Laser beam output device

Abstract

The present invention adjusts the output of a laser beam output device. The laser beam output device (1) comprises: an excitation laser (10) that outputs a laser beam of a specified wavelength (W1) as a first pulse (P1) of a specified frequency; an acousto-optic modulator (12) that receives the first pulse (P1) and determines the optical path to be one or more of two optical paths (OP1, OP2) for each of the first pulses and outputs it; a wavelength changer (14) that receives traveling light (second pulse (P2a)) that travels in the two optical paths (OP1, OP2) and changes it to different wavelengths (W2, W3) when the power of the traveling light exceeds a threshold value and outputs it; and a dichroic mirror (16) that combines the output (second pulse (P2b)) of the wavelength changer. The ratio of the first power of the traveling light that travels in one of the two optical paths as the traveling light to the second power of the traveling light that travels in the other of the two optical paths as the traveling light, i.e., the power ratio, can be changed.

Description

Technical Field

[0001] The present invention relates to a technology for outputting laser beams of multiple wavelengths as pulses. Background Art

[0002] Conventionally, there is known a laser beam output device that irradiates pulse light of a certain wavelength and then immediately irradiates pulse light of another wavelength (see Patent Document 1).

[0003] In addition, although not directly related to the laser beam output device mentioned above, patent documents 2 and 3 disclose variable optical attenuators (VOAs), patent documents 4 and 5 disclose multiple optical paths, and patent document 6 discloses a technology for applying current to a light-emitting element.

[0004] Prior art literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2020-166235

[0006] Patent Document 2: Japanese Patent Application Publication No. 2010-286672

[0007] Patent Document 3: Japanese Patent Application Publication No. 2010-256784

[0008] Patent Document 4: Japanese Patent Application Publication No. 2015-222414

[0009] Patent Document 5: Japanese Patent Application Publication No. 2004-029152

[0010] Patent Document 6: Japanese Patent Application Publication No. 2007-273435 Summary of the invention

[0011] Problems to be solved by the invention

[0012] Here, in the above-mentioned conventional laser beam output device, the output of the laser beam varies due to, for example, temporal output variation and ambient temperature dependency of the excitation laser and temporal change in conversion efficiency of the PPLN (photorefractive effect).

[0013] Therefore, an object of the present invention is to adjust the output of a laser beam output device.

[0014] Means for solving problems

[0015] The first laser beam output device of the present invention is constructed to include: a pulsed laser output unit, which outputs a laser beam of a specified wavelength as a first pulse; an optical path determination unit, which receives the first pulse and determines the optical path to be any one of more than two optical paths for each of the first pulses and outputs it; a wavelength change unit, which receives traveling light traveling along the more than two optical paths, and changes the traveling light to different wavelengths and outputs them when the power of the traveling light exceeds a threshold; and a combiner, which combines the output of the wavelength change unit, and the optical path determination unit can change the ratio of the first power of the traveling light traveling along one of two optical paths among the more than two optical paths as the traveling light to the second power of the traveling light traveling along the other of the two optical paths as the traveling light, that is, the power ratio.

[0016] According to the first laser beam output device constructed as described above, the pulsed laser output unit outputs a laser beam of a specified wavelength as a first pulse. The optical path determination unit receives the first pulse, and determines the optical path to be any one or more of the two or more optical paths for each of the first pulses and outputs it. The wavelength change unit receives the traveling light traveling along the two or more optical paths, and changes it to different wavelengths and outputs it when the power of the traveling light exceeds a threshold. The combiner combines the output of the wavelength change unit. In addition, the optical path determination unit is capable of changing the ratio of the first power of the traveling light traveling along one of the two or more optical paths as the traveling light to the second power of the traveling light traveling along the other of the two optical paths as the traveling light, i.e., the power ratio.

[0017] The second laser beam output device of the present invention is configured to include: a pulse laser output unit, which outputs a laser beam of a specified wavelength as a first pulse; an optical path determination unit, which receives the first pulse and determines the optical path to be any one of more than two optical paths for each of the first pulses; a parallelization unit, which makes the traveling directions of the traveling lights respectively traveling in the more than two optical paths parallel; a wavelength change unit, which receives the output of the parallelization unit and changes the output to different wavelengths when the power of the output exceeds a threshold value; a converging unit, which receives the output of the wavelength change unit and converges it; and an optical fiber, which receives the output of the converging unit through the end face of the core, the converging unit converges the output of the wavelength change unit to the end face of the core, and the optical path determination unit can change the ratio of the first power of the traveling light traveling in one of the two optical paths of the more than two optical paths as the traveling light to the second power of the traveling light traveling in the other of the two optical paths as the traveling light.

[0018] According to the second laser beam output device constructed as described above, the pulse laser output unit outputs a laser beam of a specified wavelength as a first pulse. The optical path determination unit receives the first pulse, and determines the optical path to be any one or more of the two or more optical paths for each of the first pulses and outputs it. The parallelization unit makes the traveling directions of the traveling light traveling in the two or more optical paths parallel. The wavelength change unit receives the output of the parallelization unit, and changes it to different wavelengths when the power of the output exceeds a threshold value and outputs it. The converging unit receives the output of the wavelength change unit and converges it. The optical fiber receives the output of the converging unit through the end face of the core. The converging unit converges the output of the wavelength change unit to the end face of the core. The optical path determination unit is capable of changing the ratio of the first power of the traveling light traveling in one of the two or more optical paths as the traveling light to the second power of the traveling light traveling in the other of the two optical paths as the traveling light, that is, the power ratio.

[0019] In addition, the first and second laser beam output devices of the present invention can also be constructed such that the optical path determination unit makes the power of the traveling light traveling only in any one optical path among the traveling light exceed the threshold value, and when the first power exceeds the threshold value, the power ratio can be made to take more than two types, and when the second power exceeds the threshold value, the power ratio can also be made to take more than two types.

[0020] Furthermore, the first and second laser beam output devices of the present invention may be configured to determine the threshold value for each of the optical paths.

[0021] In addition, the first and second laser beam output devices of the present invention can also be constructed as follows: the optical path determination unit has: a power ratio change signal giving unit, which provides a power ratio change signal for changing the power ratio, and the optical path determination unit is an acousto-optic modulator.

[0022] In addition, the first and second laser beam output devices of the present invention can also be constructed such that the power ratio change signal giving unit has: a carrier source, which outputs a carrier; a mixer, which mixes the carrier and a voltage-variable modulation signal and outputs a modulated signal; and an amplitude changer, which changes the amplitude of the modulated signal and outputs the power ratio change signal.

[0023] In addition, the first and second laser beam output devices of the present invention can also be configured to include: an output measuring unit that measures the output of the wavelength changing unit, and the power ratio change signal giving unit that changes the size of the power ratio change signal based on the measurement result of the output measuring unit.

[0024] In addition, the first and second laser beam output devices of the present invention can also be constructed such that the optical path determining unit is an acousto-optic modulator, and the two optical paths are the optical path of the 0th-order light and the optical path of the 1st-order light of the acousto-optic modulator.

[0025] Furthermore, the first and second laser beam output devices of the present invention may be configured such that the wavelength changing unit is a PPLN.

[0026] Furthermore, the first and second laser beam output devices of the present invention may be configured such that the wavelength changing unit is an OPO or an OPG. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a diagram showing the structure of the laser beam output device 1 according to the first embodiment.

[0028] Figure 2 It is a plan view of the wavelength changing section 14 according to the first embodiment.

[0029] Figure 3 This is a timing chart of the first pulse P1, the second pulse (before wavelength conversion) P2a, the second pulse (after wavelength conversion) P2b, and the third pulse P3 in the first embodiment.

[0030] Figure 4 It is a plan view of the wavelength changing section 14 according to the first modification example of the first embodiment.

[0031] Figure 5 It is a diagram showing the structure of a laser beam output device 1 according to a second modified example of the first embodiment.

[0032] Figure 6 : is a graph showing the relationship between the power P of the diffraction efficiency control signal and the diffraction efficiency η.

[0033] Figure 7 : is a functional block diagram showing the structure of the diffraction efficiency control unit 120 .

[0034] Figure 8 : is a diagram showing the correspondence between the voltage of the modulation signal and the power P of the diffraction efficiency control signal.

[0035] Fig. 9 1 is a diagram showing the relationship between the excitation light energy and the signal light energy of the wavelength changing section (PPLN) 14 .

[0036] Fig.10 : is a diagram showing the correspondence between the power P of the diffraction efficiency control signal and the power of the second pulse P2b.

[0037] Fig.11This is a timing chart of a first pulse P1 , a second pulse (before wavelength conversion) P2 a , a second pulse (after wavelength conversion) P2 b , and a third pulse P3 according to a third modification of the first embodiment.

[0038] Fig.12 It is a diagram showing the structure of a laser beam output device 1 according to the second embodiment.

[0039] Fig.13 It is a plan view of the wavelength changing section 14 according to the second embodiment.

[0040] Fig.14 It is a diagram showing the structure of a laser beam output device 1 according to a modified example of the second embodiment.

[0041] Fig.15 1 is a diagram showing the first power I·(1-η) and the second power I·η when the output of the wavelength changing unit (PPLN) 14 is output from the optical path OP1.

[0042] Fig.16 1 is a diagram showing the first power I·(1-η) and the second power I·η when the output of the wavelength changing unit (PPLN) 14 is output from the optical path OP2.

[0043] Fig.17 It is a diagram showing the structure of a laser beam output device 1 according to a third embodiment.

[0044] Fig.18 It is an enlarged view of the vicinity of an optical path determining section (a first acousto-optic modulator (AOM) 12 a and a second acousto-optic modulator (AOM) 12 b ) in the laser beam output device 1 according to the third embodiment.

[0045] Fig.19 It is a diagram showing the structure of a laser beam output device 1 according to a fourth embodiment.

[0046] Fig. 20 It is an enlarged view of the vicinity of an optical path determining section (a first acousto-optic modulator (AOM) 12 a and a second acousto-optic modulator (AOM) 12 b ) in a laser beam output device 1 according to the fourth embodiment.

[0047] Fig.21 It is an enlarged view of the vicinity of an optical path determining section (a first acousto-optic modulator (AOM) 12 a and a second acousto-optic modulator (AOM) 12 b ) in a laser beam output device 1 according to a modification of the third embodiment.

[0048] Description of Reference Numerals

[0049] η Diffraction efficiency

[0050] P1 First pulse

[0051] P2a Second pulse (before wavelength conversion)

[0052] P2b Second pulse (after wavelength conversion)

[0053] P3 The third pulse

[0054] OP1, OP2 optical path

[0055] 1 Laser beam output device

[0056] 10 Excitation laser (pulse laser output unit)

[0057] 12 Acousto-optic modulator (optical path determination unit) (AOM)

[0058] 12a The first acousto-optic modulator (AOM)

[0059] 12b Second Acousto-Optic Modulator (AOM)

[0060] 120 Diffraction efficiency control unit

[0061] 13 Convex lens (parallelization part) (L1)

[0062] 131 Rhombus Prism

[0063] 130a, 130b Half-reflecting mirror

[0064] 132a, 132b Photodiode (output measurement unit) (PD)

[0065] 14, 14a, 14b Wavelength change unit (PPLN)

[0066] 142 LN crystal substrate

[0067] 144 Polarization reversal unit

[0068] 15. Reflector

[0069] 16. Dichroic Mirror (Combiner) (DCM)

[0070] 160 Achromatic lens (converging part) (L2)

[0071] 160a Convex lens

[0072] 160b Concave lens

[0073] 172, 174, 176, 178 Filter (F)

[0074] 18 Fiber (MMF)

[0075] 19 Timing control circuit (timing control unit). DETAILED DESCRIPTION

[0076] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0077] First embodiment

[0078] Figure 1 It is a diagram showing the structure of the laser beam output device 1 according to the first embodiment. Figure 2 It is a plan view of the wavelength changing section 14 according to the first embodiment. Figure 3 1 is a timing diagram of the first pulse P1, the second pulse (before wavelength conversion) P2a, the second pulse (after wavelength conversion) P2b, and the third pulse P3 of the first embodiment. Figure 3 In the diagram, the thickness of the line representing the pulse and the type of line (solid line or dotted line) are changed according to the wavelength.

[0079] The laser beam output device 1 of the first embodiment includes an excitation laser (pulse laser output unit) 10, an acousto-optic modulator (optical path determination unit) (AOM) 12, a wavelength change unit (PPLN) 14, a reflection mirror 15, a dichroic mirror (combiner) (DCM) 16, filters (F) 172, 174, an optical fiber (MMF) 18, a timing control circuit (timing control unit) 19, a diffraction efficiency control unit (power ratio change signal giving unit) 120, half mirrors 130a, 130b, and photodiodes (output measurement unit) (PD) 132a, 132b.

[0080] The excitation laser (pulse laser output unit) 10 emits a laser beam of a predetermined wavelength W1 [nm] as a first pulse P1 (see Figure 3 The pumping laser 10 is, for example, a Yb:YAG laser.

[0081] The acousto-optic modulator (optical path determination unit) (AOM) 12 receives the first pulse P1, and determines the optical path to be one or more of the two optical paths OP1 and OP2 for each first pulse P1 and outputs it. In addition, the two optical paths OP1 and OP2 are the optical path of the 0th-order light and the optical path of the 1st-order light of the acousto-optic modulator 12, respectively. When the diffraction efficiency η of the acousto-optic modulator 12 is 0, the first pulse P1 only travels on the optical path OP1. When the diffraction efficiency η exceeds 0, the first pulse P1 travels on the optical path OP1 and the optical path OP2. When the power of the first pulse P1 received by the acousto-optic modulator 12 is set to I, a pulse with a power of I·(1-η) travels on the optical path OP1, and a pulse with a power of I·η travels on the optical path OP2.

