JP5438576B2 - Laser amplification apparatus and laser amplification method - Google Patents

Description

  The present invention relates to a laser amplification device and a laser amplification method for amplifying signal light with pump light.

  Recent progress in high power lasers is remarkable. Since the laser light is coherent light having a uniform spatial phase, when the laser light is converged, it is possible to obtain extremely high condensed luminance compared to incoherent light such as sunlight. Utilizing such properties of laser light, laser processing (cutting, welding, drilling, modification, etc.) using high-power lasers has become widespread in the industry, and high-density physical research (laser particles) in the field of scientific research. Acceleration, elucidation of space physics by laser, etc.) and laser fusion research.

  In order to realize high output of laser light, it is considered to use optical parametric amplification (OPA). When the signal light and the pump light are incident on the nonlinear crystal so as to satisfy the phase matching condition, energy is converted from the pump light to the signal light, the signal light is amplified, and idler light is generated at the same time. This process is called optical parametric amplification. Non-Patent Document 1 describes a laser amplifying apparatus in which signal light is sequentially incident on a plurality of nonlinear crystals arranged in series, and the signal light is amplified by optical parametric amplification in each nonlinear crystal.

Okada Univ., 10 others, “Generation of broadband light in optical parametric chirp pulse amplification system”, J. Plasma Fusion Res. Vol.85, No.6 (2009), p. 384-388, Japan Society for Plasma and Fusion Research, June 25, 2009

  However, in a laser amplifying apparatus as described in Non-Patent Document 1, a laser beam with higher intensity is incident on a later-stage nonlinear crystal. Therefore, since it is necessary to prevent the occurrence of laser damage (damage due to incidence of high-intensity laser light) in the subsequent nonlinear crystal, the laser amplification apparatus described in Non-Patent Document 1 There is a limit to high output.

  Accordingly, an object of the present invention is to provide a laser amplification apparatus and a laser amplification method capable of obtaining high-quality laser light with high output.

In order to solve the above-described problems, a laser amplification device according to the present invention is a laser amplification device that amplifies signal light with pump light, a signal light output unit that outputs signal light, and pump light that outputs pump light. An output unit, a non-linear crystal that receives the signal light output from the signal light output unit and the pump light output from the pump light output unit, amplifies the signal light with the pump light, and outputs the non-linear crystal. A plurality of pump lights are incident on one signal light so that the phase matching condition of optical parametric amplification is satisfied , and the plurality of pump lights are different from each other on the light incident surface of the nonlinear crystal. One signal light is incident on the nonlinear crystal body so as to include a plurality of positions where a plurality of pump lights are incident on the light incident surface of the nonlinear crystal body. Ru brought Isa, characterized in that.

The laser amplification method according to the present invention is a laser amplification method for amplifying signal light with pump light, and a plurality of pump lights are supplied to one signal light so as to satisfy a phase matching condition of optical parametric amplification. Incident into the nonlinear crystal , multiple pump lights are incident on different positions on the light incident surface of the nonlinear crystal, and one signal light is incident on the nonlinear crystal. It is made to inject into a nonlinear crystal body so that the several position to be made may be included .

  In these laser amplifying apparatuses and laser amplifying methods, a plurality of pump lights are incident on the nonlinear crystal body with respect to one signal light so as to satisfy the phase matching condition of optical parametric amplification. As a result, energy is converted from a plurality of pump lights to one signal light, and the signal light is amplified. At this time, even if the phases of the plurality of pump lights incident on the nonlinear crystal are not the same, the random phase difference between the signal light and each pump light shifts to idler light. It is amplified without being affected by the phase information of the pump light. That is, one signal light is amplified as coherent light by a plurality of pump lights. Therefore, according to these laser amplification devices and laser amplification methods, one signal light can be obtained as a high-quality laser light with high output.

