JP2007248581A - Laser module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser module with which a high output can be obtained and in which the overall size can be reduced. <P>SOLUTION: In the prior art, light emitted from each of a plurality of light sources is converted once into parallel light by a collimator lens, with the parallel light converged by a condensing lens and made incident on an optical fiber. In one embodiment, by properly setting a space between the optical axis J2 (center axis of emission) of the light sources 12 and the optical axis J3 (center axis) of a lens 22, the lens 22 can be substituted for the collimator lens and the condensing lens conventionally required for a laser module. Accordingly, the laser module 1 can reduce the number of components compared with a conventional optical system. Also, the laser module 1 can be miniaturized. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laser module, and more particularly to a laser module that can obtain high-power light by using a plurality of laser light sources and is miniaturized.

  Conventionally, lasers that convert infrared light from solid-state lasers excited by semiconductor lasers into third harmonics in the ultraviolet region, excimer lasers, Ar lasers, etc. are practically used as devices that generate ultraviolet laser beams. Has been.

  However, the excimer laser has a problem of high cost and maintenance due to its large size. In addition, since the wavelength conversion laser that converts infrared light into the third harmonic in the ultraviolet region has very low wavelength conversion efficiency, it is very difficult to obtain a high output. Moreover, the Ar laser has a very low electro-light efficiency of 0.005%.

  In view of this, an optical power combining optical system that condenses light from a plurality of light sources (for example, GaN-based semiconductor lasers) at one place and couples the light to an optical fiber or the like has been proposed. For example, Japanese Patent Application Laid-Open No. 2002-202442 (Patent Document 1) discloses a combined laser light source and an exposure apparatus using the combined laser light source.

  FIG. 20 is a diagram illustrating a configuration of a combined laser light source disclosed in Japanese Patent Laid-Open No. 2002-202442 (Patent Document 1).

  Referring to FIG. 20, this combined laser light source includes seven semiconductor lasers LD1 to LD7 arranged and fixed on a heat block 110, and collimator lenses 111 respectively provided corresponding to the semiconductor lasers LD1 to LD7. ˜117, one condenser lens 120, and one multimode optical fiber 130. Beams B1 to B7 emitted from the semiconductor lasers LD1 to LD7 are collimated by collimator lenses 111 to 117, respectively. The parallel beams B1 to B7 are collected by the condenser lens 120 and converge on the incident end face of the core 130a of the multimode optical fiber 130.

  The beams B <b> 1 to B <b> 7 that have entered the core 130 a are combined into a single beam B and emitted from the multimode optical fiber 130. Therefore, according to this laser light source, a high-power laser beam can be obtained.

  FIG. 21 is a diagram illustrating another configuration of the combined laser light source disclosed in Japanese Patent Laid-Open No. 2002-202442 (Patent Document 1).

  Referring to FIG. 21, this combined laser light source is composed of five semiconductor lasers LD11 to LD15 and a combined optical system 250. The semiconductor lasers LD11 to LD15 are arranged along an arc.

  The multiplexing optical system 250 is provided with condensing lenses H11 to H15 for condensing the beams B11 to B15 emitted from the semiconductor lasers LD11 to LD15, respectively. Each of the semiconductor lasers LD 11 to 15 is arranged so that its optical axis faces one point on one end surface of the core 251 a of the multimode optical fiber 251. The condensing lenses H11 to H15 are arranged to converge the beams B11 to B15 on this one point.

  The beams B11 to B15 incident on the core 251a are combined into one beam B10 and emitted from the multimode optical fiber 251. The maximum incident angle θ of the beams B11 to B15 is a value within the maximum light receiving angle corresponding to the NA (numerical aperture) of the multimode optical fiber 251.

Further, an optical power combining optical system disclosed in Japanese Patent Application Laid-Open No. 2005-114977 (Patent Document 2) is used as a combined laser light source disclosed in Japanese Patent Application Laid-Open No. 2002-202442 (Patent Document 1) from a collimating lens. The anamorphic optical element (for example, prism array etc.) for narrowing the width of the parallel light is combined. As a result, the optical power combining optical system disclosed in Japanese Patent Application Laid-Open No. 2005-114977 (Patent Document 2) can reduce the optical path length, and thus can be miniaturized.
JP 2002-202442 A JP 2005-149777 A

  The conventional optical system as shown in FIG. 20 and FIG. 21 needs to include a plurality of collimating lenses and one large-diameter condensing lens corresponding to each of the plurality of light sources. Therefore, these optical systems have a complicated structure due to the large number of parts. In these optical systems, a plurality of light sources are arranged one-dimensionally. Therefore, the aperture of the condenser lens must be increased as the number of light sources increases. In other words, the scale of these optical systems inevitably increases.

