Laser Module

Abstract

To obtain a laser module having a high output and high productivity.SOLUTION: A laser module 50 includes: a multi-emitter laser 51 having a plurality of emitters disposed in a row; a set of collimating lenses 52 that brings a plurality of beams emitted from the plurality of emitters incorporated in the multi-emitter laser 51 into parallel beams; a set of displacement prisms 53 that has two parallel reflection surfaces opposite to each other and rearranges the plurality of beams brought into the parallel beams to parallel beams in a plurality of rows in such a manner that parts of the plurality of beams brought into the parallel beams by the set of collimating lenses 52 are twice reflected by the two reflection surfaces so as to be moved in parallel; and a condensing lens 54 that condenses the parallel beams in the plurality of rows rearranged by the set of displacement prisms 53 onto an end face 55A of an optical fiber 55. The respective two reflection surfaces are inclined with respect to both two directions orthogonal to a direction in which the plurality of beams brought into the parallel beams by the collimating lenses 52 advances toward the displacement prisms 53.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present disclosure relates to a laser module that outputs light. [Background technology]

[0002] In laser processing machines and laser welding machines, laser modules coupled to optical fibers are often used to guide laser light to a desired position and to oscillate and amplify the laser light. In order to make the laser module high-power and small-sized, a multi-emitter laser in which a single-chip laser diode has multiple light-emitting points is sometimes used as a laser light source. The light-emitting points are emitters. Optical fibers have upper limits on the incidence angle and focused diameter that can be coupled, which are design constraints on the number of emitters and therefore the optical output. In response to this constraint, a configuration is known that improves the optical output that can be coupled to an optical fiber by rearranging the arrangement of beams arranged in a single row into two or more rows using two sets of mirror pairs (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-61727 A Summary of the Invention [Problem to be solved by the invention]

[0004] Fig. 1 is a perspective view showing a schematic configuration of a laser module 1 disclosed in Patent Document 1. As shown in Fig. 1, the laser module 1 of Patent Document 1 converts a beam B emitted from a light emitting unit 2 into a parallel beam by a collimator lens 3, and rearranges the beam B by a first rhomboid prism 4 and a second rhomboid prism 5. When assembling the first rhomboid prism 4 and the second rhomboid prism 5 into the laser module 1, there is a problem in the process and work of holding each of the first rhomboid prism 4 and the second rhomboid prism 5 and applying an adhesive for fixing them in order to adjust the postures of each of the first rhomboid prism 4 and the second rhomboid prism 5.

[0005] In each of the first rhomboid prism 4 and the second rhomboid prism 5, the transmitting surface and the reflecting surface of the beam B cannot be used for holding and applying adhesive, and only four surfaces indicated by the arrows 6A, 6B, 7A, and 7B can be used for holding and applying adhesive. If the four limited surfaces are held, adhesive is applied, and each of the first rhomboid prism 4 and the second rhomboid prism 5 is fixed to another member with adhesive, the configuration of the assembly device becomes complicated to hold each of the first rhomboid prism 4 and the second rhomboid prism 5 in the air, and productivity is reduced. In addition, since precise adjustment is required, when adjusting while grasping the traveling direction of the beam B in the light-emitting state, it is necessary to avoid interference between each of the holding arms and adhesive and the beam B, which makes the configuration of the assembly device even more complicated.

[0006] The present disclosure has been made in view of the above, and has an object to obtain a laser module that has high output and high productivity. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the laser module of the present disclosure includes a multi-emitter laser having multiple emitters arranged in a row and emitting beams, a collimating lens that converts multiple beams emitted by the multiple emitters of the multi-emitter laser into parallel beams, a displacement prism having two opposing parallel reflective surfaces that reflects a portion of the multiple beams converted into parallel beams by the collimating lens twice by the two reflective surfaces and translates them in parallel to rearrange the multiple beams converted into parallel beams into multiple rows of parallel beams, an optical fiber, and a focusing lens that focuses the multiple rows of parallel beams rearranged by the displacement prism onto the end face of the optical fiber. The arrangement direction of the multiple emitters of the multi-emitter laser is defined as the x direction, the direction in which the multiple beams collimated by the collimator lens travel to the displacement prism is defined as the z direction, and the direction perpendicular to both the x direction and the z direction is defined as the y direction. Each of the two reflecting surfaces is In the x and y directions It is tilted in both directions. The displacement prism splits the multiple beams collimated by the collimating lens into multiple beam groups, and guides each of the multiple beam groups to an optical path different from that of the other beam groups among the multiple beam groups. The laser module according to the present disclosure further includes a polarization rotation means arranged in the optical path of one or more beam groups among the multiple beam groups, and a polarizing beam splitter. The polarization rotation means rotates the polarization of the beam group in the optical path in which it is arranged. The polarizing beam splitter combines a polarization-rotated beam group, which is a beam group whose polarization has been rotated by the polarization rotation means, with one or more beam groups among the multiple beam groups other than the polarization-rotated beam group. Effect of the Invention

