JP2024058271A - Laser Module - Google Patents

Abstract

To provide a laser module that can be miniaturized.SOLUTION: An arrayed laser beam generation unit 21 generates and emits an arrayed laser beam in which laser beams are arrayed. The array laser beam is incident on an optical unit 123. The optical unit 123 includes a polarizing beam splitter 12, and a wave plate 13 that is integrated with the polarizing beam splitter 12 by being joined by diffusion bonding to a first incident surface of the polarizing beam splitter 12 into which the arrayed laser beam is incident. The polarizing beam splitter 12 and the wave plate 13 are formed into a rectangular parallelepiped in which the first dimension in the direction perpendicular to the arrangement direction of the arrayed laser beams on the first incidence surface and the second incidence surface of the wave plate 13 into which the arrayed laser beams are incident is smaller than the second dimension in the arrangement direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to a laser module.

A laser module such as that described in Patent Document 1 is used as an excitation light source for a laser oscillator.

JP 2021-180273 A

In recent years, there has been a demand for higher output laser modules. To increase the output of a laser module, the output of the laser diode itself, which is the light source, can be improved, or the number of laser diodes can be increased. The output of the laser beam emitted from a laser diode is from a few watts to a few tens of watts, and there is a limit to how much the output can be increased. Therefore, it is possible to increase the output of a laser module by increasing the number of laser diodes.

The laser beams emitted from multiple laser diodes have the same wavelength, but have different optical path lengths before entering the optical fiber for transmission. Each of the multiple laser beams with the same wavelength enters or is reflected by the optical components for each laser beam and is transmitted to the optical fiber. At this time, each laser beam must be transmitted to the optical fiber in a state where the multiple laser beams are aligned in the height direction so that their progression is not impeded by the optical components for the other laser beams.

As a result, the optical components in the laser module must be large in size because they must be able to receive multiple laser beams aligned in the height direction. Larger optical components also mean larger laser modules, which increases costs. There is a demand for smaller laser modules to reduce their cost.

One aspect of one or more embodiments provides a laser module that includes an arrayed laser beam generating unit that generates and emits an arrayed laser beam in which laser beams are arrayed, and an optical unit to which the arrayed laser beam is incident, the optical unit including a polarizing beam splitter and a wave plate that is integrated with the polarizing beam splitter by being bonded by diffusion bonding to a first incident surface of the polarizing beam splitter to which the arrayed laser beam is incident, the polarizing beam splitter and the wave plate being formed into a rectangular parallelepiped in which a first dimension in a direction perpendicular to the array direction of the arrayed laser beam at the first incident surface and a second incident surface of the wave plate to which the arrayed laser beam is incident is smaller than a second dimension in the array direction.

According to one aspect of one or more embodiments, the polarizing beam splitter and the wave plate are bonded by diffusion bonding, thereby miniaturizing the laser module. According to one aspect of one or more embodiments, the polarizing beam splitter and the wave plate are formed into a rectangular parallelepiped in which a first dimension in a direction perpendicular to the array direction of the arrayed laser beams is smaller than a second dimension in the array direction, thereby further miniaturizing the laser module.

The laser module according to one or more embodiments allows the laser module to be miniaturized.

FIG. 1 is a plan view showing a laser module according to the first embodiment. FIG. 2 is a perspective view showing a preferred configuration of an optical unit in the laser module according to the first embodiment. FIG. 3 is a partial plan view showing a laser module according to the second embodiment. FIG. 4 is a perspective view showing a preferred configuration of an optical unit in the laser module according to the second embodiment.

The laser module according to one or more embodiments includes an arrayed laser beam generating unit that generates and emits an arrayed laser beam in which laser beams are arrayed, and an optical unit on which the arrayed laser beam is incident. The optical unit includes a polarizing beam splitter and a wave plate that is integrated with the polarizing beam splitter by being bonded by diffusion bonding to a first incident surface of the polarizing beam splitter on which the arrayed laser beam is incident. The polarizing beam splitter and the wave plate are formed into a rectangular parallelepiped in which a first dimension in a direction perpendicular to the array direction of the arrayed laser beam at the first incident surface and a second incident surface of the wave plate on which the arrayed laser beam is incident is smaller than a second dimension in the array direction.

The laser modules according to each embodiment will be described in detail below with reference to the attached drawings.