  Further, the optical fiber has a NA (numerical aperture) limit. In order to efficiently couple light to a light receiver having a NA limitation, it is necessary to make the NA of the condenser lens smaller than the NA of the light receiver. However, when a condensing lens having an NA smaller than the NA of the light receiver is used in the optical system, the diameter of the condensing lens increases and the focal length increases. This increases the size of the optical system.

  Furthermore, when the focal length of the condensing lens is increased, the diameter of the condensed light beam is also increased. For this reason, when light is to be coupled to a light receiver having a small light receiving area such as an optical fiber, it is likely that not all light enters the light receiving area.

  An object of the present invention is to provide a laser module that can obtain high-power light and can be miniaturized.

  In summary, the present invention is a laser module comprising a plurality of laser light sources, an optical fiber, and a plurality of lenses. The plurality of laser light sources are two-dimensionally arranged on the same plane and emit a plurality of laser beams, respectively. The optical fiber receives a plurality of laser beams. The plurality of lenses are provided corresponding to the plurality of laser light sources, respectively, and condenses the laser beams received from the corresponding laser light sources to be coupled to the end face of the optical fiber.

  Thereby, the laser module can obtain high power light. Further, it is easy to fix a plurality of laser light sources, and the optical system can be made small.

Preferably, each of the plurality of laser light sources is a surface emitting semiconductor laser.
In general, a surface emitting semiconductor laser has a smaller laser beam spread than an edge emitting semiconductor laser (in other words, the directivity of the laser beam is stronger). By using a surface emitting semiconductor laser for each of the plurality of laser light sources, the power of light output from the laser module can be increased as compared with the case of using an edge emitting semiconductor laser.

  More preferably, the plurality of laser light sources includes a first laser light source and a plurality of second laser light sources arranged to surround the first laser light source.

  By arranging the first laser light source and the second laser light source in this way, the laser beam can be converged on the incident end face of the optical fiber, so that the power of the light output from the laser module can be reduced. Can be increased.

  More preferably, the plurality of lenses includes a first lens and a plurality of second lenses. The first lens is provided corresponding to the first laser light source, and is arranged so that the central axis overlaps the optical axis of the first laser light source. The plurality of second lenses are provided corresponding to the plurality of second laser light sources, respectively, and are arranged so that the optical axis and the central axis of the corresponding second laser light sources are shifted.

  By appropriately setting the distance between the optical axis of the second laser light source and the optical axis of the second lens, the collimating lens and the condensing lens necessary for the conventional laser module can be obtained with the second lens. Can be substituted. Therefore, the laser module of the present invention can reduce the number of parts and can be miniaturized as compared with the conventional optical system.

Preferably, each of the plurality of lenses is a spherical lens.
By using a spherical lens for each of the plurality of lenses, the plurality of lenses can be easily arrayed. Therefore, high integration, that is, downsizing of the optical system can be achieved. Further, the cost of the optical system can be reduced by using a plurality of arrayed lenses.

Preferably, each of the plurality of lenses is a drum lens.
Compared to a spherical lens, the drum lens has fewer portions through which the laser beam from the light source does not pass. By using a drum lens for each of the plurality of lenses, the laser module can be made smaller than when a spherical lens is used.

Preferably, the plurality of lenses are integrated as a microlens array.
By integrating a plurality of lenses, it becomes possible to reduce the size of the optical system as compared with a case where a single lens is provided individually.

  According to the laser module of the present invention, light can be coupled to an optical fiber with high efficiency and downsizing can be achieved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

[Embodiment 1]
FIG. 1 is an overall view of the laser module according to the first embodiment.

  Referring to FIG. 1, a laser module 1 is an apparatus used for, for example, processing of products or soldering of components on a circuit board.

  The laser module 1 includes a light source 11 and a plurality of light sources 12 as a plurality of laser light sources. The laser module 1 includes a lens 21 and a plurality of lenses 22 as a plurality of lenses provided corresponding to each of the plurality of light sources. The lens 21 is provided corresponding to the light source 11, and the lens 22 is provided corresponding to the light source 12. The plurality of lenses 22 are provided around the lens 21. Details of the arrangement of the light source and the lens will be described later.

  The laser module 1 further includes an optical fiber 3. The laser beams emitted from the light sources 11 and 12 are condensed by the lenses 21 and 22 on the incident end face of the core of the optical fiber 3. The light reaching the incident end face from each light source propagates through the core, is combined into one laser beam, and is emitted from the optical fiber 3. Therefore, the laser module 1 can obtain high power light.

