the alignment key 4 and An additional pattern 4A can be constructed. Alternatively, the alignment key 4 and the additional pattern 4A may be configured by a dielectric film designed to have a high reflectance with respect to light used for detection of the alignment key 4.
[0117]
Further, in the optical waveguide device having the planar optical waveguide 3, the constituent material of the protective film 5 provided on the surface of the substrate 1 for protecting the alignment key 4 and adjusting the position of the planar optical waveguide 3 in the height direction. In the above description₂However, the film may be a film made of other appropriate materials used in the art. For example, Al₂O_FiveAnd Ta₂O_FiveA film of a material that has a lower refractive index than the substrate and is transparent to the fundamental and harmonics can be used.
[0118]
In the above description, the alignment adjustment in the direction along the normal direction of the light emitting end face of the semiconductor laser and the alignment adjustment in the direction parallel to the light incident end face of the optical waveguide device are strictly It does not have to be along that direction. When adjusted at a certain angle from those directions, that is, in a direction substantially along the normal direction of the light emitting end face of the semiconductor laser, and in a direction substantially parallel to the light incident end face of the optical waveguide device, respectively. The present invention can also be applied to the case where alignment adjustment is performed, and the same effect can be obtained.
[0119]
【The invention's effect】
As described above, according to the present invention, in an optical waveguide device having a planar optical waveguide, a small alignment key that gives only a small waveguide loss to the planar optical waveguide can be formed with high positional accuracy.
[0120]
Further, according to the present invention, it is possible to mount a semiconductor laser and an optical waveguide device having a planar optical waveguide by a single alignment adjustment, and a highly accurate alignment adjustment can be performed. Therefore, an integrated optical module excellent in mass productivity is provided.
[0121]
Furthermore, according to the present invention, variations in coupling efficiency between samples of the integrated optical module are reduced. It is also possible to omit alignment adjustment for the semiconductor laser.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a configuration of an optical waveguide device having a planar optical waveguide in a first embodiment of the present invention.
2 is a perspective view for explaining a process for forming the optical waveguide device of FIG. 1; FIG.
FIG. 3 is a perspective view showing a configuration of a wavelength conversion device using a planar optical waveguide as a specific example of an optical waveguide device having a planar optical waveguide in the first embodiment of the present invention.
FIG. 4 is a diagram schematically illustrating an example of a second harmonic generation curve of a second harmonic generation device in which the allowable wavelength width is expanded.
5 is a diagram schematically showing an example of a second harmonic generation curve when an alignment key is formed in the vicinity of a planar optical waveguide in the second harmonic generation device having the characteristics of FIG. is there.
FIGS. 6A and 6B are a side view and a plan view showing a configuration of an integrated optical module configured according to the second embodiment of the present invention. FIGS.
FIGS. 7A and 7B are a side view and a plan view showing a configuration of an integrated optical module configured according to the third embodiment of the present invention. FIGS.
FIGS. 8A to 8E are diagrams illustrating each step of a method of mounting an integrated optical module according to the fourth embodiment of the present invention.
FIG. 9 is a perspective view schematically showing a configuration of an optical module according to a conventional technique.
FIG. 10 is a cross-sectional view schematically showing a configuration of another conventional optical module.
FIGS. 11A and 11B are diagrams schematically showing recognition images of an alignment key on a semiconductor laser and a wavelength conversion device obtained by a detection apparatus in the integrated optical module according to the present invention, respectively. is there.
FIG. 12 is a diagram schematically illustrating a configuration example of an integrated optical module using a planar optical waveguide device having an oblique end surface to which the present invention can be applied.
[Explanation of symbols]
1 Mg-doped LiNbO_Threesubstrate
2 Stripe mask
2A opening
3 Planar type optical waveguide
4 Alignment key
4-1 Alignment key
4-2 Alignment key
4A additional patterns
5 Protective film
7 Polarization inversion region
11 Semiconductor laser
13 Si submount
14 Metal film
15 Solder layer
17 Alignment key
17-1 Alignment key
17-2 Alignment key
19 Laser emission part
21 Metal film
23 electrodes
24 AlN submount
136 Detector
161 chip hand
162 chip hand
26 Si submount
27 Semiconductor laser
28 V groove
29 Optical fiber
125 chip mounting area
126 Alignment key
127 Alignment key
30 DBR semiconductor laser
31 Active layer region
32 DBR area
33 Wavelength conversion device using planar optical waveguide
34 Planar type optical waveguide
35 Polarization inversion region
36 Mg-doped LiNbO_Threesubstrate
37 Submount
38 Submount
39 Wiring
40 Bonding wire
41 Support member
50 Semiconductor laser
51 Planar type optical waveguide device
52 Planar type optical waveguide
53 Submount
100 Optical waveguide device having a planar optical waveguide (planar optical waveguide device)
200 Wavelength Conversion Device Using Planar Type Optical Waveguide
300 Integrated optical module
400 Integrated optical module
500 Integrated optical module
A1 center of gravity
A2 center of gravity
B1 center of gravity
B2 center of gravity
M1 center line
M2 center line