[0082] In this way, the acousto-optic modulator (optical path determination unit) (AOM) 12 can change the power ratio (1-η:η) between the first power I·(1-η) of the pulse traveling in one of the two optical paths OP1 and OP2 as the traveling light and the second power I·η of the pulse traveling in the other of the two optical paths OP1 and OP2 as the traveling light. The traveling light refers to the light traveling in each of the two optical paths OP1 and OP2.

[0083] A diffraction efficiency control signal is given to the acousto-optic modulator 12 from a diffraction efficiency control unit (power ratio change signal giving unit) 120. The diffraction efficiency η changes according to the power P of the diffraction efficiency control signal. The power P of the diffraction efficiency control signal is greater than or equal to 0 and less than or equal to Pmax. The diffraction efficiency control signal is changed from an electrical signal to an acoustic wave by a transducer (not shown) and given to the acousto-optic modulator 12.

[0084] Figure 6 : is a graph showing the relationship between the power P of the diffraction efficiency control signal and the diffraction efficiency η. When the power P of the diffraction efficiency control signal is 0 [W], the diffraction efficiency η = 0. When 0 < P < P0, the diffraction efficiency η increases monotonically. When P = P0, η takes the maximum value ηmax. When P0 < P < Pmax, the diffraction efficiency η decreases monotonically.

[0085] Fig.15 1 is a diagram showing the first power I·(1-η) and the second power I·η when the output of the wavelength changing unit (PPLN) 14 is output from the optical path OP1. Fig.16 1 is a diagram showing the first power I·(1-η) and the second power I·η when the output of the wavelength changing unit (PPLN) 14 is output from the optical path OP2.

[0086] Reference Fig.15 , when the diffraction efficiency η=0 (refer to Fig.15 In the case of (a), the first power is 1 and the second power is 0. When the diffraction efficiency η = η11 (> 0) (refer to Fig.15 In the case of (b), the first power is I(1~η11) and the second power is I·η11. When the diffraction efficiency η=η21(>η11) (refer to Fig.15 In the case of (c), the first power is I(1-η21) and the second power is I·η21. Thus, as the diffraction efficiency η increases, the first power continues to decrease.

[0087] Reference Fig.16 , when the diffraction efficiency η=ηmax (refer to Fig.16 In the case of (a)), the first power is I(1-ηmax) and the second power is I·ηmax. When the diffraction efficiency η=η12(<ηmax) (refer to Fig.16 In the case of (b), the first power is I(1-η12) and the second power is I·η12. When the diffraction efficiency η=η22(<η12) (refer to Fig.16 In the case of (c), the first power is I(1-η22) and the second power is I·η22. Thus, as the diffraction efficiency η decreases, the second power continues to decrease.

[0088] An optical attenuator (not shown) may be provided between the acousto-optic modulator 12 and the wavelength changing unit (PPLN) 14 .

[0089] The wavelength changer (PPLN) 14 receives the traveling light (i.e., the second pulse P2a) traveling in the two optical paths OP1 and OP2, respectively, and changes the traveling light to different wavelengths and outputs them when the power of the traveling light exceeds the oscillation threshold (described later). The output of the wavelength changer 14 is the second pulse (after wavelength conversion) P2b. In addition, the wavelength changer (PPLN) 14 is PPLN. In addition, the wavelength changer 14 is OPO (optical parametric oscillation) or OPG (optical parametric generation).

[0090] Fig. 9 : This is a diagram showing the relationship between the excitation light energy and the signal light energy of the wavelength changer (PPLN) 14. However, the excitation light is supplied from the optical paths OP1 and OP2, and the signal light is output from the optical paths OP1 and OP2. Therefore, the excitation light (traveling light) supplied from the optical path OP1 is the 0th-order light of the acousto-optic modulator 12, and the signal light (the output of the wavelength changer 14) generated by the excitation light is output from the optical path OP1. In addition, the excitation light (traveling light) supplied from the optical path OP2 is the 1st-order light of the acousto-optic modulator 12, and the signal light (the output of the wavelength changer 14) generated by the excitation light is output from the optical path OP2.

[0091] The wavelength changer 14 is an OPO or OPG, and therefore has an oscillation threshold. That is, when the excitation light energy (the power of the traveling light) exceeds the oscillation threshold, the signal light (the output of the wavelength changer 14) is output. When the excitation light energy exceeds the oscillation threshold, if the excitation light energy increases, the signal light energy also increases.

[0092] In addition, the oscillation threshold of the excitation light (0th order light) provided from the optical path OP1 is greater than the oscillation threshold of the excitation light (1st order light) provided from the optical path OP2. However, this is only an example, and there may be a case where the oscillation threshold of the excitation light (0th order light) is smaller than the oscillation threshold of the excitation light (1st order light). In addition, there may be a case where the oscillation threshold of the excitation light (0th order light) is equal to the oscillation threshold of the excitation light (1st order light).

[0093] Furthermore, as described above, the oscillation thresholds are determined for the optical paths OP1 , OP2 .

[0094] The acousto-optic modulator 12 causes the power (first power I·(1-η) or second power I·η) of the traveling light traveling only in either optical path (OP1 or OP2) among the traveling light to exceed the oscillation threshold.

[0095] For example, in Fig.15 In the case shown, only the power of the traveling light traveling along the optical path OP1 (first power I·(1-η)) exceeds the oscillation threshold.

[0096] At diffraction efficiency η = 0 (ref. Fig.15 In the case of (a), the first power I exceeds the oscillation threshold, the output of the wavelength changer 14 is J01, and is output from the optical path OP1. Since the second power O is less than the oscillation threshold, the output of the wavelength changer 14 is not output from the optical path OP2.

[0097] At diffraction efficiency η=η11(>0)(refer to Fig.15 In the case of (b), the first power is I(1-η11) and the second power is I·η11. The first power I(1-η11) exceeds the oscillation threshold, and the output of the wavelength changer 14 is J11, which is output from the optical path OP1. In addition, compared with the case where the diffraction efficiency η=0, the first power is reduced by the amount of I·η11, so the output J11 of the wavelength changer 14 is also smaller than J01. In addition, since the second power I·η11 is less than the oscillation threshold, the output of the wavelength changer 14 is not output from the optical path OP2.

[0098] At diffraction efficiency η=η21(>η11)(refer to Fig.15 In the case of (c), the first power is I(1-η21) and the second power is I·η21. The first power I(1-η21) exceeds the oscillation threshold, and the output of the wavelength changer 14 is J21, which is output from the optical path OP1. In addition, compared with the case where the diffraction efficiency η=η11, the first power is reduced by the amount of I·(η21-η11), so the output J21 of the wavelength changer 14 is also smaller than J11. In addition, since the second power I·η21 is less than the oscillation threshold, the output of the wavelength changer 14 is not output from the optical path OP2.

[0099] In this way, when the first power I·(1-η) exceeds the oscillation threshold, the acousto-optic modulator 12 can set the power ratio (1-η:η) to two or more. For example, the power ratio can be set to 1:0 (see Fig.15 (a)), 1-η11: η11 (refer to Fig.15 (b)), 1-η21: η21 (refer to Fig.15 (c)). Thus, the output of the wavelength changing unit 14 can be changed from J01 (refer to Fig.15 (a)) decays to J11 (refer to Fig.15(b)), from J11 (refer to Fig.15 (b)) decays to J21 (refer to Fig.15 (c)).

[0100] The power ratio can be as low as two, for example, it is also possible to consider setting the power ratio to 1-η11:η11 (refer to Fig.15 (b)), 1-η21: η21 (refer to Fig.15 (c)). Thus, the output of the wavelength changing unit 14 can be changed from J11 (refer to Fig.15 (b)) decays to J21 (refer to Fig.15 (c)).

[0101] For example, in Fig.16 In the case shown in the figure, the power of the traveling light (second power I·η) traveling only along the optical path OP2 exceeds the oscillation threshold.

[0102] At diffraction efficiency η = ηmax (refer to Fig.16 In the case of (a), the second power I·ηmax exceeds the oscillation threshold, and the output of the wavelength changer 14 is J02, which is output from the optical path OP2. Since the first power I(1-ηmax) is less than the oscillation threshold, the output of the wavelength changer 14 is not output from the optical path OP1.

[0103] At diffraction efficiency η=η12(<ηmax)(refer to Fig.16 In the case of (b), the first power is I(1-η12) and the second power is I·η12. The second power I·η12 exceeds the oscillation threshold, and the output of the wavelength changer 14 is J21, which is output from the optical path OP2. In addition, compared with the case where the diffraction efficiency η=ηmax, the second power is reduced by the amount of I·(ηmax-η12), so the output J12 of the wavelength changer 14 is also smaller than J02. In addition, since the first power I(1-η12) is less than the oscillation threshold, the output of the wavelength changer 14 is not output from the optical path OP1.

[0104] At diffraction efficiency η=η22(<η12)(refer to Fig.16 In the case of (c), the first power is I(1-η22) and the second power is I·η22. The second power I·η22 exceeds the oscillation threshold, and the output of the wavelength changer 14 is J22, which is output from the optical path OP2. In addition, compared with the case where the diffraction efficiency η=η12, the second power is reduced by I·(η12-η22), so the output J22 of the wavelength changer 14 is also smaller than J12. In addition, since the first power I(1-η22) is less than the oscillation threshold, the output of the wavelength changer 14 is not output from the optical path OP1.

[0105] In this way, when the second power I·η exceeds the oscillation threshold, the AOM 12 can set the power ratio (1-η:η) to be two or more. For example, the power ratio can be set to 1-ηmax:ηmax (see Fig.16 (a)), 1-η12: η12 (refer to Fig.16 (b)), 1-η22: η22 (refer to Fig.16 (c)). Thus, the output of the wavelength changing unit 14 can be changed from J02 (refer to Fig.16 (a)) decays to J12 (refer to Fig.16 (b)), from J12 (refer to Fig.16 (b)) decays to J22 (refer to Fig.16 (c)).

[0106] The power ratio can be as low as two, for example, it is also considered to set the power ratio to 1-η12:η12 (refer to Fig.16 (b)), 1-η22: η22 (refer to Fig.16 (c)). Thus, the output of the wavelength changing unit 14 can be changed from J12 (refer to Fig.16 (b)) decays to J22 (refer to Fig.16 (c)).

[0107] Here, refer to Figure 1 as well as Figure 3 , at the time point when the AOM 12 receives the odd-numbered (1st, 3rd, ...) pulses of the first pulse P1, only the power of the traveling light traveling on the optical path OP1 (first power I·(1-η)) exceeds the oscillation threshold. The power of the traveling light traveling on the optical path OP2 (second power I·η) is less than the oscillation threshold. For example, at the time point when the AOM 12 receives the first pulse of the first pulse P1, the power ratio is set to 1-η11:η11 (refer to Fig.15 (b)). At the time point when the AOM 12 receives the third pulse of the first pulse P1, the power ratio is set to 1-η21:η21 (refer to Fig.15 (c)).

[0108] In addition, at the time point when the AOM 12 receives the even-numbered (second, fourth, ...) pulses of the first pulse P1, only the power of the traveling light traveling on the optical path OP2 (second power I·η) exceeds the oscillation threshold. The power of the traveling light traveling on the optical path OP1 (first power I·(1-η)) is less than the oscillation threshold. For example, at the time point when the AOM 12 receives the second pulse of the first pulse P1, the power ratio is set to 1-η12:η12 (refer to Fig.16(b)). At the time point when the acousto-optic modulator 12 receives the fourth pulse of the first pulse P1, the power ratio is set to 1-η22:η22 (refer to Fig.16 (c)).

[0109] Thus, the acousto-optic modulator 12 outputs a second pulse (before wavelength conversion) P2a (wherein pulses smaller than the oscillation threshold are ignored) from the multiple optical paths OP1 and OP2 respectively. The second pulse (before wavelength conversion) P2a is a pulse having a frequency (1 kHz) obtained by dividing a specified frequency (for example, 2 kHz) by the number of multiple optical paths (2) and having phases that differ by 180 degrees.

[0110] The timing control circuit (timing control unit) 19 matches the output of the acousto-optic modulator (optical path determination unit) 12 with the timing of the output of the first pulse P1. The result of the timing matching is shown in FIG. Figure 3 Furthermore, the timing control circuit 19 receives a signal synchronized with the timing of outputting the first pulse P1 from the pumping laser (pulsed laser output unit) 10, and controls the output timing of the acousto-optic modulator 12 based on the signal.

[0111] Reference Figure 3 The wavelength changing unit 14 receives the pulses (wavelength W1 [nm]) traveling along the optical path OP1 (the 1st, 3rd, ... pulses exceeding the oscillation threshold value) among the second pulses P2a, and converts them into the second pulses P2b (wavelength W2 [nm]). However, even if the second pulses P2a receive the pulses (wavelength W1 [nm]) traveling along the optical path OP1 (the 2nd, 4th, ... pulses less than the oscillation threshold value), the second pulses P2b (wavelength W2 [nm]) are not output.

[0112] In addition, the wavelength changer 14 receives the pulses (wavelength W1 [nm]) traveling along the optical path OP2 (the 2nd, 4th, ... pulses exceeding the oscillation threshold value) among the second pulses P2a, and converts them into second pulses P2b (wavelength W3 [nm]). However, even if the second pulses P2a receive the pulses (wavelength W1 [nm]) traveling along the optical path OP2 (the 1st, 3rd, ... pulses less than the oscillation threshold value), the second pulses P2b (wavelength W2 [nm]) are not output.

[0113] Fig.10 : is a diagram showing the corresponding relationship between the power P of the diffraction efficiency control signal and the power of the second pulse P2b. When the power P of the diffraction efficiency control signal is 0, the diffraction efficiency η=0 (refer to Figure 6 ), the power of the second pulse P2b (the pulse traveling in the optical path OP1) is J01 (refer to Fig.15 (a)). As the power P increases, the diffraction efficiency η increases (refer to Figure 6), the power of the second pulse P2b (the pulse traveling along the optical path OP1) continues to decrease (refer to Fig.15 ). Soon, the second pulse P2a (pulse traveling along the optical path OP1) is below the oscillation threshold, and the second pulse P2b (pulse traveling along the optical path OP1) is not output.

