JP2002374031A - Convergence system for semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain miniaturization and increase in the output of laser light, and to provide degrees of freedom for alignment. SOLUTION: A convergence system 1 for semiconductor laser is provided with a semiconductor laser bar 20 for emitting a plurality of laser light, while being installed on an Si substrate 10, a rod lens 30 for controlling the focal distance of laser light emitted from the semiconductor laser bar 20, an optical waveguide device 40 for converging the laser light from the rod lens 30, a plurality of optical fibers 50 for guiding the laser light from the optical waveguide device 40, and a condenser lens 60 for converging the laser light emitted from each of the optical fibers 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a condensing system for a semiconductor laser, and more particularly to a condensing system for a semiconductor laser for condensing laser light using an optical waveguide.

[0002]

2. Description of the Related Art In Japanese Patent Application Laid-Open No. 5-93828, the emission surfaces 12, 14, 1 of a laser diode bar 10 are shown in FIG.
6, the optical fibers 18, 20, 22 of the optical fiber bundle 24;
Accordingly, a technique for condensing a laser beam to increase the density (hereinafter, referred to as “prior art 1”) has been proposed.

However, since the laser diode bar 10 has a large number of emission surfaces, one emission surface is provided for all the emission surfaces.
Connecting optical fibers one by one is very cumbersome and limits the number of optical fibers that can be connected to the emission surface. Therefore, even if an optical fiber is connected to the emission surface to condense laser light, there is a limit in the energy density of the condensed laser light.

On the other hand, when trying to collect the laser light emitted from many emission surfaces, the outer diameter of the optical fiber bundle 24 becomes large, and it becomes difficult to collect the laser light in practical use. That is, in order to reduce the size of the light focusing system, it is desirable that the outer diameter of the optical fiber bundle be small.

On the other hand, in Japanese Patent Application Laid-Open No. Hei 7-168040, as shown in FIG. 2 of the publication, semiconductor lasers (laser bars) 1b having a plurality of light sources are stacked, and light emitted from the stacked semiconductor lasers 1b is emitted. an optical splitter 2b ₁ for focusing in the transverse direction, the semiconductor laser light collector comprising an optical splitter 2b ₂ for focusing the light emitted from the optical splitter 2b ₁ in the vertical direction (hereinafter referred to as "prior art 2". ) Has been proposed.

However, the conventional art 2, the optical axis adjustment of the laser beam to match the emitting position of the laser beam of the stacked semiconductor laser 1b, the optical splitter 2b ₁ and the incident position of the laser beam with high precision There is a need. Furthermore, the semiconductor laser 1 after optical axis adjustment, the optical splitter 2b ₁ and the optical splitter 2
It is also difficult to hold the arrangement state of b _2. For this reason, misalignment of the positions at the connection portions is likely to occur, and as a result, there is a problem that the laser light cannot be efficiently collected.

Japanese Unexamined Patent Application Publication No. 2000-19362 discloses an array type semiconductor laser coupling device (hereinafter referred to as “prior art 3”) provided with a light concentrator 10 for converging laser light emitted from each light emitting portion of the array type semiconductor laser. ").).

However, in the prior art 3, as the number of semiconductor lasers increases, the length of the optical concentrator 10 in the longitudinal direction (the direction parallel to the direction of incidence of the laser beam) increases, which cannot be accommodated in a practical size. There is a problem of not being large. In order to shorten the longitudinal direction of the optical concentrator 10, it is necessary to sharply bend the optical waveguide formed in the optical concentrator, but if it is sharply bent, there is a problem that the radiation loss of laser light increases.

SUMMARY OF THE INVENTION The present invention has been proposed to solve the above-mentioned problem, and has a small size, a high output of laser light, and a degree of freedom of alignment for a semiconductor laser. The purpose is to provide.

[0010]

According to the first aspect of the present invention,
A semiconductor laser having a plurality of light-emitting sources or a plurality of semiconductor lasers having a single light-emitting source; a laser light incident portion formed on one end face; and a laser light incident portion formed on the other end face and being incident on each laser light incident portion. An optical waveguide device having an optical waveguide formed with at least one laser light emitting unit for combining and emitting laser light from each of the light emitting sources; a semiconductor laser and the optical waveguide having a cooling function; An installation board on which the device is installed.

