TWI869957B - Solid-state laser device and solid-state laser processing device - Google Patents

Abstract

A solid-state laser device (1) comprises a light source (10), a solid-state amplifier (20), a stimulated Raman scattering generating element (30), and a wavelength filter (40). The light source (10) outputs a pulse light (LS) of a first wavelength. The solid-state amplifier (20) has a solid active medium (21) and outputs a pulse amplified light (L0) of a first wavelength that amplifies the pulse light (LS). The stimulated Raman scattering generating element (30) is arranged at the rear section of the solid-state amplifier (20) and converts the pulse amplified light (L0) into a second wavelength at a wavelength conversion efficiency of more than 1% by stimulated Raman scattering, thereby outputting a first pulse light (L1) of the first wavelength and a second pulse light (L2) of the second wavelength. The wavelength filter (40) separates the second pulse light (L2) from the optical path of the first pulse light (L1) output from the stimulated Raman scattering generating element (30) by utilizing the difference in wavelength.

Description

Solid-state laser device and solid-state laser processing device

The present disclosure relates to a solid-state laser device for emitting laser light used in laser processing and a solid-state laser processing device.

In recent years, solid-state laser devices that output short-pulse light have been widely used as laser light sources for micromachining. In such solid-state laser devices, the Master Oscillator Power Amplifier (MOPA) method is mostly used, where the weak short-pulse light output from the light source is amplified and output by a solid-state amplifier containing a solid active medium. The advantages of the MOPA method include the ease of controlling the repetition frequency and the ease of obtaining high output by increasing the number of solid-state amplifiers.

When processing with a MOPA-type solid-state laser device, sometimes you want to temporarily stop the output of pulse light, or sometimes you want to change the repetition frequency of pulse light during processing. In this case, when the pulse interval of the pulse light input to the solid active medium of the solid amplifier is lengthened by the excitation light source, the energy stored in the solid active medium by the excitation light source is excessive. As a result, the pulse light input to the solid active medium is over-amplified, and a pulse light with an extremely large peak output is output. Hereinafter, the pulse light output in this way is also referred to as a "giant pulse". Such a huge pulse may cause damage to the optical components arranged in the subsequent stage and reduce the processing quality.

Patent document 1 discloses a laser light source device that can avoid damage caused by overexcitation of a solid-state amplifier when the output of pulse light from the device is temporarily stopped, and can avoid degradation of the beam propagation characteristics after the output is restarted. The laser light source device described in patent document 1 includes an optical fiber amplifier and a solid-state amplifier, a nonlinear optical element, an optical switch element, and a control unit. The optical fiber amplifier and the solid-state amplifier use a gain switching method to amplify the pulse light output from the seed light source. The nonlinear optical element converts the wavelength of the pulse light output from the solid-state amplifier. The optical switch element allows or prevents the pulse light from propagating from the optical fiber amplifier to the solid-state amplifier. The control unit controls the seed light source and the optical switch element.

In the laser light source device described in Patent Document 1, during the output period of the pulse light from the seed light source, the optical switch element is controlled by the control unit in such a manner as to prevent the propagation of the pulse light from the optical fiber amplifier to the solid-state amplifier. Thus, an output stop state can be achieved in which the output of the pulse light from the nonlinear optical element can be stopped even without stopping the seed light source. Furthermore, in the output stop state, since the optical switch element is controlled by the control unit in such a manner as to allow the propagation of light during a period different from the output period of the pulse light from the seed light source, the spontaneous radiation light noise generated by the optical fiber amplifier at the front stage is propagated to the solid-state amplifier at the rear stage, so that the energy of the active region of the solid-state amplifier in the excited state by the excitation light source is released. [Prior Art Document] [Patent Document]

[Patent Document 1] International Publication No. 2015/122375

[The problem the invention is trying to solve]

However, in the technology described in Patent Document 1, the energy of the active region of the solid-state amplifier in an excited state is released by using the spontaneous radiation light output from the optical fiber amplifier disposed between the seed light source and the solid-state amplifier. Therefore, the technology described in Patent Document 1 cannot be applied to a general solid-state laser device that does not use an optical fiber amplifier between the seed light source and the solid-state amplifier. In other words, it is difficult to prevent the occurrence of giant pulses in a general solid-state laser device that does not have an optical fiber amplifier. Furthermore, in Patent Document 1, although a technology for preventing the occurrence of giant pulses is disclosed, it is difficult to suppress the damage of optical components disposed in the rear section of the optical fiber amplifier and the solid-state amplifier or the reduction in processing quality when a giant pulse occurs. Therefore, according to the technology described in Patent Document 1, there is a problem in that the solid-state laser device cannot avoid damage to optical elements and the like due to the unintentional generation of large pulses.

This disclosure is made in view of the above situation, and its purpose is to obtain a solid-state laser device that can suppress the damage of optical elements arranged in the rear section of the solid active medium due to the occurrence of giant pulses. [Means for solving the problem]

In order to solve the above problems and achieve the purpose, the solid-state laser device disclosed in the present invention includes a light source, a solid-state amplifier, a stimulated Raman scattering generating element, and a wavelength filter. The light source outputs a pulse light of a first wavelength. The solid-state amplifier has a solid active medium that outputs a pulse amplified light of a first wavelength. The stimulated Raman scattering generating element is arranged at the back end of the solid-state amplifier, and converts the pulse amplified light into a second wavelength with a wavelength conversion efficiency of more than 1% by stimulated Raman scattering, and outputs a first pulse light of the first wavelength and a second pulse light of the second wavelength. The wavelength filter separates the second pulse light from the optical path of the first pulse light output by the stimulated Raman scattering generating element by using the difference in wavelength. [Effect of the invention]

The solid-state laser device disclosed herein has the effect of suppressing damage to optical elements disposed at the rear of a solid active medium due to the occurrence of giant pulses.