[0008] The laser module according to the present disclosure has the advantages of high output and high productivity. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing a schematic configuration of a laser module disclosed in Patent Document 1. [Diagram 2] Fig. 1 to explain the conservation law of brightness and beam parameter product with respect to the half angle of collection when collecting laser light. [Diagram 3] Fig. 2 is a diagram for explaining the conservation law of brightness and beam parameter product with respect to the half angle of collection when collecting laser light. [Figure 4] Diagram to explain how beam quality is determined by optical fiber [Diagram 5] Diagram illustrating coupling of beams from a multi-emitter laser into an optical fiber. [Figure 6] Diagram showing beam blanking areas within the range of maximum acceptance angle [Figure 7] A diagram showing the fast axis and slow axis directions of a semiconductor laser. [Figure 8]Diagram showing how beam shifting can reduce beam blank areas [Figure 9] FIG. 1 is a perspective view showing a schematic configuration of a laser module according to a first embodiment; [Figure 10] FIG. 1 is a top view showing a schematic configuration of a laser module according to a first embodiment; [Figure 11] FIG. 1 is a diagram showing a displacement prism and a beam when the laser module according to the first embodiment is viewed from the +z direction side toward the -z direction side. [Figure 12] FIG. 1 is a diagram showing a displacement prism and a beam when the laser module according to the first embodiment is viewed from the +x direction side toward the -x direction side. [Figure 13] FIG. 11 is a perspective view showing a schematic configuration of a laser module according to a second embodiment; [Figure 14] FIG. 11 is a top view showing a schematic configuration of a laser module according to a second embodiment. [Figure 15] FIG. 13 is a diagram showing a displacement prism when the laser module according to the second embodiment is viewed from the -z direction side toward the +z direction side. [Figure 16] FIG. 1 is a diagram for explaining a beam rotating element included in a beam rotating means of a laser module according to a second embodiment of the present invention; [Figure 17] FIG. 2 is a diagram for explaining a beam rotating element included in a beam rotating means of a laser module according to a second embodiment of the present invention; [Figure 18] FIG. 13 is a diagram showing a state in which the beam in the second embodiment is viewed from the -z direction side toward the +z direction side. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Laser modules according to embodiments will be described in detail below with reference to the drawings.

[0011] The basic idea of ​​this disclosure. Before describing specific embodiments, the following describes the beam brightness and quality, which are factors that determine the processing speed and processing quality of laser welding or cutting, and the basic idea of ​​the present disclosure for improving the beam brightness and quality. Improving the beam brightness and quality includes suppressing the deterioration of the beam brightness and quality.

[0012] The brightness of the collected beam after propagation through space, Br0, is defined by the following equation (1):

[0013]

number

[0014] Pw is the power of light, AF is the area of ​​the focused spot, and ΩF is the focused solid angle. The focused solid angle ΩF is the divergence solid angle. wF is the radius of the focused spot, and θF is the focused half angle. The focused half angle θF is the divergence half angle. BPP0 is the beam parameter product. The beam parameter product BPP0 is an index that represents the degree of focusing ability of a beam. The degree of focusing ability of a beam means beam quality. According to the principle of light diffraction, for the same beam, the focused half angle θF and the focused spot radius wF are inversely proportional, and the following equation (2) is constant. λ in equation (2) is the wavelength of light.

[0015]

number

[0016] That is, when collecting laser light from a light emitting point 8 having the same radius wE and divergence half angle θE, as shown in FIG. 2 and FIG. 3, even if the collection half angle θF is changed, the brightness Br0 and the beam parameter product BPP0 at the collection spot FS are constant, and a kind of conservation law is established. That is, the relationship of the following formula (3) is established. FIG. 2 is a first diagram for explaining the conservation law of brightness and beam parameter product with respect to the collection half angle when collecting laser light. FIG. 2 is a diagram when the laser light is collected at the collection half angle θF. FIG. 3 is a second diagram for explaining the conservation law of brightness and beam parameter product with respect to the collection half angle when collecting laser light. FIG. 3 is a diagram when the laser light is collected at the collection half angle θF'. In FIG. 3, the radius of the collection spot FS is written as wF'. Regarding the collection half angle θF, the collection half angle θF is approximately equal to the collection NA.

[0017]

number

[0018] M 2 is a dimensionless index of beam quality and is always M 2 ≥ 1. If the beam is an ideal TEM00 Gaussian beam, M 2 = 1, and the factors that cause deterioration include higher-order modes, multimodes, aberrations, and incoherency.

[0019] Generally, when comparing at the same power, the higher the brightness, the higher the power can be concentrated in one place, and the faster the processing speed of welding and cutting by laser light can be. While lowering the brightness is low cost, improving the brightness is expensive because it requires, for example, fiber laser oscillation or wavelength multiplexing, so it is desirable to maintain the brightness as much as possible in the laser module.

[0020] Next, we will explain how to couple a beam into an optical fiber. Consider an optical fiber with a core radius of wC and a maximum acceptance angle of θC. Regarding the maximum acceptance angle θC, θC ≈ acceptance NA. In order to couple a beam into an optical fiber without loss, the conditions expressed by the following equations (4) and (5) are necessary.

[0021]

number

[0022]

number

[0023] The beam quality when the beam propagates through the inside of the optical fiber and is output into space is determined by the optical fiber, not by the beam quality of the incident beam. FIG. 4 is a diagram for explaining that the beam quality is determined by the optical fiber 9. For the fiber output beam, the radius of the focused spot FS is wC, the half-angle of spread is θC, the beam parameter product is expressed by the following formula (6), and the beam parameter product BPP0 of the incident beam B to the optical fiber 9 is the lower limit of the fiber output beam. The fiber output beam is a beam output from the optical fiber 9. The brightness BrC of the fiber output beam is expressed by the following formula (7), and the brightness Br0 of the incident beam B to the optical fiber 9 is the upper limit of the brightness of the fiber output beam. Hereinafter, BPPC will be referred to as the fiber-coupled beam parameter product, and BrC will be referred to as the fiber-coupled brightness.