Claims (6)

A semiconductor laser having a first alignment key, and a ferroelectric optical film using a photomask used for forming a planar optical waveguide on a ferroelectric substrate and forming the planar optical waveguide. A method of mounting an integrated optical module comprising an optical waveguide device having a second alignment key formed on a substrate and at least a submount mounted thereon,
The planar optical waveguide is formed by proton exchange processing through the opening, using the photomask in which the second alignment key is previously formed at a predetermined position with respect to the opening for forming the planar optical waveguide. And forming the second alignment key by etching,
A step of fixing one of the semiconductor laser and the optical waveguide device on a surface of the submount,
Detected based on the images that are recognized in the same field of view and the second alignment key of the first alignment key and the optical waveguide device of the semiconductor laser is irradiated with infrared light from the back surface of the submount Steps,
In the surface of the submount as a reference position one of the positions of the first and second alignment keys the detected, the position of the detected other alignment key, the light incident of the optical waveguide device Adjusting the alignment in a direction substantially parallel to the end face;
A method for mounting an integrated optical module, comprising:   The integration according to claim 1, wherein the position of the second alignment key is aligned and adjusted in a direction substantially parallel to the light incident end face of the optical waveguide device, with the position of the first alignment key as a reference position. Mounting method   The integration according to claim 1, wherein the position of the first alignment key is aligned and adjusted in a direction substantially parallel to the light incident end face of the optical waveguide device, with the position of the second alignment key as a reference position. Mounting method A first mounting step of mounting the semiconductor laser on which the first alignment key is formed on the submount;
An optical device in which a planar optical waveguide is formed on a ferroelectric substrate and a second alignment key is formed on the ferroelectric substrate using a photomask used when forming the planar optical waveguide. A second mounting step of mounting a waveguide device on the submount;
Including
The second implementation step includes
The planar optical waveguide is formed by proton exchange processing through the opening, using the photomask in which the second alignment key is previously formed at a predetermined position with respect to the opening for forming the planar optical waveguide. And forming the second alignment key by etching,
The image to be recognized in the same field of view and said second alignment keys on the said first alignment key optical waveguide device on said semiconductor laser is irradiated with infrared light from the back surface of the submount based detected, in the submount in the surface, as the position reference position of the first alignment key the detected, the position of the second alignment key the detected light entrance end face of the optical waveguide device Adjusting the alignment in a direction substantially parallel to
Based on the image to be recognized in the same field of view and an edge portion of the light incident end face of the optical waveguide device and the edge portion of the light-emitting end face on said semiconductor laser is irradiated with infrared light from the back surface of the submount detected Te, by using the detection results of each of the edge portions, in a surface of the submount, the position of the semiconductor laser and the optical waveguide device, in the normal direction of the light emitting end face of said semiconductor laser A step of adjusting the alignment in a substantially along direction;
A method for mounting an integrated optical module.   5. The integrated optical module mounting method according to claim 1, wherein the second alignment key is located at a position separated by 10 μm or more from the planar optical waveguide. 6.   The integrated optical module mounting method according to claim 1, wherein the planar optical waveguide is a proton exchange planar optical waveguide formed by a proton exchange method.

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