The following is a detailed description of a solid-state laser device and a solid-state laser processing device according to an implementation method of the present disclosure based on the accompanying drawings.

Implementation method 1 FIG. 1 is a diagram schematically showing an example of the configuration of a solid laser processing device including a solid laser device of implementation method 1. The solid laser processing device 100 includes a solid laser device 1, a deflector 80, and a focusing lens 90. The solid laser device 1 is a device that uses a solid active medium 21 described later as a medium for generating stimulated radiation and emits laser light in the solid laser processing device 100. The solid laser processing device 100 is a device that processes a processing object 51 using laser light emitted from the solid laser device 1 using a solid active medium 21. That is, in the solid laser processing device 100, the laser light emitted from the solid laser device 1 is irradiated to the processing object 51 through the deflector 80 and the focusing lens 90, and is used to process the processing object 51.

The solid-state laser device 1 of embodiment 1 includes a seed light source 10, a control unit 11, a solid-state amplifier 20, an excitation light source 22, a spectroscope 23, a stimulated Raman scattering (SRS) generating element 30, a temperature control mechanism 31, a wavelength filter 40, a damper 41, and an optical system 50.

The seed light source 10 generates and outputs a pulse light LS of a first wavelength. The pulse light LS of the first wavelength is laser light amplified by a solid active medium 21. The seed light source 10 is, for example, composed of a semiconductor laser, an optical fiber laser, etc. Alternatively, the seed light source 10 may be a MOPA light source composed of the seed light source 10 and an amplifier (not shown).

The control unit 11 controls various conditions such as the wavelength, pulse width, repetition frequency, and output of the pulse light LS output from the seed light source 10.

The solid-state amplifier 20 has a solid active medium 21, which amplifies the pulse light LS output from the seed light source 10 and outputs the pulse amplified light L0 as the amplified pulse light of the first wavelength. The type of the solid active medium 21 is selected corresponding to the first wavelength (i.e., the wavelength of the pulse light LS output from the seed light source 10). In one example, when the first wavelength is 1064nm, Nd: _YVO4 or neodymium-doped yttrium aluminum garnet (Nd:YAG) is preferably used as the solid active medium 21. In the present invention, an object in which laser active ions such as Nd, Yb or Tm are doped in a solid matrix such as YAG or YVO ₄ and has the property of amplifying laser light by excitation at a predetermined wavelength (i.e., having gain) is called a solid active medium 21. The solid amplifier 20 outputs the amplified pulse amplified light L0 of the first wavelength to the SRS generating element 30.

The excitation light source 22 is a light source that outputs laser light LE for exciting the solid active medium 21. In one example, the excitation light source 22 is composed of a semiconductor laser. When the solid active medium 21 is Nd:YVO ₄ , the wavelength of the laser light LE output from the excitation light source 22 is preferably a continuous light with a wavelength of 808 nm or a wavelength of 878.6 nm or 888 nm. Hereinafter, the continuous light with a wavelength of 808 nm or a wavelength of 878.6 nm or 888 nm output from the excitation light source 22 is also referred to as the excitation light LE.

The spectroscope 23 is provided to make the pulse light LS from the seed light source 10 and the excitation light LE from the excitation light source 22 incident on the solid active medium 21 on the same axis. Here, the spectroscope 23 is configured to reflect the pulse light LS from the seed light source 10 and transmit the excitation light LE from the excitation light source 22.

The SRS generating element 30 is arranged at the rear section of the solid-state amplifier 20, and converts a part of the pulsed amplified light L0 of the first wavelength amplified by the solid active medium 21 into the second pulsed light L2 of the second wavelength by SRS, and outputs the first pulsed light L1 of the first wavelength and the second pulsed light L2 of the second wavelength. The second wavelength is longer than the first wavelength. In the first embodiment, the SRS generating element 30 converts the wavelength of the pulsed amplified light L0 into the second wavelength by SRS with a wavelength conversion efficiency of more than 1%. The SRS generating element 30 uses materials such as YVO ₄ , GdVO ₄ , Ba(NO ₃ ) ₂ , and diamond. In addition, the SRS generating element 30 can be made by using the above materials as a base material and adding laser active ions. When the first wavelength is 1064 nm and the SRS generating element 30 is Nd:YVO ₄ in which Nd as laser active ions is added to YVO ₄ , the second wavelength of the second pulse light L2 converted by the SRS generating element 30 is 1176 nm.

The SRS generating element 30 may include an anti-reflection coating for suppressing reflection of light of the first wavelength disposed on the surface (i.e., incident surface) where the pulse amplified light L0 is incident, and an anti-reflection coating for suppressing reflection of light of the first wavelength and the second wavelength disposed on the surface (i.e., exit surface) where the first pulse light L1 and the second pulse light L2 are emitted. By means of the anti-reflection coating disposed on the incident surface, the pulse amplified light L0 can be suppressed from returning to the seed light source 10, the excitation light source 22, and the solid active medium 21. Furthermore, by means of the anti-reflection coating disposed on the exit surface, the first pulse light L1 and the second pulse light L2 can be suppressed from returning to the seed light source 10, the excitation light source 22, and the solid active medium 21.