[0024]

number

[0025]

number

[0026] Consider a laser module that couples beams from a multi-emitter laser, the number of emitters of which is NE, into an optical fiber. An emitter is a light-emitting point. FIG. 5 is a diagram for explaining the coupling of a beam B from a multi-emitter laser into an optical fiber. As shown in FIG. 5, it is assumed that beam B from each of NE emitters 10 arranged in a row is collimated by a collimating lens 11 so as not to be mixed with beam B from other emitters 10, and is collected by a collecting lens 12, and NE beams B are coupled into an optical fiber. In FIG. 5, NE is 3.

[0027] Since the beam B from each of the NE emitters 10 is incoherent with respect to the beams B from the other emitters 10, the radius wF of the focused spot FS is expressed by the following equation (8), as in the case of a single emitter.

[0028]

number

[0029] Since NE emitters 10 are arranged in a row, the maximum acceptance angle θC of the optical fiber must satisfy the condition expressed by the following equation (9).

[0030]

number

[0031] For this reason, the fiber-coupled beam parameter product BPPC is expressed by the following equation (10) and is deteriorated by NE times as much as the beam parameter product BPP0.

[0032]

number

[0033] The fiber coupling brightness BrC is expressed by the following formula (11), and is reduced to 1 / NE of the brightness Br0. This reduction in brightness is due to the presence of a "blank area" where no beam B exists within the range of the maximum acceptance angle θC, as shown in Figure 6. Figure 6 is a diagram showing the blank area of ​​the beam within the range of the maximum acceptance angle θC.

[0034]

number

[0035] When the light source is a semiconductor laser, the beam quality of the laser output beam differs in the directions of two orthogonal axes in a plane perpendicular to the optical axis, which also causes a decrease in brightness. The difference in beam quality of the laser output beam in the directions of two orthogonal axes in a plane perpendicular to the optical axis is called anisotropy. FIG. 7 is a diagram showing the fast axis direction and the slow axis direction of the semiconductor laser 13. The inherent directions of anisotropy are the thickness direction of the semiconductor wafer and the emitter array direction. The thickness direction of the semiconductor wafer is the fast axis direction and the FA direction, and the emitter array direction is the slow axis direction and the SA direction. The emitter array direction is the array direction of the emitters 14 arranged in a row. Beam B is also shown in FIG. 7.

[0036] The beam parameter product in the FA direction, BPP0F, is expressed by the following formula (12). The beam parameter product in the SA direction, BPP0S, is expressed by the following formula (13). The brightness Br0 of beam B is expressed by the following formula (14).

[0037]

number

[0038]

number

[0039]

number

[0040] wFF is the radius of the focused spot in the FA direction, and wFS is the radius of the focused spot in the SA direction. θFF is the focusing half angle in the FA direction, and θFS is the focusing half angle in the SA direction. The focusing half angle is the divergence half angle. M2F is the M 2 value, and M2S is the M in the SA direction. 2 value.

[0041] In general, the beam quality in the SA direction is worse than that in the FA direction; typically, M2F is approximately 1 and M2S is approximately 5 to 10.

[0042] When beams with anisotropic beam quality are focused at the same focusing half angle θF, the focused spot becomes an ellipse with radii wFF and wFS, and the beam brightness decreases when the beam is coupled to a circular core of an optical fiber. In order to make the focused spot shape a circle with radius wC, the following conditions expressed by equations (15) and (16) are required.

[0043]

number

[0044]

number

[0045] Here, the maximum acceptance angle required to couple a beam into an optical fiber without loss is called the “required acceptance angle.” For a multi-emitter semiconductor laser, the required acceptance angle θCF in the FA direction is expressed by the following formula (17), and the required acceptance angle θCS in the SA direction is expressed by the following formula (18).

[0046]

number

[0047]

number

[0048] Since θCF is smaller than θCS, the maximum acceptance angle θC of the optical fiber must satisfy the condition expressed by the following equation (19).

[0049]

number

[0050] Therefore, for the fiber-coupled beam parameter product BPPC, the relationship expressed by the following equation (20) is obtained. The fiber-coupled luminance BrC is expressed by the following equation (21).

[0051]

number

[0052]

number

[0053] αθ is the required acceptance angle ratio, and is expressed by the following formula (22). The smaller αθ is, more precisely, the more αθ deviates from 1, the lower the fiber coupling brightness becomes. That is, in addition to the poor beam quality in the SA direction of the semiconductor laser, the semiconductor laser is a multi-emitter, which further reduces the brightness.

[0054]

number

[0055] In order to suppress the decrease in fiber coupling brightness for a multi-emitter laser, it is sufficient to bring the required acceptance angle ratio αθ closer to 1 and reduce the beam blank area within the maximum acceptance angle θC. FIG. 8 is a diagram showing that the beam blank area can be reduced by shifting beam B. The dashed lines in FIG. 8 are hidden lines. As shown in FIG. 8, there is a blank area in the direction perpendicular to the emitter array, but the beam blank area can be reduced by displacing a part of beam B aligned in the emitter array direction by beam displacement means 15. The direction perpendicular to the emitter array is the FA direction, and the emitter array direction is the SA direction.

