JP2011151288A - Laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser device which can be operated stably over a long time by suppressing fluctuations in the optical output. <P>SOLUTION: A laser device includes a plurality of optical amplifiers for amplifying a plurality of fundamental-wave laser beams from a laser beam source 11; a wavelength conversion section 20 for performing wavelength conversion, on a predetermined higher harmonic laser beam by using a wavelength conversion optical element for the plurality of amplified fundamental-wave laser beams; a power control unit 50 for splitting a portion of the higher harmonic laser beam as monitoring light and detecting the intensity of the monitor light; and a control section 60 for performing output control of the higher harmonic laser beam, by controlling an intensity of the fundamental-wave laser beam, based on the detected result of the power control unit 50. Each of the plurality of optical amplifiers is configured, to amplify the fundamental wave laser beam by supplying exciting light from an exciting light source section 70 to an optical amplification fiber EDF. The control section 60 is configured to control the intensity of the fundamental wave laser beam, by controlling only the exciting light output supplied to an optical amplifier, for amplifying the fundamental wave laser beam, to which the number of times of wavelength conversion in the wavelength conversion section 20 is set maximum among the plurality of optical amplifiers. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a laser device having a function of monitoring light output and controlling the light output constantly according to the monitoring result.

  The laser apparatus as described above is used as a light source for, for example, an exposure apparatus for forming a fine structure in a semiconductor device, various optical inspection apparatuses for observing the fine structure, a laser treatment apparatus used for ophthalmic treatment, etc. For example, laser light in the infrared wavelength region generated by a semiconductor laser and amplified by an optical amplifier is sequentially wavelength-converted in a wavelength conversion device having a plurality of wavelength conversion elements, and finally the same wavelength as the oscillation wavelength of an ArF excimer laser A configuration is known that outputs as λ = 193 nm ultraviolet light (see, for example, Patent Document 1).

  In a laser device, in order to stabilize the light output of the laser light, the light output of the laser light is detected by a light output monitoring device (generally a light receiving element such as a photodiode), and the desired light output is monitored. Various means (APC: Automatic Power Control) for feedback control of the drive current to the semiconductor laser have been proposed so that the optical output can be obtained (see, for example, Patent Document 2).

JP 2007-47332 A JP 2002-42362 A

  In a laser device that performs wavelength conversion using the wavelength conversion element as described above, it is important to stabilize the wavelength-converted output light. In order to obtain output light having a desired wavelength from the fundamental wave, wavelength conversion is performed in multiple stages. In this case, it is considered that the unstable factor of wavelength conversion in the middle stage directly affects the stability of the output light in the final stage. More specifically, like the laser device described in Patent Document 1, the fundamental wave emitted from one semiconductor laser (laser light source) is branched into a plurality of parts, and each of them is optically amplified to perform a plurality of stages of wavelength conversion. After that, in the configuration where the wavelength conversion is performed as the incident light of the sum frequency at the final stage, the influence on the stability of the output light (ultraviolet light) varies greatly depending on the wavelength conversion process until each incident light reaches the final stage. Therefore, there is a problem that the final light output becomes unstable unless the light intensity of the incident light is appropriately controlled accordingly.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a laser device having a configuration capable of suppressing long-term stable operation by suppressing fluctuations in light output. .

  In order to solve the above problems, a laser device of the present invention includes a laser light source that outputs a fundamental laser beam, a plurality of optical amplifiers that respectively amplify a plurality of fundamental laser beams from the laser light source, and a plurality of optical amplifiers. A wavelength conversion unit that converts a plurality of amplified fundamental laser beams into a predetermined harmonic laser beam using a wavelength conversion optical element, and a part of the harmonic laser beam output from the wavelength conversion unit as monitor light A light separation unit for separation, a light output monitor unit for detecting the intensity of the monitor light separated by the light separation unit, and a harmonic by operating the intensity of the fundamental laser beam based on the detection value of the light output monitor unit A plurality of optical amplifiers for supplying pumping light output from the pumping light source to the optical amplification medium and amplifying the fundamental laser light input from the laser light source. Like Each of the control units is configured such that, among the plurality of optical amplifiers, the pumping light output supplied to the optical amplifiers for amplifying the fundamental laser light having the largest number of wavelength conversions in the wavelength conversion unit Only the intensity of the fundamental laser beam is controlled by controlling only the light output based on the detection value of the light output monitor unit.

