JP2008122096A - Wavelength detection device and wavelength detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength detection device and a wavelength detection method capable of preventing an error of wavelength detection caused by positional deviation of an optical component. <P>SOLUTION: A laser light source device 10A is equipped with a laser diode 1 for emitting a light beam; a diffraction grating 3 for diffracting the light beam into a plurality of first diffracted lights including zero-order light, and returning a part of the plurality of first diffracted lights to the laser diode 1; a beam splitter 4 for separating the zero-order light in the plurality of first diffracted lights into first and second light beams, and emitting the first light beam to the outside; a diffraction grating 5 for diffracting the second light beam into a plurality of second diffracted lights including third and fourth diffracted lights; a two-split photodetector 8 for receiving the third diffracted light by a plurality of first light receiving parts; a two-split photodetector 9 for receiving the fourth diffracted light by a plurality of second light receiving parts; and an operation part for detecting a wavelength of the light beam based on a differential signal of the plurality of first light receiving parts and a differential signal of the plurality of second light receiving parts. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wavelength detection device and a wavelength detection method, and more specifically to a wavelength detection device and a wavelength detection method for detecting the wavelength of a light beam of an external resonance laser.

  Research and development of hologram recording devices that record data using holography is ongoing.

  In the hologram recording apparatus, two of modulated signal light and unmodulated reference light are generated from laser light, and these are irradiated to the same location of the hologram recording medium. Thereby, the signal light and the reference light interfere on the hologram recording medium, and a diffraction grating (hologram) is formed at the irradiation point. As a result, data is recorded on the hologram recording medium. When the signal light is modulated, data is superimposed on the signal light.

  By irradiating the recorded hologram recording medium with reference light, diffracted light (reproduced light) is generated from the diffraction grating formed during recording. Since the reproduction light includes data superimposed on the signal light at the time of recording, the recorded signal can be reproduced by receiving the data with a light receiving element.

  A light source for hologram recording / reproduction requires a single-mode laser light source with extremely good coherency, such as a gas laser or SHG (Second Harmonic Generation) laser. Since a normal laser diode is a multimode, it is not sufficient as a light source for hologram recording and reproduction in terms of coherency.

  However, if the laser diode is configured as an external resonance laser, a light source for hologram recording / reproduction with good coherency can be realized. A blue laser diode that is small and power-saving can also be used as a hologram light source by adopting an external resonance type.

  What is important when using laser light for hologram recording is wavelength reproducibility. In particular, when performing wavelength multiplexing for recording information by changing the wavelength, the wavelength of the output light must be controlled to the intended length. When wavelength multiplexing is performed, for example, a wavelength variable type external resonator laser can be used.

  As an external resonator in the external resonator laser, for example, there is a Littrow type. In such an external resonator, first, a laser beam emitted from a laser diode is converted into parallel light by a collimating lens, and is irradiated onto a reflective diffraction grating. The light beam reflected by the diffraction grating is separated into zero-order light and first-order light. The primary light passes through the incoming optical path as it is and returns to the laser diode.

  As described above, the external cavity laser is composed of a laser diode and a reflective diffraction grating. The laser diode oscillates at a wavelength determined by the grating shape of the reflective diffraction grating and the distance between the reflective diffraction grating and the laser diode. A means for detecting the wavelength of such a laser light source is disclosed in Patent Document 1, for example. In Patent Document 1, the wavelength of light is detected using a simplified device. Specifically, it is as follows.

FIG. 12 is a diagram showing a schematic configuration of a conventional laser light source device 100.
Referring to FIG. 12, a conventional laser light source apparatus 100 includes a laser diode 101, a collimating lens 102, a diffraction grating 103, a control unit 110, an incomplete mirror 111, and a two-divided photodetector 112. The laser diode 101 emits multimode laser light, for example, blue laser light of about 410 nm. The collimating lens 102 converts the laser light emitted from the laser diode 101 into parallel light.

  FIG. 13 is a diagram showing a state of laser light incident on the diffraction grating 103 in the laser light source device 100 of FIG.

  As shown in FIG. 13, the diffraction grating 103 receives the laser light from the laser diode 101, generates 0th-order light L0 in a predetermined direction, and primary light L1a, L1b, L1k in different directions for each wavelength. Is generated. Most of the laser light emitted from the laser diode 101 is reflected like a mirror as the 0th-order light L0 of the diffraction grating 103.

  The angle between the diffraction grating 103 and the laser diode 101 is set so that the primary light L1k having a specific wavelength (for example, 410 nm) out of the primary lights L1a, L1b, and L1k returns to the laser diode 101. Thereby, only the wavelength component is amplified in the laser diode 101. As a result, the laser diode 101 performs single mode oscillation.

  Returning to FIG. 12, the incomplete mirror 111 reflects a part of the zero-order light L0 diffracted by the diffraction grating 103 as a light beam Lr toward the outside of the laser light source device 100 and transmits the other part. .

  FIG. 14 is a diagram showing an example of the configuration of the two-divided photodetector 112 in the laser light source apparatus 100 of FIG. As shown in FIG. 14, the two-divided photodetector 112 is arranged at a position where the light beam SP transmitted through the incomplete mirror 111 is irradiated, and has light receiving portions 112A and 112B divided into two.

  FIG. 15 is a diagram showing the relationship between the oscillation wavelength of the laser diode 101 and the angle of the diffraction grating 103.