  The laser module 1 further includes a package 4. A package for mounting a power device can be applied to the package 4. FIG. 1 shows a TO-220 type package as a specific example of the package 4. In the package 4, the light sources 11 and 12 are arranged on the same plane (mounting surface 41). The portion of the mounting surface 41 is made of a material having high thermal conductivity (for example, Cu-W) in order to increase heat dissipation.

  For example, also in the configuration of the optical system shown in FIG. 21, the beam can be condensed on the optical fiber only by the combination of the semiconductor laser and the condenser lens. However, according to the configuration of FIG. 21, since the package for fixing and radiating the semiconductor laser is arranged on the arc, the scale of the optical system increases. On the other hand, in the laser module 1, since the light source 11 and the plurality of light sources 12 are two-dimensionally arranged on the same plane (mounting surface 41), the light sources 11 and 12 can be easily fixed and the optical system can be used. Can be small.

  The laser module 1 further includes a sleeve 5 for fixing the optical fiber 3 on the package 4.

  FIG. 2 is a diagram for explaining the positional relationship between the light source and the lens in the laser module 1 of FIG.

  Referring to FIG. 2, two light sources 12 are arranged on both sides of light source 11 with light source 11 as the center. A lens 21 is disposed corresponding to the light source 11, and a lens 22 is disposed corresponding to the light source 12. The light source 11 emits a beam B11, and the light source 12 emits a beam B12.

  The light source 11 and the lens 21 are arranged so that the optical axis of the light source 11 and the optical axis (center axis) of the lens 21 overlap. Each optical axis (indicated as optical axis J1 in FIG. 2) overlaps the central axis of the optical fiber 3. On the other hand, the optical axis J2 of the light source 12 and the optical axis J3 of the lens 22 are arranged so that their optical axes are shifted from each other. However, the distance between the optical axis J2 and the optical axis J3 is set so that the laser beam converges on the incident end face of the optical fiber 3. In the example of FIG. 2, the distance between the optical axis J2 and the optical axis J3 is about 0.2 mm.

  The distance from the light source 11 to the center of the lens 21 and the distance from the light source 12 to the center of the lens 22 are about 1.5 mm. The distance from each center of the lenses 21 and 22 to the incident end face of the optical fiber 3 is about 15 mm.

  In the prior art, light emitted from each of a plurality of light sources is once converted into parallel light by a collimating lens, and the parallel light is collected by a condenser lens and enters an optical fiber. In the first embodiment, the distance between the optical axis J2 (light emission central axis) of the light source 12 and the optical axis J3 (central axis) of the lens 22 is set appropriately, so that the collimating lens necessary for the conventional laser module is used. And the condensing lens can be substituted by the lens 22. Therefore, the laser module 1 can reduce the number of parts compared to the conventional optical system. Further, the laser module 1 can be miniaturized.

  Each of the light sources 11 and 12 is a surface emitting semiconductor laser (Vertical Cavity Surface Emitting Laser; VCSEL) having an oscillation wavelength band of 850 nm. The surface-emitting semiconductor laser can make the beam spread smaller than the edge-emitting semiconductor laser.

  In FIG. 2, the incident angle of the beam B12 at the incident end face of the optical fiber 3 is shown to be spread by an angle θ1. The angle θ1 is larger in the edge-emitting semiconductor laser than in the surface-emitting semiconductor laser. Therefore, when an edge-emitting semiconductor laser is used as the light source 12, a part of the light beam B <b> 12 tends to enter the core 31 at an angle larger than the maximum light receiving angle of the optical fiber 3.

  When light enters the core 31 of the optical fiber 3 at an angle larger than the maximum light receiving angle, the light escapes from the side surface of the optical fiber 3 to the outside. Therefore, the output of the laser module is reduced. In general, a surface emitting semiconductor laser has a smaller laser beam spread than an edge emitting semiconductor laser (in other words, the directivity of the laser beam is strong), so that the distance between the light emission central axis of the light source 12 and the central axis of the lens 22 is set. If set appropriately, light that escapes from the side of the optical fiber can be reduced. Therefore, the power of light output from the laser module 1 can be increased.

  Although not specifically shown, the beam diameter of this surface emitting semiconductor laser is about 28 μm. Further, the spread angle of the beam B11 emitted from the lens 21 is equal to the angle θ1 and is about 3 degrees.