  In addition, it is a preferable aspect of the present invention that the predetermined harmonic laser beam is ultraviolet light having a wavelength of 200 nm or less. Furthermore, it is also a preferable aspect that the wavelength conversion optical element is used in a temperature rising state heated to a predetermined temperature by the temperature adjustment unit in the wavelength conversion unit. Also, the optical amplifier is composed of a plurality of stages in which a plurality of optical amplifying media are connected in series, and the control unit supplies the optical amplifying medium at the final stage among the plurality of optical amplifying media based on the detection value of the optical output monitor unit It is also a preferable aspect to control only the excitation light output.

  According to the present invention, it is possible to improve the controllability of the laser light output because the intensity of only the unstable fundamental wave component with a large number of wavelength conversions is manipulated. Therefore, it is possible to realize a stable operation in the long term by reliably suppressing fluctuations in the light output.

It is a schematic block diagram of the laser apparatus shown as an example of application of this invention. It is a schematic block diagram of the laser head in the said laser apparatus. It is a schematic block diagram of the wavelength conversion part and power control unit in the said laser apparatus.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. As a typical example of a laser apparatus to which the present invention is applied, a schematic configuration of a laser apparatus 1 used as a light source apparatus of an exposure apparatus that transfers a reticle pattern to a substrate is shown in FIG. The schematic configuration is shown in FIG. 2, and first, the laser device 1 will be outlined with reference to these drawings.

  For convenience in application to a laser system that uses this device as a light source device, the laser device 1 has a small box-shaped laser head 2 that has an output function of outputting ultraviolet light and that is easily incorporated into the laser system. The laser head 2 is provided with a control rack 3 which is provided separately from the laser head 2 and has a control function. The laser head 2 and the control rack 3 are connected to various electric cables and light for pumping light transmission. It is configured to be interconnected by an interface 4 such as a fiber, a purge gas supply gas tube, and a cooling water pipe.

  The laser head 2 includes a laser light generation unit 10 that emits fundamental wave laser light in the infrared to visible region, and a wavelength conversion unit 20 that converts the wavelength of the fundamental wave laser light emitted from the laser light generation unit 10 into ultraviolet light. It is comprised so that ultraviolet light may be output from the output end.

The laser light generator 10 includes a laser light source 11 that generates laser light (seed light) Ls that serves as seed light, and an optical amplifier 12 that amplifies the seed light Ls generated from the laser light source 11. . As the laser light source 11 and the optical amplifying unit 12, those having an appropriate oscillation wavelength and amplification factor are used according to the application and function of the laser system using the laser device 1. As such a laser light source 11, a distributed feedback semiconductor laser (DFB semiconductor laser) that generates laser light having a single wavelength of wavelength λ ₁ = 1.547 [μm] is used, and seed light Ls output from the laser light source 11. Is branched into three by a fiber coupler or the like (not shown), and is applied as an erbium-doped fiber amplifier (EDFA) in the optical amplification unit 12 as a first optical amplification fiber EDF1 A configuration in which the second optical amplification fiber EDF2 and the third optical amplification fiber EDF3 are used for amplification is exemplified.

The optical amplifying unit 12 moves the seed light from the laser light source 11 and the inside of the control rack 3 in addition to the optical amplification fibers EDF1, EDF2, and EDF3 as optical amplification media that amplify the pumping light energy by moving it to the seed light. The optical couplers WDM1, WDM2, and WDM3 for combining the pumping light (pump light) from the pumping light source unit 70 are provided. Each optical amplification fiber EDF is an optical fiber in which an Er element (rare earth element) is added to the core region. The excitation light source unit 70 includes two pump lasers P1 and P2 configured by, for example, a Raman laser or the like, and has a wavelength (for example, λ ₂ = 1.480 [μm] capable of exciting the Er element added to the optical amplification fiber EDF. ]) With the intensity according to the control signal instruct | indicated from the control part 60 in the control rack 3 mentioned later for details. The pumping light from the pump laser P1 is incident on the first optical amplification fiber EDF1 via the optical coupler WDM1. The pump light from the pump laser P2 is branched into two at a predetermined distribution ratio by the fiber coupler 71, one of which enters the second optical amplification fiber EDF2 via the optical coupler WDM2, and the other enters the optical coupler WDM3. And enters the third optical amplification fiber EDF3.