According to the first aspect of the present invention, the optical waveguide provided in the light converging device may be a Y-branch type or a taper type. Then, the semiconductor laser and the optical waveguide device are installed on the installation substrate having a cooling function, whereby the semiconductor laser and the optical waveguide device are directly cooled simultaneously. As a result, the semiconductor laser can obtain high output oscillation characteristics, and the optical waveguide device can suppress damage due to heat.

According to a second aspect of the present invention, in the first aspect of the present invention, a plurality of optical fibers, one end of which is connected to each of the laser light emitting portions, and which emits laser light from the other end, A condenser lens for condensing the laser light emitted from the other end of the fiber.

According to the second aspect of the present invention, since the laser light can be guided to the condenser lens by using the optical fiber, the high density of the laser light can be obtained even if the laser light emitting portions of the optical waveguide device are far apart. Can be achieved.

According to a third aspect of the present invention, in the second aspect of the present invention, the installation substrate is provided with a guide groove at or near an optical axis of laser light emitted from each laser light emitting portion of the optical waveguide device. The optical fiber holding member is formed with the optical fiber, and one end of the optical fiber is aligned with the guide groove.

According to the third aspect of the present invention, since the guide groove can be easily formed with high precision on the optical fiber holding member, the optical waveguide device and the optical fiber can be positioned with high precision. , High efficiency coupling can be performed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, a semiconductor laser condensing system 1 according to an embodiment of the present invention includes a semiconductor laser bar 20 that emits a plurality of laser beams while being mounted on a Si substrate 10; A rod lens 30 for adjusting the focal length of the laser light emitted from the laser bar 20, and an optical waveguide device 4 for focusing the laser light from the rod lens 30
0, a plurality of optical fibers 50 for guiding the laser light from the optical waveguide device 40, and a condenser lens 60 for condensing the laser light emitted from each optical fiber 50.

The Si substrate 10 is formed precisely in a plate shape. Therefore, when the semiconductor laser bar 20 and the optical waveguide device 40 are arranged on the main surface 11, the Si substrate 10 precisely regulates the position of the laser bar 20 and the optical waveguide device 40 in the height direction.

As shown in FIG. 2A, on the main surface 11 of the Si substrate 10 and between the semiconductor laser bar 20 and the optical waveguide device 40, the laser light emitted from the semiconductor laser bar 20 Along the direction perpendicular to the optical axis,
A concave groove 12 is formed. The length of the concave groove 12 in the width direction is smaller than the diameter of the rod lens 30. Then, the rod lens 30 is arranged on the concave groove 12 and its position is regulated.

Furthermore, the Si substrate 10 has good thermal conductivity, and is directly cooled by a plate-shaped cooling substrate 13 as shown in FIG. The cooling board 13 is provided with a water passage (not shown) through which the cooling medium passes. The refrigerant supply device 14 supplies the refrigerant to the cooling board 13 via the refrigerant hose 15 and the refrigerant input / output port 16, and sends the used refrigerant to the output port 17 and the refrigerant hose 1.
8 and supply the cooling medium to the cooling substrate 13 again. Thereby, the cooling substrate 13 can always cool the Si substrate 10.

Therefore, the Si substrate 10 is
3, the semiconductor laser bar 20 and the optical waveguide device 40 can be sufficiently cooled. As a result, it is possible to reduce an increase in the laser oscillation threshold of the semiconductor laser bar 20 and damage to the optical waveguide device 40 due to heat.

The coolant substrate 13 is made of Si
Although a water-cooling type for cooling the substrate 10 is used, an air-cooling type for cooling the Si substrate 10 by cooling fins may be used.

The semiconductor laser bars 20 are arranged on the Si substrate 10 at predetermined intervals in a direction orthogonal to the optical axis of the laser light. The semiconductor laser bar 20 is driven by a drive power supply supplied from a drive power supply 21, and emits laser light from a plurality of laser light emission units 22 in the same direction as shown in FIG.

As shown in FIG. 2A, the position of the rod lens 30 is regulated by the concave groove 12 formed in the Si substrate 10, and the rod lens 30 focuses the laser light emitted from the semiconductor laser bar 20 to determine the focal position. The adjusted laser light is incident on the optical waveguide device 40.

