External resonator type semiconductor laser device

Abstract

An external resonator type semiconductor laser device (1A) comprises: an external resonator (5) composed of one or more laser diode light sources (2) and a VBG (6); an optical fiber (7) for outputting output light (La) from the laser diode light source (2) to the VBG (6) and for inputting return light (Lb) from the VBG (6); and a displacement section (8) for displacing the configuration position of the VBG (6) relative to an input / output end face (9) of the optical fiber (7).

Description

Technical Field

[0001] The present invention relates to an external resonator type semiconductor laser device. Background Art

[0002] Generally, semiconductor laser devices have excellent characteristics such as high efficiency, small size, light weight, and long life. Therefore, semiconductor laser devices are used in a wide range of fields such as material processing, solid laser excitation, environmental measurement, spectroscopic analysis, and medical treatment. On the other hand, the laser output from the semiconductor laser device has a large radiation angle and a wide spectral band. Therefore, for example, in the field of solid laser excitation, a technology is required to stably narrow the oscillation spectrum of the laser.

[0003] As a technology for stably narrowing the oscillation spectrum of laser, for example, an external resonator type semiconductor laser device can be cited. For example, Patent Document 1 discloses a laser device that uses a plurality of LD light sources and VBG to constitute an external resonator for the purpose of increasing the output and stabilizing the laser. For example, Patent Document 2 discloses a light emitting device that adjusts the output characteristics of a laser light source by causing light focused by a lens to be incident on a VBG (Volume Bragg Grating).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: U.S. Patent Application No. 7212554

[0007] Patent Document 2: Japanese Patent Application No. 2007-527616 Summary of the invention

[0008] Problems to be solved by the invention

[0009] For further application of semiconductor laser devices, in addition to stable narrowband laser, output adjustment of laser is also an important factor. However, in laser devices such as those disclosed in Patent Documents 1 and 2, in order to adjust the output of laser, the VBG constituting the external resonator needs to be replaced with a VBG having a different reflectivity, which results in problems such as difficulty in obtaining operability of output adjustment.

[0010] The present invention has been made to solve the above-mentioned technical problems, and an object of the present invention is to provide an external resonator type semiconductor laser device that can stably narrow the frequency band of laser light and can easily perform output adjustment.

[0011] Technical means of solving problems

[0012] An external resonator type semiconductor laser device according to one aspect of the present invention includes: an external resonator composed of one or more laser diode light sources and a VBG; an optical fiber that outputs output light from the laser diode light source to the VBG and inputs return light from the VBG; and a displacement unit that displaces the configuration position of the VBG relative to the input and output end faces of the output light and the return light in the optical fiber.

[0013] In the external resonator type semiconductor laser device, by using VBG to constitute an external resonator, the wavelength of the light resonating in the external resonator can be selected. Therefore, the laser can be stably narrow-banded. In addition, in the external resonator type semiconductor laser device, the configuration position of the VBG can be displaced relative to the input and output end faces of the optical fiber by the displacement unit. As a result, the return condition of the return light from the VBG can be changed on the input and output end faces of the optical fiber, and the light amount of the return light optically coupled to the input and output end faces can be adjusted. Therefore, the output adjustment of the laser can be easily implemented.

[0014] In the external resonator type semiconductor laser device, the displacement unit may also displace the VBG in the direction along the optical axis of the light. In this case, the diffusion condition of the return light from the VBG can be changed on the input and output end faces of the optical fiber by the displacement of the VBG. Therefore, the light amount of the return light optically coupled to the input and output end faces can be easily adjusted.

[0015] In an external resonator type semiconductor laser device, a focusing lens may be disposed between the input / output end face of the optical fiber and the VBG. In this case, the amount of change in the diffusion state of the return light from the VBG relative to the displacement amount of the VBG can be suppressed. Therefore, the amount of return light optically coupled to the input / output end face can be adjusted more finely.

[0016] In an external resonator type semiconductor laser device, a collimating lens may be disposed between the input / output end face of the optical fiber and the VBG, and the displacement portion may displace the VBG in a direction intersecting the optical axis of the output light. In this case, the amount of light reflected by the VBG may be changed by the displacement of the VBG. Therefore, the amount of return light optically coupled to the input / output end face may be easily adjusted.

[0017] Effects of the Invention

[0018] According to the present invention, it is possible to stably narrow the bandwidth of laser light and to easily perform output adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 1 is a schematic diagram showing the structure of an external cavity type semiconductor laser device according to the first embodiment.