  Here, the laser amplifying apparatus according to the present invention includes a light intensity detection unit that detects the intensity of a plurality of pump lights incident on the nonlinear crystal body, and a plurality of pump light intensities detected by the light intensity detection unit are predetermined. It is preferable to further include a control unit that controls the pump light output unit so as to satisfy the following relationship. According to this configuration, a predetermined relationship can be given to the intensity distribution of the amplified signal light.

  At this time, it is preferable that the control unit controls the pump light output unit so that the intensities of the plurality of pump lights detected by the light intensity detection unit are uniform with each other. According to this configuration, the intensity distribution of the signal light after amplification can be made uniform.

  The nonlinear crystal body has a plurality of nonlinear crystal parts, and one signal light is incident on the nonlinear crystal body so as to include a plurality of nonlinear crystal parts, and the plurality of pump lights are provided for each nonlinear crystal part. It is preferably incident on the nonlinear crystal. According to this configuration, even if the intensity of the pump light incident on each nonlinear crystal part is suppressed so that laser damage in the nonlinear crystal part is prevented, the number of nonlinear crystal parts is increased to increase the number of nonlinear crystal parts. The output of the signal light can be increased.

  Further, each of the plurality of pump lights may have a predetermined wavelength. Each pump light is incident on the nonlinear crystal so as to satisfy the phase matching condition of optical parametric amplification, so even if a plurality of pump lights each have a predetermined wavelength, one signal light is amplified as coherent light. Can be made.

  According to the present invention, high-quality laser light can be obtained with high output.

It is a block diagram of the laser amplifier of one Embodiment of this invention. It is a figure which shows the image acquired by the light intensity detection part of FIG. It is a conceptual diagram which shows the principle of the optical parametric amplification in the laser amplifier of FIG. It is a block diagram of the experimental apparatus for demonstrating the principle of optical parametric amplification in the laser amplifier of FIG. It is a figure which shows the near-field image of the pump light obtained by the experimental apparatus of FIG. It is a figure which shows the interference pattern of the pump light, the far field image of pump light, the far field image of idler light, and the far field image of signal light obtained by the experimental apparatus of FIG. It is a figure which shows the interference pattern of the pump light, the far field image of pump light, the far field image of idler light, and the far field image of signal light obtained by the experimental apparatus of FIG. It is a graph which shows the condensable energy of the signal light after the amplification in the experimental apparatus of FIG. It is a partial block diagram of the laser amplifier of other embodiment of this invention. It is a partial block diagram of the laser amplifier of other embodiment of this invention. It is a partial block diagram of the laser amplifier of other embodiment of this invention. FIG. 12 is a partially enlarged view of the laser amplification device of FIG. 11.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same or an equivalent part, and the overlapping description is abbreviate | omitted.

As shown in FIG. 1, the laser amplifying apparatus 1 includes one laser light source (signal light output unit) 2 and a plurality of laser light sources (pump light output units) 3 _{1 to} 3 _n (n: an integer of 2 or more). And a nonlinear crystal body 9. The laser light source 2 outputs signal light L _s having a wavelength of 1054 nm, for example. The laser light sources 3 _{1 to} 3 _n output pump lights L _{p1 to} L _pn having a wavelength of 532 nm, for example. The nonlinear crystal body 9 is made of, for example, a type 1 type BBO (beta-barium borate) crystal. When the signal light L _s and the pump light L _{p1 to} L _pn are input, the nonlinear crystal body 9 amplifies the signal light L _s with the pump light L _{p1 to} L _pn and outputs the amplified signal light. As described above, the laser amplifying apparatus 1 amplifies the signal light L _s with the pump lights L _{p1 to} L _pn .

The signal light L _s emitted from the laser light source 2 is subjected to output adjustment and polarization control by the wave plate 4 and the polarizer 5 to be linearly polarized light. The beam size (beam diameter) is adjusted by the beam expansion / reduction lens system 6 for the signal light L _{s that} has been linearly polarized. A predetermined portion of the signal light L _s whose beam size has been adjusted is cut out by the aperture 7, and the cut out image is transferred onto the non-linear crystal 9 by the image transfer vacuum telescope 8. Thereby, the beam divergence resulting from the diffraction effect is suppressed.

