Laser oscillation method, laser oscillation system, generation method, generation device, estimation program

Abstract

To easily and accurately create a phase pattern for implementing a desired oscillation state.SOLUTION: A laser oscillation method includes oscillating laser light in a resonance path, on which an SLM 16 is arranged, by irradiating a laser medium 13 with excitation light. The laser oscillation method includes: a data acquisition step of irradiating the laser medium 13 with the excitation light to acquire data associated with the current oscillation; an estimation step of using an estimation program for outputting a parameter associated with a phase pattern to be displayed on the SLM 16 depending on input of information showing data associated with oscillation and a target oscillation state to estimate a parameter associated with a phase pattern depending on the data associated with the current oscillation acquired in the data acquisition step and the target oscillation state; and a control step of controlling a phase pattern to be displayed on the SLM 16 on the basis of the parameter estimated in the estimation step.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a laser oscillation method, a laser oscillation system, a generation method, a generation device, and an estimation program.

Background Art

[0002] Patent Document 1 discloses a configuration in which a spatial light modulator is used as a reflection mirror in a laser oscillation system.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, in order to realize a desired oscillation state, it is difficult to create a phase pattern (modulation pattern) to be displayed on a spatial light modulator with high precision in a short period of time by input.

[0005] The present disclosure has been made in view of the above circumstances, and an object thereof is to easily and highly accurately create a phase pattern that realizes a desired oscillation state.

Means for Solving the Problems

[0006] A laser oscillation method according to an aspect of the present disclosure is a laser oscillation method in which a spatial light modulator is disposed on a resonance path, and laser light is oscillated in the resonance path by irradiating an excitation light to a laser medium, the method including: a data acquisition step of irradiating the laser medium with the excitation light and acquiring data related to the current oscillation; an estimation step of estimating parameters related to a phase pattern according to the data related to the current oscillation acquired in the data acquisition step and a target oscillation state by using an estimation program that outputs parameters related to the phase pattern displayed on the spatial light modulator in response to an input of the data related to the oscillation and information indicating the target oscillation state; and a control step of controlling the phase pattern displayed on the spatial light modulator based on the parameters estimated in the estimation step.

[0007] In the laser oscillation method according to an aspect of the present disclosure, data related to the current oscillation in the resonance path is acquired by irradiating the laser medium with the excitation light, and parameters related to the phase pattern are estimated by an estimation program according to the data related to the current oscillation and the target oscillation state. Then, the phase pattern displayed on the spatial light modulator is controlled based on the parameters. In this way, by automatically controlling the phase pattern using a previously prepared estimation program, the phase pattern can be easily created. Further, since the estimation program takes as input data related to the current oscillation and the target (desired) oscillation state, a phase pattern that realizes the desired oscillation state can be created with high precision. As described above, according to the laser oscillation method according to an aspect of the present disclosure, a phase pattern that realizes a desired oscillation state can be easily and highly accurately created.

[0008] In the data acquisition step, data related to a non-oscillation state may be acquired as data related to the current oscillation, and in the estimation step, parameters related to the phase pattern may be estimated so as to transition from the non-oscillation state to the oscillation state. According to such a configuration, a phase pattern that appropriately transitions from a non-oscillating state to a desired oscillation state can be easily and highly accurately created.

[0009] In the data acquisition step, as data related to the current oscillation, data regarding fluorescence emitted from the laser medium may be acquired. According to such a configuration, even in the state before oscillation, data related to oscillation can be appropriately acquired, for example, from the ASE (Amplified Spontaneous Emission) intensity or the like. By this, a phase pattern for realizing a desired oscillation state can be created with higher precision.

[0010] In the data acquisition step, as data related to the current oscillation, data related to the oscillation state is acquired, and in the estimation step, parameters related to the phase pattern may be estimated so as to transition from the current oscillation state to another oscillation state. According to such a configuration, modulation parameters for appropriately transitioning from the oscillation state to a desired other oscillation state can be created easily and with high precision.

[0011] In the data acquisition step, as data related to the current oscillation, data regarding the laser oscillation light may be acquired. According to such a configuration, in the oscillating state, data related to oscillation can be appropriately acquired. By this, a phase pattern for realizing a desired oscillation state can be created with higher precision.

[0012] The above laser oscillation method may further include a learning step of generating an estimation program by performing multiple learning on a data set in which first learning data related to a phase pattern displayed on a spatial light modulator is associated with second learning data related to oscillation. In this way, by associating and learning a large amount of data related to the phase pattern and oscillation (for example, ASE intensity, beam image of laser oscillation light, etc.), the accuracy of the estimation program can be improved. That is, by providing the learning step, an estimation program with high estimation accuracy of parameters related to the phase pattern can be generated, and a phase pattern for realizing a desired oscillation state can be created with higher precision.

[0013] The second learning data may include at least one of a beam image of the laser oscillation light, intensity, spectrum, temporal waveform, type of the laser medium, fluorescence emitted from the laser medium, information on the excitation light, temperature in the data acquisition environment, and position of the optical system. According to such a configuration, it becomes possible to generate an estimation program with high estimation accuracy for parameters related to the phase pattern.

[0014] In the learning step, the data related to the current oscillation acquired in the data acquisition step may be used as the second learning data. According to such a configuration, since the learning step is incorporated into (simultaneously performed with) other steps related to oscillation control, it becomes possible to update the estimation program so as to improve the accuracy of the estimation program while performing oscillation control.

[0015] A laser oscillation system according to an aspect of the present disclosure is a laser oscillation system that oscillates laser light in a resonance path by irradiating a laser medium with excitation light, including: a spatial light modulator that is disposed on the resonance path and displays an arbitrary phase pattern; an acquisition unit that acquires data related to the current oscillation; and an estimation unit that estimates parameters related to the phase pattern according to the data related to the current oscillation acquired by the acquisition unit and the target oscillation state, using an estimation program that outputs parameters related to the phase pattern displayed on the spatial light modulator in response to an input of the data related to the oscillation and information indicating the target oscillation state, and a control unit that controls the phase pattern displayed on the spatial light modulator based on the parameters estimated by the estimation unit.

[0016] The acquisition unit may acquire data related to the non-oscillation state as the data related to the current oscillation, and the estimation unit may estimate parameters related to the phase pattern so as to transition from the non-oscillation state to the oscillation state.