[0020] Figure 2It is shown Figure 1 FIG. 1 is a schematic diagram showing the state of output adjustment in an external cavity type semiconductor laser device.

[0021] Figure 3 It is a figure which shows the result of the effect confirmation test of this invention.

[0022] Figure 4 FIG. 1 is a schematic diagram showing the structure of an external cavity type semiconductor laser device according to a second embodiment.

[0023] Figure 5 FIG. 1 is a schematic diagram showing the structure of an external cavity type semiconductor laser device according to a third embodiment. DETAILED DESCRIPTION

[0024] Hereinafter, preferred embodiments of an external resonator type semiconductor laser device according to one aspect of the present invention will be described in detail with reference to the accompanying drawings.

[0025] [First embodiment]

[0026] Figure 1 1 is a schematic diagram showing the structure of an external resonator type semiconductor laser device according to the first embodiment. As shown in the figure, the external resonator type semiconductor laser device 1A according to the first embodiment is configured to include: a light source unit 4, which is optically coupled to one or more laser diode light sources 2 through a focusing system 3; a VBG (Volume Bragg Grating) 6 constituting an external resonator 5 between the laser diode light source 2; an optical fiber 7 that guides light between the light source unit 4 and the VBG 6; and a displacement unit 8 that displaces the configuration position of the VBG 6.

[0027] In the present embodiment, the light source unit 4 is composed of a plurality of laser diode light sources 2. In addition, the focusing system 3 is composed of, for example, a fiber coupler or the like. The optical fiber 7 is composed of, for example, a multimode optical fiber with a core of 100 μm. The end of the optical fiber 7 on the side of the light source unit 4 is optically coupled to the focusing system. The end of the optical fiber 7 on the side of the VBG 6 is an input / output end face 9 that outputs light from the light source unit 4 (hereinafter referred to as "output light La") and inputs light from the VBG 6 (hereinafter referred to as "return light Lb"). A connector or a ferrule may also be provided on the input / output end face 9 as required. When a connector is used, it is preferable to use a coaxial connector such as an SMA connector.

[0028] VBG 6 is an optical element that exhibits narrow wavelength selectivity and narrow angle selectivity by Bragg reflection of input light. Here, a reflective VBG having a reflectivity of 90% or more with respect to the output light La is used. VBG 6 is formed in a plate shape with a side of 1 mm and a thickness of 2 mm, for example. VBG 6 is arranged on a base 10 so as to be located on the optical axis of the output light La output from the input / output end face 9 of the optical fiber 7. In the present embodiment, the optical axis of the output light La is orthogonal to the input / output end face 9 of the optical fiber 7. In addition, in the present embodiment, a focusing lens 11 is arranged between the input / output end face 9 of the optical fiber 7 and VBG 6. The output light La output from the input / output end face 9 of the optical fiber 7 is focused by the focusing lens 11 and is incident on VBG 6. In VBG 6, a specific wavelength component in the incident output light La is Bragg reflected to become return light Lb. The return light Lb is optically coupled to the input / output end face 9 and guided to the optical fiber 7, and is returned to the active layer of each laser diode light source 2 via the focusing system 3.

[0029] The displacement section 8 is a portion that displaces the configuration position of the VBG 6 relative to the input / output end face 9 of the optical fiber 7. In the present embodiment, the displacement section 8 is constituted by, for example, a micro screw 12 mounted on the base 10. The micro screw 412 is provided on the back side of the VBG 6 as viewed from the input / output end face 9 side. By operating the micro screw 12, the VBG 6 is displaced in the direction along the optical axis of the output light La. The displacement section 8 is not limited to the micro screw 12, and may be constituted by other mechanisms such as a piezoelectric element, a pantograph, or a spring. The displacement section 8 may also be a structure that displaces the VBG 6 on the base by a non-contact mechanism such as an electromagnetic force. Although it depends on the selection of the focusing lens 11, the amount of movement of the VBG 6 by the displacement section 8 is about several mm. As an example, when the diameter of the focusing lens 11 is φ10 mm and the focal length is 7.5 mm, the amount of movement of the VBG 6 by the displacement section 8 is about ±2 mm.