FIG. 2 schematically shows another example of the configuration of the SRS generating element. As shown in FIG. 2, the SRS generating element 30 may not be provided with an anti-reflection coating on the incident surface 301 of the pulsed amplified light L0 and the exit surface 302 of the first pulsed light L1 and the second pulsed light L2. In addition, the SRS generating element 30 is configured such that the pulsed amplified light L0 is incident at a Brewster angle θBi with respect to the incident surface 301 of the SRS generating element 30, and the first pulsed light L1 and the second pulsed light L2 are emitted at a Brewster angle θBo with respect to the exit surface 302 of the SRS generating element 30.

Typically, an anti-reflection coating is provided on the incident and output surfaces of a transmission type optical element. The damage threshold of the anti-reflection coating is usually lower than that of the bulk or interface of the optical element. On the other hand, as shown in FIG. 2, when pulsed light enters and exits the optical element at Brewster angles θBi and θBo, the reflectivity at the incident and output surfaces can be reduced even without an anti-reflection coating. Therefore, damage to the anti-reflection coating can be avoided, and damage to the optical element is unlikely to occur. Furthermore, when pulsed light enters and exits the optical element at Brewster angles θBi and θBo, since an anti-reflection coating need not be provided on the incident surface 301 and the output surface 302 of the SRS generating element 30, there is an advantage in that damage to the anti-reflection coating can be avoided.

Returning to FIG. 1, the temperature control mechanism 31 controls the temperature of the SRS generating element 30. In one example, the temperature control mechanism 31 includes a heating unit that heats the SRS generating element 30 to a predetermined temperature and a heating control unit that controls the heating of the heating unit. As described later, the temperature control mechanism 31 controls the temperature of the SRS generating element 30 so that the wavelength conversion efficiency of the SRS generating element 30 is 1% or more.

The wavelength filter 40 separates the second pulse light L2 from the first pulse light L1 and the second pulse light L2 output from the SRS generating element 30 by using the difference in wavelength. That is, the wavelength filter 40 separates the second pulse light L2 from the optical path of the first pulse light L1 output from the SRS generating element 30. In the example of FIG. 1 , the wavelength filter 40 transmits one of the first pulse light L1 and the second pulse light L2 output from the SRS generating element 30 and reflects the other. Thus, the first pulse light L1 and the second pulse light L2, which are lights of two wavelengths, are spatially separated. In the example of FIG. 1 , the wavelength filter 40 transmits the first pulse light L1 and reflects the second pulse light L2.

The damper 41 is disposed on the optical path of the second pulse light L2 reflected by the wavelength filter 40. The damper 41 attenuates the second pulse light L2. In addition, the damper 41 may be a measuring instrument such as a power meter.

The optical system 50 is arranged on the optical path of the first pulse light L1 through the wavelength filter 40. The first pulse light L1 separated by the wavelength filter 40 passes through the optical system 50. Although the optical system 50 is composed of a lens or a reflector for transmitting the first pulse light L1, it can be appropriately configured corresponding to the purpose of the solid-state laser device 1 disclosed in the present invention. In one example, in the case of further amplifying the output of the first pulse light L1, a solid-state amplifier can be provided in the optical system 50. Alternatively, in the case of converting the wavelength of the first pulse light L1 into a second, third or fourth harmonic by harmonic generation, a nonlinear optical element for harmonic generation can be provided in the optical system 50. The third pulse light L3 is a pulse light that is appropriately processed by the optical system 50 and is output from the solid-state laser device 1.

The deflector 80 deflects the third pulse light L3 output from the solid-state laser device 1. Specifically, the deflector 80 arbitrarily displaces the irradiation position of the third pulse light L3 on the processing object 51. It is preferable to provide two deflectors 80 so that the irradiation position of the third pulse light L3 can be displaced in two mutually orthogonal directions on the processing object 51. An example of the deflector 80 is a galvanometer scanner. In addition, when the solid-state laser device 1 does not have the optical system 50, the deflector 80 deflects the pulse light output from the wavelength filter 40.

The focusing lens 90 focuses the pulse light (the third pulse light L3 in the case of FIG. 1 ) deflected by the deflector 80 at an arbitrary position of the object 51 for irradiation. Thus, the third pulse light L3 is irradiated to the object 51, and laser processing is performed.

In addition, although FIG. 1 shows a case where the wavelength filter 40 transmits the first pulse light L1 and reflects the second pulse light L2, it is also possible to reflect the first pulse light L1 and transmit the second pulse light L2. In this case, it is preferable that the damper 41 is arranged on the transmission side of the wavelength filter 40 and the optical system 50 is arranged on the reflection side of the wavelength filter 40.

In implementation method 1, SRS is used for wavelength conversion of pulse light. The wavelength conversion of pulse light using such SRS has advantages over harmonic generation, which is a general wavelength conversion method. In harmonic generation, the wavelength of pulse light incident on a nonlinear optical element is wavelength-converted to 1/2 times or less. Generally, as the wavelength of the incident pulse light becomes shorter, the damage threshold of the optical element body or coating becomes lower. Therefore, when the wavelength of a giant pulse is converted by harmonic generation, there is a problem that optical elements such as nonlinear optical elements and wavelength filter 40 are easily damaged by the giant pulse with a shorter wavelength. On the other hand, in SRS, although part of the pulse light of the first wavelength is wavelength-converted into the pulse light of the second wavelength, the second wavelength is longer than the first wavelength. Therefore, compared with the first wavelength, the large pulse of the second wavelength is less likely to damage the optical elements such as the SRS generating element 30 and the wavelength filter 40.