[0017] The acquisition unit may acquire data related to fluorescence emitted from the laser medium as the data related to the current oscillation.

[0018] The acquisition unit may acquire data related to the oscillation state as data related to the current oscillation, and the estimation unit may estimate parameters related to the phase pattern so as to transition from the current oscillation state to another oscillation state.

[0019] The acquisition unit may acquire data related to the laser oscillation light as data related to the current oscillation.

[0020] The laser oscillation system may further include a learning unit that generates an estimation program by performing multiple learning on a data set in which first learning data related to the phase pattern displayed on the spatial light modulator is associated with second learning data related to the oscillation.

[0021] The second learning data may include at least one of a beam image of the laser oscillation light, intensity, spectrum, time waveform, type of the laser medium, fluorescence emitted from the laser medium, information on the excitation light, temperature in the data acquisition environment, and position of the optical system.

[0022] The learning unit may use the data related to the current oscillation acquired by the acquisition unit as the second learning data.

[0023] A generation method according to an aspect of the present disclosure is a method for generating an estimation program that outputs parameters related to a phase pattern displayed on a spatial light modulator on a resonance path, the method including: a learning data collection step of collecting a plurality of first learning data related to the phase pattern displayed on the spatial light modulator and second learning data related to the oscillation in the resonance path; and a learning step of generating an estimation program by performing multiple learning on a data set in which the first learning data and the second learning data collected in the learning data collection step are associated with each other.

[0024] A generating device according to an aspect of the present disclosure is a generating device for an estimation program that outputs parameters related to a phase pattern displayed on a spatial light modulator on a resonance path, the collecting unit collecting a plurality of first learning data related to the phase pattern displayed on the spatial light modulator and second learning data related to oscillation in the resonance path, and a learning unit that generates an estimation program by performing multiple learning on a data set in which the first learning data and the second learning data collected by the collecting unit are associated with each other.

[0025] An estimation program according to an aspect of the present disclosure is an estimation program that outputs parameters related to a phase pattern displayed on a spatial light modulator arranged on a resonator, the acquisition process of acquiring data related to the current oscillation detected by irradiating an excitation light to a laser medium, and the estimation process of outputting parameters related to the phase pattern displayed on the spatial light modulator based on the data related to the current oscillation acquired in the acquisition process and the information indicating the target oscillation state, and causing a computer to execute.

Advantages of the Invention

[0026] According to an aspect of the present disclosure, a phase pattern that realizes a desired oscillation state can be created easily and with high precision.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0028] Hereinafter, this embodiment will be described in detail with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted.

[0029] First, the outline of the laser oscillation system according to this embodiment will be described with reference to FIG. 1. FIG. 1 is a diagram for explaining the outline of the laser oscillation system according to this embodiment. The laser oscillation system according to this embodiment realizes a desired oscillation state by controlling the phase pattern displayed on the SLM: Spatial Light Modulator using machine learning technology in a laser oscillator configuration where the SLM is arranged on the resonance path. In a laser oscillator using general optical elements, there are restrictions on resonance conditions, but in a laser oscillator using an SLM, various resonance conditions that are difficult to achieve when using general optical elements can be realized by adjusting the phase pattern displayed on the SLM. Although the phase patterns that can be displayed on the SLM are very diverse, by performing machine learning using a large amount of data as learning data, such diverse phase patterns can be created easily and with high accuracy. According to such a laser oscillation system, new oscillation characteristics that could not be realized conventionally can be obtained.

[0030] Specifically, as shown in FIG. 1, an estimation program is prepared by machine learning, taking data related to various oscillations in a laser oscillator as input parameters and parameters related to the phase pattern displayed on the SLM as output parameters. The data related to the oscillation here refers to information such as the intensity (output power) of the laser beam, the beam intensity distribution, the ASE intensity, the spectrum, and the fluorescence waveform. When the data related to the oscillation in the laser oscillator is input into the estimation program as input parameters, the parameters related to the phase pattern corresponding to the data related to the oscillation are output as output parameters, and the phase pattern corresponding to the output parameters is displayed on the SLM. By repeating such processing, it is possible to obtain desired oscillation characteristics while appropriately adjusting the phase pattern displayed on the SLM using the measured values of the data related to the oscillation.

[0031] FIG. 2 is a diagram schematically showing the configuration of the laser oscillation system 1. As shown in FIG. 2, the laser oscillation system 1 includes a laser oscillator 10, a detection unit 20, a control unit 30, a computer 40 (acquisition unit, estimation unit, learning unit), and a monitor 50.

[0032] The laser oscillator 10 has a laser diode 11, a mirror 12, a laser medium 13, a quarter-wave plate 14, a polarization beam splitter 15, an SLM 16, and a mirror 17. In this way, the laser oscillator 10 has an optical configuration in which one of the two resonator mirrors included in its configuration is replaced by the SLM 16. The laser oscillator 10 oscillates laser light in the resonance path by irradiating the laser medium 13 with excitation light.

[0033] The laser diode 11 is a light source that irradiates the laser medium 13 with excitation light. The laser diode 11 irradiates the laser medium 13 with excitation light having an oscillation wavelength corresponding to the laser medium 13, for example, excitation light of 940 nm. Note that another light source may be used instead of the laser diode 11. The excitation light emitted from the laser diode 11 is irradiated onto the laser medium 13 via the mirror 12.

[0034] The laser medium 13 is a substance that amplifies light by causing stimulated emission at a rate exceeding absorption in the oscillation of the laser. The laser medium 13 may be composed of, for example, rod-shaped Yb:YaG ceramics or the like. The laser medium 13 may be composed of other solids such as Nd:YAG and YVO4, may be composed of gases such as He-Ne gas, Ar gas, and CO2 gas, may be composed of a liquid of an organic solvent system having dye molecules, or may be composed of a semiconductor. The light amplified by the laser medium 13 reaches the SLM 16 through polarization optical elements such as a quarter-wave plate 14 and a polarization beam splitter 15.