The pump lights L _{p1 to} L _pn emitted from the laser light sources 3 _{1 to} 3 _n are the wave plate 4, the polarizer 5, the beam expanding / reducing lens system 6, the aperture 7, and the image transfer, similarly to the signal light L _s. It propagates through the vacuum telescope 8 for use. However, the polarization directions of the pump lights L _{p1 to} L _pn are adjusted to be orthogonal to the polarization direction of the signal light L _{s in} order to satisfy the phase matching condition of the optical parametric amplification in the nonlinear crystal body 9. The pump lights L _{p1 to} L _pn are reflected by the mirror 11 so as to be arranged in a matrix on the light incident surface of the nonlinear crystal body 9 and further reflected by the dichroic mirror 12 to the nonlinear crystal body 9 side. The signal light L _s passes through the dichroic mirror 12 to the nonlinear crystal body 9 side.

A plurality of pump lights L _{p1 to} L _pn are incident on the nonlinear crystal body 9 with respect to one signal light L _s so as to satisfy the phase matching condition of optical parametric amplification. That is, when the signal light L _s having a wavelength of 1054 nm and the pump lights L _{p1 to} L _pn having a wavelength of 532 nm are incident on the nonlinear crystal 9 made of type 1 type BBO crystal, the refractive index of the nonlinear crystal 9 is made equal. And the crystal cutting angle (angle formed by the crystal axis of the nonlinear crystal body 9 and the propagation direction of the laser light (signal light L _s , pump light L _{p1 to} L _pn )) is 22.8 °. Then, the polarization direction of the pump light L _{p1 to} L _pn is the plane direction (abnormal ray plane direction, e-axis direction) formed by the crystal axis of the nonlinear crystal body 9 and the propagation direction of the laser beam, and the polarization of the signal light L _s The direction is a direction orthogonal to the e-axis direction (normal light plane direction, O-axis direction).

At this time, since the nonlinear crystal body 9 is installed on the stage 13 having a rotation and tilt adjustment mechanism, the angle of the nonlinear crystal body 9 with respect to the signal light L _s and the pump lights L _{p1 to} L _pn depends on the optical parametric amplification. Are fine-tuned with high accuracy so as to satisfy the phase matching condition. Thereby, in the nonlinear crystal body 9, energy is converted from the pump lights L _{p1 to} L _pn to the signal light L _s to amplify the signal light L _s , and the amplified signal light L _s is emitted from the nonlinear crystal body 9. The At the same time, idler light is generated in the nonlinear crystal 9, but the signal light L _s and the pump light L _{p1 to} L _pn are adjusted by the dichroic mirror 12 so as to propagate at an angle of several degrees. The generated idler light is easily removed.

The signal light L _s emitted from the nonlinear crystal body 9 passes through the interference filter 14 and is emitted to the outside. On the other hand, the pump lights L _{p1 to} L _{pn that} have not been used for energy conversion pass through the nonlinear crystal body 9 and are then blocked by the interference filter 14. The pump lights L _{p1 to} L _pn that have not been used for energy conversion may be reused as pump light in other nonlinear crystal bodies 9.

The laser amplification device 1 further includes a control unit 15 and a light intensity detection unit 16. The control unit 15 emits the laser light source 2 and the laser light sources 3 _{1 to} 3 _n so that the signal light L _s and the pump light L _{p1 to} L _pn reach the nonlinear crystal body 9 at the same time by a delay circuit such as an electric circuit. Control timing. Thereby, the maximum amplification gain can be obtained with the nonlinear crystal body 9.