  Each of the lenses 21 and 22 is a spherical lens. By using a spherical lens as the type of these lenses, a plurality of lenses can be easily arrayed, so that high integration, that is, downsizing of the optical system can be achieved. Further, the cost of the optical system can be reduced by using a plurality of arrayed lenses.

  The diameter of the spherical lens is 2 mm and the refractive index is about 1.5. The material of the lenses 21 and 22 is BK-7 (a kind of crown glass) generally used for lenses.

  The lenses 21 and 22 are preferably subjected to an antireflection coating process. Thereby, the transmittance of the laser beam in the lenses 21 and 22 can be increased, so that the coupling efficiency at the incident end face of the optical fiber 3 can be increased. Therefore, the power of light output from the laser module 1 can be increased.

  The optical fiber 3 has a large-diameter core 31. By increasing the diameter of the core 31, the coupling efficiency can be increased in the optical coupling between the light sources 11 and 12 and the optical fiber 3. When a surface emitting semiconductor laser having a beam diameter of 20 μm to 30 μm is used as a light source, the core diameter of the optical fiber 3 is desirably about 300 μm to about 800 μm. In the first embodiment, the core 31 has a diameter of 600 μm. The NA of the optical fiber 3 is about 0.2.

  The maximum incident angle of the laser beam is required to be a value within the maximum light receiving angle corresponding to the NA (numerical aperture) of the optical fiber 3. For example, when NA = 0.2, the maximum light receiving angle is about 11 degrees, so that the maximum incident angle θ of the laser beam, that is, the angle of the beam B12 with reference to the optical axis J1 of the light source 11 is also within about 11 degrees. Set to. As a result, the laser beam incident on the end face of the optical fiber 3 can be prevented from escaping from the side face of the optical fiber 3, so that the power of light output from the laser module 1 can be increased.

FIG. 3 is a plan view for explaining the arrangement of the light source 11 and the plurality of light sources 12 in FIG. 2.
Referring to FIG. 3, when viewed from a direction perpendicular to mounting surface 41 (a direction along optical axis J <b> 1 in FIG. 2), a plurality (six in FIG. 3) of light sources 12 centering on light source 11 surround light source 11. It is arranged with. Each of the two light sources 12 located on the X axis is provided at a position 2.22 mm away from the light source 11. In addition, four light sources 12 are provided at positions that are 1.93 mm apart from the X axis with the X axis interposed therebetween. These four light sources 12 are provided at a position where the distance from the Y axis is 1.11 mm.

  When a plurality of light sources are arranged one-dimensionally (for example, in the X-axis direction), a plurality of lenses are also arranged in the X-axis direction. Therefore, in the laser module 1 of FIG. . As shown in FIG. 3, by arranging a plurality of light sources 12 around the light source 11, the size of the laser module 1 can be reduced as a whole.

FIG. 4 is a plan view for explaining the arrangement of the lens 21 and the plurality of lenses 22 in FIG. 2.
Referring to FIG. 4, when viewed from a direction perpendicular to package 4, six lenses 22 are arranged radially so as to surround lens 21 with lens 21 as the center. Each of the two lenses 22 positioned on the X-axis is provided at a position that is 2.02 mm away from the lens 21. Further, four lenses 22 are provided at a position sandwiching the X axis and 1.75 mm away from the X axis.

  Next, a schematic structure of a surface emitting semiconductor laser used as a laser light source in the laser module of the first embodiment will be described. The light sources 11 and 12 have the same configuration. Therefore, below, the structure of the light source 11 will be described as a representative, and the subsequent description of the structure of the light source 12 will not be repeated.

FIG. 5 is a cross-sectional view schematically showing the configuration of the light source 11 of FIG.
Referring to FIG. 5, a light source 11, that is, a surface emitting semiconductor laser, includes a substrate 53, a lower DBR (Distributed Bragg Reflector) layer 54, an active layer 55, an upper DBR layer 56, an upper electrode 60, and a light emitting window. 61 and a back electrode 62. The diameter of the light emission window 61 is, for example, about 30 μm.

  In general, in a surface emitting semiconductor laser, a semiconductor multilayer reflector having a high reflectance (a film having a high refractive index and a low refractive index) is formed on the upper and lower layers of the active layer 55 (the lower DBR layer 54 and the upper DBR layer 56 in FIG. 5). The film is repeatedly laminated). The edge-emitting semiconductor laser extracts light from the cleavage plane (chip end face) after cleaving the substrate, whereas the surface-emitting semiconductor laser extracts the beam B1 from the chip main surface.