First Embodiment
1, a laser module 100 according to the first embodiment includes chip-on-submounts (hereinafter, COS) 1a to 1k and 1m in a housing 10. An unspecified COS among COS 1a to 1m will be referred to as COS 1. Each COS 1 includes a laser diode 2 that emits a laser beam. The laser diodes 2 of COS 1a to 1f emit laser beams that mainly include P-polarized light in the +X direction, and the laser diodes 2 of COS 1g to 1m emit laser beams that mainly include P-polarized light in the -X direction. The laser beams emitted from the laser diode 2 of each COS 1 have the same wavelength.

COS 1a to 1f are fixed to placement surfaces 6a to 6f, respectively, which are provided in a stepped manner on the bottom surface of the housing 10. Of the placement surfaces 6a to 6f, placement surface 6a is at the highest position, and the surfaces decrease in order from placement surface 6a to placement surface 6f. COS 1g to 1k and 1m are fixed to placement surfaces 6g to 6k and 6m, respectively, which are provided in a stepped manner on the bottom surface of the housing 10. Of the placement surfaces 6g to 6k and 6m, placement surface 6g is at the highest position, and the surfaces decrease in order from placement surface 6g to placement surface 6m.

Fast axis collimating lenses 3a to 3f are arranged on each end face of COS 1a to 1f so as to face the laser diode 2. Fast axis collimating lenses 3g to 3k and 3m are arranged on each end face of COS 1g to 1k and 1m so as to face the laser diode 2. A fast axis collimating lens that does not specify which of the fast axis collimating lenses 3a to 3m it is will be referred to as a fast axis collimating lens 3. The exit surface of each fast axis collimating lens 3 has a curved surface that collimates the laser beam in the fast axis direction.

Slow-axis collimating lenses 4a to 4f and mirrors 5a to 5f are fixed to the arrangement surfaces 6a to 6f, respectively. Slow-axis collimating lenses 4g to 4k and 4m and mirrors 5g to 5k and 5m are fixed to the arrangement surfaces 6g to 6k and 6m, respectively. A slow-axis collimating lens that does not specify which of the slow-axis collimating lenses 4a to 4m is referred to as a slow-axis collimating lens 4, and a mirror that does not specify which of the mirrors 5a to 5m is referred to as a mirror 5. The exit surface of each slow-axis collimating lens 4 has a curved surface that collimates the laser beam in the slow-axis direction.

The laser beams collimated in both the fast axis direction and the slow axis direction by each fast axis collimating lens 3 and each slow axis collimating lens 4 are reflected by each mirror 5 and their traveling direction is bent by 90 degrees. Since mirrors 5a to 5f are arranged on stepped arrangement surfaces 6a to 6f, the laser beams emitted in the +Y direction from mirrors 5a to 5f become a first arranged laser beam that travels in an array in the height direction. Similarly, since mirrors 5g to 5m are arranged on stepped arrangement surfaces 6g to 6m, the laser beams emitted in the +Y direction from mirrors 5g to 5m become a second arranged laser beam that travels in an array in the height direction.

COS 1a-1f, fast axis collimating lenses 3a-3f, slow axis collimating lenses 4a-4f, and mirrors 5a-5f constitute a first array laser beam generating unit 21 that generates and emits a first array laser beam. COS 1g-1m, fast axis collimating lenses 3g-3m, slow axis collimating lenses 4g-4m, and mirrors 5g-5m constitute a second array laser beam generating unit 22 that generates and emits a second array laser beam.

A triangular prism-shaped mirror 11, an optical unit 123 in which a polarizing beam splitter 12 and a half-wave plate 13 are integrated, a wavelength stabilizing element 14, a fast-axis focusing lens 15, and a slow-axis focusing lens 16 are fixed to the bottom surface of the end of the +Y direction of the housing 10. The polarizing beam splitter 12 and the half-wave plate 13 are optical components. The second array laser beam, which is mainly P-polarized light and is emitted from the second array laser beam generating unit 22, is reflected by the optical thin film 11a of the mirror 11, and its traveling direction is bent by 90 degrees, and it enters the polarizing beam splitter 12. The optical thin film 11a is made of a dielectric multilayer film. The second array laser beam reflected by the mirror 11 passes through the optical thin film 12a of the polarizing beam splitter 12 and travels in the -X direction.