In such an optical amplifying unit 12, when the excitation light having the wavelength λ ₂ output from the excitation light source unit 70 is incident on the optical amplification fiber EDF, erbium (Er) ions added to the core region are excited. The energy stored in the Er ions in the excited state is converted into light of the same wavelength (λ ₁ ) by stimulated emission when seed light of wavelength λ ₁ is incident from the laser light source 11 and is amplified. Produces an effect. The fundamental laser light amplified by stimulated emission in the optical amplification fiber EDF is output to the wavelength conversion unit 20 as parallel laser beams Lr ₁ , Lr ₂ , and Lr ₃ through a collimator or the like (not shown). Is done. The outputs of the fundamental laser beams Lr ₁ , Lr ₂ , and Lr ₃ from the laser beam generator 10 are controlled by the pumping light output (pumping intensity) supplied from the pumping light source unit 70 to the optical amplifying unit 12. It has become.

  The wavelength conversion unit 20 converts the wavelength of the laser light (fundamental laser beam amplified by the optical amplification unit 12) Lr emitted from the laser light generation unit 10 into ultraviolet light having a predetermined wavelength. In the laser device 1, the fundamental wave laser light having a wavelength λ = 1.547 [μm] emitted from the laser light generation unit 10 is sequentially wavelength-converted by a plurality of wavelength conversion optical elements, and finally, the fundamental wave 8. Ultraviolet light having a wavelength λ = 193 [nm], which is the same wavelength as that of the ArF excimer laser, is output as a harmonic (eighth harmonic).

As described above, there are various known configurations for the configuration (type and combination of wavelength conversion optical elements) of the wavelength conversion unit that converts the wavelength of the fundamental laser beam Lr in the infrared region (or visible region) into ultraviolet light. . In the present embodiment, as an example of the wavelength conversion unit, the laser beam generation unit 10 branches the fundamental laser beam emitted from one laser light source into three, and is amplified by the optical amplification unit 12 and amplified 3. Two fundamental laser beams Lr (Lr ₁ , Lr ₂ , Lr ₃ ) are made incident on the wavelength converter 20, and the fundamental wave, second harmonic (λ = 774 [nm]) and fifth harmonic (λ = 309 [nm] )), And the sum frequency generation generates a seventh harmonic (λ = 221 [nm]) and an eighth harmonic (λ = 193 [nm]). FIG. The configuration of the conversion unit 20 will be briefly described with reference to FIG.

First, the first fundamental laser beam Lr ₁ incident as P-polarized light is condensed and incident on the wavelength conversion optical element 21 by the lens 31, and the frequency of the fundamental wave (ω) is generated by the second harmonic generation (SHG). A double wave of twice (2ω) and half the wavelength λ is generated. The double wave of the P-polarized light generated by the wavelength conversion optical element 21 and the fundamental wave of the P-polarized light transmitted through the wavelength conversion optical element 21 are condensed and incident on the wavelength conversion optical element 22 by the lens 32 to generate a sum frequency ( (ω + 2ω) generates a harmonic whose frequency is three times the fundamental wave (3ω). In these wavelength conversion optical elements 21 and 22, for example, a PPLN crystal is used as the wavelength conversion optical element 21 for generating the second harmonic wave, and an LBO crystal is used as the wavelength conversion optical element 22 for generating the third harmonic wave. In addition, as the wavelength conversion optical element 21, a PPKTP crystal, a PPSLT crystal, an LBO crystal, or the like can be used.

  The third harmonic wave of the S-polarized light generated by the wavelength conversion optical element 22 and the fundamental wave and the second harmonic wave of the P-polarized light transmitted through the wavelength conversion optical element 22 are transmitted through the two-wavelength wavelength plate 41 and only the second harmonic wave is transmitted. Convert to S-polarized light. As the two-wavelength wave plate, for example, a wave plate made of a uniaxial crystal flat plate cut parallel to the optical axis of the crystal is used. This wave plate rotates the polarization with respect to light of one wavelength (second harmonic), and reduces the thickness of the wave plate (crystal) to the light of the other wavelength so that the polarization does not rotate. It is configured by cutting so as to be an integral multiple of λ / 2 with respect to light of the wavelength of λ and an integral multiple of λ with respect to light of the other wavelength.