  In the edge-emitting semiconductor laser, since the length of the light emitting region in the chip vertical direction is short, light is diffracted greatly in the direction perpendicular to the chip. For this reason, in the edge-emitting semiconductor laser, the laser beam greatly spreads in the direction perpendicular to the chip, so that the shape of the laser beam is close to an ellipse. On the other hand, since the surface emitting semiconductor laser has a larger light emitting region than the edge emitting semiconductor laser, the diffraction effect is weaker than that of the edge emitting semiconductor laser, and the shape of the laser beam is close to a circle.

  Thus, by using a surface emitting semiconductor laser as the light source 11 and the light source 12, the spread of the laser beam can be made smaller than when an edge emitting semiconductor laser is used. Therefore, optical coupling between the light source and the optical fiber can be facilitated.

  In this embodiment, the description will be made assuming that the oscillation wavelength band of the VCSEL is the 850 nm band, but the oscillation wavelength band may be a shorter wavelength. For example, when a product is processed using light emitted from the optical fiber 3, there is an advantage that the fine processing becomes easier as the wavelength of the light is shorter.

  Next, optical characteristics of the surface emitting semiconductor laser used in the laser module of the present embodiment will be described.

  FIG. 6 is a diagram showing the temperature dependence of the current versus light output characteristic (IL characteristic) of the surface emitting semiconductor laser.

  Referring to FIG. 6, it can be seen that the optical output for a certain operating current decreases as the temperature increases. Note that “temperature” in the graph of FIG. 6 is the ambient temperature of the surface emitting semiconductor laser.

FIG. 7 is a diagram showing temperature characteristics of the threshold current of the surface emitting semiconductor laser.
With reference to FIG. 7, the temperature dependence of the threshold current (Ith) is shown for each of the ten samples prepared as the light source of the laser module 1 of FIG. In the graph of FIG. 001 to 010 indicate sample numbers. It can be seen from FIG. 7 that the temperature change of the threshold current has almost similar characteristics among the 10 samples.

FIG. 8 is a diagram showing a spectrum of a surface emitting semiconductor laser.
Referring to FIG. 8, the horizontal axis of the graph indicates the wavelength, and the vertical axis indicates the emission intensity in dB. It can be seen from FIG. 8 that the peak wavelength of the oscillation wavelength is approximately 850 nm.

  FIG. 9 is a diagram showing a change in temperature of the current-voltage characteristics (IV characteristics) of the surface emitting semiconductor laser.

  Referring to FIG. 9, it can be seen that the operating voltage of the surface emitting semiconductor laser generated for a certain operating current decreases as the temperature increases.

  Next, characteristics of the laser module 1 in FIG. 1 will be described. First, the coupling efficiency obtained by simulation is shown. The following simulation results can be obtained by using a ray tracing method (a method of dividing a laser beam into a number of rays and tracing the locus of each ray).

FIG. 10 is a diagram illustrating a simulation result of coupling efficiency.
Referring to FIGS. 10 and 2, the graph shows the coupling efficiency when the divergence angle of the laser beam emitted from the light source 11 is 30 degrees and neither the light is absorbed nor reflected by the lens 21 and the end face of the optical fiber 3. Indicates. The core 31 of the optical fiber 3 has a diameter of 600 μm.

  The graph of FIG. 10 shows how much the coupling efficiency changes as the mounting position of the surface emitting semiconductor laser chip is shifted from the position (design position) shown in FIG. The horizontal axis of the graph indicates the amount of movement from the design position when the light source 11 is moved in the range of −100 μm to +100 μm in the X-axis direction from the design position, and the vertical axis of the graph indicates the coupling efficiency. The four curves indicate that the light source 11 is in the range of −100 μm to +100 μm from the design position to the X axis direction when the deviation of the light source 11 from the design position in the Y axis direction is 0, −20, −40, and −60 μm, respectively. It is a curve which shows the change of coupling efficiency when making it move.

  When the center axis of the core 31 and the optical axis J1 of the light source 11 coincide as shown in FIG. 2 (the value of the horizontal axis of the graph is 0, and the difference between the mounting position of the light source 11 and the design position is 0 μm) The coupling efficiency is the highest. At this time, the coupling efficiency between the light source 11 and the optical fiber 3 is 99% or more. The coupling efficiency between the light source 12 and the optical fiber 3 is 98% or more.

  However, the coupling efficiency decreases as the chip mounting position moves in the X-axis or Y-axis direction of FIG. From the result of FIG. 10, for example, by setting the deviation between the mounting position of the chip and the design position to be ± 20 μm or less in both the X-axis and Y-axis directions, a significant decrease in coupling efficiency can be prevented.