[0035] The SLM 16 is arranged on the resonance path, has an input portion for a control signal, and displays a phase pattern based on the control signal. The SLM 16 may modulate the light passing through the resonance path by displaying the phase pattern. The SLM 16 is, for example, a spatial light modulator of a reflective liquid crystal (LCOS: Liquid Crystal on Silicon). The phase pattern is generated, for example, by a computer 40 with its parameters, and is displayed on the SLM 16 according to a control signal from the control unit 30. The phase pattern may be, for example, a hologram pattern. Note that "arranged on the resonance path" includes not only the case of being arranged inside the resonance path (for example, when a transmissive SLM 16 is used), but also the case of being arranged as a resonance mirror at the end of the resonance path.

[0036] SLM16 displays, for example, a lens pattern as a phase pattern. A Fresnel lens pattern may be used as the lens pattern. When a Fresnel lens is used, the "parameters related to the phase pattern" which are the output parameters described above may be three parameters: the focal length (f) indicating the radius of curvature, the horizontal axis (x) indicating the display coordinates on the SLM16, and the vertical axis (y) indicating the display coordinates on the SLM16. These three parameters are the training data in the training for generating the estimation program described later. Specifically, for the changes in the above three parameters, the data related to the oscillation detected by the detection unit 20 (for example, the ASE intensity distribution) is recorded, and the mapping between the parameters of f, x, y and the ASE intensity is performed to prepare a training dataset for machine learning (details will be described later). Then, a learning model is prepared to determine the focal length (f) and coordinates (x, y) of the Fresnel lens so as to achieve the target oscillation state according to the data related to the oscillation state, and the learning is executed.

[0037] Hereinafter, it will be described on the assumption that the phase pattern is a Fresnel lens pattern, but it is not limited thereto, and the lens pattern may be another lens pattern such as an aspherical lens pattern. Further, the phase pattern may be a pattern created by Zernike terms, a pattern that can be drawn with sin, cos, etc. FIG. 3 shows a phase pattern in which a coma aberration correction component (pattern) created using Zernike terms is superimposed on a condensing component created using Zernike terms as an example of the pattern to be displayed on the SLM16. When the phase pattern is other than the Fresnel lens pattern, the above-mentioned "parameters related to the phase pattern" are not limited to f, x, and y.

[0038] Hereinafter, it will be described on the assumption that the SLM16 is a reflective liquid crystal spatial light modulator disposed on the resonance path, but a transmissive SLM may be used. Further, the arrangement location of the SLM is not limited to the resonance path, and it may be arranged on the laser diode 11 side (for excitation), or may be arranged on both the resonance path and for excitation.

[0039] The light reflected by the SLM 16 is reflected by the polarization beam splitter 15 and reaches the detection unit 20 via the mirror 17. In FIG. 2, the dotted line represents the excitation light, and the solid line represents the laser oscillation light. The resonance path in FIG. 2 is from the mirror 12 to the SLM 16. Optical amplification by stimulated emission is performed by reciprocating the laser between the mirror 12 and the SLM 16. A part of the amplified laser oscillation light and the excitation light is extracted from the polarization beam splitter 15 and travels toward the mirror 17. The mirror 12 is a plane mirror that transmits the excitation light and reflects the oscillation light. The quarter-wave plate 14 determines the polarization of the light incident on the SLM 16. The mirror 17 reflects only the laser oscillation light and transmits the excitation light. In this way, the laser oscillation light reflected by the mirror 17 is detected by the detection unit 20. The transmitted excitation light is blocked by a beam damper (not shown) disposed behind the mirror 17. Instead of the mirror 17, a band-pass filter such as a high-pass filter that allows only the laser oscillation light (e.g., 1030 nm) to pass through and blocks the excitation light (e.g., 940 nm) may be used. However, when the power of the excitation light is high, the filter tends to generate heat, so it is preferable to use the mirror 17 to transmit the excitation light.

[0040] The detection unit 20 detects the laser oscillation light or fluorescence. According to this optical system, in the detection unit 20, both the laser oscillation light and the fluorescence (spontaneous emission light) emitted from the laser medium can be monitored. This is because the wavelength of the fluorescence has a peak at the same wavelength as the laser oscillation light (1030 nm in this embodiment). Note that, separately from the detection unit 20, a second detection unit for detecting the fluorescence emitted from the laser medium may be provided in proximity to the laser medium. In this way, the fluorescence can be monitored with a relatively large signal intensity. The detection unit 20 may be any device that can detect the change in light before and after oscillation, for example, a PD (Photodiode), or a power meter, a spectrum analyzer, a spectroscope, a CMOS camera, a CCD camera, etc. that monitor the output intensity. The information detected (monitored) by the detection unit 20 may be, for example, the ASE intensity. When the detection unit 20 detects the state before oscillation (non-oscillation state), for example, it may detect the fluorescence intensity, the fluorescence spectrum, the time waveform of the fluorescence, etc. When the detection unit 20 detects the state after oscillation (oscillation state), for example, it may detect the intensity and spectrum of the output laser light, the oscillation beam shape, the intensity, the time waveform of the oscillation light, etc. The detection unit 20 outputs the detection result to the computer 40 as "data related to the current oscillation".

[0041] The computer 40 functions as an acquisition unit, an estimation unit, a learning unit, and a generation device. The computer 40 acquires information from the detection unit 20 and performs the display of information to the monitor 50 and the output of information to the control unit 30.

[0042] The computer 40 mainly performs the processing of the learning phase and the processing of the estimation phase. As the processing of the estimation phase, it performs the processing of the oscillation phase that transitions from the non-oscillation state to the oscillation state and the processing of the oscillation characteristic phase that transitions from the oscillation state to another oscillation state. Hereinafter, the processing of each phase will be described in order.

[0043] (Learning Phase) The computer 40 generates an estimation program by performing multiple learning on a data set in which the first learning data related to the phase pattern displayed on the SLM 16 is associated with the second learning data related to oscillation. The estimation program is a learning model that outputs parameters related to the phase pattern displayed on the SLM 16 in response to the input of data related to oscillation and information indicating the target oscillation state. The estimation program is a program that causes the computer 40 to execute an acquisition process of acquiring data related to the current oscillation detected by irradiating the laser medium 13 with the excitation light, and an estimation process of outputting parameters related to the phase pattern displayed on the SLM 16 based on the data related to the current oscillation acquired in the acquisition process and the information indicating the target oscillation state.