  As shown in FIG. 15, the oscillation wavelength of the laser diode 101 changes according to the angle of the diffraction grating 103. Referring to FIG. 12, a part of 0th-order light L0 diffracted by diffraction grating 103 passes through imperfect mirror 111 as light beam SP. The light beam SP transmitted through the incomplete mirror 111 is incident on the dividing line of the two-divided photodetector 112.

For this reason, the light beam SP on the two-divided photodetector 112 varies in the direction of the arrow in FIG. 14 according to the oscillation wavelength of the laser diode 101. In the two-divided photodetector 112, the output varies between the light receiving unit 112A and the light receiving unit 112B in accordance with the variation of the light beam SP. The laser light source device 100 detects the oscillation wavelength of the laser diode 101 by detecting this output fluctuation.
JP 2006-114183 A

  The conventional laser light source device 100 shown in FIG. 12 detects the light fluctuation amount (wavelength change) by the differential output of one two-divided photodetector 112. However, the optical components such as the two-divided photodetector 112 and the incomplete mirror 111 may be displaced due to a change in environmental temperature or a secular change. When the position of the optical component is shifted in the conventional laser light source apparatus 100, the differential output level changes, which causes a wavelength detection error.

  SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a wavelength detection device and a wavelength detection method that can prevent an error in wavelength detection due to a positional shift of an optical component.

  According to an aspect of the present invention, there is provided a wavelength detection device that detects the wavelength of a light beam of an external resonance laser, a light source that emits a light beam, and a plurality of first diffracted light beams that include zero-order light. And the first diffraction grating for returning a part of the plurality of first diffracted lights to the light source, and the zero-order light of the plurality of first diffracted lights are separated into the first and second light beams, and the first An optical separation unit that emits the light beam to the outside, a second diffraction grating that diffracts the second light beam into a plurality of second diffracted lights including the third and fourth diffracted lights, and a third diffracted light The first photodetection unit that receives light at the plurality of first light-receiving units, the second photodetection unit that receives the fourth diffracted light at the plurality of second light-receiving units, and the differential between the plurality of first light-receiving units And an arithmetic unit that detects a wavelength of the light beam based on the signal and the differential signals of the plurality of second light receiving units.

  Preferably, the first and second light detection units are arranged on both sides of the 0th order light included in the plurality of second diffracted lights.

  Preferably, in the first and second light detection units, the light receiving unit is divided in a direction perpendicular to the direction of the plurality of second diffracted lights when viewed from the second light beam traveling direction.

  Preferably, the second diffraction grating is divided into a plurality of diffraction parts including the first and second diffraction parts. The first photodetecting unit includes a third photodetecting unit that receives the third diffracted light diffracted by the first diffracting unit by a plurality of third light receiving units, and a first diffracted by the second diffracting unit. And a fourth photodetecting unit that receives the diffracted light 3 by the plurality of fourth light receiving units. The second light detection unit includes a fifth light detection unit that receives the fourth diffracted light diffracted by the first diffraction unit by a plurality of fifth light receiving units, and a second light detection unit diffracted by the second diffraction unit. And a sixth light detection unit that receives the four diffracted lights by the plurality of sixth light receiving units. The computing unit is based on the differential signals of the plurality of third light receiving units, the differential signals of the plurality of fourth light receiving units, the differential signals of the plurality of fifth light receiving units, and the differential signals of the plurality of sixth light receiving units. To detect the wavelength of the light beam.

  Preferably, a condensing unit for condensing the second light beam with an arbitrary curvature on the first and second light detection units via the second diffraction grating is further provided.

  Preferably, the first and second light detection units are arranged on one side of the 0th-order light included in the plurality of second diffracted lights.

  Preferably, in the first and second light detection units, the light receiving unit is divided in a direction parallel to the direction of the plurality of second diffracted lights when viewed from the traveling direction of the second light beam.

  Preferably, the second diffraction grating condenses the second light beam on the first and second light detection units with an arbitrary curvature.

  Preferably, the second diffraction grating is divided into a plurality of diffraction parts including the first and second diffraction parts. The first light detection unit includes a third light detection unit that receives the third diffracted light diffracted by the first diffraction unit by a plurality of third light receiving units. The second light detection unit includes a fourth light detection unit that receives the third diffracted light diffracted by the second diffraction unit by a plurality of fourth light receiving units. The computing unit detects the wavelength of the light beam based on the differential signals of the plurality of third light receiving units and the differential signals of the plurality of fourth light receiving units.

Preferably, the second diffraction grating is a multi-segment hologram.
According to another aspect of the present invention, there is provided a wavelength detection method for detecting the wavelength of a light beam of an external resonant laser, wherein the light beam emitted from a light source is diffracted into a plurality of first diffracted lights including zeroth-order light. And returning a part of the plurality of first diffracted lights to the light source, separating the zero-order light of the plurality of first diffracted lights into the first and second light beams, and bringing the first light beam to the outside Emitting, diffracting the second light beam into a plurality of second diffracted lights including the third and fourth diffracted lights, and receiving the third diffracted lights with the plurality of first light receiving parts. , Detecting the wavelength of the light beam based on the step of receiving the fourth diffracted light by the plurality of second light receiving units and the differential signals of the plurality of first light receiving units and the differential signals of the plurality of second light receiving units. And a step of performing.

  According to the present invention, it is possible to prevent an error in wavelength detection due to a positional shift of the optical component.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Embodiment 1]
FIG. 1 is a diagram showing a schematic configuration of a laser light source apparatus 10A according to Embodiment 1 of the present invention.