The light intensity detector 16 detects the intensities of the plurality of pump lights L _{p1 to} L _pn incident on the nonlinear crystal body 9. The light intensity detection unit 16 includes an achromatic lens (achromatic lens) 17 and a CCD camera 18 that are matched to the wavelengths of the pump lights L _{p1 to} L _pn . Thereby, as shown in FIG. 2, the light intensity detection unit 16 acquires an image indicating the intensity distribution of the pump lights L _{p1 to} L _pn arranged in a matrix on the light incident surface of the nonlinear crystal body 9.

The light intensity detection unit 16 transmits the acquired image to the control unit 15. Based on the received image, the control unit 15 controls the laser light sources 3 ₁ to 3 so that the intensities of the pump lights L _{p1 to} L _pn arranged in a matrix on the light incident surface of the nonlinear crystal 9 are uniform. 3 _Perform feedback control of _n . Thus, be caused to enter the pumping light L _p1 ~L _pn at different positions in the light incident surface of the nonlinear crystal 9, the variation of the gain due to the incident position of the pumping light L _p1 ~L _pn is suppressed . Note that. The output control of the pump lights L _{p1 to} L _pn is performed, for example, by adjusting the output of the excitation light sources (semiconductor laser, flash lamp, etc.) of the laser light sources 3 _{1 to} 3 _n .

  Here, the principle of optical parametric amplification in the laser amplification apparatus 1 described above will be described.

As shown in FIG. 3, the non-linear crystal 9, the signal light _{L s} and the pump light _L p1 _{~L pn} is input from the nonlinear crystal 9, amplified by the pumping light _L p1 _{~L pn} Signal Light L _s and idler light L _{i1 to} L _in are output. Note that the signal light L _s , the pump light L _{p1 to} L _pn, and the idler light L _{i1 to} L _in overlap on the light incident surface 9a and the light exit surface 9b of the nonlinear crystal body 9, but are shown separately in FIG. 3 for convenience. ing.

If the wavelengths of the signal light L _s , the pump light L _{p1 to} L _pn and the idler light L _{i1 to} L _in are λ _s , λ _p , and λ _i , respectively, the phase matching condition for optical parametric amplification is satisfied. The relationship of the following equation (1) is established between λ _s , λ _p , and λ _i (2π / λ _p , 2π / λ _s , 2π / λ _i : wave number vector). Accordingly, the wavelength lambda _s of the signal light _{L s} is 1054 nm, and if the wavelength lambda _p of the pump light _L p1 _{~L pn} is a 532 nm, the wavelength lambda _i of the idler light _L i1 _{~L in} becomes 1074 nm.
2π / λ _p = 2π / λ _s + 2π / λ _i (1)

If the phases of the signal light L _s , the pump light L _{p1 to} L _pn and the idler light L _{i1 to} L _in are φ _s , φ _pj and φ _ij (j: 1 to n), phase matching of optical parametric amplification Since the condition is satisfied, the relationship of the following equation (2) is established among the phases φ _s , φ _pj , and φ _ij .
φ _pj −φ _s −φ _ij = π / 2 (2)

Here, the characteristic is that even if the phases φ _{pj of} the plurality of pump lights L _{p1 to} L _pn incident on the nonlinear crystal 9 are not the same, the signal light L _s and the pump lights L _{p1 to} L _pn The random phase difference shifts to idler lights L _{i1 to} L _in , and one signal light L _s is amplified without being affected by the phase information of the plurality of pump lights L _{p1 to} L _pn . This means the same thing as coherent coupling from a plurality of laser beams having a random phase (pump beams L _{p1 to} L _pn ) to one laser beam having a uniform phase (signal beam L _s ).

  An experiment was conducted to verify the principle of optical parametric amplification described above. In this experiment, the beam characteristics of amplified signal light and idler light generated by optical parametric amplification were evaluated in each of the case where the pump light was divided into two beams and the case where the pump light was divided into a multi-beam array. did.

  The experimental apparatus is as shown in FIG. As the laser light source 2 for signal light, an Nd: YLF laser (wavelength 1053 nm, pulse width 20 ns, repetition rate 10 Hz) was used. As the laser light source 3 for pump light, a second harmonic of a Nd: YAG laser (wavelength 532 nm, pulse width 5 ns, repetition rate 10 Hz) was used.