  Further, when the laser module 1 is assembled, it is conceivable that the optical axis J1 of the light source 11 in FIG.

  FIG. 11 is a diagram showing a change in light output with respect to the magnitude of the deviation between the central axis of the core 31 and the optical axis J1 of the light source 11 when the diameter of the core 31 in FIG. 2 is 600 μm.

  FIG. 12 is a diagram showing a change in light output with respect to the magnitude of deviation between the central axis of the core 31 and the optical axis J1 of the light source 11 when the diameter of the core 31 in FIG. 2 is 800 μm.

  Referring to FIGS. 11 and 12, the horizontal axis of the graph indicates the amount of deviation of the optical axis J1 of the light source 11 with respect to the central axis of the core 31, and the vertical axis indicates the power of light output from the laser module. Each of the graphs of FIGS. 11 and 12 shows two curves when the optical axis J1 of the light source 11 is shifted in the X-axis direction and the Y-axis direction with respect to the central axis of the core 31, respectively. The light output of the laser module 1 is an output when an operating current of 140 mA in total is applied to the light source 11 and the six light sources 12.

  As can be seen from FIGS. 11 and 12, the larger the core diameter, the more light is incident on the core, so the light output increases. Further, as the core diameter is wider, the change in the light output is smaller even if the optical axis J1 of the light source 11 is shifted from the central axis of the core 31.

Subsequently, measurement results of the characteristics of the laser module of the first embodiment will be shown.
FIG. 13 is a diagram showing the measurement result of the combined light output characteristic (pulse current-L characteristic) with respect to the pulse current in the laser module 1 of FIG.

  Referring to FIG. 13, the horizontal axis of the graph represents the operating current, and the vertical axis represents the value obtained by dividing the combined light output Pf during pulse oscillation by the duty of the pulse. The operating current application period (pulse width) is 5 μS. FIG. 13 shows that the characteristics are almost the same even when the duty is changed from 1% to 50%. The reason why such a result is obtained is that, as shown in FIG. 3, by mounting the laser chip on the same mounting surface 41, the heat dissipation of the chip is improved.

  When the operating current is 200 mA, the optical output is about 112 mW. The coupling efficiency at this time is about 80%. Compared with the simulation results of FIG. 10, the actual coupling efficiency is low, because the antireflection coating is not applied to the lens and the fiber end face.

  FIG. 14 is a diagram showing the measurement result of the coupled light output characteristic (DC current-L characteristic) with respect to the DC current in the laser module 1 of FIG.

  Referring to FIG. 14, the horizontal axis of the graph indicates the operating current, and the vertical axis indicates the combined light output Pf during continuous oscillation. FIG. 14 shows the IL characteristics when the ambient temperature is changed from 0 degrees to 70 degrees. Compared with FIG. 6, the light output is almost 7 times. This is because the laser module 1 has good heat dissipation of the chip, so that the light output can be increased in proportion to the number of light sources.

  In the graph of FIG. 14, the combined light output Pf slightly decreases as the temperature rises, but this is a characteristic of the semiconductor laser and not the characteristic of the laser module of the present embodiment.

  Referring to FIGS. 14 and 6, for example, the temperature characteristic of the optical output when the operating current is 140 mA and the temperature characteristic of the optical output when the operating current is 20 mA are similar. From this, it can be seen that in the laser module of the present embodiment, the coupling efficiency is stable (constant) regardless of the ambient temperature. This point will be described in more detail.

FIG. 15 is a diagram showing the temperature dependence of the coupling efficiency in the laser module 1.
In FIG. 15, the horizontal axis of the graph indicates temperature, and the vertical axis of the graph indicates coupling efficiency. As can be seen from FIG. 15, the coupling efficiency is substantially constant and stable at each temperature, and is less than ± 0.5 dB (about + 12% to about −10%) of the laser module reliability standard (Telcodia GR-468-CORE). ). The results shown in FIG. 15 indicate that the coupling efficiency in the conventional laser module is as good as or better than the temperature dependence.

  If the variation of the coupling efficiency is ± 10% or less at an atmospheric temperature of 0 to 70 degrees, there is no practical problem. In the results shown in FIG. 15, the fluctuation of the coupling efficiency is ± 5% or less at the atmospheric temperature from 0 to 70 ° C., and the condition “± 10% or less” is sufficiently satisfied.