  The second and third harmonics, both of which are S-polarized light, are condensed and incident on the wavelength conversion optical element 23 by the lens 33, and a fifth harmonic (5ω) is generated by sum frequency generation (2ω + 3ω). From the wavelength conversion optical element 23, the fifth harmonic of the P-polarized light generated by the wavelength conversion optical element 23, the second and third harmonics of the S-polarized light transmitted through the wavelength conversion optical element 23, and the basics of the P-polarization A wave is emitted. For example, an LBO crystal is used as the wavelength conversion optical element 23 for generating the fifth harmonic wave, but a BBO crystal or a CBO crystal can also be used. Here, the fifth harmonic wave emitted from the wavelength conversion optical element 23 has an elliptical cross section for walk-off. Accordingly, the elliptical cross-sectional shape is shaped into a circle by the two cylindrical lenses 34v and 34h, and is incident on the dichroic mirror 44.

On the other hand, the second fundamental laser beam Lr ₂ incident as P-polarized light is condensed and incident on the wavelength conversion optical element 24 by the lens 35, and a second harmonic is generated by the second harmonic generation. From the wavelength conversion optical element 24, a double wave and a fundamental wave of P-polarized light generated by the wavelength conversion optical element 24 are emitted and are incident on the dichroic mirror 45 through the lenses 36 and 37. As the wavelength conversion optical element 24, a PPLN crystal can be used, and a PPKTP crystal, a PPSLT crystal, an LBO crystal, or the like may be used.

The third fundamental laser beam Lr ₃ incident as S-polarized light is incident on the dichroic mirror 45 via the lens 38. The dichroic mirror 45 is configured to transmit light in the fundamental wavelength band and reflect light in the second wavelength band. The dichroic mirror 45 is incident on the dichroic mirror 45 and is converted into a wavelength converter. The P-polarized second harmonic generated by the optical element 24 is synthesized on the same axis.

  The synthesized fundamental wave of S-polarized light and second harmonic wave of P-polarized light are incident on the dichroic mirror 44. The dichroic mirror 44 is configured to transmit light in the fundamental wavelength band and the second harmonic waveband and reflect light in the fifth harmonic waveband. The S-polarized fundamental wave incident on the dichroic mirror 44 is formed. And the 2nd harmonic of P-polarized light and the 5th harmonic of P-polarized light generated by the wavelength conversion optical element 23 are combined on the same axis.

  The fundamental wave of S-polarized light, the second harmonic of P-polarized light, and the fifth harmonic of P-polarized light thus combined on the same axis are incident on the wavelength conversion optical element 25. Here, lenses (34v, 34h, 36, 37, 38) are provided in the optical paths of the fundamental wave, the second harmonic wave, and the fifth harmonic wave, respectively, and the light of each wavelength synthesized on the same axis is wavelength-converted. The light is focused and incident on the optical element 25. In the wavelength conversion optical element 25, sum frequency generation (2ω + 5ω) is performed by the 2nd harmonic of P-polarized light and the 5th harmonic of P-polarized light to generate 7th harmonic (7ω). From the wavelength conversion optical element 25, the light of each wavelength transmitted through the wavelength conversion optical element 25 is emitted together with the seventh harmonic wave of the S-polarized light generated by the wavelength conversion optical element 25. For example, a CLBO crystal is used as the wavelength conversion optical element 25 that generates the seventh harmonic wave.

  These lights enter the wavelength conversion optical element 26, where the S-polarized fundamental wave and the S-polarized 7th harmonic are combined by sum frequency generation (ω + 7ω) to generate the P-polarized 8th harmonic (8ω). Is done. For example, a CLBO crystal is used as the wavelength conversion optical element 26 that generates the eighth harmonic wave. The wavelength conversion optical element 26 emits light of other wavelength components such as a fundamental wave and a second harmonic wave transmitted through the wavelength conversion optical element 26 in addition to the eighth harmonic wave generated by the wavelength conversion optical element 26. However, when only the 8th harmonic wave is output from the wavelength conversion unit 20 (laser device 1), these may be separated by using a dispersion prism, a dichroic mirror, a polarization beam splitter, or the like. The eighth harmonic wave emitted from the wavelength conversion optical element 26 enters the power control unit 50 arranged on the optical path.