The first array laser beam, which is emitted from the first array laser beam generating unit 21 and contains mainly P-polarized light, is incident on the half-wave plate 13 and converted to mainly S-polarized light. The first array laser beam, which has been converted to mainly S-polarized light, is reflected by the optical thin film 12a of the polarizing beam splitter 12, and its traveling direction is bent by 90 degrees and travels in the -X direction. A composite array laser beam, which is a combination of the first array laser beam and the second array laser beam, is emitted from the optical unit 123.

The composite array laser beam is incident on the wavelength stabilizing element 14 to stabilize the wavelength, and is focused in the fast axis direction and the slow axis direction by the fast axis focusing lens 15 and the slow axis focusing lens 16. The wavelength of the laser beam is arbitrary. An optical fiber 18 is attached to the housing 10 via a cylindrical fiber holding portion 17. The focused composite array laser beam is incident on the end face 18e of the optical fiber 18 and transmitted.

The laser beams emitted from the laser diode 2 of each COS1 and incident on the optical fiber 18 have different optical path lengths. Each laser beam emitted from the laser diode 2 of COS1a to 1f is transmitted without being impeded by optical components for other laser beams, and is transmitted as a first arrayed laser beam arranged so as not to interfere with each other. Preventing the progression of a laser beam from being impeded by optical components for other laser beams means, for example, preventing the progression of the laser beam emitted from COS1a from being impeded by mirrors 5b to 5f.

In addition, each laser beam emitted from the laser diodes 2 of COS 1g to 1m is transmitted without being impeded by optical components for other laser beams, and is transmitted as a second array laser beam arranged so as not to interfere with each other. Therefore, the composite array laser beam generated by the laser module 100 is highly efficient.

In the laser module 100 configured as above, the optical unit 123 is preferably configured as follows. The polarizing beam splitter 12 is made of colorless optical glass, and the half-wave plate 13 is made of quartz. Therefore, the polarizing beam splitter 12 and the half-wave plate 13 are made of different materials, and therefore have different thermal expansion coefficients. An adhesive may be used to join two members with different thermal expansion coefficients. However, since a high-power laser beam is incident on the optical unit 123, if the polarizing beam splitter 12 and the half-wave plate 13 are joined with an adhesive, the adhesive will burn out. Therefore, it is not appropriate to use an adhesive to join the polarizing beam splitter 12 and the half-wave plate 13.

As a direct bonding method for two components such as glass without using adhesive, optical contact is sometimes used, which utilizes the molecular attraction between the two components to bond the two components. However, because optical contact has a weak bonding strength, if optical contact is used to bond the polarizing beam splitter 12 and the 1/2 wavelength plate 13, which have different thermal expansion coefficients, the bonded 1/2 wavelength plate 13 will peel off due to temperature changes that rise to nearly 100 degrees.

Therefore, in the first embodiment, the polarizing beam splitter 12 and the half-wave plate 13 are bonded together using diffusion bonding, in which the polarizing beam splitter 12 and the half-wave plate 13 are heat-treated at a high temperature at which atomic diffusion occurs at the bonding surface between them. If the surface of the polarizing beam splitter 12 on which the first array laser beam is incident is defined as the first incident surface, the half-wave plate 13 is bonded to the first incident surface by diffusion bonding, and is integrated with the polarizing beam splitter 12.

In the first embodiment, instead of disposing the polarizing beam splitter and the half-wave plate at a distance from each other as described in Patent Document 1, the laser module 100 can be made smaller by using an optical unit 123 in which the polarizing beam splitter 12 and the half-wave plate 13 are integrated. Moreover, since the polarizing beam splitter 12 and the half-wave plate 13 are integrated by diffusion bonding without using an adhesive, there is no problem with the adhesive being burned out, and there is almost no problem with the half-wave plate 13 peeling off due to high heat.

Furthermore, it is preferable to configure the optical unit 123 as follows. The surface of the half-wave plate 13 on which the first array laser beam is incident is the second incident surface. As shown in FIG. 2, the width of the first incident surface of the polarizing beam splitter 12 and the second incident surface of the half-wave plate 13 is W1, and the height is H1. The width W1 is the first dimension between both ends in the direction perpendicular to the array direction of the first array laser beam on the first and second incident surfaces. The height H1 is the second dimension between both ends in the array direction on the first and second incident surfaces. The optical unit 123 is a rectangular parallelepiped with the width W1 (first dimension) smaller than the height H1 (second dimension).