Furthermore, since nonlinear optical elements such as lithium triborate (LiB ₃ O ₅ , LBO) and cesium lithium borate (CsLiB ₆ O ₁₀ , CLBO) used for harmonic generation are hygroscopic, humidity management is required. On the other hand, since Nd:YVO ₄ , etc. used for solid laser media, can be used in the SRS generating element 30, special environments and processing such as LBO and CLBO are not required, and it can be easily introduced into the interior of a known solid laser device.

In the first embodiment, the wavelength conversion efficiency of the SRS generating element 30 is preferably set to 1% or more. The intensity _ISRS of the SRS light output from the SRS generating element 30 is given by the following formula (1).

I _SRS =I _Raman0・exp(g _Raman・I _Pump・L)…(1)

Here, I _Raman0 is the intensity of the second wavelength pulse light at the incident surface 301 of the SRS generating element 30, g _Raman is the Raman gain coefficient of the SRS generating element 30, I _Pump is the peak intensity of the first wavelength pulse amplified light L0 incident on the SRS generating element 30, and L is the length of the SRS generating element 30. The length L of the SRS generating element 30 is the length in the traveling direction of the pulse light of the SRS generating element 30. In addition, the wavelength conversion efficiency η of the SRS can be expressed by the following formula (2).

η = _ISRS / _IPump …（2）

As can be seen from equations (1) and (2), since the wavelength conversion efficiency η of the SRS increases nonlinearly with respect to the peak intensity of the first pulse light L1, when the peak intensity of the incident pulse light increases more than the determined rated peak intensity, the wavelength conversion efficiency η increases. That is, with respect to the first pulse light L1 having a peak intensity exceeding the rated peak intensity, the SRS generating element 30 functions as an attenuator. By excluding the second pulse light L2 emitted from the SRS generating element 30 from the optical path of the first pulse light L1 through the wavelength filter 40, when a giant pulse occurs, damage to the optical system 50 and reduction in processing quality of the processing object 51 caused by the giant pulse can be avoided. That is, even if a giant pulse occurs, the wavelength conversion efficiency η increases, and a large amount of second pulse light L2 is generated in the SRS generating element 30 and absorbed by the damper 41. This can prevent the peak intensity of the first pulse light L1 output from the SRS generating element 30 from becoming excessively high.

In order to make the wavelength conversion efficiency η greater than 1%, in the exponential function of formula (1), the value of g _Raman・I _Pump・L is preferably set to "15" or more and "30" or less. In one example, when Nd:YVO ₄ is used for the SRS generating element 30, since the Raman gain coefficient at 893cm ^-1 where the Raman gain coefficient is the largest in the Raman mode of Nd:YVO ₄ is 4.5cm/GW, I _Pump and L are set so that the value of I _Pump・L is preferably "3GW/cm" or more and "7 GW/cm" or less.

On the other hand, g _Raman has the property that it becomes smaller as the temperature increases and becomes larger as the temperature decreases. That is, by adjusting the temperature of the SRS generating element 30 by the temperature control mechanism 31, the same effect as changing I _Pump or L can be obtained. Therefore, as described above, in the solid-state laser device 1 of the first embodiment, it is preferable to include the temperature control mechanism 31 for controlling the temperature of the SRS generating element 30. By adjusting the temperature of the SRS generating element 30 by the temperature control mechanism 31, a wavelength conversion efficiency of 1% or more can be obtained for any I _Pump・L. Therefore, by controlling the temperature of the SRS generating element 30 using the fact that the intensity of the SRS depends on the temperature of the SRS generating element 30, the wavelength conversion efficiency of the SRS can be controlled, and the damage of the SRS generating element 30 and the wavelength filter 40 arranged in the rear section of the solid active medium 21 due to giant pulses can be avoided.

As described above, when g _Raman can be kept constant, I _Pump and L can be set so that the wavelength conversion efficiency η is 1% or more, and the solid-state laser device may not have the temperature control mechanism 31. On the other hand, when I _Pump and L are set arbitrarily, in order to change g _Raman so that the wavelength conversion efficiency η is 1% or more, it is preferable that the solid-state laser device 1 includes the temperature control mechanism 31.

FIG. 3 is a diagram showing an example of wavelength conversion characteristics for SRS when Nd:YVO ₄ is used for an SRS generating element and a pulsed light of 1064 nm is incident on the SRS generating element. The horizontal axis shows the 1064 nm incident average output, that is, the incident average output of the pulsed light of 1064 nm, the left vertical axis shows the 1064 nm exit average output, that is, the exit average output of the pulsed light of 1064 nm, and the right vertical axis shows the 1176 nm exit average output, that is, the exit average output of the pulsed light of 1176 nm as the SRS wavelength. In this experiment, since the beam diameter, pulse width and repetition frequency of the incident pulse light are constant, the peak output and peak intensity of 1064nm are proportional to the average output. SRS occurs when the incident average output of 1064nm is above a certain value, and it can be confirmed that the average output of 1064nm is reduced and the average output of 1176nm is increased.