[0114] In addition, as the power P increases, the diffraction efficiency η increases (refer to Figure 6 ), the second pulse P2a (the pulse traveling on the optical path OP2) exceeds the oscillation threshold, and the second pulse P2b (the pulse traveling on the optical path OP2) is output (refer to Fig.16 ).

[0115] The range of the power of the second pulse P2b when the second pulse P2b travels only along the optical path OP1 (not along the optical path OP2) is referred to as output range 1. Within the output range 1, the power of the second pulse P2b traveling only along the optical path OP1 can be adjusted.

[0116] The range of the power of the second pulse P2b when the second pulse P2b travels only along the optical path OP2 (not along the optical path OP1) is referred to as output range 2. Within the output range 2, the power of the second pulse P2b traveling only along the optical path OP2 can be adjusted.

[0117] Reference Figure 2 The wavelength change unit 14 includes an LN crystal substrate 142 and a polarization inversion unit 144. Figure 2 For the convenience of illustration, Figure 1 In contrast, the x-axis direction of the LN crystal substrate 142 is shown as being parallel to the horizontal direction of the paper.

[0118] The polarization reversal section 144 is used to propagate the traveling light (i.e., the second pulse P2a). The polarization reversal section 144 includes a polarization reversal section for propagating the second pulse P2a traveling along the optical path OP1 and a polarization reversal section for propagating the second pulse P2a traveling along the optical path OP2. Figure 2 Here, it is PPLN (periodically polarized reverse lithium niobate), but it is not limited to this. For example, it can also be PPLT (lithium tantalate) or PPKTP.

[0119] The polarization reversal portions 144 for propagating the second pulse P2a traveling on the optical path OP1 are arranged at predetermined intervals D1. The polarization reversal portions 144 for propagating the second pulse P2a traveling on the optical path OP2 are arranged at predetermined intervals D2. The predetermined intervals differ for each traveling light. That is, the predetermined interval D1 is different from the predetermined interval D2.

[0120] The polarization reversal portion 144 is formed on the LN crystal substrate 142. There is only one LN crystal substrate 142, and all polarization reversal portions 144 are formed thereon. In addition, in the first embodiment, the LN crystal substrate 142 may not be an LN crystal substrate, but may be a nonlinear optical crystal substrate. Similarly, in other embodiments, a nonlinear optical crystal substrate may be used instead of the LN crystal substrate.

[0121] The centroid 144c of the polarization reversal portion 144 for the second pulse P2a traveling on the optical path OP1 to propagate is arranged on a straight line parallel to the x-axis of the LN crystal substrate 142. The centroid 144c of the polarization reversal portion 144 for the second pulse P2a traveling on the optical path OP2 to propagate is also arranged on a straight line parallel to the x-axis of the LN crystal substrate 142. In addition, the centroid 144c of the polarization reversal portion 144 coincides with the center of gravity when gravity acts uniformly on the polarization reversal portion 144.

[0122] The reflection mirror 15 receives the pulse of the second pulse (after wavelength conversion) P2 b that travels along the optical path OP2 , and reflects the pulse toward the dichroic mirror 16 .

[0123] The dichroic mirror (combiner) (DCM) 16 receives the pulse that travels on the optical path OP1 among the second pulse (after wavelength conversion) P2b output by the wavelength changer 14. The dichroic mirror 16 also receives the pulse that travels on the optical path OP2 among the second pulse (after wavelength conversion) P2b output by the wavelength changer 14 from the reflector 15. Furthermore, the dichroic mirror 16 combines the pulse that travels on the optical path OP1 and the pulse that travels on the optical path OP2 among the second pulse (after wavelength conversion) P2b output by the wavelength changer 14, and outputs a third pulse P3 having a predetermined frequency (2 kHz).

[0124] However, the output of the wavelength changer 14 is mixed with the laser beam (excitation light) of wavelength W1 [nm] output by the excitation laser 10 and the idle light in the infrared region generated by the wavelength changer 14. In addition, when the laser beam (excitation light) is provided to the wavelength changer 14, the signal light and the idle light described above are generated due to the generation of optical parameters. The signal light is the output of the wavelength changer 14 (the second pulse (after wavelength conversion) P2b) (the same is true for the wavelength changer of other embodiments).

[0125] The filters (F) 172 and 174 remove the pump light and the idle light from the second pulse (after wavelength conversion) P2b output from the wavelength changer 14 and traveling along the optical paths OP1 and OP2, respectively, and output them to the dichroic mirror 16 and the reflector 15. In addition, in order to prevent the pump light and the idle light from entering the photodiodes 132a and 132b, the filters 172 and 174 are respectively arranged between the half mirrors 130a and 130b and the wavelength changer 14.

[0126] The optical fiber (MMF) 18 receives the third pulse P3 outputted from the dichroic mirror 16 at one end thereof, and outputs the third pulse P3 from the other end.

[0127] The half mirrors 130a and 130b respectively reflect a portion of the second pulse (after wavelength conversion) P2b outputted from the wavelength changer 14 and traveling along the optical paths OP1 and OP2, and provide the pulses to the photodiodes (output measuring units) (PD) 132a and 132b.

[0128] The photodiodes (output measuring unit) (PD) 132a and 132b measure the output of the wavelength changing unit 14 received via the half mirrors 130a and 130b, respectively.

[0129] The diffraction efficiency control unit (power ratio change signal providing unit) 120 provides a diffraction efficiency control signal (power ratio change signal) to the acousto-optic modulator (optical path determining unit) (AOM) 12. According to the diffraction efficiency control signal, the diffraction efficiency η changes, and the power ratio (1-η:η) changes.

[0130] Figure 7 1 is a functional block diagram showing the structure of the diffraction efficiency control unit 120. The diffraction efficiency control unit 120 includes a carrier source 122, a modulation signal output unit 124, a mixer (mixer) 126, and amplifiers (amplitude changers) 128a and 128b.

[0131] The carrier source 122 outputs a carrier. The modulation signal output unit 124 outputs a modulation signal of variable voltage. The mixer 126 mixes the carrier and the modulation signal and outputs a modulated signal. The mixer 126 has an LO port, an IF port, and an RF port. For example, it is considered that a carrier is provided to the LO port, a modulation signal is provided to the IF port, and a modulated signal is output from the RF port. The amplifiers (amplitude changers) 128a and 128b change the amplitude of the modulated signal and output a diffraction efficiency control signal (power ratio change signal).

[0132] Figure 8 : is a diagram showing the correspondence between the voltage of the modulation signal and the power P of the diffraction efficiency control signal. As the voltage of the modulation signal increases from 0, the power P of the diffraction efficiency control signal also increases from 0 to Pmax.

[0133] In this way, by changing the voltage of the modulation signal, the power P of the diffraction efficiency control signal (the size of the power ratio change signal) can be changed. For example, the modulation signal output unit 124 of the diffraction efficiency control unit (power ratio change signal providing unit) 120 changes the size of the power P of the diffraction efficiency control signal (the size of the power ratio change signal) based on the measurement results of the photodiodes (output measurement units) (PD) 132a and 132b, thereby changing the power P of the diffraction efficiency control signal (the size of the power ratio change signal).

[0134] Next, the operation of the first embodiment will be described.

[0135] First, the excitation laser 10 emits a laser beam of a predetermined wavelength W1 [nm] as a first pulse P1 of a predetermined frequency (for example, 2 kHz) (see Figure 3 ) output. The first pulse P1 is provided to the AOM 12. The timing control circuit 19 controls the output timing of the AOM 12 (refer to Figure 3 ).

[0136] In addition, the diffraction efficiency control unit 120 provides a diffraction efficiency control signal to the AOM 12 to adjust the diffraction efficiency η (see Figure 6 ).

[0137] At the time point when the acousto-optic modulator 12 receives the odd-numbered (1st, 3rd, ...) pulses of the first pulse P1, the power of the traveling light traveling only on the optical path OP1 (first power I·(1-η)) exceeds the oscillation threshold. Therefore, the traveling light traveling on the optical path OP1 is the second pulse (before wavelength conversion) P2a (wherein pulses smaller than the oscillation threshold are ignored), and the second pulse (before wavelength conversion) P2a has a frequency (1 kHz) of a value obtained by dividing a predetermined frequency (for example, 2 kHz) by the number of the plurality of optical paths (2).

[0138] At the time point when the acousto-optic modulator 12 receives the even-numbered (second, fourth, ...) pulses of the first pulse P1, the power (second power I·η) of the traveling light traveling only on the optical path OP2 exceeds the oscillation threshold. Therefore, the traveling light traveling on the optical path OP2 is the second pulse (before wavelength conversion) P2a (wherein pulses smaller than the oscillation threshold are ignored), and the second pulse (before wavelength conversion) P2a has a frequency (1 kHz) of a value obtained by dividing a predetermined frequency (for example, 2 kHz) by the number of the plurality of optical paths (2).

[0139] Moreover, the phase of the traveling light (second pulse (before wavelength conversion) P2a) traveling on the optical path OP1 is 180 degrees different from the phase of the traveling light (second pulse (before wavelength conversion) P2a) traveling on the optical path OP2 (wherein pulses smaller than the oscillation threshold are ignored).

[0140] The traveling light (second pulse (before wavelength conversion) P2a: wavelength W1 [nm]) traveling along the optical path OP1 (wherein pulses smaller than the oscillation threshold are ignored) propagates through the polarization reversal section 144 arranged at a predetermined interval D1 in the wavelength change section 14, and the wavelength is converted to W2 [nm] to become the second pulse (after wavelength conversion) P2b, which is provided to the dichroic mirror 16.

[0141] The traveling light (second pulse (before wavelength conversion) P2a: wavelength W1 [nm]) (wherein pulses smaller than the oscillation threshold are ignored) traveling along the optical path OP2 is propagated by the polarization reversal section 144 arranged at a predetermined interval D2 in the wavelength change section 14, and the wavelength is converted to W3 [nm] to become the second pulse (after wavelength conversion) P2b, which is reflected by the reflector 15 and provided to the dichroic mirror 16.

[0142] The pulse of wavelength W2 [nm] and the pulse of wavelength W3 [nm] in the second pulse (after wavelength conversion) P2b outputted from the wavelength changer 14 are combined by the dichroic mirror 16 to form a third pulse P3 having a predetermined frequency (2 kHz).

[0143] The third pulse P3 is supplied to one end of the optical fiber 18 and output from the other end.

[0144] In addition, the second pulse (after wavelength conversion) P2b output by the wavelength changer 14 is provided to the photodiodes (output measurement unit) (PD) 132a and 132b via the half mirrors 130a and 130b. Based on the measurement results of the photodiodes 132a and 132b, the diffraction efficiency control unit 120 determines the size of the diffraction efficiency control signal provided to the acousto-optic modulator 12.

[0145] According to the first embodiment, the third pulse P3 can be output from the optical fiber 18. The third pulse P3 is a pulse in which a pulse light of another wavelength W3 [nm] is irradiated immediately (for example, 500 microseconds) after irradiating a pulse light of a wavelength W2 [nm]. That is, according to the first embodiment, a pulse light of another wavelength can be irradiated immediately after irradiating a pulse light of a certain wavelength.

[0146] In addition, according to the first embodiment, referring to Fig.15 By increasing the power of the traveling light traveling on the optical path OP2 (the second power I·η) (wherein, it is set to be less than the oscillation threshold, and the output of the wavelength change unit 14 is not output from the optical path OP2), the power of the traveling light traveling on the optical path OP1 (the first power I·(1-η)) can be reduced. Thus, by attenuating the output of the wavelength change unit 14 (from the optical path OP1), the output (the third pulse P3) of the laser beam output device 1 can be adjusted.

[0147] And, according to the first embodiment, referring to Fig.16 By increasing the power of the traveling light traveling on the optical path OP1 (the first power I·(1-η)) (wherein, it is set to be less than the oscillation threshold and the output of the wavelength change unit 14 is not output from the optical path OP1), the power of the traveling light traveling on the optical path OP2 (the second power I·η) can be reduced. Thus, by attenuating the output of the wavelength change unit 14 (from the optical path OP2), the output (the third pulse P3) of the laser beam output device 1 can be adjusted.

[0148] Compared with a variable optical attenuator having a half-wave plate and a polarizer in which the half-wave plate is rotated by a motor (see Patent Document 3), the output of the wavelength changing unit 14 can be attenuated by a high-speed and compact device.

[0149] First Modification

[0150] In the first embodiment, the centroid 144 c of the polarization inversion portion 144 is arranged on a straight line parallel to the x-axis of the LN crystal substrate 142 (see Figure 2 ), but regarding the configuration of the centroid 144c of the polarization reversal portion 144, the following modification example is considered.

[0151] Figure 4 FIG. 1 is a top view of the wavelength changing section 14 of the first modified example of the first embodiment. Figure 4 For the convenience of illustration, Figure 1 Different from Figure 2 Likewise, the x-axis direction of the LN crystal substrate 142 is shown as being parallel to the horizontal direction of the paper.

[0152] Reference Figure 4 In the wavelength changing section 14 of the first modified example of the first embodiment, the polarization reversal sections 144 for propagating the traveling light (the second pulse P2a traveling on the optical path OP1) are arranged at a predetermined interval D1, and the centroid 144c thereof is arranged on a straight line parallel to the traveling direction of the traveling light (the second pulse P2a traveling on the optical path OP1) (for example, in the traveling direction). In addition, the polarization reversal sections 144 for propagating the traveling light (the second pulse P2a traveling on the optical path OP2) are arranged at a predetermined interval D2, and the centroid 144c thereof is arranged on a straight line parallel to the traveling direction of the traveling light (the second pulse P2a traveling on the optical path OP2) (for example, in the traveling direction).