[0030] When the VBG 6 is moved away from the focusing position of the output light La by the displacement unit 8, as shown in FIG. Figure 1 As shown in FIG. 1 , the diffusion of the return light Lb from the VBG 6 on the input / output end face 9 can be reduced. In contrast, when the VBG 6 is brought closer to the input / output end face 9 by the displacement portion 8, as shown in FIG. Figure 2 As shown, the diffusion condition of the return light Lb from the VBG 6 on the input / output end face 9 can be increased. As a result, the light amount of the return light Lb optically coupled to the input / output end face 9 of the optical fiber 7 can be adjusted, and the output adjustment of the laser light (not shown) output from the external resonator type semiconductor laser device 1A can be performed.

[0031] Figure 3: is a graph showing the results of the effect confirmation test of the present invention. In the effect confirmation test, the spectral profile of the laser light output from the semiconductor laser device was measured for the case where no external resonator was formed (curve A), the case where the VBG was located at the focusing position of the focusing lens by the displacement part (curve B), and the case where the VBG was located near the input and output end faces of the optical fiber by the displacement part (curve C). The value of the driving current applied to each laser diode light source was set to 1.8A. Figure 3 The horizontal axis is wavelength and the vertical axis is intensity (arbitrary units).

[0032] from Figure 3 The results shown show that when the external resonator is formed using VBG, a steep peak with a narrow wavelength range can be obtained compared to the case where the external resonator is not formed. In addition, it can be seen that when the VBG is located at the focusing position of the focusing lens and in the vicinity of the input and output end faces of the optical fiber, only the intensity changes while the peak waveform is maintained. Therefore, it can be concluded that the structure in which the configuration position of the VBG is displaced by the displacement part contributes to the realization of both stable narrow-band laser and output adjustment.

[0033] As described above, in the external resonator type semiconductor laser device 1A, the wavelength of the light resonating in the external resonator 5 can be selected by configuring the external resonator 5 using the VBG 6. Therefore, the stable narrowbanding of the laser light can be performed. In addition, in the external resonator type semiconductor laser device 1A, the configuration position of the VBG 6 can be displaced relative to the input / output end face 9 of the optical fiber 7 by the displacement portion 8. Thus, the return condition of the return light Lb from the VBG 6 can be changed on the input / output end face 9 of the optical fiber 7, and the light amount of the return light Lb optically coupled to the input / output end face 9 can be adjusted. Therefore, the output adjustment of the laser light can be easily performed.

[0034] In this embodiment, the displacement unit 8 displaces the VBG 6 in the direction along the optical axis of the light. In this case, the diffusion condition of the return light Lb from the VBG 6 can be changed on the input / output end face 9 of the optical fiber 7 by the displacement of the VBG 6. Therefore, the light amount of the return light Lb optically coupled to the input / output end face 9 can be easily adjusted, and the output adjustment of the laser can be easily implemented.

[0035] In the present embodiment, the condenser lens 11 is disposed between the input / output end face 9 of the optical fiber 7 and the VBG 6. In this case, the amount of change in the diffusion condition of the return light Lb from the VBG 6 relative to the displacement amount of the VBG 6 can be suppressed. Therefore, the light amount of the return light Lb optically coupled to the input / output end face 9 can be adjusted more finely.

[0036] As an advantage of using VBG 6 to constitute the external resonator 5, it is possible to ensure the angle selectivity of the return light Lb compared to the case of using an element such as a partial reflector. When VBG 6 is used, the output light La is Bragg reflected at VBG 6. In the reflection on a normal mirror, the incident angle θ and the reflection angle α are equal. On the other hand, in the reflection on VBG 6, the reflection angle is α±2Δθ with respect to the incident angle θ, and has an angular width of 2Δθ (Δθ=nλcosθ n / Dsin2θ: where n is the refractive index of VBG, λ is the wavelength of incident light, and D is the thickness of VBG). Therefore, even if an angle deviation of 2Δθ occurs in VBG 6, the return light Lb of a specific wavelength component can be optically coupled to the input / output end face 9 of the optical fiber 7.

[0037] [Second Embodiment]

[0038] Figure 4 1 is a schematic diagram showing the structure of an external resonator type semiconductor laser device according to a second embodiment. As shown in the figure, the external resonator type semiconductor laser device 1B according to the second embodiment is different from the first embodiment in that the arrangement of the focusing lens 11 between the input and output end face 9 of the optical fiber 7 and the VBG 6 is omitted. As in the first embodiment, the VBG 6 is formed in a plate shape with a side of 1 mm and a thickness of 2 mm, for example.