[0056] When NE beams B arranged in one row are rearranged into a matrix of NL rows, the required acceptance angle ratio αθ′ is improved as expressed by the following equation (23).

[0057]

number

[0058] Since the decrease in fiber coupling brightness can be suppressed more as αθ' approaches 1, it is desirable that the number of rows NL is close to the value expressed by the following formula (24) as a guideline. NLS in formula (24) is referred to as the standard number of rows.

[0059]

number

[0060] The beam displacement means 15 can be realized by a pair of two parallel reflecting surfaces.

[0061] In the above description, the beam B is rearranged in a matrix, but the beam B may be rearranged in a staggered manner. Assuming that the beam shape of the beam B is elliptical and the range of the maximum acceptance angle is circular, when the beam B is rearranged in a staggered manner, the blank area can be made smaller with respect to the range of the maximum acceptance angle and the beam shape.

[0062] Embodiment 1 Fig. 9 is a perspective view showing a schematic configuration of a laser module 50 according to the first embodiment. Fig. 10 is a top view showing a schematic configuration of a laser module 50 according to the first embodiment. The laser module 50 includes a plurality of emitters 51E arranged in a row and emitting beams. iE A multi-emitter laser 51 having a plurality of emitters 51E iE and a collimating lens 52 that converts the multiple beams emitted by the collimator 52 into parallel beams.

[0063] The laser module 50 further includes a displacement prism 53. The displacement prism 53 has two parallel reflecting surfaces facing each other. The displacement prism 53 reflects a part of the multiple beams, which have been converted into parallel beams by the collimating lens 52, twice by the two reflecting surfaces and translates the multiple beams, which have been converted into parallel beams, into multiple rows of parallel beams. Each of the two reflecting surfaces of the displacement prism 53 is inclined in both the x-direction and the y-direction. The laser module 50 further includes a condenser lens 54 and an optical fiber 55. The condenser lens 54 condenses the multiple rows of parallel beams, which have been converted into parallel beams by the displacement prism 53, onto an end face 55A of the optical fiber 55. Each of the multiple components constituting the laser module 50 will be further described below.

[0064] The multi-emitter laser 51 is a semiconductor laser and has N-E emitters 51E arranged in the x direction. iE NE is an integer equal to or greater than 2. iE is a number from 1 to NE. In FIG. 9 and FIG. 10, NE emitters 51E iE Only one emitter 51E1 is given a reference number. iE are arranged in a row. The multi-emitter laser 51 emits NE beams B iE The z direction is perpendicular to the x direction. In Figs. 9 and 10, NE beams B iE Only one beam, B1, is given a code.

[0065] The collimating lens 52 includes an FA collimating lens 52A and an SA collimating lens 52B, and NE beams B iE The FA collimator lens 52A collimates each of the light beams emitted from the multiple emitters of the multi-emitter laser 51 into a parallel beam. The SA collimator lens 52B is a lens array having NE cylindrical lenses. That is, the collimator lens 52 has a first cylindrical lens and a second cylindrical lens. The FA collimator lens 52A is an example of a first cylindrical lens, and the NE cylindrical lenses of the SA collimator lens 52B are an example of a second cylindrical lens. The first cylindrical lens and the second cylindrical lens collimate the light beams traveling along two orthogonal axes in a plane orthogonal to the optical axis of the beam emitted from each of the multiple emitters of the multi-emitter laser 51.

[0066] Since the collimator lens 52 includes the FA collimator lens 52A and the SA collimator lens 52B, the focal lengths of the FA collimator lens 52A and the SA collimator lens 52B can be designed so that the focused spot is circular, taking into consideration the beam quality in two orthogonal directions. As a result, the brightness of the light output by the laser module 50 is improved.

[0067] The displacement prism 53 includes one single prism 53A and NP single prisms 53D. iP NP is a number that is one less than NE. iP is a number between 1 and NP. The single prism 53A has a reflecting surface 53A. iP is formed. iP is located in one plane. Single prism 53D iP Includes 53DR reflective surface iP is formed. iP Reflective Surface 53DR iP The displacement prism 53 divides the NE parallel beams B iE The positions of some of the beams B are translated in the -x and -y directions, and NE beams B iEare rearranged into NE rows. For example, NE parallel beams B iE are rearranged into beams in a NE row in the y direction by a displacement prism 53, which is orthogonal to the x and z directions. The displacement prism 53 will be further described below.

[0068] The condenser lens 54 condenses NE parallel beams B iE The laser beam is focused on an end face 55A of the optical fiber 55. The multi-emitter laser 51, the collimator lens 52, the displacement prism 53, the condenser lens 54, and the optical fiber 55 are mounted on one plane of a support base 56 to form a laser module 50. The support base 56 is shown in Figs. 11 and 12. The support base 56 is one of a plurality of components that form the laser module 50.

[0069] Next, a detailed description will be given of the structure of the displacement prism 53 in consideration of the productivity of the laser module 50. FIG. 11 shows the displacement prism 53 and the beam B when the laser module 50 according to the first embodiment is viewed from the +z direction side to the -z direction side. iE 11, the symbol pE is the emitter pitch, and the symbol pL is the rearrangement row pitch. FIG. 12 is a diagram showing the displacement prism 53 and the beam B when the laser module 50 according to the first embodiment is viewed from the +x direction side toward the -x direction side. iE FIG.