  The pump light emitted from the laser light source 3 is subjected to output adjustment and polarization control by the wave plate 4 and the polarizer 5, and the beam diameter is adjusted by the beam expansion / reduction lens system 6. In the subsequent stage, when splitting the pump light into two beams, the prism pairs 21 and 22 were used, and the phase adjusting prism 23 was used to adjust the phase difference between the two beams. On the other hand, when the pump light is divided into multi-beam arrays with random phases, a random phase plate 24 is used.

  Then, the pump light converted into two beams or multiple beams was passed through the aperture 7 and then transferred onto the nonlinear crystal 9 by the image transfer vacuum telescope 8. As the nonlinear crystal 9, BBO (beta barium borate) crystal was used.

  The signal light emitted from the laser light source 2 is subjected to output adjustment and polarization control by the wave plate 4 and the Glan laser prism 25, and the signal light is transferred onto the nonlinear crystal 9 by the image transfer vacuum telescope 8. did. The dichroic mirror 12 was used to align the pump light and the signal light on the same axis.

  FIG. 5A is a near-field image of pump light converted into two beams by the experimental apparatus shown in FIG. On the other hand, FIG. 5B is a near-field image of pump light converted into multiple beams by the experimental apparatus shown in FIG.

  Subsequently, using the Mach-Zehnder interferometer, the interference pattern of the two-beam pump light is measured, and in that case, the far-field image of the pump light, the far-field image of the amplified signal light, and the optical parametric amplification The far-field image of idler light generated in the above was measured. The measurement results are as shown in FIG. The phase difference between the two beams was changed to 0 rad, π / 2 rad, π rad, 3π / 2 rad, 2π rad by the phase adjusting prism 23.

  As shown in FIGS. 6A and 6E, when the phase difference between the two beams in the pump light is set to 0 rad and 2π rad, the condensing pattern of the far-field image of the pump light becomes a single spot, and the idler The condensing pattern of the far-field images of light and signal light was also a single spot. As shown in FIGS. 6B and 6D, when the phase difference between the two beams is π / 2 rad and 3π / 2 rad in the pump light, the condensing pattern of the far-field image of the pump light interferes. Divided into two. At this time, the condensing pattern of the far-field image of idler light was also divided into two, but the condensing pattern of the far-field image of the signal became a single spot. As shown in FIG. 6C, similar results were obtained when the phase difference between the two beams in the pump light was πrad.

  Thus, regardless of the phase difference between the two beams in the pump light, the condensing pattern of the far-field image of the amplified signal light did not change with a single spot. From this, it was proved that the phase information of the two-beam pump light is shifted to idler light, and the signal light is amplified without being influenced by the phase information of the two-beam pump light.

  On the other hand, a Mach-Zehnder interferometer is used to measure the interference pattern of the multi-beam pump light, and in that case, the far-field image of the pump light, the far-field image of the amplified signal light, and optical parametric amplification A far-field image of the generated idler light was measured. The measurement results are as shown in FIG.

  As shown in FIG. 7, the condensing pattern of the far-field image of the pump light converted into multiple beams by the random phase plate 24 becomes a speckle pattern due to interference. At this time, the condensing pattern of the far-field image of idler light was also a speckle pattern, but the condensing pattern of the signal far-field image was a single spot.

  Thus, regardless of the phase difference between multiple beams in the pump light, the condensing pattern of the far-field image of the amplified signal light became a single spot. From this, it was proved that the phase information of the multi-beam pump light is shifted to the idler light, and the signal light is amplified without being influenced by the phase information of the multi-beam pump light.

  Next, in order to quantitatively evaluate that the beam quality of the amplified signal light is not affected by the number and phase of the pump light, the condensable energy of the signal light was measured. The measurement results are as shown in FIG.