[0039] In such a second embodiment, the wavelength of the light resonating in the external resonator 5 can also be selected by configuring the external resonator 5 using the VBG 6. Therefore, the stable narrowbanding of the laser can be performed. In addition, in this second embodiment, the configuration position of the VBG 6 can also be displaced relative to the input / output end face 9 of the optical fiber 7 by the displacement portion 8. Thus, the return condition of the return light Lb from the VBG 6 can be changed on the input / output end face 9 of the optical fiber 7, and the light amount of the return light Lb optically coupled to the input / output end face 9 can be adjusted. Therefore, the output adjustment of the laser can be easily performed.

[0040] In the second embodiment, the condenser lens 11 is not disposed between the input / output end face 9 of the optical fiber 7 and the VBG 6. Therefore, the amount of change in the diffusion state of the return light Lb from the VBG 6 relative to the displacement of the VBG 6 can be increased compared to the first embodiment. Therefore, the amount of the return light Lb optically coupled to the input / output end face 9 can be greatly adjusted by only slightly displacing the configuration position of the VBG 6.

[0041] [Third Embodiment]

[0042] Figure 5Schematic diagram showing the structure of an external resonator type semiconductor laser device according to the third embodiment. As shown in the figure, in the external resonator type semiconductor laser device 1C according to the third embodiment, the displacement direction of the VBG 6 by the displacement portion 8 is different from that in the first embodiment.

[0043] More specifically, in the present embodiment, a collimating lens 13 is arranged between the input / output end face 9 of the optical fiber 7 and the VBG 6 instead of the condensing lens 11. The collimating lens 13 is an element that collimates the output light La output from the input / output end face 9. In the present embodiment, the VBG 6 is formed in a plate shape with, for example, a side of 1 cm and a thickness of 2 mm. The VBG 6 is arranged on the base 10 so as to straddle the beam edge of the output light La collimated by the collimating lens 13. In the VBG 6, a specific wavelength component in a part of the collimated output light La is Bragg reflected to become the return light Lb. The rest of the output light La is not incident on the VBG 6 and is blocked by, for example, an absorption component or a shielding component not shown in the figure so as not to return to the input / output end face 9.

[0044] In the present embodiment, a micro screw 12 constituting the displacement section 8 is provided on the side surface of the VBG 6. By operating the micro screw 12, the VBG 6 is displaced in a direction intersecting (orthogonal in this case) with the optical axis of the output light La. When the VBG 6 is displaced in a direction advancing toward the output light La side by the displacement section 8, the range of the output light La reflected by the VBG 6 becomes wider, and the light amount of the return light Lb optically coupled to the input / output end face 9 can be increased. On the other hand, when the VBG 6 is displaced in a direction retreating from the output light La side by the displacement section 8, the range of the output light La reflected by the VBG 6 becomes narrower, and the light amount of the return light Lb optically coupled to the input / output end face 9 can be reduced.

[0045] In the third embodiment, the wavelength of the light resonating in the external resonator 5 can be selected by configuring the external resonator 5 using the VBG 6. Therefore, the stable narrowbanding of the laser light can be performed. In addition, in the third embodiment, the configuration position of the VBG 6 can be displaced relative to the input / output end face 9 of the optical fiber 7 by the displacement portion 8. Thus, the return condition of the return light Lb from the VBG 6 can be changed on the input / output end face 9 of the optical fiber 7, and the light amount of the return light Lb optically coupled to the input / output end face 9 can be adjusted. Therefore, the output adjustment of the laser light can be easily performed.

[0046] Explanation of symbols

[0047] 1A to 1C…external resonator type semiconductor laser device, 2…laser diode light source, 6…VBG, 7…optical fiber, 8…displacement unit, 9…input and output end faces, 11…condensing lens, 13…collimating lens, La…output light, Lb…return light.

Claims

1. An external resonator type semiconductor laser device, characterized in that: include: an external resonator consisting of one or more laser diode light sources and a VBG; an optical fiber that outputs the output light from the laser diode light source to the VBG and is input with the return light from the VBG; and a displacement unit that displaces the configuration position of the VBG relative to the input and output end faces of the output light and the return light in the optical fiber, A focusing lens is arranged between the optical fiber and the displacement portion. The displacement unit displaces the arrangement position of the VBG in a direction along the optical axis of the output light so that the light amount of the return light from the VBG to the optical fiber changes.

2. The external resonator type semiconductor laser device according to claim 1, wherein: The condenser lens is arranged between the input and output end faces of the optical fiber and the VBG.

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