[0044] The first learning data is, for example, three parameters of the focal length (f) indicating the radius of curvature of the Fresnel lens pattern, the horizontal axis (x), and the vertical axis (y). The second learning data includes, for example, at least one of the beam image, intensity, spectrum, time waveform of the laser oscillation light, the type of the laser medium 13, information on the excitation light, the temperature in the data acquisition environment, and the position of the optical system. The type of the laser medium 13 may be distinguished by the discharge volume or the enclosed gas pressure when the laser medium 13 is a gas, may be distinguished by the molecular design when it is a liquid, or may be distinguished by the size, concentration, and shape when it is a solid. The information on the excitation light may include the current, the incident angle to the laser medium 13, the excitation region, etc. The temperature may be the room temperature, the cooling temperature of the excitation light source, the cooling temperature of the laser medium, etc. The position of the optical system may be the position, angle, arrangement, etc. of the optical element, the SLM 16, the laser medium 13, and various measuring instruments. The learning data may be a data set in which the phase pattern displayed on the SLM 16 is associated with the data related to oscillation, and an appropriate one may be selected according to the target oscillation state.

[0045] The computer 40 may execute the learning phase during the oscillation phase or the oscillation characteristic phase, which will be described later. That is, the computer 40 may generate an estimation program using the "data related to the current oscillation" acquired during the oscillation phase or the oscillation characteristic phase as the second learning data described above.

[0046] (Oscillation phase) As described above, the oscillation phase is a phase in which the state transitions from the pre-oscillation state (non-oscillation state) to the oscillation state. The computer 40 functions as an acquisition unit that acquires "data related to the current oscillation" from the detection unit 20. The computer 40 stores the acquired information. In the oscillation phase, the computer 40 acquires at least data related to the non-oscillation state as data related to the current oscillation. The data related to the non-oscillation state is data that enables estimation of the light state even before oscillation, and examples thereof include ASE intensity, fluorescence intensity, fluorescence spectrum, fluorescence time waveform, and the like. Thus, the computer 40 may acquire data related to the fluorescence emitted from the laser medium 13 as data related to the non-oscillation state.

[0047] The computer 40 functions as an estimation unit that estimates the parameters related to the phase pattern displayed on the SLM 16 by inputting data related to the current oscillation (data related to the non-oscillation state) and information indicating the target oscillation state into the estimation program. Here, the computer 40 estimates the parameters related to the phase pattern so as to transition from the non-oscillation state to the oscillation state. The information indicating the target oscillation state is, here, data that proves oscillation, such as the oscillation wavelength, etc. The parameters related to the phase pattern are, for example, three parameters of the focal length (f), the horizontal axis (x), and the vertical axis (y), which are coefficients for forming a Fresnel lens. As an optimization method for determining the parameters related to the phase pattern, for example, the Nelder-Mead method may be used, or grid search, gradient descent method, Newton method, Levenberg-Marquardt method, etc. may be used. Estimating the parameters related to the phase pattern may be synonymous with creating a phase pattern (for example, a Fresnel lens pattern). The computer 40 transmits the estimated parameters related to the phase pattern (output parameters) to the control unit 30.

[0048] The control unit 30 controls the phase pattern displayed on the SLM 16 based on the output parameters estimated by the computer 40. The control unit 30 transmits a control signal to the SLM 16 so that a phase pattern corresponding to the output parameters is displayed on the SLM 16. The SLM 16 displays a phase pattern corresponding to the control signal, that is, a phase pattern that causes a transition from the non-oscillation state to the oscillation state.

[0049] (Oscillation characteristic phase) As described above, the oscillation characteristic phase is a phase in which the oscillation state transitions from an already oscillating state (oscillation state) to another oscillation state. The computer 40 functions as an acquisition unit that acquires "data related to the current oscillation" from the detection unit 20. The computer 40 stores the acquired information. In the oscillation characteristic phase, the computer 40 acquires, as data related to the current oscillation, at least data related to the oscillation state. The data related to the oscillation state is data that enables the estimation of the state of light after oscillation, and examples thereof include the intensity and spectrum of the output laser light, the oscillation beam shape, intensity, the time waveform of the oscillating light, and the like. Thus, the computer 40 may acquire data related to the laser oscillating light as data related to the oscillation state.

[0050] The computer 40 functions as an estimation unit that estimates the parameters related to the phase pattern displayed on the SLM 16 by inputting the data related to the current oscillation (data related to the oscillation state) and the information indicating the target oscillation state into the estimation program. Here, the computer 40 estimates the parameters related to the phase pattern so as to transition from the current oscillation state to another oscillation state. The information indicating the target oscillation state is, here, data related to the oscillation characteristics to be targeted, such as intensity. The parameters related to the phase pattern are, for example, three parameters of the focal length (f), the horizontal axis (x), and the vertical axis (y), which are coefficients for forming a Fresnel lens. The computer 40 transmits the estimated parameters related to the phase pattern (output parameters) to the control unit 30.

[0051] The control unit 30 controls the phase pattern displayed on the SLM 16 based on the output parameters estimated by the computer 40. The control unit 30 transmits a control signal to the SLM 16 so that a phase pattern corresponding to the output parameters is displayed on the SLM 16. The SLM 16 displays a phase pattern corresponding to the control signal, that is, a phase pattern that causes a transition from the oscillation state to another oscillation state.

[0052] Next, the processing of each of the above-described phases will be described with reference to FIGS. 4 to 8.

[0053] FIG. 4 is a flowchart showing the procedure of the oscillation characteristic phase. As shown in FIG. 4, in the oscillation characteristic phase, first, a target oscillation state is determined in the computer 40 (step S1). The target oscillation state (for example, the oscillation characteristics to be targeted) may be obtained and determined by, for example, an input from the user. The oscillation characteristics to be targeted may be, for example, the maximization of intensity or the like.

[0054] Subsequently, in the computer 40, the oscillation characteristics with respect to the current state (oscillator state) are obtained (step S2). The oscillation characteristics with respect to the current state may be, for example, data related to the current oscillation obtained from the detection unit 20.

[0055] Subsequently, in the computer 40, data related to the current oscillation (data related to the oscillation state) and information indicating the target oscillation state are input to the estimation program which is a learning model, and the output parameters related to the phase pattern are estimated (step S3).