[0153] According to the first modification of the first embodiment as described above, the longitudinal length (length in the Y-axis direction) of the polarization inversion portion 144 can be shortened compared to the case of the first embodiment.

[0154] In the first embodiment, the wavelength changing section 14 is provided with a polarization inversion section 144 (see Figure 2 as well as Figure 4 ), but a modified example in which the polarization reversal unit 144 is not provided but a nonlinear optical crystal for propagating the traveling light is also considered. For example, the wavelength changing unit 14 can be set to OPO (optical parametric oscillation) based on BPM (birefringence phase matching), SHG (second harmonic generation) or THG (third harmonic generation), etc.

[0155] Second Modification

[0156] In addition, in the first embodiment, there is only one LN crystal substrate 142 , but a modified example in which an LN crystal substrate is provided for each traveling light beam that propagates is considered.

[0157] Figure 5 This is a diagram showing the structure of the laser beam output device 1 according to the second modified example of the first embodiment. The parts different from the first embodiment are the rhombus prism 131 and the wavelength changers (PPLN) 14a and 14b. The other parts are the same as the first embodiment, so the description thereof is omitted.

[0158] The rhombic prism 131 receives the pulse traveling along the optical path OP2 among the second pulses (before wavelength conversion) P2a, and changes the optical path to be parallel to and away from the optical path OP1.

[0159] The wavelength changer (PPLN) 14a receives the pulses (wavelength W1 [nm]) traveling along the optical path OP1 among the second pulses P2a from the acousto-optic modulator 12, and converts only the pulses exceeding the oscillation threshold into the second pulses P2b (wavelength W2 [nm]). The structure of the wavelength changer 14a is equivalent to Figure 2 or Figure 4 The polarization reversal portion 144 is arranged at a predetermined interval D1 in the LN crystal substrate 142 on which the polarization reversal portion 144 is formed.

[0160] The wavelength changer (PPLN) 14b receives the pulses (wavelength W1 [nm]) of the second pulse P2a traveling along the optical path OP2 from the rhombic prism 131, and converts only the pulses exceeding the oscillation threshold into the second pulse P2b (wavelength W3 [nm]). The structure of the wavelength changer 14b is equivalent to Figure 2 or Figure 4 The polarization reversal portion 144 is arranged at a predetermined interval D2 and the LN crystal substrate 142 on which the polarization reversal portion 144 is formed.

[0161] In addition, the LN crystal substrate included in the wavelength changer 14a and the LN crystal substrate included in the wavelength changer 14b are different substrates. That is, the LN crystal substrate included in the wavelength changer 14a and the LN crystal substrate included in the wavelength changer 14b are provided for each traveling light (traveling light traveling along the optical path OP1 and traveling light traveling along the optical path OP2) that propagates.

[0162] According to the second variant of the first embodiment, an LN crystal substrate is provided for each propagating traveling light (traveling light traveling on the optical path OP1 and traveling light traveling on the optical path OP2), so that the manufacturing conditions of the polarization reversal portion 144 corresponding to the specified intervals D1 and D2 can be set, and the manufacture of the wavelength changing portions 14a and 14b becomes easy.

[0163] Third Modification

[0164] In the first embodiment, after irradiating “one” pulse light of a certain wavelength W2 [nm], “one” pulse light of another wavelength W3 [nm] is immediately irradiated (see Figure 3 However, it is also considered that after irradiating "multiple" pulses of light of a wavelength W2 [nm] (within a specified time range TR1), "multiple" pulses of light of a wavelength W3 [nm] (within a specified time range TR2) are immediately irradiated (refer to Fig.11 A variation like P3).

[0165] The laser beam output device 1 of this modification is different from the first embodiment in which the frequency of the first pulse P1 is constant (for example, 2 kHz) in that the frequency of the first pulse P1 is not constant.

[0166] Fig.11 : is a timing diagram of the first pulse P1, the second pulse (before wavelength conversion) P2a, the second pulse (after wavelength conversion) P2b, and the third pulse P3 of the third modified example of the first embodiment. Fig.11 In the diagram, the thickness of the line representing the pulse and the type of line (solid line or dotted line) are changed according to the wavelength. Fig.11 , the case where the diffraction efficiency η=η11, η12 is illustrated.

[0167] The excitation laser (pulse laser output unit) 10 emits a laser beam of a predetermined wavelength W1 [nm] as a first pulse P1 (see Fig.11 ) output. The excitation laser 10 is, for example, a Yb:YAG laser. Fig.11The first pulse P1 is a pseudo-random signal (e.g., an M-sequence signal) output in a predetermined time range TR1, TR2. In addition, the length of the predetermined time range TR1, TR2 is equivalent to one cycle of the M-sequence signal. In addition, since the first pulse P1 is a pseudo-random signal, the frequency of the first pulse is not constant, unlike the first embodiment.

[0168] The acousto-optic modulator (optical path determination unit) (AOM) 12 receives the first pulse P1, determines the optical path to be one or more of the two optical paths OP1 and OP2 for each of the first pulses P1, and outputs the optical path.

[0169] For example, refer to Fig.11 , at the time point when the AOM 12 receives multiple pulses within the specified time range TR1 of the first pulse P1, the power of the traveling light traveling only on the optical path OP1 (first power I·(1-η)) exceeds the oscillation threshold. The power of the traveling light traveling on the optical path OP2 (second power I·η) is less than the oscillation threshold. For example, at the time point when the AOM 12 receives multiple pulses within the specified time range TR1 of the first pulse P1, the power ratio is set to 1-η11:η11 (refer to Fig.15 (b)).

[0170] In addition, at the time point when the AOM 12 receives a plurality of pulses within the specified time range TR2 of the first pulse P1, the power of the traveling light (second power I·η) traveling only on the optical path OP2 exceeds the oscillation threshold. The power of the traveling light (first power I·(1-η)) traveling on the optical path OP1 is less than the oscillation threshold. For example, at the time point when the AOM 12 receives a plurality of pulses within the specified time range TR2 of the first pulse P1, the power ratio is set to 1-η12:η12 (refer to Fig.16 (b)).

[0171] Thus, the acousto-optic modulator 12 outputs multiple pulses within the first pulse P1 within the specified time ranges TR1 and TR2 from multiple optical paths OP1 and OP2 respectively, and the pulses within the specified time ranges are different (non-repeating), namely, the second pulse (before wavelength conversion) P2a (pulses that only exceed the oscillation threshold).

[0172] That is, the acousto-optic modulator 12 outputs a plurality of pulses within the first pulse P1 within the predetermined time range TR1 from the optical path OP1 (see Fig. 9 Furthermore, the acousto-optic modulator 12 outputs a plurality of pulses within the first pulse P1 within a predetermined time range TR2 from the optical path OP2 (refer to Fig. 9The pulses (P2a(OP1)) in the second pulse P2a traveling on the optical path OP1 (only the pulses exceeding the oscillation threshold) and the pulses (P2a(OP2)) in the second pulse P2a traveling on the optical path OP2 (only the pulses exceeding the oscillation threshold) have different prescribed time ranges (not repeated).

[0173] The wavelength changer (PPLN) 14 receives the traveling light (ie, the second pulse P2a) traveling along each of the plurality of optical paths OP1 and OP2, changes the wavelengths to different ones, and outputs them. The output of the wavelength changer 14 is the second pulse (after wavelength conversion) P2b.

[0174] Reference Fig.11 The wavelength changer 14 receives the pulse (wavelength W1 [nm]) (only the pulse exceeding the oscillation threshold value) of the second pulse P2a traveling along the optical path OP1, and converts it into the second pulse P2b (wavelength W2 [nm]). In addition, the wavelength changer 14 receives the pulse (wavelength W1 [nm]) (only the pulse exceeding the oscillation threshold value) of the second pulse P2a traveling along the optical path OP2, and converts it into the second pulse P2b (wavelength W3 [nm]).

[0175] According to the third variation of the first embodiment, the third pulse P3 can be output from the optical fiber 18. The third pulse P3 is a pulse in which a plurality of pulse lights of wavelength W2 [nm] are irradiated immediately after a plurality of pulse lights of wavelength W3 [nm]. That is, according to the third variation of the first embodiment, a pulse light of another wavelength can be irradiated immediately after a pulse light of a certain wavelength is irradiated.

[0176] Second embodiment

[0177] The laser beam output device 1 of the second embodiment includes a convex lens (parallelizing unit) (L1) 13 and an achromatic lens (converging unit) (L2) 160 instead of the dichroic mirror (combiner) (DCM) 16 of the first embodiment.

[0178] Fig.12 It is a diagram showing the structure of a laser beam output device 1 according to the second embodiment. Fig.13 It is a plan view of the wavelength changing section 14 according to the second embodiment.

[0179] The laser beam output device 1 of the second embodiment includes an excitation laser (pulse laser output unit) 10, an acousto-optic modulator (optical path determination unit) (AOM) 12, a convex lens (parallelization unit) (L1) 13, a wavelength change unit (PPLN) 14, an achromatic lens (convergence unit) (L2) 160, filters (F) 172, 174, an optical fiber (MMF) 18, a timing control circuit (timing control unit) 19, a diffraction efficiency control unit (power ratio change signal giving unit) 120, half mirrors 130a, 130b, and photodiodes (output measurement units) (PD) 132a, 132b. Hereinafter, the same reference numerals are given to the same parts as those in the first embodiment, and the description thereof is omitted.

[0180] The excitation laser (pulse laser output unit) 10, the acousto-optic modulator (optical path determination unit) (AOM) 12, the filters (F) 172, 174, the timing control circuit (timing control unit) 19, the diffraction efficiency control unit (power ratio change signal giving unit) 120, the half-mirror 130a, 130b, the photodiode (output measurement unit) (PD) 132a, 132b are the same as those in the first embodiment, and the description thereof is omitted.

[0181] The convex lens (parallelizing unit) (L1) 13 makes the traveling directions of the traveling lights traveling along the two optical paths OP1 and OP2 parallel to each other. In addition, a prism can be used as the parallelizing unit instead of the convex lens 13.

[0182] In addition, if the maximum value of the distance between the outputs of the convex lens (parallelization unit) 13 is set to Ymax, Ymax is the distance between the optical path OP1 and the optical path OP2 located from the convex lens 13 to the achromatic lens 16 (refer to Fig.13 ).

[0183] The wavelength changer (PPLN) 14 is the same as the first embodiment, but receives the output of the convex lens (parallelization unit) 13, that is, the pulse (i.e., the second pulse P2a) of the traveling light traveling in the two optical paths OP1 and OP2 passing through the convex lens 13, and changes the output to different wavelengths when the power of the output of the convex lens (parallelization unit) 13 exceeds the oscillation threshold. The output of the wavelength changer 14 is the second pulse (after wavelength conversion) P2b.

[0184] In addition, any of the outputs of the acousto-optic modulator 12 (for example, the traveling light traveling on the optical path OP1) may also pass through the optical axis of the convex lens 13. In this case, the convex lens 13 changes the traveling direction of the traveling light traveling on the optical path OP1, but does not change the traveling direction of the traveling light traveling on the optical path OP2 and makes it parallel to the optical path OP1.

[0185] Reference Figure 3The wavelength changer 14 receives the pulse (wavelength W1 [nm]) traveling along the optical path OP1 among the second pulses P2a, and converts it into the second pulse P2b (wavelength W2 [nm]) (only the pulse exceeding the oscillation threshold). In addition, the wavelength changer 14 receives the pulse (wavelength W1 [nm]) traveling along the optical path OP2 among the second pulses P2a, and converts it into the second pulse P2b (wavelength W3 [nm]) (only the pulse exceeding the oscillation threshold). In addition, the oscillation threshold of the wavelength changer 14 is the same as that of the first embodiment, and the description thereof is omitted (refer to Fig. 9 ).

[0186] Reference Fig.13 The wavelength change unit 14 includes an LN crystal substrate 142 and a polarization inversion unit 144. Figure 2 In, with Figure 1 Likewise, the X-axis direction of the LN crystal substrate 142 is shown as being parallel to the horizontal direction of the paper.

[0187] The polarization reversal section 144 is used to propagate the output of the convex lens 13 (i.e., the second pulse P2a). The polarization reversal section 144 has a polarization reversal section for propagating the second pulse P2a traveling along the optical path OP1 and a polarization reversal section for propagating the second pulse P2a traveling along the optical path OP2. Fig.13 In the figure, the polarization reversal portion 144 is PPLN (periodically polarized reversed lithium niobate), but is not limited thereto, and may be, for example, PPLT (lithium tantalate) or PPKTP.

[0188] The polarization reversal portions 144 for propagating the second pulse P2a traveling along the optical path OP1 are arranged at a predetermined interval D1. The polarization reversal portions 144 for propagating the second pulse P2a traveling along the optical path OP2 are arranged at a predetermined interval D2. The predetermined intervals differ according to the output of the convex lens 13. That is, the predetermined interval D1 is different from the predetermined interval D2.

[0189] The polarization reversal portion 144 is formed on the LN crystal substrate 142. There is only one LN crystal substrate 142, and all polarization reversal portions 144 are formed thereon. In addition, in the second embodiment, the LN crystal substrate 142 may not be an LN crystal substrate, as long as it is a nonlinear optical crystal substrate. In other embodiments, a nonlinear optical crystal substrate may be used instead of an LN crystal substrate.

[0190] The centroid 144c of the polarization reversal portion 144 for the second pulse P2a traveling on the optical path OP1 to propagate is arranged on a straight line parallel to the X-axis of the LN crystal substrate 142. The centroid 144c of the polarization reversal portion 144 for the second pulse P2a traveling on the optical path OP2 to propagate is also arranged on a straight line parallel to the X-axis of the LN crystal substrate 142. In addition, the centroid 144c of the polarization reversal portion 144 coincides with the center of gravity when gravity acts uniformly on the polarization reversal portion 144.