  Referring to FIG. 1, a laser light source device 10 </ b> A according to Embodiment 1 includes a laser diode 1, a collimating lens 2, a diffraction grating 3, a beam splitter 4, and a light detection unit 11. The light detection unit 11 includes a diffraction grating 5 and two-divided photodetectors 8 and 9.

  The laser diode 1 emits multimode laser light, for example, blue laser light of about 405 nm. The collimating lens 2 converts the laser light emitted from the laser diode 1 into parallel light. As described with reference to FIG. 13, the diffraction grating 3 receives the laser light from the laser diode 1 and generates zero-order light in a predetermined direction, and generates primary light in a different direction for each wavelength. .

  Most of the laser light emitted from the laser diode 1 is diffracted like a mirror as zero-order light of the diffraction grating 3. The angle between the diffraction grating 3 and the laser diode 1 is set so that the primary light of a specific wavelength (for example, 405 nm) out of the primary light returns to the laser diode 1. As a result, only the wavelength component is amplified in the laser diode 1. As a result, the laser diode 1 performs single mode oscillation.

  The beam splitter 4 reflects a part of the zero-order light diffracted by the diffraction grating 3 as a light beam RL toward the outside of the laser light source device 10A, and transmits the other part as a light beam TL. The reflected light beam RL becomes a light source used for recording or reproducing a hologram, for example. The transmitted light beam TL enters the diffraction grating 5 of the light detection unit 11 and is diffracted into 0th-order light 0L and ± 1st-order diffracted lights + 1L and −1L. The ± first-order diffracted lights + 1L and −1L are incident on the two-divided photodetectors 8 and 9, respectively.

  The laser light source device 10A is configured such that the reflected light beam RL is incident on the diffraction grating 5 of the light detection unit 11 and the transmitted light beam TL is emitted toward the outside of the laser light source device 10A. Also good.

  FIG. 2 is a top view showing a more specific configuration of the light detection unit 11 in the laser light source device 10A of FIG.

  Referring to FIG. 2, the two-divided photodetector 8 is disposed at a position where the −1st-order diffracted light −1L diffracted by the diffraction grating 5 is irradiated, and has light receiving portions 8A and 8B divided into two. . The two-divided photodetector 9 is disposed at a position where the + 1st order diffracted light + 1L diffracted by the diffraction grating 5 is irradiated, and has light receiving portions 9A and 9B divided into two. The diffraction direction of ± first-order diffracted light + 1L and −1L and the dividing line direction of the two-divided photodetectors 8 and 9 are perpendicular to each other when viewed from above.

  The two-divided photodetector 8 receives the spot light 8S of the −1st order diffracted light-1L on the dividing line. The two-divided photodetector 9 receives the + 1st order diffracted light + 1L spot light 9S on the dividing line. Here, when the wavelength of the light beam TL transmitted through the beam splitter 4 in FIG. 1 changes, the diffraction angles of the ± first-order diffracted lights + 1L and −1L of the diffraction grating 5 slightly change accordingly. As a result, the position of the spot light 8S can fluctuate in a direction perpendicular to the dividing line, like the spot lights 8SL and 8SS. Similarly, the position of the spot light 9S can vary in a direction perpendicular to the dividing line, like the spot lights 9SL and 9SS.

  FIG. 3 is a diagram showing an example of a configuration for processing signals output from the two-divided photodetectors 8 and 9.

  Referring to FIG. 3, laser light source device 10 </ b> A further includes adders 11 </ b> A and 11 </ b> B and subtractor 12 on the output side of two-divided photodetectors 8 and 9. Here, signals output from the light receiving portions 8A and 8B of the two-divided photodetector 8 are referred to as output signals 8SA and 8SB, respectively. Similarly, signals output from the light receiving portions 9A and 9B of the two-divided photodetector 9 are referred to as output signals 9SA and 9SB, respectively.

  The adder 11A adds the output signal 8SA and the output signal 9SA. The adder 11B adds the output signal 8SB and the output signal 9SB. The subtractor 12 subtracts the output signal 8SB + 9SB of the adder 11B from the output signal 8SA + 9SA of the adder 11A and outputs the epi-illumination position fluctuation SPH. As described with reference to FIG. 2, when the positions of the spot lights 8S and 9S change according to the change in the wavelength of the light beam TL, the values of the output signals 8SA, 8SB, 9SA, and 9SB of the two-divided photodetectors 8 and 9 correspond to the change. Also changes.

  When the wavelength of the light beam TL is shortened, the values of the output signals 8SA and 9SA are decreased in the light receiving portions 8A and 9A, and the values of the output signals 8SB and 9SB are increased in the light receiving portions 8B and 9B. That is, when the wavelength becomes shorter, 8SA <8SB and 9SA <9SB. Conversely, when the wavelength becomes longer, 8SA> 8SB and 9SA> 9SB. The incident position fluctuation SPH of the spot lights 8S, 9S is obtained by the following arithmetic expression based on the output signals 8SA, 8SB, 9SA, 9SB.

SPH = (8SA + 9SA)-(8SB + 9SB)
FIG. 4 is a diagram showing the incident positions of the ± first-order diffracted light beams + 1L and −1L when the two-divided photodetectors 8 and 9 are displaced in FIG.