As described above, when multi-stage wavelength conversion is performed by the wavelength conversion optical elements 21 to 26 in order to obtain a double wave of a desired wavelength (λ = 193 [nm] in the present embodiment) from the fundamental wave, in the middle stage It is considered that the unstable factor of wavelength conversion affects the output stability of the output light at the final stage. Here, as the unstable element of the wavelength conversion, for example, temperature control of the wavelength conversion optical elements 21 to 26 (particularly, when temperature control is performed on an optical crystal having deliquescence used in a temperature rising state, And fluctuations in conversion efficiency due to fluctuations in temperature control for achieving temperature phase matching in accordance with matching conditions, and reductions in conversion efficiency due to damage / degradation of the wavelength conversion optical elements 21 to 26. When wavelength conversion is performed by sum frequency generation, it is considered that among the incident light components to the final-stage wavelength conversion optical element 26, high-frequency components having a larger number of wavelength conversions are dominant in the output stability of the final stage. . That is, in the present embodiment, among the incident light components to the wavelength conversion optical element 26 in the final stage (the stage where the eighth harmonic is generated), the fundamental wave component that is dominant in output stability is up to that stage. This is a fifth harmonic system (first fundamental laser beam Lr ₁ ) having the highest number of wavelength conversions compared to other high frequency components. Therefore, in the present embodiment, the first fundamental laser beam Lr ₁ for generating the fifth harmonic wave is desired based on the detection result of the power control unit 50 described below so that the output of the laser device 1 is constant. It has a function of feedback-controlling the output of the pump laser P1 for optically amplifying to the intensity of. Now, the configuration of the power control unit 50 and the like will be described in detail.

  The power control unit 50 includes a beam splitter 51 and an optical output monitoring device 52, which are an entrance for introducing laser light emitted from the wavelength conversion optical element 26 into the inside and deep ultraviolet light that is an eighth harmonic wave. It is configured to be accommodated in a rectangular box-shaped unit case (not shown) in which an emission port for deriving the laser beam Lv to the outside is formed. In this unit case, the above-described dispersion prism for separating the 8th harmonic wave emitted from the wavelength conversion optical element 26 and light of other wavelength components may be accommodated.

  The beam splitter 51 reflects a part of the eighth harmonic wave incident from the wavelength conversion optical element 26 (for example, 1% of the total light amount) and guides it to the optical output monitor device 52 as monitor light, and the eighth harmonic wave remains. The amount of light is transmitted, and travels straight along the optical axis, and is output to the outside as output light (ultraviolet laser light Lv) of the laser device 1.

  The optical output monitor device 52 is configured to include a light receiving element such as a photodiode (Photo Diode), for example, and receives the monitor light (a part of the eighth harmonic wave) transmitted by the beam splitter 51. A current signal corresponding to the intensity (power) of the monitor light is generated. This current signal is converted into a voltage signal amplified by a predetermined gain by an amplification circuit (not shown) built in the optical output monitor device 52 and output to the control unit 60 in the control rack 3.

The control rack 3 includes a control unit 60 that controls the operation of each unit constituting the laser device 1 to control the output of the ultraviolet light Lv from the laser head 2, and the excitation light source unit that excites the optical amplification unit 12. 70. Adjusting the temperature of a wavelength conversion optical element (for example, an optical element having deliquescence or an optical element used for temperature phase matching) used in a temperature rising state heated to a predetermined temperature (for example, about 150 ° C.) A gas supply unit (not shown) for supplying an inert gas such as N ₂ gas to each part of the laser device 1 such as the temperature adjustment unit 80 and the power control unit 50 through a gas tube passing through the interface 4 is provided. ing.

The control unit 60 includes, for example, a so-called microcomputer including a CPU (Central Processing Unit), a ROM (Read On Memory), a RAM (Random Access Memory), etc., and an optical output monitor. Based on the detection value of the device 52, the intensity of the fundamental wave laser beam Lr ₁ of the fifth harmonic wave is manipulated to adjust the intensity of the seventh harmonic wave incident on the wavelength conversion optical element 26 for generating the eighth harmonic wave. In other words, the control unit 60 controls the excitation light source unit 70 so that the output of the laser device 1 is constant based on the detection value of the light output monitoring device 52 (so that the monitoring result is a preset specified value). The output of the pumping light of the pump laser P1 is feedback-controlled, and the intensity of the output light such as the fundamental laser light Lr ₁ , the fifth harmonic, the seventh harmonic, and the eighth harmonic is controlled. Therefore, when the output of the laser device 1 is reduced (the intensity of the monitor light is lower than the specified value), the output of the pump laser P1 is increased, and conversely, the output of the laser device 1 is increased (the intensity of the monitor light is the specified value). The output of the pump laser P1 is decreased to control the intensity of the ultraviolet laser beam Lv (eighth harmonic wave) that is finally output to be constant. At this time, regardless of the detection value of the light output monitor device 52, the output of the pump laser P2 is controlled to be constant by the controller 60.