[0070] As described above, the reflective surface 53A iP are reflective surfaces located on one plane, and are formed on one single prism 53A. Reflective surface 53A4 is shown in FIG. 9. Reflective surfaces 53A1, 53A2, 53A3, and 53A4 are shown in FIG. 11. A gripping portion 53B that can be gripped is provided on the surface of single prism 53A in the +y direction. Grip portion 53B is provided when a gripping arm of an assembly device or an adhesive is applied to reflective surface 53A. iP or Beam B iEThe surface of the single prism 53A in the -y direction is provided with an adhesive portion 53C that is to be attached to the support base material 56. The adhesive portion 53C is provided with a beam B iE This allows the adhesive to be applied and secured to the supporting substrate 56 without interference with the

[0071] Reflective surface 53DR iP is a single prism 53D out of NP single prisms made of glass. iP In FIG. 9, the reflecting surface 53DR4 is shown. iP The surface in the +y direction of the iP 9, 11 and 12 show the grip portion 53E4. iP The gripping arms of the assembly equipment and adhesives are reflective surfaces. iP or Beam B iE This allows the prism to be held during assembly without interfering with the other prisms. iP The surface in the -y direction of the substrate 53 is bonded to the support substrate 56. iP 9, 11 and 12 show the adhesive portion 53F4. iP Beam B iE This allows the adhesive to be applied and secured to the supporting substrate 56 without interference with the

[0072] Since the displacement prism 53 has the above-mentioned structure, the manufacturer can generate the beam B iE It is possible to precisely adjust one or both of the position and angle of each element while grasping the traveling direction of the laser beam, thereby enabling the manufacture of a high-output laser module 50 with high productivity.

[0073] Gripping part 53B, adhesive part 53C, gripping part 53E iP and adhesive part 53F iP Beam B iEThis is a feature of the laser module 50 that allows the translation of the laser beam to be achieved with only one pair of parallel reflective surfaces.

[0074] Single prism 53A and single prism 53D iP Each of the reflecting surfaces 53A is made of optical glass to suppress light loss. iP and Reflective Surface 53DR iP Each of the first and second reflectors is preferably a total reflection film formed of a dielectric multilayer film.

[0075] Table 1 below shows an example of optical design parameters according to the first embodiment.

[0076] [Table 1]

[0077] The standard number of columns NLS is expressed by the following equation (25).

[0078]

number

[0079] The actual number of columns is also set to NL=5.

[0080] Parallel beam B iE The radius wBF in the FA direction of the parallel beam B is expressed by the following equation (26). iE The radius wBS in the SA direction is expressed by the following equation (27).

[0081]

number

[0082]

number

[0083] If the light receiving NA=NAC of the optical fiber 55 is converted into the effective diameter of the focusing lens 54, and the value obtained by the conversion is taken as the maximum focusing radius wBC, the following formula (28) is obtained.

[0084]

number

[0085] As shown in Figure 11, an elliptical beam B with radii wBF and wBS and NE of 5 iE are aligned in the FA direction, the elliptical beam B iE goes outside the circle of maximum focusing radius wBC, but the displacement prism 53 creates an elliptical beam B iE are rearranged in the SA direction into NL=5 rows, forming an elliptical beam B iE All of these are contained within a circle with a maximum focusing radius wBC. The radius of the focused spot FS at the end face 55A of the optical fiber 55 is expressed by the following equations (29) and (30), and since it is smaller than the core radius wC, the beam is coupled into the optical fiber 55 without loss.

[0086]

number

[0087]

number

[0088] As described above, the laser module 50 according to the first embodiment can rearrange the beam by the displacement prism 53. That is, the laser module 50 can maintain the fiber coupling brightness of the beam emitted from the multi-emitter laser 51. Since the laser module 50 shifts the beam parallel to the two reflecting surfaces, the degree of freedom in designing the structure including the gripping part and the adhesive part during assembly of the laser module 50 can be increased, and the assembly workability can be ensured. Therefore, the laser module 50 has the effect of high output and high productivity.

[0089] The laser module 50 may further include known components such as one or both of a water-cooled heat sink for cooling the multi-emitter laser 51 and a filter for cutting return light from the optical fiber 55. By including the known components described above in the laser module 50, the performance and reliability of the laser module 50 are improved.

[0090] The multi-emitter laser 51 may be one in which multiple emitters are formed on one semiconductor chip, or one in which multiple semiconductor chips are arranged in a row. The specific material of each element is selected by considering the trade-off between cost and required performance. The lens is also selected by considering the trade-off between cost and required performance. In other words, one of a plano-convex lens and a double-sided lens is selected, and one of a spherical lens and an aspherical lens is selected by considering the trade-off between cost and required performance.

[0091] Embodiment 2 Fig. 13 is a perspective view showing a schematic configuration of a laser module 60 according to the second embodiment. Fig. 14 is a top view showing a schematic configuration of a laser module 60 according to the second embodiment. The laser module 60 has a multi-emitter laser 51, an FA collimator lens 52A, a beam rotating means 61, an SA collimator lens 52B, a displacement prism 62, a half-wave plate 63, a merging mirror 64, a polarizing beam splitter 65, a condenser lens 54, an optical fiber 55, and a support base material 56. In the second embodiment, the same points as those in the first embodiment will not be described.