[0191] In addition, in the output of the wavelength changer 14, in addition to the second pulse P2b, a laser beam (excitation light) of wavelength W1 [nm] output by the excitation laser 10 and an idle light in the infrared region generated by the wavelength changer 14 are mixed. In addition, when the laser beam (excitation light) is provided to the wavelength changer 14, signal light and the idle light described above are generated due to optical parameter generation. The signal light is the output of the wavelength changer 14 (the second pulse (after wavelength conversion) P2b) (the same is true for the wavelength changer of other embodiments).

[0192] The achromatic lens (converging unit) (L2) 160 receives and converges the output of the wavelength changing unit 14. The achromatic lens 160 includes a convex lens 160a and a concave lens 160b. The convex lens 160a is arranged closer to the pumping laser 10 than the concave lens 160b. The convex surface of the convex lens 160a contacts the concave surface of the concave lens 160b.

[0193] The achromatic lens 160 is a lens that reduces the difference in focal length (chromatic aberration) caused by the difference in wavelength between the second pulse P2b (wavelength W2 [nm]) (pulse traveling on the optical path OP1) and the second pulse P2b (wavelength W3 [nm]) (pulse traveling on the optical path OP2).

[0194] Furthermore, when the difference between the wavelength W2 [nm] and the wavelength W3 [nm] is small, a single convex lens 160 a may be used as the converging portion instead of the achromatic lens 160 .

[0195] The optical fiber (MMF) 18 has a core, and the core has an end face 18E. The optical fiber 18 receives the output of the achromatic lens 160 through the end face 18E of the core. The achromatic lens 160 converges the output of the wavelength changing unit 14 to the end face 18E of the core.

[0196] In order to converge the output of the wavelength changing unit 14 on the end face 18E of the core, when the focal length of the achromatic lens 160 is f and the numerical aperture of the optical fiber 18 is NA, it is preferable that NA>Ymax / (2f).

[0197] The optical fiber (MMF) 18 outputs the output (third pulse P3) of the wavelength changing unit 14 from the other end and converges on the end face 18E of the core (see Figure 3 ).

[0198] Next, the operation of the second embodiment will be described.

[0199] The operations related to the pumping laser 10, the acousto-optic modulator 12, and the timing control circuit 19 are the same as those in the first embodiment, and the description thereof is omitted.

[0200] The traveling light traveling along the optical path OP1 passes straight through the convex lens 13 along its optical axis direction and becomes a second pulse (before wavelength conversion) P2a (see Figure 3 )(where pulses smaller than the oscillation threshold are ignored).

[0201] The traveling light traveling along the optical path OP2 changes its traveling direction to be parallel to the optical path OP1 by the convex lens 13 and passes through the convex lens 13 to become a second pulse (before wavelength conversion) P2a (see Figure 3 )(where pulses smaller than the oscillation threshold are ignored).

[0202] Moreover, the phase of the pulse (second pulse (before wavelength conversion) P2a) of the traveling light traveling on the optical path OP1 passing through the convex lens 13 is 180 degrees different from the phase of the pulse (second pulse (before wavelength conversion) P2a) of the traveling light traveling on the optical path OP2 passing through the convex lens 13 (wherein pulses smaller than the oscillation threshold are ignored).

[0203] The traveling light traveling along the optical path OP1 passes through the convex lens 13 and the pulse (second pulse (before wavelength conversion) P2a: wavelength W1 [nm]) (wherein pulses smaller than the oscillation threshold are ignored) is propagated by the polarization reversal section 144 arranged at a predetermined interval D1 in the wavelength changing section 14, and the wavelength is converted to W2 [nm], becoming the second pulse (after wavelength conversion) P2b (refer to Figure 3 ), the excitation light and idle light are removed by filter 172 and provided to the achromatic lens 16.

[0204] The traveling light traveling along the optical path OP2 passes through the convex lens 13 and the pulse (second pulse (before wavelength conversion) P2a: wavelength W1 [nm]) (wherein pulses smaller than the oscillation threshold are ignored) propagates through the polarization reversal section 144 arranged at a predetermined interval D2 in the wavelength changing section 14, and the wavelength is converted to W3 [nm], becoming the second pulse (after wavelength conversion) P2b (see Figure 3), the excitation light and idle light are removed by filter 174 and provided to the achromatic lens 16.

[0205] The second pulse (after wavelength conversion) P2b outputted from the wavelength changer 14 has a wavelength of W2 [nm] and a wavelength of W3 [nm], which are converged on the end face 18E of the core of the optical fiber 18 by the achromatic lens 16 to become a third pulse P3 (which is the same as the wavelength of the wavelength changer 14) having a predetermined frequency (2 kHz). Figure 3 same waveform as P3).

[0206] The third pulse P3 is output from the other end of the optical fiber 18 .

[0207] The operations related to the half mirrors 130a and 130b, the photodiodes (output measuring unit) (PD) 132a and 132b, and the diffraction efficiency control unit 120 are the same as those in the first embodiment, and the description thereof is omitted.

[0208] According to the second embodiment, the same effects as those of the first embodiment are obtained.

[0209] Furthermore, according to the second embodiment, there is no need for a combiner (for example, a dichroic mirror) for combining the pulse of wavelength W2 [nm] and the pulse of wavelength W3 [nm] in the second pulse (after wavelength conversion) P2b outputted from the wavelength changer 14. Since it is difficult to adjust the optical axis and change the wavelength W2 [nm] and the wavelength W3 [nm] of the second pulse (after wavelength conversion) P2b using a dichroic mirror, it is possible to reduce the labor by eliminating the need for a dichroic mirror.

[0210] In addition, the second embodiment may also be combined with the third modification example of the first embodiment (see Fig.11 ), after irradiating “multiple” pulses of light of a certain wavelength W2 [nm] (within a specified time range TR1), immediately irradiate “multiple” pulses of light of a certain wavelength W3 [nm] (within a specified time range TR2).

[0211] Modifications

[0212] In the second embodiment, there is only one LN crystal substrate 142 , but a modified example in which an LN crystal substrate is provided for each traveling light beam that propagates is considered.

[0213] Fig.14 This is a diagram showing the configuration of a laser beam output device 1 according to a modification of the second embodiment. The only difference from the second embodiment is the wavelength changing units (PPLN) 14a and 14b, and the other parts are the same as the second embodiment, so description thereof is omitted.

[0214] The wavelength changer (PPLN) 14a receives the pulses (wavelength W1 [nm]) of the second pulse P2a traveling along the optical path OP1 from the acousto-optic modulator 12 via the convex lens 13, and converts only the pulses exceeding the oscillation threshold into the second pulse P2b (wavelength W2 [nm]). The structure of the wavelength changer 14a is equivalent to Fig.13 The polarization reversal portion 144 is arranged at a predetermined interval D1 in the LN crystal substrate 142 on which the polarization reversal portion 144 is formed.

[0215] The wavelength changer (PPLN) 14b receives the pulse (wavelength W1 [nm]) of the second pulse P2a traveling along the optical path OP2 from the acousto-optic modulator 12 via the convex lens 13, and converts only the pulse exceeding the oscillation threshold into the second pulse P2b (wavelength W3 [nm]). The structure of the wavelength changer 14b is equivalent to Fig.13 The polarization reversal portion 144 is arranged at a predetermined interval D2 and the LN crystal substrate 142 on which the polarization reversal portion 144 is formed.

[0216] In addition, the LN crystal substrate included in the wavelength changer 14a and the LN crystal substrate included in the wavelength changer 14b are different substrates. That is, the LN crystal substrate included in the wavelength changer 14a and the LN crystal substrate included in the wavelength changer 14b are provided according to the output of the convex lens 13 (the traveling light traveling along the optical path OP1 and the traveling light traveling along the optical path OP2) to be propagated.

[0217] According to a variation of the second embodiment, the LN crystal substrate is arranged according to the propagating traveling light (the traveling light traveling on the optical path OP1 and the traveling light traveling on the optical path OP2), so that the manufacturing conditions of the polarization reversal portion 144 corresponding to the specified intervals D1 and D2 can be set, and the manufacture of the wavelength changing portions 14a and 14b becomes easy.

[0218] Third embodiment

[0219] In the laser beam output device 1 of the first embodiment and the second embodiment, two optical paths (optical path OP1 and optical path OP2) are provided. Therefore, the wavelength of the third pulse output from the other end of the optical fiber 18 is also two types, W2 and W3.

[0220] However, the number of optical paths may exceed two. In the laser beam output device 1 of the third embodiment, three optical paths (optical path OP1, optical path OP2, and optical path OP3) are provided, which is different from the first embodiment. Therefore, the wavelength of the third pulse output from the other end of the optical fiber 18 is also three types: W2, W3, and W4.

[0221] The main difference between the laser beam output device 1 of the third embodiment and the laser beam output device 1 of the first embodiment is that two acousto-optic modulators (a first acousto-optic modulator (AOM) 12a and a second acousto-optic modulator (AOM) 12b) are used as the optical path determination unit.

[0222] Fig.17 It is a diagram showing the structure of a laser beam output device 1 according to a third embodiment. Fig.18 It is an enlarged view of the vicinity of an optical path determining section (a first acousto-optic modulator (AOM) 12 a and a second acousto-optic modulator (AOM) 12 b ) in the laser beam output device 1 according to the third embodiment.

[0223] The laser beam output device 1 of the third embodiment includes an excitation laser (pulse laser output unit) 10, optical attenuators (ATT) 11a, 11b, 11c, a first acousto-optic modulator (AOM) 12a, a second acousto-optic modulator (AOM) 12b, rhombus prisms 13a, 13b, a wavelength change unit (PPLN) 14a, 14b, 14c, a reflector 154, a dichroic mirror (combiner) (DCM) 162, 164, filters (F) 172, 174, 176, an optical fiber (MMF) 18, a timing control circuit (timing control unit) 19, a lens (L) 192, a diffraction efficiency control unit (power ratio change signal providing unit) 120, half mirrors 130a, 130b, 130c, and photodiodes (output measurement units) (PD) 132a, 132b, 132c. Hereinafter, the same reference numerals are given to the same parts as those of the first embodiment, and the description thereof is omitted.

[0224] The diffraction efficiency control unit (power ratio change signal imparting unit) 120, the half mirrors 130a, 130b, and the photodiodes (output measuring units) (PD) 132a, 132b are the same as those in the first embodiment, and their description is omitted. However, the diffraction efficiency control unit 120 changes the power P of the diffraction efficiency control signal (the size of the power ratio change signal) based on the measurement results of the photodiodes (output measuring units) (PD) 132a, 132b, and 132c, and changes the power P of the diffraction efficiency control signal (the size of the power ratio change signal).

[0225] The half mirror 130c reflects a portion of the second pulse (after wavelength conversion) P2b output from the wavelength changer 14 that travels along the optical path OP3, and supplies the portion to the photodiode (output measurement unit) (PD) 132c.

[0226] The photodiode (output measuring unit) (PD) 132c measures the output of the wavelength changing unit 14 received via the half mirror 130c.

[0227] The excitation laser (pulse laser output unit) 10, the optical fiber (MMF) 18, and the timing control circuit (timing control unit) 19 are the same as those in the first embodiment, and their description is omitted. However, the optical fiber (MMF) 18 receives the third pulse P3 output by the dichroic mirror 164 through one end thereof via the lens (L) 192, and outputs it from the other end. In addition, the timing control circuit 19 controls the output timing of the optical path determination unit (the first acousto-optic modulator (AOM) 12a and the second acousto-optic modulator (AOM) 12b).

[0228] The reflection mirror 154 receives the pulse of the second pulse (after wavelength conversion) P2 b that travels along the optical path OP3 , and reflects it toward the dichroic mirror 162 .

[0229] The dichroic mirror (combiner) (DCM) 162 combines the pulse in the second pulse (after wavelength conversion) P2b traveling along the optical path OP2 and the reflected light from the reflector 154 (the pulse in the second pulse (after wavelength conversion) P2b traveling along the optical path OP3), and reflects them toward the dichroic mirror 164.

[0230] The dichroic mirror (combiner) (DCM) 164 combines the pulse in the second pulse (after wavelength conversion) P2b traveling on the optical path OP1 and the light from the dichroic mirror 162 (a pulse obtained by combining the pulse in the second pulse (after wavelength conversion) P2b traveling on the optical path OP2 and the pulse traveling on the optical path OP3), and outputs a third pulse P3 with a specified frequency (2kHz).

[0231] The optical path determining unit includes a first acousto-optic modulator (AOM) 12a and a second acousto-optic modulator (AOM) 12b. The planar shapes of the first acousto-optic modulator (AOM) 12a and the second acousto-optic modulator (AOM) 12b are both rectangular.

[0232] The long side of the first AOM 12a receives the first pulse P1. The short side of the first AOM 12a is tilted counterclockwise by θB (Bragg angle) with respect to the optical path OP2.

[0233] The long side of the second AOM 12b receives the output of the first AOM 12a, and the short side of the second AOM 12b is inclined clockwise by θB (Bragg angle) with respect to the optical path OP2.

[0234] The first acousto-optic modulator (AOM) 12a receives the first pulse P1, and outputs the optical path of each of the first pulses P1 as any one or more of the plurality of optical paths OP1 and OP2. In the third embodiment, the first acousto-optic modulator (AOM) 12a outputs each of the first pulses P1 as diffracted (optical path OP1) (when the diffraction efficiency η>0, a pulse less than the oscillation threshold is also output in the optical path OP2) or straight (optical path OP2) (when the diffraction efficiency η=0).