  In the graph of FIG. 8, the horizontal axis represents the diameter represented by the product of the F number (focal length f / beam diameter D of the condenser lens) and the wavelength λ, and the output that has passed through the aperture having the diameter is normalized. Is the vertical axis. And the signal light (Example 1) amplified by the pump light (with phase difference) converted into two beams, the signal light (Example 2) amplified by the pump light (with phase difference) converted into multiple beams, The signal light before amplification (comparative example) was evaluated.

  The diameter that can be collected by the diffraction effect is limited, and when the spatial beam profile is a Gaussian type, the diffraction limited beam diameter is 2.4 Fλ. As shown in FIG. 8, in Examples 1 and 2, as in the comparative example, the signal light condensing characteristic was 80% or more at the diffraction limited beam diameter.

  From the above experiments, it was confirmed that uniform-wavefront signal light with uniform phase can be obtained from a plurality of pump lights with non-uniform phases. As a result, it has been demonstrated that coherent coupling is performed from a plurality of laser beams (pump beams) having a random phase to a single laser beam (signal) having a uniform phase.

As described above, in the laser amplifying apparatus 1 (and the laser amplifying method performed in the apparatus 1), a plurality of pumps are used for one signal light L _s so as to satisfy the phase matching condition of optical parametric amplification. Lights L _{p1 to} L _pn are incident on the nonlinear crystal body 9. As a result, energy is converted from the plurality of pump lights L _{p1 to} L _pn to one signal light L _s , and the signal light L _s is amplified. At this time, even if the phases of the plurality of pump lights L _{p1 to} L _pn incident on the nonlinear crystal body 9 are not the same, the random phase difference between the signal light L _s and each of the pump lights L _{p1 to} L _pn is an idler. Since the light L _{i1 to} L _in moves, one signal light L _s is amplified without being affected by the phase information of the plurality of pump lights L _{p1 to} L _pn . That is, one signal light L _s is amplified as coherent light by the plurality of pump lights L _{p1 to} L _pn . Therefore, according to the laser amplifying apparatus 1 (and the laser amplifying method performed in the apparatus 1), the plurality of pump lights L _{p1 to} L _pn are dispersed so that the occurrence of laser damage in the nonlinear crystal body 9 is prevented. Thus, one signal light L _s can be obtained as high-quality laser light with high output.

In the laser amplifying apparatus 1, the intensity of the plurality of pump lights L _{p1 to} L _pn incident on the nonlinear crystal body 9 is detected by the light intensity detector 16, and the plurality of pumps detected by the light intensity detector 16. The laser light sources 3 _{1 to} 3 _n are controlled by the control unit 15 so that the intensities of the lights L _{p1 to} L _pn are uniform. Thus, be caused to enter the pumping light L _p1 ~L _pn at different positions in the light incident surface of the nonlinear crystal 9, the variation of the gain due to the incident position of the pumping light L _p1 ~L _pn is suppressed Therefore, the intensity distribution of the amplified signal light L _s can be made uniform.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment.

For example, in the above-described embodiment, the laser light source 2 and the laser light sources 3 _{1 to} 3 _n are arranged so that the signal light L _s and the pump light L _{p1 to} L _pn reach the nonlinear crystal body 9 simultaneously by the delay circuit by the electric circuit. Although the emission timing is controlled, when higher accuracy is required, the laser amplifying apparatus 1 may be configured as follows.

That is, as shown in FIG. 9, a common laser light source 26 is used, and the laser light emitted from the laser light source 26 is used for the seed light for the signal light L _s and the pump lights L _{p1 to} L _pn . It is branched to the seed light. Seed light for the signal light L _s is may be used as it is as the signal light L _s, may be used after the broadening of spectral bands using the nonlinear effect due to the propagation of the hollow fiber 27. By widening the signal light L _s , a shorter pulse width can be obtained, and as a result, a higher intensity output can be obtained. Here, a signal light output unit is configured by the laser light source 26 and the hollow fiber 27.