A typical polarizing beam splitter is a cube type. If a cube type polarizing beam splitter is used as the polarizing beam splitter to which the arranged laser beams are incident, the installation area on the bottom surface of the housing 10 increases as the number of arrangements increases, and the laser module 100 cannot be made compact. By making the optical unit 123 a rectangular parallelepiped, it is possible to make the laser module 100 compact.

In FIG. 2, it is preferable that the width W1 is the same as the third dimension, which is the width in a direction perpendicular to the array direction of the first array laser beam. In the example shown in FIG. 1, the height H1 may be set to a height that allows six laser beams to be incident in the height direction of the first array laser beam. By making the width W1 of the optical unit 123 the same as the width of the first array laser beam, the installation area on the bottom surface of the housing 10 can be minimized, and the laser module 100 can be further miniaturized.

Second Embodiment
3, the first array laser beam generating unit 23 includes nine sets of a COS 1, a fast axis collimating lens 3, a slow axis collimating lens 4, and a mirror 5. The second array laser beam generating unit 24 also includes nine sets of a COS 1, a fast axis collimating lens 3, a slow axis collimating lens 4, and a mirror 5.

The first array laser beam generating unit 23 generates and emits a first array laser beam, similar to the first array laser beam generating unit 21 in FIG. 1. The second array laser beam generating unit 24 generates and emits a second array laser beam, similar to the second array laser beam generating unit 22 in FIG. 1. Each laser beam constituting the first and second array laser beams is transmitted without being impeded by optical components for other laser beams, and is arranged so as not to interfere with each other. In FIG. 3, the housing 10 is not shown.

The first array laser beam is reflected by mirror 31, its traveling direction is bent by 90 degrees, and enters optical unit 123'. The second array laser beam is reflected by mirror 32, its traveling direction is bent by 90 degrees, and enters optical unit 123'. Optical unit 123' includes polarizing beam splitter 12' and 1/2 wavelength plate 13', and 1/2 wavelength plate 13' is bonded to the first entrance surface of polarizing beam splitter 12' by diffusion bonding, integrating the two. The first array laser beam and the second array laser beam enter 1/2 wavelength plate 13' in a state where they are aligned in a direction perpendicular to the laser beam array direction.

The first and second arrayed laser beams are reflected by the optical thin film 12a' of the polarizing beam splitter 12' and their direction of travel is bent by 90 degrees.

As shown in FIG. 4, the width of the first incident surface of the polarizing beam splitter 12' and the second incident surface of the 1/2 wavelength plate 13' are W2 and H2, respectively. The width W2 is a first dimension between both ends of the first and second incident surfaces in a direction perpendicular to the arrangement direction of the first and second arrayed laser beams. The height H2 is a second dimension between both ends of the first and second incident surfaces in the arrangement direction. The optical unit 123' is a rectangular parallelepiped with the width W2 (first dimension) smaller than the height H2 (second dimension). By making the optical unit 123' a rectangular parallelepiped, it is possible to miniaturize the laser module 200.

In FIG. 4, it is preferable that the width W2 is the same as the fourth dimension in the direction perpendicular to the arrangement direction of the first and second arrayed laser beams. In the example shown in FIG. 3, the height H2 may be set to a height that allows nine laser beams to be incident in the height direction of the first and second arrayed laser beams. By making the width W2 of the optical unit 123' the same as the width of the first and second arrayed laser beams, the installation area on the bottom surface of the housing 10 can be minimized, and the laser module 200 can be further miniaturized.

As an example, when the width and height of the aligned first and second arrayed laser beams are 16 mm and 32 mm, the width W2 may be 16 mm and the height H2 may be 35 mm. The height H2 may also be 32 mm. Note that, since there is naturally an error in the dimensions, even when the width W2 is set to the same width as the aligned first and second arrayed laser beams, there may be a deviation of about ±0.1 mm. Even in such a case, it can be said that the width W2 is the same width as the aligned first and second arrayed laser beams.

In the second embodiment described above, two aligned laser beams are incident on the optical unit 123' in a lined up state, but three or more aligned laser beams may be incident on the optical unit in a lined up state. Even in this case, it is preferable to make the width of the optical unit the same as the width of the aligned aligned laser beams.