[0092] The displacement prism 62 splits the multiple beams collimated by the collimator lens 52 into multiple beam groups, and guides each of the multiple beam groups to an optical path different from that of the other beam groups among the multiple beam groups. The collimator lens 52 has an FA collimator lens 52A and an SA collimator lens 52B. In other words, the laser module 60 can improve performance, for example, by increasing brightness by polarization synthesis, by separating the optical paths of each of the multiple beam groups and inserting a different optical element for each optical path. Furthermore, each of the multiple beam groups is separated from the other beam groups among the multiple beam groups in the arrangement direction of the multiple emitters.

[0093] Specifically, in the second embodiment, the displacement prism 62 has a single prism 62A, a single prism 62D1, and a single prism 62D2. The single prism 62A has a reflecting surface 62A1 and a reflecting surface 62A2. The reflecting surface 62A1 and the reflecting surface 62A2 are not located on a single plane. The single prism 62D1 has a reflecting surface 62DR1. The reflecting surface 62A1 is parallel to the reflecting surface 62DR1. The single prism 62D2 has a reflecting surface 62DR2. The reflecting surface 62A2 is parallel to the reflecting surface 62DR2. That is, the displacement prism 62 has two sets of two parallel reflecting surfaces facing each other.

[0094] Each of the reflecting surfaces 62A1, 62A2, 62DR1, and 62DR2 of the displacement prism 62 is inclined with respect to a plane perpendicular to the direction in which the multiple beams collimated by the collimator lens 52 travel to the displacement prism 62. The reflecting surfaces 62A1 and 62DR1 collimate the parallel beam B iE The position of a part of the beam is translated in the -x and -y directions, and the parallel beam B iE The position of another part of the parallel beam B is translated in the -x and -y directions. iE are rearranged into two rows in the y direction and two beam groups Bx and By that are spaced apart from each other in the x direction.

[0095] 15 is a diagram showing the displacement prism 62 when the laser module 60 according to the second embodiment is viewed from the -z direction side toward the +z direction side. iE The single prism 62A is provided with a gripping portion 62B that can grip and hold the reflective surface 62A1 and the reflective surface 62A2 in the +y direction when viewed from the outside. iE The single prism 62A is provided with an adhesive portion 62C on the surface in the -y direction that is to be adhered to the support base material 56. The single prism 62A is configured to receive the beam B iE The adhesive is applied to the support substrate 56 without interfering with the other components.

[0096] The single prism 62D1 is provided with a gripping portion 62E1 that can be gripped in the -x direction as viewed from the reflecting surface 62DR1. The single prism 62D1 is designed to prevent the gripping arm or adhesive of an assembly device from coming into contact with the reflecting surface 62DR1 or the beam B iE The single prism 62D2 is provided with a gripping portion 62E2 that can be gripped in the +x direction as viewed from the reflecting surface 62DR2. The single prism 62D2 is designed to prevent the gripping arm or adhesive of an assembly device from coming into contact with the reflecting surface 62DR2 or the beam B from interfering with the reflecting surface 62DR2. iE The single prism 62D1 has a surface in the -y direction provided with an adhesive portion 62F1 that is adhered to the support base material 56. The single prism 62D2 has a surface in the -y direction provided with an adhesive portion 62F2 that is adhered to the support base material 56. The single prism 62D1 and the single prism 62D2 are arranged such that the beam B iE The adhesive is applied to the support substrate 56 without interfering with the other components.

[0097] Since the displacement prism 62 has the above-mentioned structure, the manufacturer can generate the beam B iE By precisely adjusting each element while grasping the direction of travel of the laser beam, a high-performance laser module 60 can be manufactured.

[0098] Next, the configuration and function of the beam rotation means 61 will be described. The beam rotation means 61 rotates the beam B emitted from each of the multiple emitters of the multi-emitter laser 51. iE Specifically, the beam rotation means 61 includes NE beam rotation elements 61. iE and beam B iE is rotated 90° around the optical axis.

[0099] FIG. 16 shows a beam rotating element 61 included in a beam rotating means 61 of a laser module 60 according to the second embodiment. iE FIG. 17 is a first diagram for explaining a beam rotating element 61 included in a beam rotating means 61 of a laser module 60 according to the second embodiment. iE FIG. 2 is a second diagram for explaining the beam rotating element 61. iE As shown in FIG. 16, this is a Keplerian equal-magnification beam expander that is composed of a pair of cylindrical lenses with a curvature in the 45° direction.

[0100] As shown in Figure 17, beam B iE , beam rotating element 61 iE When the beam passes through the beam B, it is inverted by 45°, and the beam profile in the x direction and the beam profile in the y direction are interchanged. iE In the x direction, it becomes a parallel beam with beam quality M2F and beam radius wBF, and in the y direction, it becomes a divergent beam with beam quality M2S and half-angle of divergence θLS.

[0101] The standard number of rows NLS in the beam rearrangement in the displacement prism 62 is expressed by the following formula (31) when the beam rotation means 61 is not present, and is expressed by the following formula (32) when the beam rotation means 61 is present.

[0102]

number

[0103]

number

[0104] Since NLS is larger than NLSB and the number of rows is relatively small, the design of the arrangement of the reflecting surfaces of the displacement prism 62 and the structure of the gripping part is easy. More specifically, the beam rotation means 61 switches the direction of FA and the direction of SA while leaving the arrangement of the beams as they are, so that the ratio of SA to FA of the focusing NA for making the focused spot circular is set to NE×M2F / M2S, which is smaller than the ratio NE×M2S / M2F when the beam rotation means 61 does not exist. In other words, the beam rotation means 61 can reduce the optimal number of rows when the displacement prism 62 rearranges the beams, and the design of the arrangement of the reflecting surfaces and the structure of the gripping part and adhesive part is easy.