Here, the laser beam has a divergence angle of θ 速 in the fast axis direction and θ // (<θ⊥) in the slow axis direction, and directly couples the semiconductor laser bar 20 and the optical waveguide device 40. However, sufficient coupling efficiency cannot be obtained. Therefore, the rod lens 30 installed between the semiconductor laser bar 20 and the optical waveguide device 40 converts the spot diameter and the spread angle of the laser beam in the fast axis direction.

Since the beam divergence angle θ // is generally small (about 10 ° in FWHM), highly efficient coupling can be realized only by shortening the distance between the semiconductor laser bar 20 and the optical waveguide device 40. On the other hand, the beam spread angle θ
Since ⊥ is not as small as the beam divergence angle θ // (FWHM
, The diameter of the rod lens 30 must be reduced. Therefore, the semiconductor laser bar 20 and the optical waveguide device 40 are brought extremely close to each other, and the rod lens 3
It is necessary to reduce the diameter of 0.

Assuming that the focal length of the rod lens 30 is f, the refractive index of the medium of the rod lens 30 is n, and the radius of the rod lens 30 is r, the focal length f is expressed by equation (1).

[0028]

(Equation 1)

As shown in FIG. 2B, the width of the emitter (length in the width direction of the active layer) in the semiconductor laser bar 20 is w _LD , the width of the optical waveguide 42 is W _g , Assuming that the distance between the rod lenses 30 is S ₁ , the distance between the rod lens 30 and the optical waveguide device 40 is S ₂ , and the incident angle that can propagate in the optical waveguide is θ, equation (2) holds.

[0030]

(Equation 2)

From the equation (2), the radius r needs to approximately satisfy the following equation (3).

[0032]

(Equation 3)

According to the equation (2), the distances S ₁ and S ₂ need to satisfy the following equation (4).

[0034]

(Equation 4)

As described above, the rod lens 30 is disposed on the Si substrate 10 so as to satisfy the equations (3) and (4).

As shown in FIG. 4, in the optical waveguide device 40, a Y-branch type optical waveguide 42 is formed on an optical waveguide substrate 41 formed as a whole in a flat plate shape. Optical waveguide 4
2 is SiO ₂ as a cladding material and G as a core material.
It has a step index structure using SiO ₂ to which eO ₂ is added.

The optical waveguide 42 is formed on a plurality of laser light incident portions 43 to which the laser light from the rod lens 30 is input, and on the other end side of the laser light incident portion 43 and is incident from the laser incident port 33. A laser light emitting unit 44 for emitting laser light.

Each laser beam incident portion 43 is provided at one end of the optical waveguide 42 at each laser emitting portion 22 of the semiconductor laser bar 20.
Respectively. Optical waveguide 4
2 are linearly formed in parallel with each other from the laser beam incident portions 43, and further gather at the center as the laser beam travels, and are joined at a joint point 45; Are formed in a straight line. Therefore, the laser light incident from each laser light incident part 43 propagates inside the optical waveguide 42 and is coupled at the coupling point 45,
The light is emitted from the laser light emitting unit 44. Note that a plurality of such optical waveguides 42 are formed in a direction perpendicular to the optical axis of the laser light emitted from the semiconductor laser bar 20.

The optical waveguide device 40 is a PLC (Planar
Lightwave Circuit) technology and are patterned with very high precision. Here, the PLC technique is a technique based on a technique for producing an optical fiber, and refers to a technique for producing an optical circuit on a flat substrate. In general,
A light guide path is formed by producing a SiO ₂ film on a Si substrate or a quartz substrate, and a film in which a small amount of a TiO ₂ film, a GeO ₂ film, or the like is added to the SiO ₂ film. Note that the method of manufacturing the optical waveguide device 40 is not limited to the PLC technique, but may use an ion exchange method, a thermal diffusion method, or the like. Therefore, only by integrally fixing the semiconductor laser bar 20 and the optical waveguide device 40 on the Si substrate 10, they can be aligned and coupled with high precision.

The optical fiber 50 is connected to the optical waveguide device 40.
And the same number as the respective laser light emitting portions 44.
The laser beam incident side of the optical fiber 50 is fixed by an optical fiber holding member 55 as shown in FIG.