  FIG. 4 shows a change in incident position of ± first-order diffracted light + 1L and −1L when the two-divided photodetectors 8 and 9 are displaced in the X direction in FIG. As shown in FIG. 4, when the two-divided photodetectors 8 and 9 are displaced in the X direction, the light amounts of ± first-order diffracted light + 1L and −1L incident on the light receiving portions 8B and 9A increase, and the light receiving portions 8A and 9B. The amount of ± first-order diffracted light + 1L and -1L incident on the light becomes small. That is, when it deviates in the + X direction, 8SA <8SB, 9SA> 9SB. On the other hand, when the shift is in the −X direction, 8SA> 8SB and 9SA <9SB.

  As described above, when the two-divided photodetectors 8 and 9 are displaced in the ± X direction (in-plane direction), the incident position fluctuation SPH of the spot lights 8S and 9S is different from the case of the wavelength change and is incremented in parentheses. The decrement cancels out. As a result, the epi-illumination position fluctuation SPH due to the misalignment of the two-divided photodetectors 8 and 9 becomes zero. That is, the laser light source device 10A can detect the epi-illumination position variation SPH accompanying the wavelength change without being affected by the positional deviation of the two-divided photodetectors 8 and 9.

  As described above, the laser light source device 10A according to Embodiment 1 outputs the output signals 8SA, 8SB, and 9SA of the two-divided photodetectors 8 and 9 with respect to the positional deviation in the in-plane direction of the optical elements such as the two-divided photodetectors 8 and 9. , 9SB can be used to cancel the influence. Thereby, the epi-illumination position fluctuation SPH accompanying the wavelength change can be detected without being affected by the positional deviation of the optical element.

  FIG. 5 is a top view showing a more specific configuration of the light detection unit 11 when the diffraction grating 5 rotates.

  As shown in FIG. 5, when the undivided diffraction grating 5 rotates in the R direction in the figure due to a change over time, the positions of the spot lights 8S and 9S change symmetrically like the spot lights 8SR and 9SR. To do. Specifically, the values of the output signals 8SA and 9SA are reduced in the light receiving portions 8A and 9A, and the values of the output signals 8SB and 9SB are increased in the light receiving portions 8B and 9B. That is, 8SA <8SB, 9SA <9SB. As described above, when the diffraction grating 5 is not divided, the rotation of the diffraction grating 5 affects the value of the epi-illumination position fluctuation SPH, which may cause a wavelength detection error of the light beam TL.

  FIG. 6 is a top view showing a configuration of a light detection unit 11M which is a modification of the light detection unit 11 in the laser light source device 10A of FIG.

  Referring to FIG. 6, the light detection unit 11M includes a diffraction grating 5M and two-divided photodetectors 8a, 8b, 9a, 9b. Unlike the diffraction grating 5 shown in FIGS. 2 and 5, the diffraction grating 5M includes diffraction parts 51a and 51b divided into two parts. The diffracting unit 51a diffracts the light beam TL into 0th-order light 0L and ± 1st-order diffracted lights + 1La and −1La. The diffraction unit 51b diffracts the light beam TL into 0th-order light 0L and ± 1st-order diffracted lights + 1Lb and −1Lb.

  The two-divided photodetector 8a is disposed at a position where the −1st-order diffracted light −1La diffracted by the diffracting portion 51a is irradiated, and has light receiving portions 8A and 8B divided into two. The two-divided photodetector 8b is disposed at a position where the −1st-order diffracted light −1Lb diffracted by the diffracting unit 51b is irradiated, and has light receiving units 8C and 8D divided into two. The two-divided photodetector 9a is disposed at a position where the + 1st order diffracted light + 1La diffracted by the diffracting unit 51a is irradiated, and has light receiving units 9A and 9B divided into two. The two-divided photodetector 9b is disposed at a position where the + 1st-order diffracted light + 1Lb diffracted by the diffraction unit 51b is irradiated, and has light receiving units 9C and 9D divided into two.

  Here, signals output from the light receiving portions 8A and 8B of the two-divided photodetector 8a are referred to as output signals 8SA and 8SB, respectively. Similarly, signals output from the light receiving portions 8C and 8D of the two-divided photodetector 8b are referred to as output signals 8SC and 8SD, respectively. The signals output from the light receiving portions 9A and 9B of the two-divided photodetector 9a are referred to as output signals 9SA and 9SB, respectively. Similarly, signals output from the light receiving portions 9C and 9D of the two-divided photodetector 9b are referred to as output signals 9SC and 9SD, respectively.

  In the configuration of the light detection unit 11M in FIG. 6, the incident position fluctuation SPHm of the spot lights 8aS, 8bS, 9aS, and 9bS is obtained by the following arithmetic expression based on the output signals 8SA to 8SD and 9SA to 9SD.

SPHm = (8SA + 8SC + 9SA + 9SC)
-(8SB + 8SD + 9SB + 9SD)
As shown in FIG. 6, when the diffraction grating 5M rotates in the R direction in the figure due to a change with time, the positions of the spot lights 8aS, 8bS, 9aS, 9bS are as in the spot lights 8aSR, 8bSR, 9aSR, 9bSR. It changes to point symmetry. Specifically, the values of the output signals 8SA, 8SD, 9SB, and 9SC are reduced in the light receiving portions 8A, 8D, 9B, and 9C, and the output signals 8SB, 8SC, 9SA, and 9SD are decreased in the light receiving portions 8B, 8C, 9A, and 9D. The value increases.

  That is, when rotating in the + R direction, 8SA <8SB, 8SC> 8SD, 9SA> 9SB, 9SC <9SD. Conversely, when rotating in the −R direction, 8SA> 8SB, 8SC <8SD, 9SA <9SB, 9SC> 9SD.