In the first and second embodiments described above, the wavelength plate is a 1/2 wavelength plate 13, and an optical unit 123 is used in which the polarizing beam splitter 12 and the 1/2 wavelength plate 13 are integrated. Even in a configuration using an optical unit in which the polarizing beam splitter 12 and a 1/4 wavelength plate or 1/8 wavelength plate are integrated, the laser module can be made smaller by making the optical unit a rectangular parallelepiped. A 1/4 wavelength plate is an optical component that converts linearly polarized light into circularly polarized light, and a 1/8 wavelength plate is an optical component that converts circularly polarized light into elliptically polarized light.

Even in an optical unit in which the polarizing beam splitter 12 and a quarter-wave plate or a one-eighth-wave plate are integrated, the width of the rectangular parallelepiped can be made the same as the width of the arrayed laser beam or the width of multiple aligned arrayed laser beams, making it possible to further miniaturize the laser module.

The present invention is not limited to one or more of the embodiments described above, and various modifications are possible within the scope of the present invention. In the laser modules 100 and 200 shown in FIG. 1, the bottom surface of the housing 10 is a horizontal plane, so the dimension in the vertical direction perpendicular to the horizontal plane is expressed as the height, and the dimension in the direction parallel to the horizontal plane is expressed as the width. Depending on how the laser module 100 is arranged, the dimension in a direction different from the case where the bottom surface of the housing 10 is a horizontal plane may be referred to as the height or width. Regardless of how the laser module 100 is arranged, the dimension in the direction perpendicular to the arrangement direction of the arrayed laser beams at the first and second incident surfaces of the polarizing beam splitter 12 or 12' and the wave plate (1/2 wave plate 13 or 13') is the first dimension, and the dimension in the arrangement direction is the second dimension. The dimension in the direction perpendicular to the arrangement direction of the arrayed laser beams is the third dimension, and the dimension in the direction perpendicular to the arrangement direction of the aligned first and second arrayed laser beams is the fourth dimension.

REFERENCE SIGNS LIST 1, 1a to 1k, 1m Chip-on submount 2 Laser diode 3, 3a to 3k, 3m Fast axis collimating lens 4, 4a to 4k, 4m Slow axis collimating lens 5, 5a to 5k, 5m, 11 Mirror 10 Housing 12 Polarizing beam splitter 13 ½ wavelength plate 14 Wavelength stabilizing element 15 Fast axis focusing lens 16 Slow axis focusing lens 17 Fiber holding section 18 Optical fiber 21, 23 First array laser beam generating section 22, 24 Second array laser beam generating section 100, 200 Laser module 123 Optical unit

Claims (3)

an arrayed laser beam generating unit that generates and emits an arrayed laser beam in which laser beams are arrayed;
an optical unit onto which the array laser beam is incident;
Equipped with
The optical unit includes a polarizing beam splitter and a wave plate that is integrated with the polarizing beam splitter by being bonded by diffusion bonding to a first incident surface of the polarizing beam splitter on which the array laser beam is incident;
A laser module, wherein the polarizing beam splitter and the wave plate are formed into a rectangular prism having a first dimension in a direction perpendicular to the arrangement direction of the arrayed laser beams at the first incident surface and a second incident surface of the wave plate on which the arrayed laser beams are incident, which is smaller than a second dimension in the arrangement direction. The laser module according to claim 1, wherein the polarizing beam splitter and the wave plate are formed as a rectangular parallelepiped in which the first dimension at the first and second incident surfaces is the same as a third dimension in a direction perpendicular to the array direction of the arrayed laser beams. As the array laser beam generating unit,
a first array laser beam generating unit that generates and emits a first array laser beam in which laser beams are arrayed in the array direction;
a second array laser beam generating unit that generates and emits a second array laser beam in which laser beams are arrayed in the array direction;
Equipped with
The first arrayed laser beam and the second arrayed laser beam are incident on the polarizing beam splitter and the wave plate in a state where they are aligned in a direction perpendicular to the array direction,
3. The laser module of claim 2, wherein the polarizing beam splitter and the wave plate are formed as a rectangular prism having a first dimension at the first and second incident surfaces that is the same as a fourth dimension in a direction perpendicular to the arrangement direction of the aligned first and second arrayed laser beams.

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