[0056] Subsequently, the phase pattern based on the output parameters estimated by the computer 40 is displayed (reflected) on the SLM 16 of the oscillator by the control unit 30 (step S4).

[0057] And in this state, in the computer 40, the oscillation characteristics, specifically, the data related to the current oscillation are obtained (step S5), and it is determined whether the target oscillation state has been achieved (for example, whether the maximization of intensity has been realized) (step S6). As a result of the determination, if the target oscillation state has not been achieved, the output parameters are predicted again by the learning model (step S3), and if the target oscillation state has been achieved, the oscillation characteristic phase is terminated.

[0058] FIG. 5 is a flowchart showing the procedure of the oscillation phase. As shown in FIG. 5, in the oscillation phase, first, data for verifying oscillation (data that can confirm oscillation) is selected in the computer 40 (step S11). The data for verifying oscillation may be, for example, "the oscillation wavelength becomes 1030 nm".

[0059] Subsequently, information on the current state (oscillator state) is acquired in the computer 40 (step S12). The information on the current state may be, for example, data related to the current oscillation acquired from the detection unit 20, or data related to the non-oscillation state such as data (spectrum, etc.) related to the fluorescence emitted from the laser medium 13.

[0060] Subsequently, data related to the current oscillation (data related to the non-oscillation state) and information indicating the target oscillation state are input to the estimation program, which is a learning model, in the computer 40, and output parameters related to the phase pattern are estimated (step S13).

[0061] Subsequently, the phase pattern based on the output parameters estimated by the computer 40 is displayed (reflected) on the SLM 16 of the oscillator by the control unit 30 (step S14).

[0062] Then, in this state, data related to the current oscillation is acquired in the computer 40 (step S15), and it is determined whether the oscillation state is achieved (for example, whether the oscillation wavelength becomes 1030 nm) (step S16). As a result of the determination, if the oscillation state is not achieved, the output parameters are predicted again by the learning model (step S13), and if the oscillation state is achieved, the oscillation phase is terminated.

[0063] FIG. 6 is a flowchart showing the procedure of the learning phase. As shown in FIG. 6, in the learning phase, first, consideration is given to what data will be used as learning data (data preparation) (step S101). As data in the oscillation state, for example, the beam intensity distribution with respect to the phase pattern may be adopted, or as data in the non-oscillation state, for example, the ASE intensity with respect to the mirror angle may be considered for adoption.

[0064] Subsequently, the data determined in step S101 is collected (step S102). Here, a large amount of data necessary for learning is acquired. The large amount of data may be image data acquired by the detection unit 20 which is a camera, or may be the intensity acquired by the detection unit 20 which is a PD.

[0065] Subsequently, for the large amount of acquired data, data preprocessing is performed in the computer 40 (step S103). In data preprocessing, for example, selection, sorting, and expansion of necessary data are performed. Then, the preprocessed data is divided into a learning set and a verification set (step S104).

[0066] Subsequently, what model will be used for learning is selected (step S105). Here, machine learning methods, learning methods, and algorithms are selected.

[0067] Then, in the computer 40, a plurality of data sets associating the first learning data related to the phase pattern displayed on the SLM 16 and the second learning data related to oscillation are repeatedly learned, and model training is performed (step S106).

[0068] Thereafter, the performance of the learning model is evaluated (step S107), and parameter tuning is performed. The processes of steps S103 to S107 described above are repeatedly performed until an optimal model is obtained. Through the above processes, an optimal model is completed (step S108).

[0069] FIG. 7 is a flowchart showing the procedure when the learning phase is carried out during the oscillation characteristic phase. As shown in FIG. 7, in the oscillation characteristic phase, first, a target oscillation state is determined in the computer 40 (step S201). Subsequently, the oscillation characteristics with respect to the current state (oscillator state) are acquired in the computer 40 (step S202).

[0070] Subsequently, in the computer 40, data related to the current oscillation (data related to the oscillation state) and information indicating the target oscillation state are input to the estimation program which is the learning model, and the output parameters related to the phase pattern are estimated (step S203). Subsequently, the phase pattern based on the output parameters estimated by the computer 40 is displayed (reflected) on the SLM 16 of the oscillator by the control unit 30 (step S204).

[0071] And in this state, in the computer 40, the oscillation characteristics, specifically, the data related to the current oscillation are acquired (step S205), and it is determined whether the target oscillation state is achieved (for example, whether the maximization of the intensity is realized) (step S206). As a result of the determination, if the target oscillation state is not achieved, the output parameters are predicted again by the learning model (step S203), and if the target oscillation state is achieved, the learning model is updated and the oscillation characteristic phase is terminated.

[0072] Also, the data related to the current oscillation acquired in step S205 is used as the second learning data, and preprocessing is performed (step S301). Then, the above-described data division (step S302), model selection (step S303), model training (step S304), and model evaluation (step S305) are carried out, and the optimal model is updated as needed so that the target oscillation state is achieved (step S306). The learning model updated in this way is used as the estimation program, and the processes such as step S203 are carried out.

[0073] FIG. 8 is a flowchart showing the procedure when shifting from the oscillation phase to the oscillation characteristic phase. As shown in FIG. 8, in the oscillation phase, first, data for verifying oscillation (data that can confirm oscillation) is selected in the computer 40 (step S401). The data for verifying oscillation may be, for example, "the ASE intensity becomes ○○ or more".

[0074] Subsequently, information regarding the current state (oscillator state) is acquired in the computer 40 (step S402). The information regarding the current state is, for example, data related to the current oscillation acquired from the detection unit 20, and may also be data related to a non-oscillation state such as the ASE intensity.

[0075] Subsequently, data related to the current oscillation (data related to the non-oscillation state) and information indicating the target oscillation state are input into the estimation program, which is a learning model, in the computer 40, and output parameters related to the phase pattern are estimated (step S403). Note that there may be, for example, two or more output parameters, and they may be a phase pattern generation coefficient, an excitation current, or the like.

[0076] Subsequently, the output parameters estimated by the computer 40 are reflected in the oscillator by the control unit 30 (step S404). Specifically, a phase pattern may be displayed on the SLM16 and an excitation current may be set.