In the configuration of the first embodiment, when the material of the SRS generating element 30, the length in the optical axis direction, and the beam diameter of the pulsed amplified light L0 incident on the SRS generating element 30 are constant, the peak output of the pulsed amplified light L0 is preferably set in such a way that the peak output of the first pulsed light L1 emitted from the SRS generating element 30 is maximized. According to FIG. 3 , in the 1064nm incident average output where the 1064nm emission average output is the maximum, when the 1064nm incident average output varies by ±10%, the variation of the 1064nm emission average output is less than ±1%. Specifically, in the range of 1064nm incident average output on the horizontal axis from 40W to 50W, the 1064nm output average output on the left vertical axis is a constant value of about 36W. In other words, the variation of the 1064nm output average output relative to the variation of the 1064nm incident average output is reduced, and the stability of the output average output is improved. As described above, since the variation of the average output in the experiment of Figure 3 means the variation of the peak output, the same effect can be obtained by setting the 1064nm incident peak output so that the 1064nm output peak output is maximized. However, in order to maximize the 1064nm emission peak output (i.e., transmission transmission power), it is necessary to determine conditions other than the output related to the generation of SRS, i.e., the material of the SRS generating element 30 and its length in the optical axis direction, and the beam diameter of the pulse amplified light L0 incident on the SRS generating element 30.

In the first embodiment, the larger the beam diameter of the pulse light passing through the SRS generating element 30 and the wavelength filter 40, the better. In the case where a giant pulse is generated by the configuration of the first embodiment, the SRS generating element 30 may be damaged by the giant pulse of the first wavelength. In addition, the SRS generating element 30 and the wavelength filter 40 may be damaged by the wavelength conversion into the giant pulse of the second wavelength. Generally speaking, the damage threshold of an optical element due to pulse light depends on the peak intensity of the pulse light. That is, the larger the beam diameter of the pulse light incident on the optical element, the less likely it is to be damaged. On the other hand, the threshold of SRS depends on the peak intensity of the pulse light and the medium length. That is, when the peak intensity of the pulse light is reduced by expanding the beam diameter of the pulse light passing through the SRS generating element 30, it is possible to generate the desired SRS light by increasing the medium length of the SRS generating element 30. As a result, when a giant pulse occurs, it is possible to stably avoid damage to the SRS generating element 30 and the wavelength filter 40 arranged at the rear stage of the solid active medium 21 due to the giant pulse.

As a means of increasing the diameter of the light beam passing through the SRS generating element 30, it is preferable to increase the divergence angle of the pulse amplified light L0 emitted from the solid active medium 21. Alternatively, the SRS generating element 30 may be configured in such a manner that the pulse amplified light L0 is emitted from the solid active medium 21 in a convergent state, and after the pulse amplified light L0 changes again to a divergent state behind the light collection point, the pulse amplified light L0 is incident on the SRS generating element 30.

According to the first embodiment, when the peak output of the pulse amplified light L0 is greater than the determined rated peak output, the pulse amplified light L0 is wavelength-converted by the SRS generating element 30 and separated from the optical path by the wavelength filter 40. As a result, it is possible to suppress the damage of the optical element arranged at the rear stage of the solid active medium 21 and the reduction of the processing quality of the processing object 51 due to the generation of giant pulses.

Implementation method 2 In implementation method 2, the SRS generating element 30 can be the same material as the solid active medium 21, or the SRS generating element 30 can be a non-doped material or a low-doped material with the same substrate as the solid active medium 21. That is, the SRS generating element 30 can be a low-doped material doped with the same laser active ions as the laser active ions doped into the solid active medium 21 at a concentration lower than the concentration of the laser active ions of the solid active medium 21 relative to the substrate of the solid active medium 21. Alternatively, the SRS generating element 30 can also be a non-doped material with the same substrate as the substrate of the solid active medium 21 that does not contain laser active ions. It is better to configure the non-doped material or low-doped material in the rear section of the solid active medium 21. In addition, the non-doped material or low-doped material can be separated from the solid active medium 21 and configured in the rear section of the solid active medium 21, or can be connected to the surface of the solid active medium 21 from which the pulse amplified light L0 is emitted.

4 to 6 are diagrams showing examples of the configuration of the solid active medium and the SRS generating element of the solid laser device of Embodiment 2. In one example, in the SRS generating element 30 in which Nd as a laser active ion is doped in YVO ₄ as a substrate at 0.2 at.%, Nd:YVO ₄ is used as the solid active medium 21, and the materials shown in FIGS. 4 to ₆ can be used. In FIG. 4, the SRS generating element 30 is shown to be a material of the same material as the solid active medium 21, and the doping concentration is 0.2 at.%. FIG. 5 shows a case where the SRS generating element 30 is a doped material (i.e., non-doped YVO ₄ ) that is the same substrate as the substrate of the solid active medium 21 and is not doped with laser active ions. FIG. 6 shows a case where the SRS generating element 30 is a low-doped material doped with Nd, which is the same as the laser active ions doped into the solid active medium 21, at a concentration lower than the concentration of the laser active ions of the solid active medium 21, relative to YVO ₄ of the same substrate as the substrate of the solid active medium 21. In FIG. 6, Nd:YVO ₄ with a doping concentration of 0.1 at.% is used as the SRS generating element 30.

Therefore, by using the same material as the solid active medium 21, a non-doped material with the same base material as the solid active medium 21, or a low-doped material with a laser active ion concentration lower than that of the solid active medium 21 in the SRS generating element 30, the number of components or types of components of the solid laser device 1 can be reduced. In addition, by bonding the SRS generating element 30 to the surface of the solid active medium 21 from which the pulse amplified light L0 is emitted, the solid laser device 1 including the solid active medium 21 and the SRS generating element 30 can be miniaturized.