  As described above, when the diffraction grating 5M rotates in the ± R direction, the incident position fluctuation SPHm of the spot lights 8aS, 8bS, 9aS, and 9bS differs from the case of the undivided diffraction grating 5 in increments within parentheses. The decrement cancels out. As a result, the incident position fluctuation SPHm due to the rotation of the diffraction grating 5M becomes zero. That is, the laser light source device 10A can detect the epi-illumination position fluctuation SPHm accompanying the wavelength change without being influenced by the rotation of the diffraction grating 5M by using the light detection unit 11M.

  In the light detection unit 11M, even if the diffraction grating 5M is divided into three or more, the two-divided photodetectors 8 and 9 can be configured accordingly.

  As described above, the laser light source device according to Embodiment 1 includes a laser light source that emits multimode laser light, a collimator lens that collimates laser light emitted from the laser light source, and collimated light that is converted into parallel light. A first diffraction grating (external resonator) that reflects the first-order diffracted light in the direction of the laser light source and reflects or transmits the zero-order light in a direction other than the laser light source, and the first diffraction grating And a second diffraction grating that diffracts the zero-order light in two different directions and guides them to different photodetectors (for example, a two-divided photodetector).

  With the above configuration, when the wavelength changes, the diffraction angle of ± first-order diffracted light at the second diffraction grating changes. Therefore, a change in wavelength can be detected by calculating the output of each photodetector. Preferably, the ± first-order diffracted light of the second diffraction grating is incident on the dividing lines of the two-divided photodetectors. At this time, the diffraction direction of the second diffraction grating and the dividing line direction of the two-divided photodetector are perpendicular to each other when viewed from above, and each two-divided photodetector is opposite to the 0th-order incident light position of the second diffraction grating. Need to be deployed.

  Preferably, in the laser light source device of the first embodiment, each photodetector is divided by at least one dividing line in the direction perpendicular to the diffraction direction. The ± 1st-order diffracted lights of the second diffraction grating are incident on the dividing lines of the different photodetectors. The wavelength of the laser beam is detected by calculating the output of each photodetector.

  With the above configuration, regarding the positional deviation in the in-plane direction of each photodetector, optical component, etc., the offset is canceled by calculating the output of each photodetector. Therefore, it is possible to reduce the influence of the positional deviation of the photodetector or the like.

  Preferably, in the laser light source device of the first embodiment, the second diffraction grating is divided into a plurality of regions. Each photodetector is provided so as to be point-symmetric with respect to the 0th-order incident light position of the second diffraction grating.

  With the above configuration, even when the second diffraction grating rotates in a plane perpendicular to the optical axis, the offset is canceled by calculating the output of each photodetector. Thereby, the influence of the rotational deviation of the second diffraction grating can be reduced.

  Preferably, in the laser light source device according to the first embodiment, the calculation based on the output signal of the photodetector performs the element output on the side close to the sum of the element outputs on the side far from the 0th-order light incident position of the second diffraction grating. This is a calculation for detecting the wavelength by the difference from the sum.

  By the above calculation method, it is possible to easily cancel the offset of the output signal of each photodetector due to the positional deviation and rotational deviation in the in-plane direction of the optical component such as the photodetector.

[Embodiment 2]
FIG. 7 is a diagram showing a schematic configuration of a laser light source apparatus 10B according to Embodiment 2 of the present invention.

  Referring to FIG. 7, a laser light source device 10B according to the second embodiment includes a laser diode 1, a collimating lens 2, a diffraction grating 3, a beam splitter 4, a light detection unit 11, and a condensing lens 15. Is provided. Thus, the laser light source device 10B of the second embodiment is different from the laser light source device 10A of the first embodiment in that the condensing lens 15 is added. Since the other configuration is the same as that of the first embodiment, the description of the overlapping part will not be repeated in principle. The light detection unit 11 includes a diffraction grating 5 and two-divided photodetectors 8 and 9.

  The laser diode 1 emits multimode laser light (for example, about 405 nm). The collimating lens 2 converts the laser light emitted from the laser diode 1 into parallel light. The diffraction grating 3 receives laser light from the laser diode 1 and generates zero-order light in a predetermined direction and generates primary light in a different direction for each wavelength.

  The beam splitter 4 reflects a part of the zero-order light diffracted by the diffraction grating 3 as a light beam RL toward the outside of the laser light source device 10B, and transmits the other part as a light beam TL. The reflected light beam RL becomes a light source used for recording or reproducing a hologram, for example. The transmitted light beam TL enters the condensing lens 15. The condensing curvature (power) of the condensing lens 15 can be set to an arbitrary curvature so that the two-divided photodetectors 8 and 9 can obtain a desired detection sensitivity.

  The condensing lens 15 is provided between the diffraction grating 3 and the diffraction grating 5. In the second embodiment, it is provided between the beam splitter 4 and the diffraction grating 5. The condensing lens 15 condenses the light beam TL on the dividing lines of the two-divided photodetectors 8 and 9 via the diffraction grating 5 of the light detection unit 11. The diffraction grating 5 diffracts the light beam TL that has passed through the condenser lens 15 into 0th-order light 0L and ± 1st-order diffracted lights + 1L and −1L. The ± first-order diffracted lights + 1L and −1L are incident on the two-divided photodetectors 8 and 9, respectively.

  FIG. 8 is a top view showing a more specific configuration of the light detection unit 11 in the laser light source device 10B of FIG.