[0077] Then, in this state, data related to the current oscillation is acquired in the computer 40 (step S405), and it is determined whether the oscillation state is reached (for example, whether the desired ASE intensity is reached) (step S406). As a result of the determination, if the oscillation state is not reached, the output parameters are predicted again by the learning model (step S403).

[0078] When the oscillation state is achieved, the process proceeds to the oscillation characteristic phase. Specifically, in the oscillation characteristic phase, a target oscillation state is determined in the computer 40 (step S407). The target oscillation state (for example, the oscillation characteristics to be targeted) may be, for example, a flat top pattern or the like.

[0079] Subsequently, in the computer 40, the oscillation characteristics with respect to the current state (oscillator state) are acquired (step S408). The oscillation characteristics with respect to the current state are, for example, data related to the current oscillation acquired from the detection unit 20, and may be an oscillation beam image or the like.

[0080] Subsequently, in the computer 40, data related to the current oscillation (data related to the oscillation state) and information indicating the target oscillation state are input to the estimation program which is a learning model, and the output parameters related to the phase pattern are estimated (step S409).

[0081] Subsequently, by the control unit 30, the phase pattern based on the output parameters estimated by the computer 40 is displayed (reflected) on the SLM 16 of the oscillator (step S410). And in this state, in the computer 40, the oscillation characteristics, specifically, data related to the current oscillation are acquired (step S411), and it is determined whether the target oscillation state is achieved (step S412). As a result of the determination, if the target oscillation state is not achieved, the output parameters are predicted again by the learning model (step S409), and if the target oscillation state is achieved, the oscillation characteristic phase is terminated. Such determination may be performed, for example, by analyzing the intensity distribution or confirming the flat top pattern.

[0082] Next, the effects of the laser oscillation method and the like according to the present embodiment will be described.

[0083] The laser oscillation method according to this embodiment is a laser oscillation method in which an SLM 16 is disposed on a resonance path and laser light is oscillated in the resonance path by irradiating an excitation light to a laser medium 13, the method including: a data acquisition step of irradiating the laser medium 13 with the excitation light and acquiring data related to the current oscillation; an estimation step of estimating parameters related to a phase pattern according to the data related to the current oscillation acquired in the data acquisition step and the target oscillation state by using an estimation program that outputs parameters related to the phase pattern displayed on the SLM 16 according to an input of the data related to the oscillation and information indicating the target oscillation state; and a control step of controlling the phase pattern displayed on the SLM 16 based on the parameters estimated in the estimation step.

[0084] In the laser oscillation method according to this embodiment, data related to the current oscillation in the resonance path is acquired by irradiating the laser medium 13 with the excitation light, and parameters related to the phase pattern are estimated by an estimation program according to the data related to the current oscillation and the target oscillation state. Then, the phase pattern displayed on the SLM 16 is controlled based on the parameters. As described above, by automatically controlling the phase pattern by using a previously prepared estimation program, the phase pattern can be easily created. Further, since the estimation program takes as an input the data related to the current oscillation and the target (desired) oscillation state, the phase pattern that realizes the desired oscillation state can be created with high precision. As described above, according to the laser oscillation method according to this embodiment, the phase pattern that realizes the desired oscillation state can be easily and highly accurately created.

[0085] In the data acquisition step, data related to a non-oscillation state may be acquired as data related to the current oscillation, and in the estimation step, parameters related to the phase pattern may be estimated so as to transition from the non-oscillation state to the oscillation state. According to such a configuration, the phase pattern that appropriately transitions from the non-oscillating state to the desired oscillation state can be easily and highly accurately created.

[0086] In the data acquisition step, as data related to the current oscillation, data regarding fluorescence emitted from the laser medium 13 may be acquired. According to such a configuration, even in the state before oscillation, data related to oscillation can be appropriately acquired, for example, from the ASE (Amplified Spontaneous Emission) intensity or the like. By this, the phase pattern for realizing the desired oscillation state can be created with higher precision. Conventionally, it was limited to the control of the transverse mode, but by focusing on the ASE intensity, it has become possible to automatically find the oscillation conditions in the state before oscillation.

[0087] In the data acquisition step, as data related to the current oscillation, data related to the oscillation state may be acquired, and in the estimation step, parameters related to the phase pattern may be estimated so as to transition from the current oscillation state to another oscillation state. According to such a configuration, a phase parameter for appropriately transitioning from the oscillation state to a desired other oscillation state can be created easily and with high precision.

[0088] In the data acquisition step, as data related to the current oscillation, data regarding the laser oscillation light may be acquired. According to such a configuration, in the oscillating state, data related to oscillation can be appropriately acquired. By this, the phase pattern for realizing the desired oscillation state can be created with higher precision.

[0089] The laser oscillation method may further include a learning step of generating an estimation program by performing multiple learning on a data set in which first learning data related to the phase pattern displayed on the SLM 16 and second learning data related to oscillation are associated. In this way, by associating and learning a large amount of data related to the phase pattern and oscillation (for example, ASE intensity, beam image of laser oscillation light, etc.), the accuracy of the estimation program can be improved. That is, by providing the learning step, an estimation program with high estimation accuracy of the parameters related to the phase pattern can be generated, and it becomes possible to create the phase pattern for realizing the desired oscillation state with higher precision.

[0090] The second learning data may include at least one of a beam image of the laser oscillation light, intensity, spectrum, time waveform, the type of the laser medium 13, information on the excitation light, the temperature in the data acquisition environment, and the position of the optical system. According to such a configuration, it becomes possible to generate an estimation program with high estimation accuracy for parameters related to the phase pattern.

[0091] In the learning step, the data related to the current oscillation acquired in the data acquisition step may be used as the second learning data. According to such a configuration, since the learning step is incorporated (simultaneously implemented) into other steps related to oscillation control, it becomes possible to update the estimation program so as to improve the accuracy of the estimation program while performing oscillation control.

[0092] As described above, the embodiments of the present disclosure have been described, but the present disclosure is not limited to the above embodiments. For example, although the configuration using the SLM 16 has been described, depending on the target laser oscillation characteristics, a deformable mirror or the like may be used instead. Specifically, when the target laser oscillation characteristics are intensity distribution control of the output beam or the like, a deformable mirror can be used.