The optical fiber holding member 55 is made of the Si substrate 10
Of the optical waveguide device 40 on the side of the laser light emitting section 44. The optical fiber holding member 55 has a V-shaped groove 56 formed at or near the optical axis of the laser light emitted from the laser light emitting section 44. Then, by aligning the laser beam incident side of the optical fiber 50 with the V-shaped groove 56, three-dimensional optical axis adjustment between the optical waveguide device 40 and the optical fiber 50 becomes unnecessary.
Passive alignment becomes possible.

In order to manufacture the optical waveguide 42 with high accuracy, it is preferable that the V-shaped groove 56 is formed by laser ablation and the end face treatment of the optical waveguide 42 is performed by a dicing saw. Alternatively, an optical fiber array may be manufactured so as to match each laser light emitting portion 44 of the optical waveguide 42, and the optical fiber array may be connected. Conversely, the V of the optical fiber holding member 55 is adjusted to match the optical fiber array.
The groove 56 may be formed.

The laser light incident from the laser light incident side of the optical fiber 50 is emitted from the laser light emission side. As described above, the laser light emitted from the optical waveguide device 40 is condensed by the condenser lens 60 via the optical fiber 50, so that the optical waveguide device 40 and the condenser lens 6
The degree of freedom of the positional relationship of 0 is sufficient, and miniaturization can be easily achieved.

As described above, the condensing system 1 for a semiconductor laser according to the embodiment of the present invention includes the semiconductor laser bar 20 and
Since the optical waveguide device 40 and the Si substrate 10 having the optical fiber holding member 55 can be each processed with high precision by a fine processing step, high-precision position adjustment by passive alignment can be performed. An efficient combination can be obtained. Further, by attaching a marker for alignment to the Si substrate 10, the semiconductor laser bar 20, and the optical waveguide device 40, the alignment can be easily performed.

The condensing system 1 for a semiconductor laser is provided with a rod lens 30 between the semiconductor laser bar 20 and the optical waveguide device 40, so that the
Can be coupled to the optical waveguide device 40 with high efficiency.

The present invention is not limited to the above-described embodiment, but can be applied to, for example, the following cases.

In the above-described embodiment, as shown in FIG. 6, the laser light emitting side of the optical fiber 50 is bundled, and the laser light emitted from the optical fiber 50 is condensed by the condenser lens 60. The following may be adopted. For example, as shown in FIG. 7, laser light emitted from a plurality of optical fibers 50 may be coupled to a large-diameter optical fiber 58, guided to a processing point, and condensed by a condenser lens 60. Note that the optical fiber 50 and the large-diameter optical fiber 58 may be coupled using a butt joint or a lens.

Further, for example, the light condensing system 1 for semiconductor lasers may be arranged in several stages in the vertical direction.
And the diameter of the bundle of optical fibers 50 increases. Thus, as shown in FIG. 8, the bundled optical fibers 50 may be stretched while being kept at a high temperature to have a gentle taper shape. Thus, the outer diameter of the optical fiber 50 can be reduced, and the output of the laser can be increased.

In the above description, the optical waveguide 42 has the step index structure. However, the optical waveguide 42 is not particularly limited as long as it is a low-loss optical waveguide. In addition, the addition amount of GeO _{2 as} a core material is gradually increased. The refractive index distribution structure may be changed. Note that the refractive index distribution structure may be formed by forming a film having a different composition and then forming a refractive index distribution by thermal diffusion, or by forming the film while gradually changing the refractive index. You may. Further, the optical waveguide 42 for multiplexing has a structure based on the Y branch, but may have a tapered structure.

In the above-described embodiment, the rod lens 30 is provided between the semiconductor laser bar 20 and the optical waveguide device 40.
As shown in (5), a distributed index lens 35 may be provided.
Thereby, the laser light emitted from the semiconductor laser bar 20 can be coupled to the optical waveguide device 40 with high efficiency.

Further, as shown in FIG. 10, the semiconductor laser bar 20 and the optical waveguide device 40 may be a simple butting connection. Alternatively, the semiconductor laser bar 20
Between the semiconductor laser bar 2 and the optical waveguide device 40.
A lens (for example, a refractive index distribution lens, a cylindrical lens, or the like) that increases the coupling efficiency by converting the numerical aperture (NA) of the laser light from 0 may be used.

Further, in this embodiment, the Si substrate 10
The semiconductor laser bar 20 and the optical waveguide device 40 are provided on the main surface 11 of the present invention, but the present invention is not limited to this. For example, the optical waveguide device 40 may be manufactured first, the dielectric constituting the optical waveguide 42 may be removed from the optical waveguide substrate 41, and the semiconductor laser bar 20 may be installed in the portion where the dielectric has been removed.