  Referring to FIG. 8, the two-divided photodetector 8 receives the spot light 8Sf of the −1st order diffracted light-1L collected on the dividing line. The two-divided photodetector 9 receives the spot light 9Sf of + 1st order diffracted light + 1L condensed on the dividing line. The diffraction directions of the ± first-order diffracted light beams + 1L and −1L and the dividing line directions of the two-divided photodetectors 8 and 9 are perpendicular to each other as viewed from the top as in the first embodiment.

  As described in the first embodiment, the incident position fluctuation SPH of the spot lights 8Sf and 9Sf is calculated by the calculation formula of SPH = (8SA + 9SA) − (8SB + 9SB) based on the output signals 8SA, 8SB, 9SA, 9SB. Desired.

  Here, when the wavelength of the light beam TL transmitted through the beam splitter 4 in FIG. 7 changes, the diffraction angles of the ± first-order diffracted lights + 1L and −1L of the diffraction grating 5 slightly change accordingly. As a result, the positions of the spot lights 8Sf and 9Sf can each vary in the direction perpendicular to the dividing line as indicated by the arrows in FIG.

  Further, in the laser light source device 10B of the second embodiment, the ± first-order diffracted lights + 1L and −1L are condensed by the condensing lens 15 on the two-divided photodetectors 8 and 9, respectively. Therefore, even if the condensing positions of the spot lights 8Sf and 9Sf due to the wavelength change of the light beam TL are slightly changed, the incident position fluctuation SPH of the spot lights 8Sf and 9Sf is greatly changed. As a result, the wavelength detection sensitivity of the light beam TL is improved.

  As described above, the laser light source device according to the second embodiment includes the condenser lens between the first diffraction grating and the second diffraction grating in addition to the configuration in the first embodiment. Each photodetector is divided by at least one dividing line perpendicular to the diffraction direction, and the ± first-order diffracted lights of the second diffraction grating are condensed on the dividing lines of different photodetectors. The wavelength of the laser beam is detected by calculating the output of each photodetector.

  In the above configuration, the diffraction direction of the second diffraction grating and the dividing line direction of the two-divided photodetector are perpendicular to each other, and each two-divided photodetector is arranged on the opposite side to the 0th-order incident light position of the second diffraction grating. Is desirable.

  With the above configuration, as in the first embodiment, it is possible to reduce the influence of the positional deviation in the in-plane direction of an optical component such as a two-divided detector. In addition, by condensing ± 1st order diffracted light on the dividing line, the detection sensitivity of the photodetector becomes very sensitive to wavelength fluctuations. This further improves the wavelength detection sensitivity of the laser light source device.

  Preferably, in the laser light source device according to the second embodiment, the calculation based on the output signal of the photodetector performs the element output on the side close to the sum of the element outputs on the side far from the 0th-order light incident position of the second diffraction grating. This is a calculation for detecting the wavelength by the difference from the sum.

  By the above calculation method, it is possible to easily cancel the offset of the output signal of each photodetector due to the positional deviation and rotational deviation in the in-plane direction of the optical component such as the photodetector.

[Embodiment 3]
FIG. 9 is a diagram showing a schematic configuration of a laser light source apparatus 10C according to Embodiment 3 of the present invention.

  Referring to FIG. 9, a laser light source device 10C according to the third embodiment includes a laser diode 1, a collimating lens 2, a diffraction grating 3, a beam splitter 4, and a light detection unit 11C. Thus, the laser light source device 10C of the third embodiment is different from the laser light source device 10A of the first embodiment in that the light detection unit 11 is replaced with the light detection unit 11C. Since the other configuration is the same as that of the first embodiment, the description of the overlapping part will not be repeated in principle. The light detection unit 11C includes a diffraction grating 5C and two-divided photodetectors 9P and 9Q.

  The laser diode 1 emits multimode laser light (for example, about 405 nm). The collimating lens 2 converts the laser light emitted from the laser diode 1 into parallel light. The diffraction grating 3 receives laser light from the laser diode 1 and generates zero-order light in a predetermined direction and generates primary light in a different direction for each wavelength.

  The beam splitter 4 reflects a part of the zero-order light diffracted by the diffraction grating 3 as a light beam RL toward the outside of the laser light source device 10C, and transmits the other part as a light beam TL. The reflected light beam RL becomes a light source used for recording or reproducing a hologram, for example. The transmitted light beam TL enters the diffraction grating 5C of the light detection unit 11C.

  The diffraction grating 5C diffracts the light beam TL into 0th-order light 0L, -1st-order diffracted light-1Lp, -1Lq, and + 1st-order diffracted light + 1Lp, + 1Lq because the diffraction part is divided into two. Furthermore, the condensing lens action is given to the diffraction grating 5C. Therefore, the + 1st order diffracted light + 1Lp is focused on the two-divided photodetector 9P and falls off. Similarly, the + 1st order diffracted light + 1Lq is condensed on the two-divided photodetector 9Q and falls off.

  FIG. 10 is a top view showing a more specific configuration of the light detection unit 11C in the laser light source device 10C of FIG.

  Referring to FIG. 10, the diffraction grating 5 </ b> C is provided with a condensing lens function and includes diffraction sections 52 a and 52 b that are divided into two. The diffraction grating 5C is, for example, a two-part hologram. The diffracting unit 52a condenses the light beam TL and diffracts it into 0th-order light 0L and ± 1st-order diffracted lights + 1Lp and −1Lp. The diffraction unit 52b condenses the light beam TL and diffracts it into 0th-order light 0L and ± 1st-order diffracted lights + 1Lq and −1Lq.