[0093] Alternatively, the configuration of the laser oscillation system according to the modified example shown in FIG. 9 may be adopted. The resonance path in FIG. 9 is from the output mirror 82 to the SLM 16. In such a configuration, since the excitation light is not incident on the SLM 16 even when the intensity of the excitation light is high, damage to the SLM 16 due to the excitation light can be prevented. The reflection mirror 81 shown in FIG. 9 is provided at an angle of 45° so as to transmit the excitation light and reflect the oscillation light. The oscillation light reflected by the reflection mirror 81 is incident on the Brewster window 84, and the polarization of the light incident on the SLM 16 is determined. Thus, the Brewster window 84 is used for the same purpose as the quarter-wave plate 14 shown in FIG. 2. The oscillation light oscillated in the resonator is extracted by the output mirror 82. The output mirror 82 may be a partial reflection mirror that reflects, for example, 95% of the excitation light and the oscillation light (transmits 5%). The light transmitted through the output mirror 82 is reflected by the oscillation light reflection mirror 83 and detected by the detection unit 20. The oscillation light reflection mirror 83 is a mirror having a characteristic of reflecting the wavelength of the oscillation light (for example, 1030 nm) and transmitting the wavelength of the excitation light (for example, 940 nm).

[0094] Finally, various exemplary aspects included in the present disclosure are described in [E1] to [E19] below.

[0095] [E1] A laser oscillation method for oscillating laser light in a resonance path by irradiating a laser medium with excitation light while arranging a spatial light modulator on the resonance path, a data acquisition step of irradiating the laser medium with the excitation light and acquiring data related to the current oscillation; an estimation step of estimating parameters related to a phase pattern displayed on the spatial light modulator according to the data related to the current oscillation acquired in the data acquisition step and a target oscillation state, using an estimation program that outputs parameters related to the phase pattern according to an input of the data related to the oscillation and information indicating the target oscillation state; A control step of controlling a phase pattern displayed on the spatial light modulator based on the parameter estimated in the estimation step, and a laser oscillation method including the same.

[0096] [E2] In the data acquisition step, data related to a non-oscillation state is acquired as data related to the current oscillation. In the estimation step, a parameter related to the phase pattern is estimated so as to transition from a non-oscillation state to an oscillation state. The laser oscillation method according to claim 1.

[0097] [E3] In the data acquisition step, data related to fluorescence emitted from the laser medium is acquired as data related to the current oscillation. The laser oscillation method according to [E2].

[0098] [E4] In the data acquisition step, data related to an oscillation state is acquired as data related to the current oscillation. In the estimation step, a parameter related to the phase pattern is estimated so as to transition from the current oscillation state to another oscillation state. The laser oscillation method according to any one of [E1] to [E3].

[0099] [E5] In the data acquisition step, data related to laser oscillation light is acquired as data related to the current oscillation. The laser oscillation method according to [E4].

[0100] [E6] The laser oscillation method according to any one of [E1] to [E5], further comprising a learning step of generating the estimation program by performing multiple learning on a data set in which first learning data related to a phase pattern displayed on the spatial light modulator is associated with second learning data related to oscillation.

[0101] [E7] The second learning data includes at least one of a beam image, intensity, spectrum, time waveform of laser oscillation light, a type of laser medium, fluorescence emitted from the laser medium, information on excitation light, temperature in a data acquisition environment, and a position of an optical system, and is the laser oscillation method described in [E6].

[0102] [E8] In the learning step, data related to the current oscillation acquired in the data acquisition step is used as the second learning data, and is the laser oscillation method described in [E6] or [E7].

[0103] [E9] A laser oscillation system that oscillates laser light in a resonance path by irradiating a laser medium with excitation light, A spatial light modulator that is disposed on the resonance path and modulates light passing through the resonance path by displaying an arbitrary phase pattern; An acquisition unit that acquires data related to the current oscillation; An estimation unit that estimates parameters related to a phase pattern according to the data related to the current oscillation acquired by the acquisition unit and a target oscillation state, using an estimation program that outputs parameters related to the phase pattern displayed on the spatial light modulator in response to an input of data related to oscillation and information indicating the target oscillation state; A control unit that controls a phase pattern displayed on the spatial light modulator based on the parameters estimated by the estimation unit, and a laser oscillation system including the same.

[0104] [E10] The acquisition unit acquires data related to a non-oscillation state as data related to the current oscillation, The estimation unit estimates parameters related to the phase pattern so as to transition from a non-oscillation state to an oscillation state, and is the laser oscillation system described in [E9].

[0105] [E11] The acquisition unit acquires data related to fluorescence emitted from the laser medium as data related to the current oscillation, for the laser oscillation system described in [E10].

[0106] [E12] The acquisition unit acquires data related to the oscillation state as data related to the current oscillation. The estimation unit estimates parameters related to the phase pattern so as to transition from the current oscillation state to another oscillation state, for the laser oscillation system according to any one of [E9] to [E11].

[0107] [E13] The acquisition unit acquires data related to the laser oscillation light as data related to the current oscillation, for the laser oscillation system described in [E12].

[0108] [E14] The laser oscillation system according to any one of [E9] to [E13] further includes a learning unit that generates the estimation program by performing complex learning on a data set in which first learning data related to the phase pattern displayed on the spatial light modulator is associated with second learning data related to oscillation.

[0109] [E15] The second learning data includes at least one of a beam image of the laser oscillation light, intensity, spectrum, time waveform, type of the laser medium, fluorescence emitted from the laser medium, information on the excitation light, temperature in the data acquisition environment, and position of the optical system, for the laser oscillation system described in [E14].

[0110] [E16] The learning unit uses the data related to the current oscillation acquired by the acquisition unit as the second learning data, for the laser oscillation system described in [E14] or [E15].

[0111] [E17] A method for generating an estimation program that outputs parameters related to a phase pattern displayed on a spatial light modulator on a resonance path, A learning data collection step of collecting a plurality of first learning data related to a phase pattern displayed on the spatial light modulator and second learning data related to oscillation in the resonance path; A learning step of generating the estimation program by performing multiple learning on a data set in which the first learning data and the second learning data collected in the learning data collection step are associated with each other. The generation method includes the above steps.

[0112] [E18] A generation device for an estimation program that outputs parameters related to a phase pattern displayed on a spatial light modulator on a resonance path, A collection unit that collects a plurality of first learning data related to a phase pattern displayed on the spatial light modulator and second learning data related to oscillation in the resonance path; A learning unit that generates the estimation program by performing multiple learning on a data set in which the first learning data and the second learning data collected by the collection unit are associated with each other. The generation device includes the above components.