[0235] The second acousto-optic modulator (AOM) 12b receives the output of the first acousto-optic modulator 12a, and for each pulse of the output of the first acousto-optic modulator 12a, determines the optical path to be any one or more of the optical paths OP1, OP2, and OP3, and outputs it. In the third embodiment, the second acousto-optic modulator (AOM) 12b receives the pulse of the first pulse that goes straight (optical path OP2), and outputs it by diffracting (optical path OP3) (when the diffraction efficiency η>0, wherein a pulse less than the oscillation threshold is also output in the optical path OP2) or going straight (optical path OP2) (when the diffraction efficiency η=0), and receives the pulse obtained by diffracting (optical path OP1) the first pulse, and outputs it by going straight (optical path OP1) (diffraction efficiency η=0).

[0236] Thus, the optical path determination unit (first acousto-optic modulator (AOM) 12a and second acousto-optic modulator (AOM) 12b) receives the first pulse P1, and for each first pulse P1, determines the optical path to be any one or more of the three optical paths OP1, OP2, and OP3 and outputs it.

[0237] For example, refer to Fig.18 At the time point when the optical path determination unit receives the 1+3Nth (1st, 4th, 7th, ...) (where N is an integer greater than 0) pulse of the first pulse P1, the first acousto-optic modulator (AOM) 12a is provided with an acoustic wave, and the second acousto-optic modulator (AOM) 12b is not provided with an acoustic wave. Thus, the 1+3Nth pulse of the first pulse P1 is located in the optical path OP1 (refer to Fig.18 ) (a pulse smaller than the oscillation threshold is also output in the optical path OP2).

[0238] In addition, at the time point when the optical path determination unit receives the 2+3Nth (2nd, 5th, 8th, ...) pulse of the first pulse P1, neither the first acousto-optic modulator (AOM) 12a nor the second acousto-optic modulator (AOM) 12b provides an acoustic wave. Therefore, the 2+3Nth pulse of the first pulse P1 is on the optical path OP2 (refer to Fig.18 ) to move forward.

[0239] In addition, when the optical path determining unit receives the 3+3Nth (3rd, 6th, 9th, ...) pulse of the first pulse P1, the first acousto-optic modulator (AOM) 12a is not provided with an acoustic wave, and the second acousto-optic modulator (AOM) 12b is provided with an acoustic wave. Fig.18 ) (a pulse smaller than the oscillation threshold is also output in the optical path OP2).

[0240] Thus, the optical path determination unit outputs the second pulse (before wavelength conversion) P2a (wherein pulses smaller than the oscillation threshold are ignored) from the three optical paths OP1, OP2, and OP3 respectively. The second pulse (before wavelength conversion) P2a is a pulse having a frequency (2 / 3kHz) obtained by dividing a specified frequency (for example, 2kHz) by the number of multiple optical paths (3) and having a phase difference of 120 degrees.

[0241] Thus, the optical path determining unit (the first acousto-optic modulator (AOM) 12a and the second acousto-optic modulator (AOM) 12b) can (1) change the ratio of the first power of the traveling light traveling on one of two optical paths (optical paths OP1 and OP2) among the three optical paths OP1, OP2, and OP3 to the second power of the traveling light traveling on the other optical path, i.e., the power ratio, by changing the diffraction efficiency of the first acousto-optic modulator (AOM) 12a; and (2) change the ratio of the first power of the traveling light traveling on one of two optical paths (optical paths OP2 and OP3) among the three optical paths OP1, OP2, and OP3 to the second power of the traveling light traveling on the other optical path, i.e., the power ratio, by changing the diffraction efficiency of the second acousto-optic modulator (AOM) 12b.

[0242] The rhombic prism 13a receives the pulse of the second pulse (before wavelength conversion) P2a traveling along the optical path OP1 and changes the optical path to be parallel to and away from the optical path OP1. The rhombic prism 13b receives the pulse of the second pulse (before wavelength conversion) P2a traveling along the optical path OP3 and changes the optical path to be parallel to and away from the optical path OP3.

[0243] The optical attenuators (ATT) 11a, 11b, 11c attenuate the light traveling along the optical path OP1 (output of the rhombus prism 13a), the light traveling along the optical path OP2, and the light traveling along the optical path OP3 (output of the rhombus prism 13b), and provide them to the wavelength changing units (PPLN) 14a, 14b, 14c.

[0244] The wavelength changing sections (PPLN) 14a and 14b are similar to the second modification of the first embodiment (see Figure 5 ), the description is omitted.

[0245] The wavelength changer (PPLN) 14c receives the pulses (wavelength W1 [nm]) of the second pulse P2a traveling along the optical path OP3 from the rhombic prism 13b, and converts only the pulses exceeding the oscillation threshold into the second pulse P2b (wavelength W4 [nm]). The structure of the wavelength changer 14c is equivalent to Figure 2 or Figure 4 A polarization reversal portion 144 is arranged at a predetermined interval D2 (wherein the predetermined interval D2 is changed to D3) and an LN crystal substrate 142 on which the polarization reversal portion 144 is formed.

[0246] Furthermore, the LN crystal substrate included in the wavelength changer 14a, the LN crystal substrate included in the wavelength changer 14b, and the LN crystal substrate included in the wavelength changer 14c are different substrates. That is, the LN crystal substrate included in the wavelength changer 14a, the LN crystal substrate included in the wavelength changer 14b, and the LN crystal substrate included in the wavelength changer 14c are provided for each traveling light (traveling light traveling along the optical path OP1, the traveling light traveling along the optical path OP2, and the traveling light traveling along the optical path OP3) that propagates.

[0247] Filters (F) 172, 174, 176 remove pump light and idle light from the outputs of the wavelength changers (PPLN) 14a, 14b, 14c, and output them to the dichroic mirrors (combiners) (DCM) 164, 162 and the reflector 154. In addition, in order to prevent the pump light and idle light from entering the photodiodes 132a, 132b, 132c, the filters 172, 174, 176 are respectively arranged between the half mirrors 130a, 130b, 130c and the wavelength changers 14a, 14b, 14c.

[0248] The lens (L) 192 receives the output of the dichroic mirror (combiner) (DCM) 164 and provides it to the optical fiber (MMF) 18 .

[0249] Next, the operation of the third embodiment will be described.

[0250] First, the excitation laser 10 outputs a laser beam of a predetermined wavelength W1 [nm] as a first pulse P1 of a predetermined frequency (e.g., 2 kHz). The first pulse P1 is provided to the first acousto-optic modulator (AOM) 12a of the optical path determining unit. The timing control circuit 19 controls the output timing of the optical path determining unit.

[0251] At the time point when the optical path determining unit receives the 1+3Nth (1st, 4th, 7th, ...) (where N is an integer greater than 0) pulse of the first pulse P1, the first acousto-optic modulator (AOM) 12a is provided with an acoustic wave, and the second acousto-optic modulator (AOM) 12b is not provided with an acoustic wave. Thus, the 1+3Nth pulse of the first pulse P1 is located on the optical path OP1 (refer to Fig.12Therefore, the traveling light traveling on the optical path OP1 is a second pulse (before wavelength conversion) P2a (wherein pulses smaller than the oscillation threshold are ignored) having a frequency (2 / 3kHz) of a value obtained by dividing a predetermined frequency (for example, 2kHz) by the number of multiple optical paths (3).

[0252] At the time point when the optical path determining unit receives the 2+3Nth (2nd, 5th, 8th, ...) pulse of the first pulse P1, neither the first acousto-optic modulator (AOM) 12a nor the second acousto-optic modulator (AOM) 12b provides an acoustic wave. Fig.12 Therefore, the traveling light traveling on the optical path OP2 is a second pulse (before wavelength conversion) P2a (wherein pulses smaller than the oscillation threshold are ignored) having a frequency (2 / 3kHz) of a value obtained by dividing a predetermined frequency (for example, 2kHz) by the number of multiple optical paths (3).

[0253] At the time point when the optical path determination unit receives the 3+3Nth (3rd, 6th, 9th, ...) pulse of the first pulse P1, the first acousto-optic modulator (AOM) 12a is not provided with an acoustic wave, and the second acousto-optic modulator (AOM) 12b is provided with an acoustic wave. Fig.12 Therefore, the traveling light traveling on the optical path OP3 is a second pulse (before wavelength conversion) P2a (wherein pulses smaller than the oscillation threshold are ignored) having a frequency (2 / 3kHz) of a value obtained by dividing a predetermined frequency (for example, 2kHz) by the number of multiple optical paths (3).

[0254] Moreover, the phase of the traveling light (second pulse (before wavelength conversion) P2a) traveling on the optical path OP1 differs by 120 degrees from the phase of the traveling light (second pulse (before wavelength conversion) P2a) traveling on the optical path OP2. The phase of the traveling light (second pulse (before wavelength conversion) P2a) traveling on the optical path OP2 differs by 120 degrees from the phase of the traveling light (second pulse (before wavelength conversion) P2a) traveling on the optical path OP3. The phase of the traveling light (second pulse (before wavelength conversion) P2a) traveling on the optical path OP1 differs by 240 degrees from the phase of the traveling light (second pulse (before wavelength conversion) P2a) traveling on the optical path OP3.

[0255] The traveling light (second pulse (before wavelength conversion) P2a: wavelength W1 [nm]) traveling along the optical path OP1 changes its optical path due to the rhombus prism 13a, is attenuated by the optical attenuator (ATT) 11a, and is provided to the wavelength changer (PPLN) 14a. The light provided to the wavelength changer (PPLN) 14a propagates through the polarization reversal section 144 arranged at a predetermined interval D1 in the wavelength changer 14a, and is converted to wavelength W2 [nm], becoming the second pulse (after wavelength conversion) P2b, which is provided to the dichroic mirror 164 after the pump light and idle light are removed by the filter (F) 172.

[0256] The traveling light (second pulse (before wavelength conversion) P2a: wavelength W1 [nm]) traveling in the optical path OP2 is attenuated by the optical attenuator (ATT) 11b and is provided to the wavelength changer (PPLN) 14b. The light provided to the wavelength changer (PPLN) 14b propagates through the polarization reversal section 144 arranged at a predetermined interval D2 in the wavelength changer 14b, and the wavelength is converted to W3 [nm] to become the second pulse (after wavelength conversion) P2b, and the pump light and idle light are removed by the filter (F) 174, and after being reflected by the dichroic mirror 162, the light is provided to the dichroic mirror 164.

[0257] The traveling light (second pulse (before wavelength conversion) P2a: wavelength W1 [nm]) traveling on the optical path OP3 changes its optical path due to the rhombus prism 13b, is attenuated by the optical attenuator (ATT) 11c, and is provided to the wavelength changer (PPLN) 14c. The light provided to the wavelength changer (PPLN) 14c propagates through the polarization reversal section 144 arranged at a predetermined interval D3 in the wavelength changer 14a, and is converted to wavelength W4 [nm], becoming the second pulse (after wavelength conversion) P2b, and the pump light and idle light are removed by the filter (F) 176, and after being reflected by the reflector 154, the light is provided to the dichroic mirror 164 via the dichroic mirror 162.

[0258] The pulses of wavelength W2 [nm], W3 [nm] and W4 [nm] in the second pulse (after wavelength conversion) P2b output by the wavelength changers 14a, 14b and 14c are combined by the dichroic mirror 164 to become the third pulse P3 having a predetermined frequency (2 kHz).

[0259] The third pulse P3 is provided to the optical fiber (MMF) 18 through the lens (L) 192 .

[0260] According to the third embodiment, the plurality of optical paths can be increased to three (optical paths OP1, OP2, OP3). Thus, after the third pulse P3 irradiates the pulse light of wavelength W2 [nm], it irradiates the pulse light of other wavelength W3 [nm] immediately (for example, 500 microseconds). Moreover, after the pulse light of wavelength W3 [nm] is irradiated, it irradiates the pulse light of other wavelength W4 [nm] immediately (for example, 500 microseconds). That is, according to the third embodiment, after irradiating the pulse light of a certain wavelength, it is possible to irradiate the pulse light of other wavelengths immediately, and immediately irradiate the pulse light of other wavelengths. In this way, according to the third embodiment, it is possible to irradiate pulse light of three wavelengths.

[0261] In the third embodiment, similarly to the first embodiment, only one LN crystal substrate 142 may be provided, and the entire polarization inversion portion 144 may be formed.

[0262] In addition, according to the third embodiment, by changing the diffraction efficiency of the first acousto-optic modulator (AOM) 12a, the power of the traveling light traveling on the optical path OP2 (or OP1) is increased (wherein, it is set to be less than the oscillation threshold, and the output of the wavelength change unit 14 is not output from the optical path OP2 (or OP1)), thereby reducing the power of the traveling light traveling on the optical path OP1 (or OP2), thereby enabling the output of the wavelength change unit 14 (from the optical path OP1 (or OP2)) to be attenuated.

[0263] In addition, when the power of the traveling light traveling on the optical path OP2 is reduced by changing the diffraction efficiency of the first acousto-optic modulator (AOM) 12a, if the diffraction efficiency of the second acousto-optic modulator (AOM) 12b is fixed to the maximum value, the power of the traveling light traveling on the optical path OP3 can be reduced.

[0264] In addition, according to the third embodiment, by changing the diffraction efficiency of the second acousto-optic modulator (AOM) 12b, the power of the traveling light traveling on the optical path OP3 (or OP2) is increased (wherein, it is set to be less than the oscillation threshold, and the output of the wavelength change unit 14 is not output from the optical path OP3 (or OP2)), thereby reducing the power of the traveling light traveling on the optical path OP2 (or OP3), thereby enabling the output of the wavelength change unit 14 (from the optical path OP2 (or OP3)) to be attenuated.

[0265] In the third embodiment, regarding the operation of the optical path determining unit (the first acousto-optic modulator (AOM) 12a and the second acousto-optic modulator (AOM) 12b), the following modified examples are conceivable.

[0266] Fig.21It is an enlarged view of the vicinity of an optical path determining section (a first acousto-optic modulator (AOM) 12 a and a second acousto-optic modulator (AOM) 12 b ) in a laser beam output device 1 according to a modification of the third embodiment.