  As described above, according to the first embodiment, a plurality of laser light sources that are installed on the same plane and respectively emit a plurality of laser beams, an optical fiber that receives a plurality of laser beams, and a plurality of laser light sources are supported. And a plurality of lenses for condensing the laser beam received from the corresponding laser light source and coupling it to the end face of the optical fiber. Therefore, the laser module of the first embodiment can output high-power light while being small.

[Embodiment 2]
In the laser module of the present invention, the output can be increased as the number of light sources is increased. However, since the laser module of the present invention requires as many lenses as the number of light sources, it is conceivable that the scale of the optical system increases when the number of light sources is increased. In the laser module of the second embodiment, an integrated lens is used. Thereby, the output of the laser module of the second embodiment can be increased while being small.

  FIG. 16 is a diagram illustrating the positional relationship between the light source and the lens in the laser module according to the second embodiment.

  FIG. 17 is a layout diagram of the lens when the lens shown in FIG. 16 is viewed from the optical fiber 3 side.

  Referring to FIGS. 16 and 17, the laser module 1A is different from the laser module 1 of FIGS. 1 and 2 in that lenses 21A and 22A that are drum lenses are provided instead of the lenses 21 and 22 that are spherical lenses. The lens 21 </ b> A is provided corresponding to the light source 11, and the plurality of lenses 22 </ b> A are provided corresponding to the light source 11. In addition, since the other part of laser module 1A has the same structure as laser module 1, the subsequent description regarding the other part of laser module 1A will not be repeated.

  The X-axis direction in FIG. 16 corresponds to the X-axis direction in FIG. That is, FIG. 16 is a cross-sectional view along the X-axis direction of FIG. As shown in FIG. 17, also in the second embodiment, the plurality of lenses 22A are arranged radially so as to surround the lens 21A. This means that the plurality of light sources 12 are arranged so as to surround the light source 11.

  A drum lens has the same lens performance as a spherical lens. Compared with the spherical lens, the drum lens can reduce the portion through which the laser beam from the light source does not pass. Therefore, the laser module 1A can be made smaller in the X-axis direction than the laser module 1 of FIG.

  In the example shown in FIG. 17, 19 drum lenses are used and integrated (arrayed). When the lens array shown in FIG. 17 and the end face of the optical fiber 3 shown in FIG. 16 are subjected to a coating process with a transmittance of 99% or more, the coupling efficiency in the laser module 1A is 90%. Therefore, when 19 surface emitting semiconductor lasers having a light output of 20 mW are used, the output of the laser module 1A is 20 mW / piece × 19 pieces × 0.9 (coupling efficiency) = 342 mW.

  For example, when 19 surface emitting semiconductor lasers having a power of 60 mW / piece or more are integrated, the optical output of the laser module 1A is 1 W or more. If the power of light is 1 W or more, the light can be sufficiently used for the product processing as described above.

  In the optical communication field, a microlens array in which minute lenses are integrated on a glass substrate or the like is often used for optical coupling between a light source and an optical fiber. Such a microlens array can also be used in the laser module of the second embodiment. In this case, more light sources and lenses can be integrated than the laser module 1A shown in FIG. That is, in the second embodiment, by integrating a plurality of lenses as a microlens array, it becomes possible to output light with higher power than the laser module of the first embodiment.

  FIG. 18 is a diagram illustrating an example in which a microlens array is applied as a plurality of lenses in the laser module of the second embodiment.

  FIG. 19 is a lens layout when the lens shown in FIG. 18 is viewed from the optical fiber 3 side.

  Referring to FIGS. 18 and 19, laser module 1B is different from laser module 1A in FIGS. 16 and 17 in that it includes a microlens array 2A in which lenses 21A and 22A are integrated. Since other parts of the laser module 1A have the same configuration as the laser module 1, the following description regarding the other parts of the laser module 1A will not be repeated. Note that the X-axis direction in FIG. 18 corresponds to the X-axis direction in FIG.

  In the microlens array 2A of FIG. 19, 37 lenses are integrated. That is, 36 lenses 22A are radially arranged around one lens 21A. Therefore, the laser module 1B can obtain light with higher output than the laser module 1A.

  Note that the number of lenses illustrated in FIGS. 16 to 19 is an example, and the number of light sources and lenses is appropriately set according to the power of light to be output. 18 and 19 show an example in which a drum lens is used for the microlens array 2A, the lens used for the microlens array 2A may be a spherical lens.

  In the second embodiment, the maximum incident angle of the laser beam is preferably within the maximum light receiving angle corresponding to the NA (numerical aperture) of the optical fiber 3 in order to increase the coupling efficiency. This is the same as in the first embodiment.