[0113] [E19] An estimation program that outputs parameters related to a phase pattern displayed on a spatial light modulator disposed on a resonator, An acquisition process of acquiring data related to current oscillation detected by irradiating an excitation light to a laser medium; A program that causes a computer to execute an estimation process of outputting parameters related to a phase pattern displayed on the spatial light modulator based on the data related to the current oscillation acquired in the acquisition process and information indicating a target oscillation state.

Explanation of Reference Numerals

[0114] 1... Laser oscillation system, 10... Laser oscillator, 13... Laser medium, 16... SLM (Spatial Light Modulator), 20... Detection unit, 30... Control unit, 40... Computer (acquisition unit, estimation unit, learning unit).

Claims

1. A laser oscillation method in which a spatial light modulator is disposed on a resonance path and laser light is oscillated in the resonance path by irradiating a laser medium with excitation light, a data acquisition step of irradiating the laser medium with the excitation light and acquiring data related to the current oscillation; an estimation step of estimating parameters related to a phase pattern displayed on the spatial light modulator according to the data related to the current oscillation acquired in the data acquisition step and a target oscillation state, using an estimation program that outputs parameters related to the phase pattern according to an input of data related to the oscillation and information indicating the target oscillation state; and a control step of controlling the phase pattern displayed on the spatial light modulator based on the parameters estimated in the estimation step. The laser oscillation method includes these steps.

2. In the data acquisition step, data related to a non-oscillation state is acquired as data related to the current oscillation, and in the estimation step, parameters related to the phase pattern are estimated so as to transition from a non-oscillation state to an oscillation state. The laser oscillation method according to Claim 1.

3. In the data acquisition step, data related to fluorescence emitted from the laser medium is acquired as data related to the current oscillation. The laser oscillation method according to Claim 2.

4. In the data acquisition step, data related to an oscillation state is acquired as data related to the current oscillation, and in the estimation step, parameters related to the phase pattern are estimated so as to transition from the current oscillation state to another oscillation state. The laser oscillation method according to Claim 1.

5. In the data acquisition step, data related to laser oscillation light is acquired as data related to the current oscillation. The laser oscillation method according to Claim 4.

6. The laser oscillation method according to any one of Claims 1 to 5 further includes a learning step of generating the estimation program by performing plural learning on a data set in which first learning data related to a phase pattern displayed on the spatial light modulator is associated with second learning data related to the oscillation.

7. The second learning data includes at least one of a beam image, intensity, spectrum, time waveform of laser oscillation light, type of laser medium, fluorescence emitted from the laser medium, information on excitation light, temperature in a data acquisition environment, and position of an optical system. The laser oscillation method according to Claim 6.

8. The laser oscillation method according to claim 6, wherein, in the learning step, data related to the current oscillation acquired in the data acquisition step is used as the second learning data.

9. A laser oscillation system for oscillating laser light in a resonance path by irradiating a laser medium with excitation light, a spatial light modulator disposed on the resonance path and displaying an arbitrary phase pattern; an acquisition unit that acquires data related to the current oscillation; an estimation unit that estimates parameters related to the phase pattern according to the data related to the current oscillation acquired by the acquisition unit and a target oscillation state, using an estimation program that outputs parameters related to the phase pattern displayed on the spatial light modulator in response to an input of data related to the oscillation and information indicating the target oscillation state; and a control unit that controls the phase pattern displayed on the spatial light modulator based on the parameters estimated by the estimation unit.

10. The acquisition unit acquires data related to a non-oscillation state as data related to the current oscillation, The laser oscillation system according to claim 9, wherein the estimation unit estimates parameters related to the phase pattern so as to transition from a non-oscillation state to an oscillation state.

11. The laser oscillation system according to claim 10, wherein the acquisition unit acquires data related to fluorescence emitted from the laser medium as data related to the current oscillation.

12. The acquisition unit acquires data related to an oscillation state as data related to the current oscillation, The laser oscillation system according to claim 9, wherein the estimation unit estimates parameters related to the phase pattern so as to transition from the current oscillation state to another oscillation state.

13. The laser oscillation system according to claim 12, wherein the acquisition unit acquires data related to laser oscillation light as data related to the current oscillation.

14. The laser oscillation system according to any one of claims 9 to 13, further comprising a learning unit that generates the estimation program by performing multiple learning on a data set in which first learning data related to the phase pattern displayed on the spatial light modulator and second learning data related to the oscillation are associated with each other.

15. The second learning data includes at least one of a beam image of laser oscillation light, intensity, spectrum, temporal waveform, type of laser medium, fluorescence emitted from the laser medium, information on excitation light, temperature in the data acquisition environment, and position of the optical system, for the laser oscillation system according to claim 14.

16. The learning unit uses, as the second learning data, the data related to the current oscillation acquired by the acquisition unit, for the laser oscillation system according to claim 14.

17. A method for generating an estimation program that outputs parameters related to a phase pattern displayed on a spatial light modulator on a resonance path, comprising: a learning data collection step of collecting a plurality of first learning data related to a phase pattern displayed on the spatial light modulator and second learning data related to oscillation in the resonance path; a learning step of generating the estimation program by performing multiple learning on a data set in which the first learning data and the second learning data collected in the learning data collection step are associated with each other.

18. A generation device for an estimation program that outputs parameters related to a phase pattern displayed on a spatial light modulator on a resonance path, comprising: a collection unit that collects a plurality of first learning data related to a phase pattern displayed on the spatial light modulator and second learning data related to oscillation in the resonance path; a learning unit that generates the estimation program by performing multiple learning on a data set in which the first learning data and the second learning data collected by the collection unit are associated with each other.

19. An estimation program that outputs parameters related to a phase pattern displayed on a spatial light modulator disposed on a resonator, comprising: an acquisition process of acquiring data related to the current oscillation detected by irradiating a laser medium with excitation light; an estimation process of outputting parameters related to a phase pattern displayed on the spatial light modulator based on the data related to the current oscillation acquired in the acquisition process and information indicating a target oscillation state, and causing a computer to execute the program.

Images