Implementation method 3 FIG. 7 is a diagram schematically showing an example of the configuration of a solid laser device of implementation method 3. In implementation method 3, since the configuration of the optical path between the solid active medium 21 and the wavelength filter 40 is different from that of implementation method 1, FIG. 7 shows the configuration of the optical path between the solid active medium 21 and the wavelength filter 40.

In the third embodiment, as shown in FIG. 7 , the solid laser device 1 further includes folding mirrors 60a, 60b, a damper 61, a moving mechanism 62, a parallel plane substrate 63, and a rotating mechanism 64 between the solid active medium 21 and the wavelength filter 40 at the rear end of the SRS generating element 30.

In the arrangement on the optical path of the light, the folding mirrors 60a and 60b are arranged between the SRS generating element 30 and the wavelength filter 40. In other words, the light passes through the SRS generating element 30, the folding mirrors 60a and 60b, and the wavelength filter 40 in sequence. In the arrangement on the optical path, at least one folding mirror 60a and 60b may be arranged between the incident surface 301 of the SRS generating element 30 and the wavelength filter 40. In the example of FIG. 7, two folding mirrors 60a and 60b are arranged to illustrate the case. Hereinafter, the folding mirrors 60a and 60b are referred to as the folding mirror 60 when they are not distinguished from each other. The folding mirror 60 reflects the first pulse light L1 of the first wavelength emitted from the SRS generating element 30, and transmits the second pulse light L2 of the second wavelength. The folding mirror 60 is arranged so that the first pulse light L1 of the first wavelength transmits the SRS generating element 30 at least twice. However, in the example of FIG. 7 , the position of the SRS generating element 30 is adjusted by the moving mechanism 62 described later, so that the first pulse light L1 transmits the SRS generating element 30 twice.

FIG. 8 is a diagram schematically showing another example of the configuration of the solid-state laser device of Embodiment 3. FIG. 8 shows a state in which the position of the SRS generating element 30 is adjusted so that all the light reflected by the folding mirror 60 (i.e., the first pulse light L1) is transmitted through the SRS generating element 30. When the SRS generating element 30 is moved upward in the paper from the state of FIG. 8, as shown in FIG. 7, the first pulse light L1 reflected by the folding mirror 60b is not transmitted through the SRS generating element 30. As shown in FIG. 8, the position in which the first pulse light L1 reflected by all the folding mirrors 60 is transmitted through the SRS generating element 30 is called the reference position. In addition, by appropriately setting the transmittance of the folding mirror 60 to the second pulse light L2, it is possible to configure the partially reflected second pulse light L2 to be incident on the SRS generating element 30, and the wavelength conversion efficiency in the SRS generating element 30 is greater than 1%.

The damper 61 attenuates the second pulse light L2 transmitted through the folding mirror 60. Therefore, in the example of Fig. 7 , the damper 61 is arranged on the transmission side of the folding mirror 60. In addition, the damper 61 may be a measuring instrument such as a power meter.

The moving mechanism 62 moves the SRS generating element 30. As shown in FIG. 8 , when the SRS generating element 30 is located at the reference position by the moving mechanism 62, the SRS generating element 30 has a size that can transmit all of the first pulse light L1 emitted from the solid active medium 21 and the first pulse light L1 reflected by the folding mirrors 60a and 60b. That is, at the reference position, the SRS generating element 30 is configured so that the number of times the first pulse light L1 is transmitted is the number of times the folding mirror 60 is + 1. The moving mechanism 62 moves the SRS generating element 30 so that the number of times the first pulse light L1 is transmitted through the SRS generating element 30 can be changed within a range from 1 time to the number of times the folding mirror 60 is + 1 time.

According to formula (1), the SRS intensity depends on the length of the SRS generating element 30 and the peak intensity of the first wavelength pulse light incident on the SRS generating element 30. In the third embodiment, the effective element length can be increased by making the first wavelength pulse light (i.e., the pulse amplified light L0 and the first pulse light L1) reciprocate through the SRS generating element 30 multiple times. In addition, since the second pulse light L2, which is the SRS component of the second wavelength, is transmitted through the folding mirror 60 and excluded from the optical path of the first wavelength, the number of times that I _Raman passes through the folding mirror 60 in formula (1) becomes substantially 0. As a result, compared with the case where the medium length of the SRS generating element 30 is long and passes through once, the attenuation rate relative to the giant pulse is improved in the third embodiment. Therefore, by moving the SRS generating element 30 with the moving mechanism 62 , the number of times the first pulse light L1 passes through the SRS generating element 30 and the passing distance of the first pulse light L1 through the SRS generating element 30 can be changed.

In addition, by moving the SRS generating element 30 in the direction of travel of the pulsed amplified light L0 emitted from the solid-state amplifier 20, the beam diameter of the first pulsed light L1 reflected by the folding mirror 60 incident on the SRS generating element 30 can be changed. In one example, as described in Embodiment 1, the moving mechanism 62 can move the SRS generating element 30 so that the beam diameter of the first pulsed light L1 incident on the SRS generating element 30 becomes larger. In addition, by changing the divergence angle of the pulsed amplified light L0 emitted from the solid active medium 21, the beam diameter incident on the SRS generating element 30 can also be changed. However, in reality, by changing the divergence angle of the pulse light LS incident on the solid active medium 21, the diameter of the light beam incident on the SRS generating element 30 is changed.