On the other hand, the seed light for each of the pump lights L _{p1 to} L _pn is amplified by the laser amplifier 28, and then is used for wavelength conversion consisting of a KDP (potassium dihydrogen phosphate) crystal, a DKDP (partial deuterium substituted KDP) crystal, or the like. Is converted to a desired wavelength by the nonlinear crystal 29. For example, pump lights L _{p1 to} L _pn with a wavelength of 527 nm, which are second harmonics with a wavelength of 1054 nm, are obtained. Here, a pump light output unit is configured by the laser light source 26, the laser amplifier 28, and the nonlinear crystal body 29.

The signal light L _s emitted from the hollow fiber 27 and the pump lights L _{p1 to} L _pn emitted from the nonlinear crystals 29 are propagated to the nonlinear crystal 9 for optical parametric amplification. Note that the mirror 11 is disposed between the laser light source 26 and the hollow fiber 27. Thus, the optical path length on the signal light L _s side is adjusted so that the signal light L _s and the pump lights L _{p1 to} L _pn reach the nonlinear crystal body 9 at the same time.

As shown in FIG. 10, the nonlinear crystal body 9 may have a plurality of nonlinear crystal portions 10. Here, a plurality of nonlinear crystal portions 10 are arranged in a matrix along a plane orthogonal to the optical axis OA. Each nonlinear crystal portion 10 is cut at an angle that satisfies the phase matching condition of optical parametric amplification. In this case, the plurality of pump lights L _{p1 to} L _pn are incident on the nonlinear crystal body 9 for each nonlinear crystal portion 10 (or for each group of the plurality of nonlinear crystal portions 10) along the optical axis OA. At this time, one signal light L _s is incident on the nonlinear crystal body 9 along the optical axis OA so as to include a plurality of nonlinear crystal portions 10 on which the plurality of pump lights L _{p1 to} L _pn are incident. .

According to such a configuration, even if the intensity of the pump lights L _{p1 to} L _pn incident on each nonlinear crystal unit 10 is suppressed so that the occurrence of laser damage in the nonlinear crystal unit 10 is prevented, the nonlinear crystal unit 10 By increasing the number of signals, it is possible to increase the output of the signal light L _s after amplification. Then, it is possible to condense to a small spot as the beam size of the signal light L _s increases, it is possible to obtain a higher light condensing intensity.

Further, the plurality of pump lights L _{p1 to} L _pn may each have a predetermined wavelength as long as they are incident on the nonlinear crystal body 9 so as to satisfy the phase matching condition of the optical parametric amplification. As an example, as shown in FIGS. 11 and 12, the pump light L _p1 having a wavelength of 500 nm, the pump light L _{p2 having} a wavelength of 650 nm, and the pump light L _p3 having a wavelength of 532 nm are applied to the nonlinear crystal body 9 made of type 1 type BBO crystal. When incident, the pump lights L _{p1 to} L _p3 must satisfy the phase matching condition with respect to the signal light L _s having a wavelength of 1054 nm. For this purpose, the phase matching angle of the pump light _L p1 _{~L p3} (the angle between the propagation direction of the crystal axis CA and the laser beam of the nonlinear crystal 9 (pump light _L p1 _{~L p3)),} respectively 23. 6 °, 20.3 °, and 22.8 °. The optical paths of the pump lights L _{p1 to} L _p3 are adjusted by the mirror 11 and intersect in the nonlinear crystal body 9.

According to such a configuration, each of the pump lights L _{p1 to} L _pn is made incident on the nonlinear crystal body 9 so as to satisfy the phase matching condition of the optical parametric amplification, so that the plurality of pump lights L _{p1 to} L _pn are respectively Even if it has a predetermined wavelength, one signal light L _s can be amplified as coherent light.