  The two-divided photodetector 9P is disposed at a position where the + 1st order diffracted light + 1Lp diffracted by the diffracting portion 52a of the diffraction grating 5C is irradiated, and has light receiving portions 9Ap and 9Bp divided into two. The two-divided photodetector 9Q is disposed at a position where the + 1st order diffracted light + 1Lq diffracted by the diffracting portion 52b of the diffraction grating 5C is irradiated, and has two light receiving portions 9Aq and 9Bq. Unlike the first and second embodiments, the diffraction directions of the + 1st order diffracted light + 1Lp and + 1Lq and the dividing line directions of the two-divided photodetectors 9P and 9Q are substantially parallel as viewed from above.

  The two-divided photodetector 9P receives the + 1st order diffracted light + 1Lp spot light 9Sfp collected on the dividing line. The two-divided photodetector 9Q receives the spot light 9Sfq of + 1st order diffracted light + 1Lq collected on the dividing line. Here, signals output from the light receiving portions 9Ap and 9Bp of the two-divided photodetector 9P are referred to as output signals 9SAp and 9SBp, respectively. Similarly, signals output from the light receiving portions 9Aq and 9Bq of the two-divided photodetector 9Q are referred to as output signals 9SAq and 9SBq, respectively.

  In the laser light source device 10C according to the third embodiment, the positions of the diffraction grating 5C and the two-divided photodetectors 9P, 9Q are set so that the differential outputs of the two-divided photodetectors 9P, 9Q are all zero at any reference wavelength. Is adjusted. Specifically, the differential output 9SAp-9SBp = 0 of the two-divided photodetector 9P. Similarly, the differential output 9SAq-9SBq = 0 of the two-divided photodetector 9Q.

  FIG. 11 is a diagram showing a condensing state on the two-divided photodetectors 9P and 9Q when the light beam TL changes from the reference wavelength.

  As shown in FIG. 11, when the light beam changes from the reference wavelength, in the two-divided photodetectors 9P and 9Q, as shown below, the condensed states of the spot lights 9Sfp and 9Sfq change from the reference wavelength due to chromatic aberration.

  When the light beam TL becomes longer than the reference wavelength, in the two-divided photodetector 9P, the spot light is reduced at the light receiving part 9Ap, and the spot light is enlarged at the light receiving part 9Bp. On the other hand, in the two-divided photodetector 9Q, the spot light is reduced at the light receiving portion 9Aq, and the spot light is enlarged at the light receiving portion 9Bq. That is, the spot lights 9Sfp and 9Sfq change to spot lights 9SLp and 9SLq, respectively. In this case, 9SAp <9SBp, 9SAq <9SBq.

  When the light beam TL is shortened from the reference wavelength, in the two-divided photodetector 9P, the spot light is enlarged at the light receiving unit 9Ap, and the spot light is reduced at the light receiving unit 9Bp. On the other hand, in the two-divided photodetector 9Q, the spot light is enlarged at the light receiving unit 9Aq, and the spot light is reduced at the light receiving unit 9Bq. That is, the spot lights 9Sfp and 9Sfq are changed to spot lights 9SSp and 9SSq, respectively. In this case, 9SAp> 9SBp, 9SAq> 9SBq.

  At this time, the condensing state change SPC in the two-divided photodetectors 9P and 9Q is obtained by the following arithmetic expression based on the output signals 9SAp, 9SBp, 9SAq, and 9SBq. Based on the condensing state change SPC, the wavelength change of the light beam TL can be detected.

SPH = (9SAp + 9SAq) − (9SBp + 9SBq)
Even if the diffraction grating 5C is divided into three or more in the light detection unit 11C, the two-divided photodetectors 9P and 9Q can be configured accordingly.

  As described above, in the laser light source device according to the third embodiment, in addition to the configuration in the first embodiment, the second diffraction grating is a two-divided hologram having a condensing lens effect. The diffracted light from is collected on two different detectors. Further, the diffraction direction and the dividing line direction may be substantially parallel.

  With the above configuration, as in the first and second embodiments, the output of each two-divided photodetector is calculated to cancel the offset, thereby reducing the influence of the positional deviation in the in-plane direction of the optical component such as the two-divided detector. it can. In addition, since it is not necessary to arrange each photodetector so as to be point-symmetric with respect to the 0th-order incident light position of the second diffraction grating, each photodetector can be arranged freely.

  Preferably, in the laser light source device of the second embodiment, each photodetector is arranged on the same side with respect to the zero-order incident light position of the second diffraction grating. As a result, the laser light source can be miniaturized.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

It is the figure which showed schematic structure of 10 A of laser light source apparatuses by Embodiment 1 of this invention. It is the top view which showed the more concrete structure of the photon detection part 11 in 10 A of laser light source apparatuses of FIG. It is the figure which showed an example of the structure which processes the signal output from the 2 division | segmentation photodetectors 8 and 9. FIG. It is the figure which showed the epi-illumination position of +/- 1st-order diffracted light + 1L, -1L when the 2 division | segmentation photodetector 8 and 9 in FIG. 6 is a top view showing a more specific configuration of the light detection unit 11 when the diffraction grating 5 rotates. FIG. It is the top view which showed the structure of the light detection part 11M which is a modification of the light detection part 11 in 10 A of laser light source apparatuses of FIG. It is the figure which showed schematic structure of the laser light source apparatus 10B by Embodiment 2 of this invention. It is the top view which showed the more concrete structure of the photon detection part 11 in the laser light source apparatus 10B of FIG. It is the figure which showed schematic structure of 10 C of laser light source apparatuses by Embodiment 3 of this invention. FIG. 10 is a top view showing a more specific configuration of a light detection unit 11C in the laser light source device 10C of FIG. It is the figure which showed the condensing state to 2 division | segmentation photodetector 9P, 9Q when the light beam TL changes from a reference wavelength. It is the figure which showed the schematic structure of the conventional laser light source apparatus. It is the figure which showed the mode of the laser beam which injects into the diffraction grating 103 in the laser light source apparatus 100 of FIG. It is the figure which showed an example of the structure of the 2 division | segmentation photodetector 112 in the laser light source apparatus 100 of FIG. FIG. 4 is a diagram showing the relationship between the oscillation wavelength of a laser diode 101 and the angle of a diffraction grating 103.