Therefore, in the third embodiment, the moving mechanism 62 changes at least one of the beam diameter of the first pulse light L1 reflected by the folding mirror 60 incident on the SRS generating element 30, the number of times the first pulse light L1 passes through the SRS generating element 30, and the passing distance of the first pulse light L1 through the SRS generating element 30.

The parallel plane substrate 63 is disposed between the folding mirror 60b disposed in front of the wavelength filter 40 and the wavelength filter 40. The parallel plane substrate 63 has an incident surface where the first pulse light L1 is incident and an emission surface where the first pulse light L1 is emitted that are parallel to each other.

The rotating mechanism 64 changes the angle between the incident surface of the parallel plane substrate 63 and the optical axis of the first pulse light L1 by rotating the parallel plane substrate 63. In one example, the rotating mechanism 64 rotates the parallel plane substrate 63 around two axes that are parallel to the incident surface of the parallel plane substrate 63 and orthogonal to each other. The rotating mechanism 64 corrects the optical axis deviation generated by the first pulse light L1 passing through the SRS generating element 30 by rotating the parallel plane substrate 63.

In the third embodiment, a moving mechanism 62 is included to change at least one of the beam diameter of the first pulse light L1 reflected by the folding mirror 60 incident on the SRS generating element 30, the number of times the first pulse light L1 passes through the SRS generating element 30, and the passing distance of the first pulse light L1 through the SRS generating element 30. By moving the SRS generating element 30 by the moving mechanism 62, the number of times the pulse light of the first wavelength passes through the SRS generating element 30 can be changed from 1 time to the number of folding mirrors 60+1 time. In addition, by changing the number of times the pulse light passes, the actual medium length of the SRS generating element 30 can be increased. In addition, the possibility of damage to the optical element can be suppressed by increasing the diameter of the light beam incident on the SRS generating element 30. Therefore, by making the first pulse light L1 reciprocate the SRS generating element 30 multiple times and removing the second pulse light L2 when reflected by each folding mirror 60, it is possible to increase the attenuation rate of the giant pulse when the giant pulse occurs.

In the third embodiment, a parallel plane substrate 63 as a parallel flat plate at the rear stage of the SRS generating element 30 and a rotating mechanism 64 for rotating the parallel plane substrate 63 are included. By using the rotating mechanism 64, the angle between the incident surface of the parallel plane substrate 63 and the optical axis of the first pulse light L1 is appropriately set, and the optical axis deviation caused by the first pulse light L1 passing through the SRS generating element 30 multiple times can be corrected.

Implementation method 4 FIG. 9 is a diagram schematically showing an example of the configuration of a solid laser device of implementation method 4. In implementation method 4, since the configuration of the optical path between the solid active medium 21 and the wavelength filter 40 is different from that of implementation method 1, FIG. 9 shows the configuration of the optical path between the solid active medium 21 and the wavelength filter 40.

In the fourth embodiment, as shown in FIG. 9 , the solid laser device 1 further includes an aperture 70. The aperture 70 is disposed at the rear section of the SRS generating element 30. The aperture 70 is a plate-shaped component forming an opening. The aperture 70 is preferably a circular opening. The aperture 70 has the function of removing the component having a divergence angle greater than a predetermined value in the pulse light (i.e., the first pulse light L1 and the second pulse light L2) passing through the aperture 70, and transmitting the component having a divergence angle less than a predetermined value.

Generally, the second wavelength SRS light generated in the non-waveguide type main body element has a component with a larger divergence angle than the first wavelength pulse light. Therefore, as in Embodiment 4, by configuring the aperture 70 at the rear section of the SRS generating element 30, it is possible to selectively remove the second wavelength pulse component with a larger divergence angle.

The configurations shown in the above embodiments are merely examples and may be combined with other known technologies, or the embodiments may be combined with each other. Part of the configuration may also be omitted or changed without departing from the scope of the present invention.

1: Solid laser device 10: Light source 11: Control unit 20: Solid amplifier 21: Solid active medium 22: Excitation light source 23: Spectroscope 30: SRS generator 31: Temperature control mechanism 40: Wavelength filter 41,61: Damper 50: Optical system 51: Processing object 60,60a,60b: Folding mirror 62: Moving mechanism 63: Parallel plane substrate 64: Rotating mechanism 70: Aperture 80: Deflector 90: Focusing lens 100: Solid laser processing device 301: Incident surface 302: Exit surface L0: Pulse amplified light L1: first pulse light L2: second pulse light L3: third pulse light LE: excitation light LS: pulse light θBi, θBo: Brewster angle

FIG. 1 is a diagram schematically showing an example of the configuration of a solid-state laser processing device including a solid-state laser device of embodiment 1. FIG. 2 is a diagram schematically showing other examples of the configuration of an SRS generating element. FIG. 3 is a diagram showing an example of the wavelength conversion characteristics for SRS when Nd:YVO ₄ is used for the SRS generating element and a pulse light of 1064 nm is incident on the SRS generating element. FIG. 4 is a diagram showing an example of the configuration of a solid active medium and an SRS generating element of a solid-state laser device of embodiment 2. FIG. 5 is a diagram showing an example of the configuration of a solid active medium and an SRS generating element of a solid-state laser device of embodiment 2. FIG. 6 is a diagram showing an example of the configuration of a solid active medium and an SRS generating element of a solid-state laser device of embodiment 2. FIG. 7 is a diagram schematically showing an example of the configuration of the solid-state laser device of the third embodiment. FIG. 8 is a diagram schematically showing another example of the configuration of the solid-state laser device of the third embodiment. FIG. 9 is a diagram schematically showing an example of the configuration of the solid-state laser device of the fourth embodiment.