[0267] The first acousto-optic modulator (AOM) 12a receives the first pulse P1, and outputs the first pulse P1 by determining the optical path to be any one of the plurality of optical paths OP1 and OP2. For example, the first acousto-optic modulator (AOM) 12a outputs each of the first pulses P1 in a diffracted manner (optical path OP1) or in a straight manner (optical path OP2). So far, the same as the third embodiment.

[0268] Here, the second acousto-optic modulator (AOM) 12b receives the output of the first acousto-optic modulator 12a, and determines the optical path of each pulse outputted by the first acousto-optic modulator 12a to be any one of the one or more optical paths OP1, OP2, and OP3, and outputs the pulse. In a modified example of the third embodiment, the second acousto-optic modulator (AOM) 12b receives the pulse obtained by the first pulse going straight (optical path OP2) and outputs it straight (optical path OP2) (the difference from the third embodiment is that it is not diffracted), and receives the pulse obtained by the diffraction of the first pulse (optical path OP1) and outputs it diffracted (optical path OP3) or straight (optical path OP1) (the difference from the third embodiment is that it is diffracted).

[0269] In addition, the short side of the second acousto-optic modulator (AOM) 12 b is tilted counterclockwise by θ B (Bragg angle) with respect to the optical path OP1 .

[0270] In addition, according to a modified example of the third embodiment, by changing the diffraction efficiency of the first acousto-optic modulator (AOM) 12a, the power of the traveling light traveling on the optical path OP2 (or OP1) is increased (wherein, it is set to be less than the oscillation threshold, and the output of the wavelength change unit 14 is not output from the optical path OP2 (or OP1)), and the power of the traveling light traveling on the optical path OP1 (or OP2) can be reduced, thereby enabling the output of the wavelength change unit 14 (from the optical path OP1 (or OP2)) to be attenuated.

[0271] In addition, when the power of the traveling light traveling on the optical path OP1 is reduced by changing the diffraction efficiency of the first acousto-optic modulator (AOM) 12a, if the diffraction efficiency of the second acousto-optic modulator (AOM) 12b is fixed to the maximum value, the power of the traveling light traveling on the optical path OP3 can be reduced.

[0272] In addition, according to a modified example of the third embodiment, by changing the diffraction efficiency of the second acousto-optic modulator (AOM) 12b, the power of the traveling light traveling on the optical path OP3 (or OP1) is increased (wherein, it is set to be less than the oscillation threshold, and the output of the wavelength change unit 14 is not output from the optical path OP3 (or OP1)), and the power of the traveling light traveling on the optical path OP1 (or OP3) can be reduced, thereby enabling the output of the wavelength change unit 14 (from the optical path OP1 (or OP3)) to be attenuated.

[0273] In the third embodiment and its modified example, as in the second embodiment, a convex lens (parallelizing unit) (L1) 13 and an achromatic lens (converging unit) (L2) 160 may be provided instead of the dichroic mirror (combiner) (DCM) 16.

[0274] Fourth embodiment

[0275] In the laser beam output device 1 of the first and second embodiments, two optical paths (optical path OP1 and optical path OP2) are provided. Therefore, the wavelength of the third pulse output from the other end of the optical fiber 18 is also two types, W2 and W3.

[0276] However, the number of optical paths may exceed two. The laser beam output device 1 of the fourth embodiment is different from the first embodiment in that four optical paths (optical path OP1, optical path OP2, optical path OP3, and optical path OP4) are provided. Therefore, the wavelength of the third pulse output from the other end of the optical fiber 18 is also four types: W2, W3, W4, and W5.

[0277] The laser beam output device 1 of the fourth embodiment uses two acousto-optic modulators (a first acousto-optic modulator (AOM) 12a and a second acousto-optic modulator (AOM) 12b) in the same manner as the third embodiment, but is mainly different from the laser beam output device 1 of the third embodiment in that it irradiates pulse light of four wavelengths.

[0278] Fig.19 It is a diagram showing the structure of a laser beam output device 1 according to a fourth embodiment. Fig. 20 It is an enlarged view of the vicinity of an optical path determining section (a first acousto-optic modulator (AOM) 12 a and a second acousto-optic modulator (AOM) 12 b ) in a laser beam output device 1 according to the fourth embodiment.

[0279] The laser beam output device 1 of the fourth embodiment includes: an excitation laser (pulse laser output unit) 10, optical attenuators (ATT) 11a, 11b, 11c, 11d, a first acousto-optic modulator (AOM) 12a, a second acousto-optic modulator (AOM) 12b, rhombus prisms 13c, 13d, 13e, 13f, a wavelength changer (PPLN) 14a, 14b, 14c, 14d, a reflection mirror 154, a dichroic mirror (combiner) (D 161, 162, 164, filters (F) 172, 174, 176, 178, optical fiber (MMF) 18, timing control circuit (timing control unit) 19, lens (L) 192, diffraction efficiency control unit (power ratio change signal giving unit) 120, half mirrors 130a, 130b, 130c, 130d, and photodiodes (output measurement unit) (PD) 132a, 132b, 132c, 132d. Hereinafter, the same reference numerals are given to the same parts as those in the third embodiment, and the description thereof is omitted.

[0280] The diffraction efficiency control unit (power ratio change signal imparting unit) 120, the half mirrors 130a, 130b, 130c, and the photodiodes (output measuring units) (PD) 132a, 132b, and 132c are the same as those in the third embodiment, and their description is omitted. The diffraction efficiency control unit 120 changes the power P of the diffraction efficiency control signal (the size of the power ratio change signal) according to the measurement results of the photodiodes (output measuring units) (PD) 132a, 132b, 132c, and 132d, and changes the power P of the diffraction efficiency control signal (the size of the power ratio change signal).

[0281] The half mirror 130d reflects a portion of the second pulse (after wavelength conversion) P2b output from the wavelength changer 14 that travels along the optical path OP4, and supplies the portion to the photodiode (output measurement unit) (PD) 132d.

[0282] The photodiode (output measuring unit) (PD) 132d measures the output of the wavelength changing unit 14 received via the half mirror 130d.

[0283] The excitation laser (pulse laser output unit) 10, optical attenuator (ATT) 11a, 11b, 11c, wavelength change unit (PPLN) 14a, 14b, 14c, reflector 154, dichroic mirror (combiner) (DCM) 162, 164, filter (F) 172, 174, 176, optical fiber (MMF) 18, timing control circuit (timing control unit) 19, lens (L) 192 are the same as those in the third embodiment, and the description is omitted.

[0284] However, the reflector 154 receives the pulse of the second pulse (after wavelength conversion) P2b traveling on the optical path OP4 and reflects it toward the dichroic mirror 161. The dichroic mirror (combiner) (DCM) 162 combines the pulse of the second pulse (after wavelength conversion) P2b traveling on the optical path OP2 and the reflected light from the dichroic mirror 161, and reflects it toward the dichroic mirror 164. The filter (F) 176 removes the pump light and the idle light from the output of the wavelength changing unit (PPLN) 14c, and outputs it to the dichroic mirror (combiner) (DCM) 161.

[0285] The filter (F) 178 removes the pump light and idler light from the output of the wavelength changer (PPLN) 14d, and outputs the result to the mirror 154. In order to prevent the pump light and idler light from entering the photodiode 132d, the filter 178 is disposed between the half mirror 130d and the wavelength changer 14d.

[0286] The optical path determining unit includes a first acousto-optic modulator (AOM) 12a and a second acousto-optic modulator (AOM) 12b. The planar shapes of the first acousto-optic modulator (AOM) 12a and the second acousto-optic modulator (AOM) 12b are both rectangular.

[0287] The long side of the first AOM 12a and the long side of the second AOM 12b are parallel to each other. In addition, the optical path OP4 is tilted clockwise by θB (Bragg angle) relative to the short side of the first AOM 12a. The long side of the first AOM 12a receives the first pulse P1, and the long side of the second AOM 12b receives the output of the first AOM 12a.

[0288] The first acousto-optic modulator (AOM) 12a receives the first pulse P1, and outputs the first pulse P1 by determining the optical path to be any one or more of the plurality of optical paths OP1 and OP4. In the fourth embodiment, the first acousto-optic modulator (AOM) 12a outputs each of the first pulses P1 diffracted (optical path OP1) (when the diffraction efficiency η>0, a pulse less than the oscillation threshold is also output in the optical path OP4) or straight (optical path OP4) (when the diffraction efficiency η=0).

[0289] The second AOM 12b receives the output of the first AOM 12a, and determines the optical path of each pulse outputted from the first AOM 12a to be one or more of the optical paths OP1, OP2, OP3, and OP4, and outputs the pulse. In the fourth embodiment, the second AOM 12b causes each pulse outputted from the first AOM 12a to be diffracted (optical paths OP2 and OP3) (when the diffraction efficiency η>0, pulses smaller than the oscillation threshold are also outputted in the optical paths OP1 and OP4) or to be outputted in a straight line (optical paths OP1 and OP4) (when the diffraction efficiency η=0). In more detail, the second acousto-optic modulator (AOM) 12b receives the pulse obtained by the straight-line (optical path OP4) of the first pulse and diffracts it (optical path OP2) (when the diffraction efficiency η>0, wherein a pulse smaller than the oscillation threshold is also output in the optical path OP4) or outputs it in a straight-line (optical path OP4) (when the diffraction efficiency η=0), receives the pulse obtained by the diffraction (optical path OP1) of the first pulse and diffracts it (optical path OP3) (when the diffraction efficiency η>0, wherein a pulse smaller than the oscillation threshold is also output in the optical path OP1) or outputs it in a straight-line (optical path OP1) (when the diffraction efficiency η=0).

[0290] Thus, the optical path determination unit (first acousto-optic modulator (AOM) 12a and second acousto-optic modulator (AOM) 12b) receives the first pulse P1, and determines the optical path to be one or more of the four optical paths OP1, OP2, OP3, and OP4 for each first pulse P1 and outputs it.

[0291] At the time point when the optical path determination unit receives the 1+4Nth (1st, 5th, 9th, ...) (where N is an integer greater than 0) pulse of the first pulse P1, the first acousto-optic modulator (AOM) 12a is provided with an acoustic wave, and the second acousto-optic modulator (AOM) 12b is not provided with an acoustic wave. Thus, the 1+4Nth pulse of the first pulse P1 is located in the optical path OP1 (refer to Fig. 20 ) (a pulse smaller than the oscillation threshold is also output in the optical path OP4).

[0292] In addition, when the optical path determining unit receives the 2+4Nth (2nd, 6th, 10th, ...) pulse of the first pulse P1, the first acousto-optic modulator (AOM) 12a is not provided with an acoustic wave, and the second acousto-optic modulator (AOM) 12b is provided with an acoustic wave. Fig. 20 ) (a pulse smaller than the oscillation threshold is also output in the optical path OP4).

[0293] In addition, at the time point when the optical path determination unit receives the 3+4Nth (3rd, 7th, 11th, ...) pulse of the first pulse P1, an acoustic wave is provided to the first acousto-optic modulator (AOM) 12a, and an acoustic wave is also provided to the second acousto-optic modulator (AOM) 12b. Fig. 20 ) (pulses smaller than the oscillation threshold are also output in the optical paths OP4 and OP1).

[0294] In addition, at the time point when the optical path determining unit receives the 4+4Nth (4th, 8th, 12th, ...) pulse of the first pulse P1, no sound wave is provided to the first acousto-optic modulator (AOM) 12a, nor is it provided to the second acousto-optic modulator (AOM) 12b. Fig. 20 ) to move forward.

[0295] Thus, the optical path determination unit outputs the second pulse (before wavelength conversion) P2a (wherein pulses smaller than the oscillation threshold are ignored) from the four optical paths OP1, OP2, OP3, and OP4 respectively. The second pulse (before wavelength conversion) P2a is a pulse having a frequency (1 / 2kHz) of a value obtained by dividing a specified frequency (for example, 2kHz) by the number of multiple optical paths (4) and having phases that differ by 90 degrees.

[0296] Therefore, with respect to the optical path determining unit (the first acousto-optic modulator (AOM) 12a and the second acousto-optic modulator (AOM) 12b), (1) by changing the diffraction efficiency of the first acousto-optic modulator (AOM) 12a, the ratio of the first power of the traveling light traveling on one of two optical paths (optical paths OP1 and OP4) among the four optical paths OP1, OP2, OP3, and OP4 to the second power of the traveling light traveling on the other side, i.e., the power ratio, can be changed; and (2) by changing the diffraction efficiency of the second acousto-optic modulator (AOM) 12b, the ratio of the first power of the traveling light traveling on one of two optical paths ((optical paths OP1 and OP3) or (optical paths OP2 and OP4)) among the four optical paths OP1, OP2, OP3, and OP4 to the second power of the traveling light traveling on the other side, i.e., the power ratio, can be changed.

[0297] The rhombus 13c receives the pulse traveling along the optical path OP1 in the second pulse (before wavelength conversion) P2a, and changes the optical path to be parallel to and away from the optical path OP1. The rhombus 13e receives the pulse traveling along the optical path OP2 in the second pulse (before wavelength conversion) P2a, and changes the optical path to be parallel to and away from the optical path OP2. The rhombus 13f receives the pulse traveling along the optical path OP3 in the second pulse (before wavelength conversion) P2a, and changes the optical path to be parallel to and away from the optical path OP3. The rhombus 13d receives the pulse traveling along the optical path OP4 in the second pulse (before wavelength conversion) P2a, and changes the optical path to be parallel to and away from the optical path OP4.

[0298] The optical attenuator (ATT) 11d attenuates the light (the output of the rhombus prism 13d) traveling on the optical path OP4, and supplies the light to the wavelength changing unit (PPLN) 14d.