  As described above, according to the second embodiment, since the number of light sources can be increased by integrating lenses, the output power can be made higher than that in the first embodiment.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is an overall view of a laser module according to a first embodiment. It is a figure explaining the arrangement | positioning relationship between the light source and lens in the laser module 1 of FIG. It is a top view explaining arrangement | positioning of the light source 11 of FIG. 2, and the some light source 12. FIG. It is a top view explaining arrangement | positioning of the lens 21 of FIG. 2, and the some lens 22. FIG. It is sectional drawing which shows the structure of the light source 11 of FIG. 1 typically. It is a figure which shows the temperature dependence of the electric current versus optical output characteristic (IL characteristic) of a surface emitting semiconductor laser. It is a figure which shows the temperature characteristic of the threshold current of a surface emitting semiconductor laser. It is a figure which shows the spectrum of a surface emitting semiconductor laser. It is a figure which shows the temperature change of the electric current-voltage characteristic (IV characteristic) of a surface emitting semiconductor laser. It is a figure which shows the simulation result of coupling efficiency. FIG. 3 is a diagram showing a change in light output with respect to the amount of deviation between the central axis of the core 31 and the optical axis J1 of the light source 11 when the diameter of the core 31 in FIG. 2 is 600 μm. FIG. 3 is a diagram showing a change in light output with respect to the amount of deviation between the central axis of the core 31 and the optical axis J1 of the light source 11 when the diameter of the core 31 in FIG. 2 is 800 μm. It is a figure which shows the measurement result of the coupling light output characteristic (pulse current-L characteristic) with respect to a pulse current in the laser module 1 of FIG. It is a figure which shows the measurement result of the coupling light output characteristic (DC current-L characteristic) with respect to DC current in the laser module 1 of FIG. It is a figure which shows the temperature dependence of the coupling efficiency in the laser module 1. FIG. FIG. 6 is a diagram for explaining an arrangement relationship between a light source and a lens in a laser module according to a second embodiment. FIG. 17 is a lens arrangement diagram when the lens shown in FIG. 16 is viewed from the optical fiber 3 side. FIG. 6 is a diagram illustrating an example in which a microlens array is applied as a plurality of lenses in the laser module according to the second embodiment. FIG. 19 is a lens arrangement diagram when the lens shown in FIG. 18 is viewed from the optical fiber 3 side. It is a figure explaining the structure of the combining laser light source disclosed by Unexamined-Japanese-Patent No. 2002-202442 (patent document 1). It is a figure explaining another structure of the combining laser light source disclosed by Unexamined-Japanese-Patent No. 2002-202442 (patent document 1).

Explanation of symbols

  1, 1A, 1B laser module, 2A micro lens array, 3 optical fiber, 4 package, 5 sleeve, 11, 12 light source, 21, 22, 21A, 22A lens, 31, 130a, 251a core, 41 mounting surface, 53 substrate , 54 Lower DBR layer, 55 Active layer, 56 Upper DBR layer, 60 Upper electrode, 61 Light emitting window, 62 Back electrode, 110 Heat block, 111-117 Collimator lens, 120 Condensing lens, 130, 251 Multimode optical fiber , 250 combining optical system, B, B1-B15 beam, H11-H15 condenser lens, J1-J3 optical axis, LD1-LD7, LD11-LD15 semiconductor laser, θ maximum incident angle, θ1 angle.

Claims (7)

A plurality of laser light sources that are two-dimensionally arranged on the same plane and respectively emit a plurality of laser beams;
An optical fiber receiving the plurality of laser beams;
A laser module comprising a plurality of lenses provided corresponding to the plurality of laser light sources, respectively, and condensing a laser beam received from the corresponding laser light source and coupling it to an end face of the optical fiber.   The laser module according to claim 1, wherein each of the plurality of laser light sources is a surface emitting semiconductor laser. The plurality of laser light sources are:
A first laser light source;
The laser module according to claim 2, further comprising: a plurality of second laser light sources disposed around the first laser light source. The plurality of lenses are:
A first lens provided corresponding to the first laser light source and disposed so that a central axis overlaps an optical axis of the first laser light source;
A plurality of second lenses, which are respectively provided corresponding to the plurality of second laser light sources, and are arranged so that the optical axes and the center axes of the corresponding second laser light sources are shifted from each other. The laser module described.   The laser module according to claim 1, wherein each of the plurality of lenses is a spherical lens.   The laser module according to claim 1, wherein each of the plurality of lenses is a drum lens.   The laser module according to claim 1, wherein the plurality of lenses are integrated as a microlens array.

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