[0053]

According to the first aspect of the present invention, a semiconductor laser and an optical waveguide device are simultaneously cooled directly by providing a cooling board and having an installation substrate on which the semiconductor laser and the optical waveguide device are installed. Accordingly, high output oscillation characteristics can be obtained, and damage of the optical waveguide device due to heat can be suppressed.

According to a second aspect of the present invention, there are provided a plurality of optical fibers each having one end connected to each of the laser light emitting portions and emitting laser light from the other end, and a laser emitted from the other end of the plurality of optical fibers. By providing a condensing lens for condensing light, laser light can be guided to the condensing lens using an optical fiber. Density can be increased.

According to a third aspect of the present invention, the installation substrate includes an optical fiber holding member having a guide groove formed at or near the optical axis of laser light emitted from each laser light emitting portion of the optical waveguide device. Since one end of the optical fiber is aligned with the guide groove, the optical waveguide device and the optical fiber can be aligned with high accuracy, and highly efficient coupling can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a condensing system for a semiconductor laser according to an embodiment of the present invention.

FIG. 2 (a) is a view showing a structure of a semiconductor laser focusing system 1;
FIG. 2 is a cross-sectional view of an i-substrate, a semiconductor laser bar, a rod lens, and an optical waveguide device, and FIG. 2B is a front view of a Si substrate, a semiconductor laser bar, a rod lens, and an optical waveguide device that constitute a condensing system 1 for a semiconductor laser.

FIG. 3 is a schematic perspective view of a semiconductor laser bar.

FIG. 4 is a diagram for explaining an optical waveguide formed in the optical waveguide device.

FIG. 5 is a diagram for explaining a state in which an optical fiber is aligned with a V-shaped groove of an optical fiber holding member.

FIG. 6 is a diagram illustrating a state in which laser light emitted from a plurality of optical fibers is condensed by a condenser lens.

FIG. 7 shows laser light emitted from a plurality of optical fibers,
FIG. 4 is a diagram for explaining a state where light is condensed by a condensing lens via a large-diameter optical fiber.

FIG. 8 is a diagram for explaining a state in which laser light emitted from a plurality of tapered optical fibers is condensed by a condenser lens and guided by a large-diameter optical fiber.

FIG. 9 shows S between the semiconductor laser bar and the optical waveguide device.
It is a figure for explaining the state where the distributed index lens was installed on the i substrate.

FIG. 10 is a diagram for explaining a state in which a semiconductor laser bar and an optical waveguide device are directly attached to each other.

[Explanation of symbols]

 Reference Signs List 10 Si substrate 20 Semiconductor laser bar 30 Rod lens 40 Optical waveguide device 50 Optical fiber 60 Condensing lens

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Morihiro Matsuda 41-Cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Laboratory, Inc. 41, Yokomichi, No. 1 F-term in Toyota Central R & D Laboratories Co., Ltd. (Reference) 2H037 AA04 BA02 BA03 BA05 BA22 DA04 DA06 DA12 DA18 DA38 2H047 LA12 MA03 MA05 MA07 RA00 TA32 5F073 AB04 AB27 AB28 EA24 EA28 FA13 FA26

Claims (3)

[Claims] 1. A semiconductor laser having a plurality of light emitting sources or a plurality of semiconductor lasers having one light emitting source; a laser beam incident portion formed on one end face; and a laser beam formed on the other end face. An optical waveguide device having an optical waveguide formed with one or more laser light emitting portions that combine and emit laser light from each of the light emitting sources incident on an incident portion; and the semiconductor having a cooling function. A condensing system for a semiconductor laser, comprising: a mounting substrate on which a laser and the optical waveguide device are mounted. 2. A plurality of optical fibers each having one end connected to each of the laser light emitting sections and emitting laser light from the other end, and condensing laser light emitted from the other end of the plurality of optical fibers. The condensing system for a semiconductor laser according to claim 1, further comprising: 3. The installation substrate includes an optical fiber holding member having a guide groove formed at or near an optical axis of laser light emitted from each laser light emitting section of the optical waveguide device. 3. The light condensing system for a semiconductor laser according to claim 2, wherein one end of the light guide is aligned with the guide groove.