In the above embodiment, the control unit 15 controls the laser light sources 3 _{1 to} 3 _n so that the intensities of the plurality of pump lights L _{p1 to} L _pn detected by the light intensity detection unit 16 are uniform. However, the present invention is not limited to this. The control unit 15 may control the laser light sources 3 _{1 to} 3 _n so that the intensities of the plurality of pump lights L _{p1 to} L _pn detected by the light intensity detection unit 16 have a predetermined relationship. According to such a configuration, it is possible to have a predetermined relationship to the intensity distribution of the signal light L _s after amplification.

Further, the nonlinear crystal body 9 is not limited to the one made of BBO crystal, and may be made of other nonlinear crystals such as KDP crystal and DKDP. Furthermore, the cross-sectional shapes of the signal light L _s and the pump lights L _{p1 to} L _pn incident on the light incident surface of the nonlinear crystal body 9 are not limited to a rectangular shape, and may be other shapes such as a circular shape. A part of the adjacent pump lights L _{p1 to} L _pn may be superimposed on the light incident surface of the nonlinear crystal body 9.

DESCRIPTION OF SYMBOLS 1 ... Laser amplifying device, 2 ... Laser light source (signal light output part), 3, 3 _{1-3 n} ... Laser light source (pump light output part), 9 ... Nonlinear crystal body, 10 ... Nonlinear crystal part, 15 ... Control part , 16 ... light intensity detection part, 26 ... laser light source (signal light output part, pump light output part), 27 ... hollow fiber (signal light output part), 28 ... laser amplifier (pump light output part), 29 ... nonlinear crystal Body (pump light output part), L _s ... signal light, L _{p1 to} L _pn ... pump light, L _{i1 to} L _in ... idler light.

Claims (8)

A laser amplification device that amplifies signal light with pump light,
A signal light output unit for outputting the signal light;
A pump light output unit for outputting the pump light;
A non-linear crystal body that receives the signal light output from the signal light output unit and the pump light output from the pump light output unit, and amplifies the signal light with the pump light and outputs the amplified signal light. ,
In the nonlinear crystal body, a plurality of pump lights are incident on one signal light so as to satisfy a phase matching condition of optical parametric amplification ,
The plurality of pump lights are incident on a plurality of different positions on the light incident surface of the nonlinear crystal body,
One of the signal light is laser amplifier, wherein the nonlinear crystal Ru allowed to enter the, and to include a plurality of said positions at which a plurality of the pump light is made incident in the light incident surface of the nonlinear crystal apparatus. The laser amplifying apparatus according to claim 1, wherein the plurality of pump lights are incident on the nonlinear crystal body in parallel with each other. A light intensity detector that detects the intensity of the plurality of pump lights incident on the nonlinear crystal;
As the intensity of a plurality of said pump light detected by said light intensity detecting unit becomes the predetermined relationship, further comprising a control unit for controlling the pump light output unit, according to claim 1 or, characterized in that 2. The laser amplification device according to 2 . 4. The laser amplification according to claim 3 , wherein the control unit controls the pump light output unit so that the intensities of the plurality of pump lights detected by the light intensity detection unit are uniform with each other. apparatus. The nonlinear crystal has a plurality of nonlinear crystal parts,
One signal light is incident on the nonlinear crystal body so as to include a plurality of the nonlinear crystal parts, and a plurality of pump lights are incident on the nonlinear crystal body for each nonlinear crystal part. laser amplifier according to any one of claims 1-4, characterized. Each of the plurality of said pump light has a predetermined wavelength, laser amplifier according to claim 1, wherein a. A laser amplification method for amplifying signal light with pump light,
In order to satisfy the phase matching condition of optical parametric amplification, a plurality of the pump lights are incident on the nonlinear crystal body with respect to one signal light ,
A plurality of the pump lights are incident on a plurality of different positions on the light incident surface of the nonlinear crystal body,
One of the signal light, the Ru said to be incident on the nonlinear crystal to include a plurality of the position for entering a plurality of the pump light in the light incident surface of the nonlinear crystal, the laser amplification wherein the. The laser amplification method according to claim 7, wherein a plurality of the pump lights are incident on the nonlinear crystal body in parallel with each other.