1: Solid-state laser device

10: Light sources

11: Control Department

20: Solid-state amplifier

21: Solid active medium

22: Excitation light source

23: Spectroscope

30:SRS generating element

31: Temperature control mechanism

40: Wavelength filter

41: Damper

50:Optical system

51: Object to be processed

80: Deflector

90: Focusing lens

100: Solid laser processing equipment

L0: Pulse amplified light

L1: First pulse of light

L2: Second pulse light

L3: The third pulse of light

LE: Excitation light

LS: Pulse Light

Claims (9)

A solid-state laser device comprises: a light source, which outputs a pulse light of a first wavelength; a solid-state amplifier, which has a solid active medium, and outputs a pulse amplified light of the first wavelength for amplifying the pulse light; a stimulated Raman scattering generating element, which is arranged at the rear section of the solid-state amplifier, and converts the wavelength of the pulse amplified light into a second wavelength with a wavelength conversion efficiency of more than 1% by stimulated Raman scattering, and outputs a first pulse light of the first wavelength and a second pulse light of the second wavelength; and a wavelength filter, which uses the difference in wavelength to filter the first pulse light outputted from the stimulated Raman scattering generating element. The second pulse light is separated from the optical path of the solid active medium, wherein the stimulated Raman scattering generating element is: relative to the substrate of the solid active medium, the same laser active ions as the laser active ions doped in the solid active medium are doped with a low-doped material at a concentration lower than the concentration of the laser active ions in the solid active medium, or a non-doped material as the substrate that does not contain the laser active ions, and is separated from the solid active medium at the rear stage of the solid active medium, or is bonded to the surface of the solid active medium from which the pulse amplified light is emitted. The solid-state laser device as described in claim 1, wherein the stimulated Raman scattering generating element is configured such that the pulse amplified light is incident at a Brewster angle relative to the incident surface of the stimulated Raman scattering generating element, and the first pulse light is emitted at a Brewster angle relative to the exit surface of the stimulated Raman scattering generating element. The solid-state laser device as described in claim 1 further includes a temperature control mechanism to control the temperature of the stimulated Raman scattering generating element. The solid laser device as described in any one of claims 1 to 3 further includes a folding mirror that reflects the first pulse light and transmits the second pulse light, wherein the folding mirror is arranged on the optical path of the light between the stimulated Raman scattering generating element and the wavelength filter in such a manner that the first pulse light reflected by the folding mirror is incident on the stimulated Raman scattering generating element. The solid-state laser device as described in claim 4 further includes a moving mechanism for moving the stimulated Raman scattering generating element, wherein the moving mechanism changes at least one of the beam diameter of the first pulse light reflected by the folding mirror incident on the stimulated Raman scattering generating element, the number of times the first pulse light passes through the stimulated Raman scattering generating element, and the passing distance of the first pulse light through the stimulated Raman scattering generating element. The solid laser device as described in claim 4 further comprises: a parallel plane substrate, arranged at the rear section of the stimulated Raman scattering generating element, having an incident surface and an exit surface parallel to each other; and a rotating mechanism, which rotates the parallel plane substrate to change the angle between the incident surface and the optical axis of the first pulse light. The solid-state laser device as described in any one of claims 1 to 3 further includes an aperture, which is arranged at the rear section of the stimulated Raman scattering generating element, removes the components of the first pulse light and the second pulse light whose divergence angle is greater than the specified value, and transmits the components whose divergence angle is less than the specified value. A solid-state laser device as described in any one of claims 1 to 3, wherein the peak output of the pulsed amplified light is determined in such a way that the peak output of the first pulsed light emitted from the stimulated Raman scattering generating element is maximized, when the material of the stimulated Raman scattering generating element and the length in the optical axis direction and the beam diameter of the pulsed amplified light incident on the stimulated Raman scattering generating element are determined. A solid-state laser processing device, comprising: a light source, outputting a pulse light of a first wavelength; a solid-state amplifier, having a solid active medium, outputting a pulse amplified light of the first wavelength for amplifying the pulse light; a stimulated Raman scattering generating element, disposed at the rear section of the solid-state amplifier, converting the wavelength of the pulse amplified light into a second wavelength at a wavelength conversion efficiency of more than 1% by stimulated Raman scattering, and outputting a first pulse light of the first wavelength and a second pulse light of the second wavelength; a wavelength filter, separating the second pulse light from the optical path of the first pulse light outputted from the stimulated Raman scattering generating element by utilizing the difference in wavelength; and a deflector, making the wavelength filter outputted from the wavelength filter Pulse light deflection; and a focusing lens, which focuses the pulse light deflected by the deflector to any position of the object to be processed for irradiation, wherein the stimulated Raman scattering generating element is: relative to the same substrate as the solid active medium, the same laser active ions as the laser active ions doped in the solid active medium are doped with a low-doped material at a concentration lower than the concentration of the laser active ions in the solid active medium, or a non-doped material as the substrate that does not contain the laser active ions, separated from the solid active medium in the rear section of the solid active medium, or bonded to the surface of the solid active medium where the pulse amplified light is emitted.