[0299] The wavelength changer (PPLN) 14d receives the pulses (wavelength W1 [nm]) of the second pulse P2a traveling along the optical path OP4 from the rhombic prism 13d, and converts only the pulses exceeding the oscillation threshold into the second pulse P2b (wavelength W5 [nm]). The structure of the wavelength changer 14b is equivalent to Figure 2 or Figure 4 A polarization reversal portion 144 is arranged at a predetermined interval D2 (wherein the predetermined interval D2 is changed to D4 which is different from D1, D2 and D3) and an LN crystal substrate 142 on which the polarization reversal portion 144 is formed.

[0300] Furthermore, the LN crystal substrates included in the wavelength changer 14a, the LN crystal substrates included in the wavelength changer 14b, the LN crystal substrates included in the wavelength changer 14c, and the LN crystal substrates included in the wavelength changer 14d are different substrates. That is, the LN crystal substrates included in the wavelength changer 14a, the LN crystal substrates included in the wavelength changer 14b, the LN crystal substrates included in the wavelength changer 14c, and the LN crystal substrates included in the wavelength changer 14d are provided for each traveling light that propagates (the traveling light that travels along the optical path OP1, the traveling light that travels along the optical path OP2, the traveling light that travels along the optical path OP3, and the traveling light that travels along the optical path OP4).

[0301] Next, the operation of the fourth embodiment will be described.

[0302] First, the excitation laser 10 outputs a laser beam of a predetermined wavelength W1 [nm] as a first pulse P1 of a predetermined frequency (e.g., 2 kHz). The first pulse P1 is provided to the first acousto-optic modulator (AOM) 12a of the optical path determining unit. The timing control circuit 19 controls the output timing of the optical path determining unit.

[0303] At the time point when the optical path determination unit receives the 1+4Nth (1st, 5th, 9th, ...) (where N is an integer greater than 0) pulse of the first pulse P1, the first acousto-optic modulator (AOM) 12a is provided with an acoustic wave, and the second acousto-optic modulator (AOM) 12b is not provided with an acoustic wave. Thus, the 1+4Nth pulse of the first pulse P1 is located in the optical path OP1 (refer to Fig.14 Therefore, the traveling light traveling on the optical path OP1 is a second pulse (before wavelength conversion) P2a (wherein pulses smaller than the oscillation threshold are ignored) having a frequency (1 / 2kHz) of a value obtained by dividing a predetermined frequency (for example, 2kHz) by the number of multiple optical paths (4).

[0304] At the time point when the optical path determining unit receives the 2+4Nth (2nd, 6th, 10th, ...) pulse of the first pulse P1, the first acousto-optic modulator (AOM) 12a is not provided with an acoustic wave, and the second acousto-optic modulator (AOM) 12b is provided with an acoustic wave. Fig.14 Therefore, the traveling light traveling on the optical path OP2 is a second pulse (before wavelength conversion) P2a (wherein pulses smaller than the oscillation threshold are ignored) having a frequency (1 / 2kHz) of a value obtained by dividing a predetermined frequency (for example, 2kHz) by the number of multiple optical paths (4).

[0305] At the time point when the optical path determining unit receives the 3+4Nth (3rd, 7th, 11th, ...) pulse of the first pulse P1, an acoustic wave is provided to the first acousto-optic modulator (AOM) 12a, and an acoustic wave is also provided to the second acousto-optic modulator (AOM) 12b. Fig.14 Therefore, the traveling light traveling on the optical path OP3 is a second pulse (before wavelength conversion) P2a (wherein pulses smaller than the oscillation threshold are ignored) having a frequency (1 / 2kHz) of a value obtained by dividing a predetermined frequency (for example, 2kHz) by the number of multiple optical paths (4).

[0306] At the time point when the optical path determining unit receives the 4+4Nth (4th, 8th, 12th, ...) pulse of the first pulse P1, no acoustic wave is provided to the first acousto-optic modulator (AOM) 12a, nor is an acoustic wave provided to the second acousto-optic modulator (AOM) 12b. Fig.14 Therefore, the traveling light traveling on the optical path OP4 is a second pulse (before wavelength conversion) P2a having a frequency (1 / 2 kHz) of a value obtained by dividing a predetermined frequency (for example, 2 kHz) by the number of the plurality of optical paths (4).

[0307] Moreover, the phase of the traveling light (the second pulse (before wavelength conversion) P2a) traveling on the optical path OP1, the phase of the traveling light (the second pulse (before wavelength conversion) P2a) traveling on the optical path OP2, the phase of the traveling light (the second pulse (before wavelength conversion) P2a) traveling on the optical path OP3, and the phase of the traveling light (the second pulse (before wavelength conversion) P2a) traveling on the optical path OP4 differ by 90 degrees.

[0308] The traveling light (second pulse (before wavelength conversion) P2a: wavelength W1 [nm]) traveling along the optical path OP1 changes its optical path through the rhombus prism 13c, is attenuated by the optical attenuator (ATT) 11a, and is provided to the wavelength changer (PPLN) 14a. The light provided to the wavelength changer (PPLN) 14a propagates through the polarization reversal section 144 arranged at a predetermined interval D1 in the wavelength changer 14a, and is converted to wavelength W2 [nm], becoming the second pulse (after wavelength conversion) P2b, which is provided to the dichroic mirror 164 after the pump light and idle light are removed by the filter (F) 172.

[0309] The traveling light (second pulse (before wavelength conversion) P2a: wavelength W1 [nm]) traveling on the optical path OP2 changes its optical path through the rhombus prism 13e, is attenuated by the optical attenuator (ATT) 11b, and is provided to the wavelength changer (PPLN) 14b. The light provided to the wavelength changer (PPLN) 14b propagates through the polarization reversal section 144 arranged at a predetermined interval D2 in the wavelength changer 14b, and is converted to wavelength W3 [nm], becoming the second pulse (after wavelength conversion) P2b, and the pump light and idle light are removed by the filter (F) 174, and after being reflected by the dichroic mirror 162, the light provided to the dichroic mirror 164 is provided.

[0310] The traveling light (second pulse (before wavelength conversion) P2a: wavelength W1 [nm]) traveling on the optical path OP3 changes its optical path through the rhombus prism 13f, is attenuated by the optical attenuator (ATT) 11c, and is provided to the wavelength changer (PPLN) 14c. The light provided to the wavelength changer (PPLN) 14c propagates through the polarization reversal section 144 arranged at a predetermined interval D3 in the wavelength changer 14c, and is converted to wavelength W4 [nm], becoming the second pulse (after wavelength conversion) P2b, and the pump light and idle light are removed by the filter (F) 176, and after being reflected by the dichroic mirror 161, the light is provided to the dichroic mirror 164 via the dichroic mirror 162.

[0311] The traveling light (second pulse (before wavelength conversion) P2a: wavelength W1 [nm]) traveling on the optical path OP4 changes its optical path through the rhombus prism 13d, is attenuated by the optical attenuator (ATT) 11d, and is provided to the wavelength changer (PPLN) 14d. The light provided to the wavelength changer (PPLN) 14d propagates through the polarization reversal section 144 arranged at a predetermined interval D4 in the wavelength changer 14d, and is converted to wavelength W5 [nm] to become the second pulse (after wavelength conversion) P2b, and the pump light and idle light are removed by the filter (F) 178, and after being reflected by the reflector 154, the light is provided to the dichroic mirror 164 via the dichroic mirrors 161 and 162.

[0312] The pulses of wavelength W2 [nm], W3 [nm], W4 [nm] and W5 [nm] in the second pulse (after wavelength conversion) P2b output by the wavelength change units 14a, 14b, 14c and 14d are combined by the color dichroic mirror 164 to become the third pulse P3 having a specified frequency (2kHz).

[0313] The third pulse P3 is provided to the optical fiber (MMF) 18 through the lens (L) 192 .

[0314] According to the fourth embodiment, while using two acousto-optic modulators (a first acousto-optic modulator (AOM) 12a and a second acousto-optic modulator (AOM) 12b) in the same manner as in the third embodiment, it is possible to irradiate pulse light of four more wavelengths than in the third embodiment.

[0315] In the fourth embodiment, similarly to the third embodiment, only one LN crystal substrate 142 is provided, but all of the polarization inversion portions 144 may be formed thereon.

[0316] In addition, according to the fourth embodiment, by changing the diffraction efficiency of the first acousto-optic modulator (AOM) 12a, the power of the traveling light traveling on the optical path OP4 (or OP1) is increased (wherein, it is set to be less than the oscillation threshold, and the output of the wavelength change unit 14 is not output from the optical path OP4 (or OP1)), and the power of the traveling light traveling on the optical path OP1 (or OP4) can be reduced, thereby enabling the output of the wavelength change unit 14 (from the optical path OP1 (or OP4)) to be attenuated.

[0317] In addition, when the power of the traveling light traveling on the optical path OP1 (or OP4) is reduced by changing the diffraction efficiency of the first acousto-optic modulator (AOM) 12a, if the diffraction efficiency of the second acousto-optic modulator (AOM) 12b is fixed to a maximum value, the power of the traveling light traveling on the optical path OP3 (or OP2) can be reduced.

[0318] In addition, according to the fourth embodiment, by changing the diffraction efficiency of the second acousto-optic modulator (AOM) 12b, the power of the traveling light traveling on the optical path OP3 (or OP1) is increased (wherein, it is set to be less than the oscillation threshold, and the output of the wavelength change unit 14 is not output from the optical path OP3 (or OP1)), and the power of the traveling light traveling on the optical path OP1 (or OP3) can be reduced, thereby enabling the output of the wavelength change unit 14 (from the optical path OP1 (or OP3)) to be attenuated.

[0319] In addition, according to the fourth embodiment, by changing the diffraction efficiency of the second acousto-optic modulator (AOM) 12b, the power of the traveling light traveling on the optical path OP4 (or OP2) is increased (wherein, it is set to be less than the oscillation threshold, and the output of the wavelength change unit 14 is not output from the optical path OP4 (or OP2)), and the power of the traveling light traveling on the optical path OP2 (or OP4) can be reduced, thereby enabling the output of the wavelength change unit 14 (from the optical path OP2 (or OP4)) to be attenuated.

[0320] In the fourth embodiment, as in the second embodiment, a convex lens (parallelizing unit) (L1) 13 and an achromatic lens (converging unit) (L2) 160 may be provided instead of the dichroic mirror (combiner) (DCM) 16.

Claims

1. A laser beam output device, characterized in that: have: a pulse laser output unit that outputs a laser beam of a specified wavelength as a first pulse; an optical path determination unit that receives the first pulse, determines the optical path to be one or more of two or more optical paths for each of the first pulses, and outputs the optical path; a wavelength changing unit that receives the traveling light traveling along the two or more optical paths, and changes the traveling light to different wavelengths for output when the power of the traveling light exceeds a threshold value; as well as a combiner for combining the outputs of the wavelength changing units, The optical path determination unit is capable of changing a power ratio, that is, a ratio of a first power of the traveling light traveling in one of two optical paths among the two or more optical paths as the traveling light to a second power of the traveling light traveling in the other of the two optical paths as the traveling light, The optical path determination unit makes the power of the traveling light traveling only along any one of the optical paths among the traveling light exceed the threshold value, When the first power exceeds the threshold, the optical path determination unit can set the power ratio to two or more types. The optical path determination unit may set the power ratio to two or more types when the second power exceeds the threshold.

2. A laser beam output device, characterized in that: have: a pulse laser output unit that outputs a laser beam of a specified wavelength as a first pulse; an optical path determination unit that receives the first pulse, determines the optical path to be one or more of two or more optical paths for each of the first pulses, and outputs the optical path; a parallelizing unit for parallelizing the traveling directions of the traveling lights traveling along the two or more optical paths; a wavelength changing unit that receives the output of the parallelizing unit and changes the output to different wavelengths when the power of the output exceeds a threshold value; a converging unit that receives and converges the output of the wavelength changing unit; and an optical fiber receiving the output of the converging portion through an end face of a fiber core, The converging unit converges the output of the wavelength changing unit to the end face of the core, The optical path determination unit is capable of changing a power ratio, that is, a ratio of a first power of the traveling light traveling in one of two optical paths among the two or more optical paths as the traveling light to a second power of the traveling light traveling in the other of the two optical paths as the traveling light, The optical path determination unit makes the power of the traveling light traveling only along any one of the optical paths among the traveling light exceed the threshold value, When the first power exceeds the threshold, the optical path determination unit can set the power ratio to two or more types. The optical path determination unit may set the power ratio to two or more types when the second power exceeds the threshold.

3. The laser beam output device according to claim 1 or 2, characterized in that: The threshold is determined for each of the optical paths.

4. The laser beam output device according to claim 1 or 2, characterized in that: The optical path determination unit includes: a power ratio change signal providing unit that provides a power ratio change signal for changing the power ratio; The optical path determining unit is an acousto-optic modulator.

5. The laser beam output device according to claim 4, characterized in that: The power ratio change signal providing unit includes: a carrier source, which outputs a carrier; a mixer that mixes the carrier and a voltage-variable modulation signal and outputs a modulated signal; and An amplitude changer changes the amplitude of the modulated signal and outputs the power ratio changed signal.

6. The laser beam output device according to claim 4, characterized in that: The laser beam output device comprises: an output measuring unit for measuring the output of the wavelength changing unit, The power ratio change signal providing unit changes the magnitude of the power ratio change signal according to the measurement result of the output measurement unit.

7. The laser beam output device according to claim 1 or 2, characterized in that: The optical path determining unit is an acousto-optic modulator, The two optical paths are the optical path of the 0th-order light and the optical path of the 1st-order light of the AOM.

8. The laser beam output device according to claim 1 or 2, characterized in that: The wavelength changing unit is a PPLN.

9. The laser beam output device according to claim 1 or 2, characterized in that: The wavelength changing unit is an OPO or an OPG.

Images