[0105] Next, the polarization synthesis will be described. By synthesizing two beams with polarizations differing by 90 degrees into one beam by the polarizing beam splitter 65, the brightness can be doubled.

[0106] The multi-emitter laser 51 is a semiconductor laser, and the beams emitted are TE polarized. In other words, the beams emitted are x polarized beams whose electric field oscillates in the x direction. All of the beams B iE is split into half beam group Bx and half beam group By, beam group Bx enters polarizing beam splitter 65 while maintaining its polarization, while beam group By has its direction of polarization rotated by half wave plate 63 to become y-polarized light, which then enters polarizing beam splitter 65. Polarizing beam splitter 65 transmits x-polarized light and reflects y-polarized light, thereby combining the beams. The x-polarized light is p-polarized light, and the y-polarized light is s-polarized light.

[0107] The half-wave plate 63 is an example of a polarization rotation means arranged in the optical path of one or more of the multiple beam groups. The polarization rotation means rotates the polarization of the beam group in the optical path in which it is arranged. The polarizing beam splitter 65 combines a polarization-rotated beam group, which is a beam group whose polarization has been rotated by the polarization rotation means, with one or more beam groups other than the polarization-rotated beam group among the multiple beam groups.

[0108] The separation of the beam group Bx and the beam group By in the x-direction provides a space margin for inserting and adjusting the half-wave plate 63 and the merging mirror 64 in the optical path of the beam group By. The provision of a space margin contributes to improving productivity.

[0109] The standard number of rows NLS in the beam rearrangement in the displacement prism 62 is expressed by the following equation (33) through polarization synthesis, and when the beam rotation means 61 is combined, it can be reduced to the value expressed by the following equation (34).

[0110]

number

[0111]

number

[0112] The phase difference between the polarizations due to the displacement prism 62 may cause light loss in the polarization synthesis.

[0113] Parallel beam B iE A part of the beam B is reflected twice by the reflecting surfaces 62A1, 62A2, 62DR1, and 62DR2 of the displacement prism 62. iE3 is a diagram showing the state when viewed from the -z direction toward the +z direction. The beam incident on the displacement prism 62 is x-polarized, but the incidence plane of the displacement prism 62 is not perpendicular to the x-axis, and the angle between the incidence plane and the y-axis is inclined θP. Therefore, the electric field ex of the beam has a p-polarized component ep and an s-polarized component es with respect to the incidence plane. ep and es are expressed by the following equation (35).

[0114]

number

[0115] If the phase difference between the p-polarized light and the s-polarized light due to two reflections at the displacement prism 62 is φP, the following equation (36) is obtained. This phase difference is the inter-polarized phase difference.

[0116]

number

[0117] Due to the phase difference between the polarizations, beam B iE changes from linearly polarized light to elliptically polarized light. The polarization component ex' in the x direction is expressed by the following equation (37), and the polarization component ey' in the y direction is expressed by the following equation (38).

[0118]

number

[0119]

number

[0120] The light intensity Ix' is expressed by the following equation (39), and the light intensity Iy' is expressed by the following equation (40).

[0121]

number

[0122]

number

[0123] Due to the inter-polarization phase difference φP, a y-polarized component Iy' that did not exist initially is generated, and the y-polarized component Iy' is lost in the polarization synthesis. This loss is called "phase difference loss." That is, a reflection loss occurs for the beam group Bx, and a transmission loss occurs for the beam group By. For the y-polarized component Iy', the following equation (41) is obtained.

[0124]

number

[0125] According to formula (41), by setting the inter-polarization phase difference φP to 6° or less, the phase difference loss can be suppressed to 0.27% or less, which is negligible compared to other losses in design and manufacturing. In addition, the inter-polarization phase difference per reflection of ≦3° is not a very strict requirement for a total reflection film made of a dielectric multilayer film, which helps to suppress cost increases.

[0126] Depending on the definition of the sign of P-polarized light with respect to reflection, a difference of 180° occurs in the inter-polarized phase difference φP, but this difference does not affect the calculation of the phase difference loss.

[0127] Table 2 below shows an example of optical design parameters according to the second embodiment.

[0128] [Table 2]

[0129] The standard number of columns is expressed by the following equation (42), and the actual number of columns is NL=2.

[0130]

number

[0131] Parallel beam B iE The radius wBF in the FA direction of the parallel beam B is expressed by the following equation (43). iE The radius wBS in the SA direction is expressed by the following equation (44).

[0132]

number

[0133]

number

[0134] The maximum light collection radius wBC for the optical fiber 55 is expressed by the following formula (45).

[0135]

number

[0136] 15, NE / 2=20 elliptical beams with radii wBF and wBS are arranged in a circle with a maximum focusing radius wBC by being rearranged into NL=2 rows by the displacement prism 62. The radius of the focused spot on the end face 55A of the optical fiber 55 is expressed by the following formulas (46) and (47), and is shorter than the core radius wC.