Explanation of symbols

  1 laser diode, 2 collimating lens, 3, 5, 5C, 5M diffraction grating, 4 beam splitter, 11, 11C, 11M photodetector, 8, 8a, 8b, 9, 9a, 9b, 9P, 9Q two-divided photodetector 10A to 10C laser light source device, 11A, 11B adder, 12 subtractor, 15 condensing lens, 100 conventional laser light source device, 101 laser diode, 102 collimating lens, 103 diffraction grating, 110 control unit, 111 incomplete mirror , 112 Two-divided photodetector.

Claims (11)

A wavelength detection device for detecting the wavelength of a light beam of an external resonant laser,
A light source that emits a light beam;
A first diffraction grating that diffracts the light beam into a plurality of first diffracted lights including zeroth-order light and returns a part of the plurality of first diffracted lights to the light source;
An optical separation unit for separating the zero-order light of the plurality of first diffracted lights into first and second light beams, and emitting the first light beams to the outside;
A second diffraction grating that diffracts the second light beam into a plurality of second diffracted lights including third and fourth diffracted lights;
A first light detection unit that receives the third diffracted light with a plurality of first light receiving units;
A second photodetecting unit for receiving the fourth diffracted light by a plurality of second photodetecting units;
A wavelength detection apparatus comprising: an arithmetic unit that detects a wavelength of the light beam based on differential signals of the plurality of first light receiving units and differential signals of the plurality of second light receiving units.   2. The wavelength detection device according to claim 1, wherein the first and second light detection units are arranged on both sides of a zero-order light included in the plurality of second diffracted lights.   The first and second light detection units are divided into light receiving units in a direction perpendicular to the direction of the plurality of second diffracted lights when viewed from the traveling direction of the second light beam. Item 3. The wavelength detection device according to Item 1 or 2. The second diffraction grating is divided into a plurality of diffraction parts including a first diffraction part and a second diffraction part,
The first light detection unit includes a third light detection unit configured to receive the third diffracted light diffracted by the first diffraction unit by a plurality of third light reception units, and the second diffraction unit. A fourth light detection unit that receives the diffracted third diffracted light with a plurality of fourth light receiving units,
The second light detection unit includes a fifth light detection unit that receives the fourth diffracted light diffracted by the first diffraction unit by a plurality of fifth light reception units, and a second diffraction unit. A sixth light detection unit that receives the diffracted fourth diffracted light with a plurality of sixth light receiving units,
The arithmetic unit includes: differential signals of the plurality of third light receiving units; differential signals of the plurality of fourth light receiving units; differential signals of the plurality of fifth light receiving units; and The wavelength detection apparatus according to claim 1, wherein the wavelength of the light beam is detected based on a differential signal.   2. The wavelength according to claim 1, further comprising a condensing unit that condenses the second light beam with an arbitrary curvature on the first and second light detection units via the second diffraction grating. Detection device.   The wavelength detection device according to claim 1, wherein the first and second light detection units are arranged on one side of zero-order light included in the plurality of second diffracted lights.   In the first and second light detection units, a light receiving unit is divided in a direction parallel to a direction of the plurality of second diffracted lights when viewed from a traveling direction of the second light beam. Item 7. The wavelength detection device according to Item 1 or 6.   The wavelength detection device according to claim 1, wherein the second diffraction grating condenses the second light beam on the first and second light detection units with an arbitrary curvature. The second diffraction grating is divided into a plurality of diffraction parts including a first diffraction part and a second diffraction part,
The first light detection unit includes a third light detection unit that receives the third diffracted light diffracted by the first diffraction unit by a plurality of third light receiving units,
The second light detection unit includes a fourth light detection unit that receives the third diffracted light diffracted by the second diffraction unit by a plurality of fourth light receiving units,
The calculation unit detects the wavelength of the light beam based on differential signals of the plurality of third light receiving units and differential signals of the plurality of fourth light receiving units. The wavelength detection apparatus as described.   The wavelength detection device according to claim 4 or 9, wherein the second diffraction grating is a multi-division hologram. A wavelength detection method for detecting the wavelength of a light beam of an external resonant laser,
Diffracting a light beam emitted from a light source into a plurality of first diffracted lights including zeroth-order light, and returning a part of the plurality of first diffracted lights to the light source;
Separating the zero-order light of the plurality of first diffracted lights into first and second light beams and emitting the first light beam to the outside;
Diffracting the second light beam into a plurality of second diffracted lights including third and fourth diffracted lights;
Receiving the third diffracted light by a plurality of first light receiving parts;
Receiving the fourth diffracted light by a plurality of second light receiving parts;
Detecting a wavelength of the light beam based on the differential signals of the plurality of first light receiving units and the differential signals of the plurality of second light receiving units.

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