[0137]

number

[0138]

number

[0139] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or the embodiments may be combined with each other. Also, parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0140] 50,60 Laser module, 51 Multi-emitter laser, 51E iE Emitter, 52 Collimating lens, 52A FA collimating lens, 52B SA collimating lens, 53,62 Displacement prism, 53A,53D iP ,62A,62D1,62D2 single prism,53A iP ,53DR iP ,62A1,62A2,62DR1,62DR2 reflective surface, 53B,53E iP ,62B,62E1,62E2 grip part, 53C,53F iP , 62C, 62F1, 62F2 adhesive portion, 54 condenser lens, 55 optical fiber, 55A end face of optical fiber, 56 support substrate, 61 beam rotation means, 61 iE Beam rotating element, 63 1 / 2 wave plate, 64 merging mirror, 65 polarizing beam splitter, B iE Beam, Bx,By beam group.

Claims

1. a multi-emitter laser having a plurality of emitters arranged in a row and emitting a beam; a collimator lens that converts a plurality of beams emitted from the plurality of emitters of the multi-emitter laser into parallel beams; a displacement prism having two opposing parallel reflecting surfaces, which reflects a part of the plurality of beams converted into the parallel beam by the collimating lens twice by the two reflecting surfaces and translates the part of the plurality of beams converted into the parallel beam, thereby rearranging the plurality of beams converted into the parallel beam into a plurality of rows of parallel beams; An optical fiber; a condenser lens that condenses the parallel beams rearranged by the displacement prism onto an end surface of the optical fiber, The arrangement direction of the plurality of emitters of the multi-emitter laser is defined as an x-direction, a direction in which the plurality of beams converted into the parallel beams by the collimator lens proceed to the displacement prism is defined as a z direction; A direction perpendicular to both the x direction and the z direction is defined as a y direction, Each of the two reflecting surfaces is inclined in both the x-direction and the y-direction; the displacement prism divides the plurality of beams converted into the parallel beams by the collimator lens into a plurality of beam groups, and guides each of the plurality of beam groups to an optical path different from that of the other beam groups among the plurality of beam groups; a polarization rotation means disposed in the optical path of one or more of the plurality of beam groups; a polarizing beam splitter; the polarization rotation means rotates the polarization of the beams in the optical path in which it is disposed; The polarizing beam splitter combines a polarization-rotated beam group, which is the beam group whose polarization has been rotated by the polarization rotation means, with one or more beam groups other than the polarization-rotated beam group among the plurality of beam groups. A laser module comprising:

2. A multi-emitter laser having a plurality of emitters arranged in a row and emitting beams; a collimator lens that converts a plurality of beams emitted from the plurality of emitters of the multi-emitter laser into parallel beams; a displacement prism having two opposing parallel reflecting surfaces, which reflects a part of the plurality of beams converted into the parallel beam by the collimating lens twice by the two reflecting surfaces and translates the part of the plurality of beams converted into the parallel beam, thereby rearranging the plurality of beams converted into the parallel beam into a plurality of rows of parallel beams; An optical fiber; a condenser lens that condenses the parallel beams rearranged by the displacement prism onto an end surface of the optical fiber, The arrangement direction of the plurality of emitters of the multi-emitter laser is defined as an x-direction, a direction in which the plurality of beams converted into the parallel beams by the collimator lens proceed to the displacement prism is defined as a z direction; A direction perpendicular to both the x direction and the z direction is defined as a y direction, Each of the two reflecting surfaces is inclined in both the x-direction and the y-direction; the displacement prism divides the plurality of beams converted into the parallel beams by the collimator lens into a plurality of beam groups, and guides each of the plurality of beam groups to an optical path different from that of the other beam groups among the plurality of beam groups; The phase difference between p-polarized light and s-polarized light due to the two reflections at the displacement prism is 6° or less. A laser module comprising:

3. Each of the plurality of beam groups is spaced apart from other beam groups among the plurality of beam groups in an arrangement direction of the plurality of emitters.

3. The laser module according to claim 1, wherein the first and second electrodes are arranged in a first direction.

4. a polarization rotation means disposed in the optical path of one or more of the plurality of beam groups; a polarizing beam splitter; the polarization rotation means rotates the polarization of the beams in the optical path in which it is disposed; The polarizing beam splitter combines a polarization-rotated beam group, which is the beam group whose polarization has been rotated by the polarization rotation means, with one or more beam groups other than the polarization-rotated beam group among the plurality of beam groups.

3. The laser module according to claim 2.

5. Each of the plurality of beam groups is separated from other beam groups among the plurality of beam groups in an arrangement direction of the plurality of emitters, a polarization rotation means disposed in the optical path of one or more of the plurality of beam groups; a polarizing beam splitter; the polarization rotation means rotates the polarization of the beams in the optical path in which it is disposed; The polarizing beam splitter combines a polarization-rotated beam group, which is the beam group whose polarization has been rotated by the polarization rotation means, with one or more beam groups other than the polarization-rotated beam group among the plurality of beam groups.

3. The laser module according to claim 2.

6. the collimating lens includes a first cylindrical lens and a second cylindrical lens, The first cylindrical lens and the second cylindrical lens collimate light traveling along two orthogonal axes in a plane orthogonal to the optical axis of a beam emitted by each of the multiple emitters of the multi-emitter laser.

6. The laser module according to claim 1, wherein the first and second electrodes are arranged in a first direction.

7. The multi-emitter laser further includes a beam rotation means for rotating the beams emitted from each of the plurality of emitters of the multi-emitter laser about an optical axis.

7. The laser module according to claim 1, wherein the first and second electrodes are arranged in a first direction.

Images