In the laser device 1 configured as described above, when multi-stage wavelength conversion is performed in order to obtain a harmonic of a desired wavelength 193 [nm] from the fundamental wave, the laser device is based on the detection value of the optical output monitor device 52. Among the incident light components (Lr ₁ , Lr ₂ , Lr ₃ ) incident on the final wavelength conversion optical element 26, the stable fundamental wave components (Lr ₂ , Lr ₃ ) Since the light intensity of only the unstable fundamental wave component (Lr ₁ ) is manipulated without manipulating the light intensity, the controllability of the laser light output can be improved. Therefore, according to the laser device 1 described above, it is possible to realize a stable operation in the long term by reliably suppressing the fluctuation of the light output.

  Although the preferred embodiment of the present invention has been described so far, the present invention is not limited to this embodiment. For example, in the above-described embodiment, the configuration in which the fundamental wave output from one laser light source 11 is branched into three and amplified by the first to third optical amplification fibers EDF has been described as an example. However, the present invention is not limited to this, and the fundamental wave output from each of the three laser light sources may be amplified by the optical amplification fiber EDF.

  Further, in the above-described embodiment, the laser light generation unit 10 amplifies the seed light generated by the laser light source 11 with the optical amplification fiber EDF having a single-stage configuration as the optical amplification unit 12 and amplified laser light. The configuration in which Lr is incident on the wavelength conversion unit 20 has been described as an example. However, the present invention is not limited to this. For example, two or more stages of optical amplification fibers are connected in series according to the output intensity and amplification factor of the laser light source 11. It is good also as a multistage structure. When the optical amplification fiber has a multi-stage configuration, the intensity of the excitation light for the preamplifier (first stage...) Is always kept constant regardless of the monitor result, and for the power amplifier (last stage). It is preferable to control the intensity of the excitation light as the manipulated variable.

  In the above-described embodiment, the pump light from the pump laser P2 is split into two by the fiber coupler 71, and each is incident on the optical amplification fibers EDF2 and EDF3 via the optical couplers WDM2 and WDM3 (that is, However, the present invention is not limited to this. For example, three pump lasers are provided in the excitation light source unit, and the three pump lasers are provided. The pumping light output from the pump laser may be incident on the optical amplification fibers EDF1, EDF2, and EDF3, respectively.

  In the above-described embodiment, the erbium-doped optical fiber (EDF) configured by adding erbium to the core region is described as an example of the optical amplifying medium of the optical amplifying unit 12, but the present invention is not limited thereto. For example, an optical amplification fiber in which a rare earth element other than erbium is added to the core region may be configured as the optical amplification medium.

  In the above-described embodiment, the description is omitted for the sake of simplification. However, an EOM that cuts out an optical pulse between the laser light source 11 and the optical amplifying unit 12 and between the optical amplifying unit 12 and the wavelength converting unit 20 is used. These optical modulators, narrowband filters that enhance monochromatic light, and the like are provided as appropriate.

The wavelength of the output light from the laser device 1 is not limited to 193 [nm], and may be the same wavelength band as that of a KrF excimer laser, F ₂ laser, or the like. Further, the application example of the laser apparatus according to the present invention is not limited to the exposure apparatus, and can be used in various other apparatuses such as various optical inspection apparatuses and laser treatment apparatuses.

DESCRIPTION OF SYMBOLS 1 Laser apparatus 2 Laser head 3 Control rack 10 Laser light generation part 11 Laser light source 12 Optical amplification part 20 Wavelength conversion parts 21-26 Wavelength conversion optical element 50 Power control unit 51 Beam splitter 52 Light output monitor apparatus 60 Control part 70 Excitation light source 80 Temperature adjusting unit EDF Optical amplification fiber P Pump laser

Claims (4)

A laser light source that outputs a fundamental laser beam;
A plurality of optical amplifiers each amplifying a plurality of fundamental laser beams from the laser light source;
A wavelength conversion unit for wavelength-converting a plurality of fundamental laser beams amplified by the plurality of optical amplifiers into a predetermined harmonic laser beam using a wavelength conversion optical element;
A light separation unit for separating a part of the harmonic laser beam output from the wavelength conversion unit as monitor light;
A light output monitor unit for detecting the intensity of the monitor light separated by the light separation unit;
A control unit that controls the output of the harmonic laser beam by manipulating the intensity of the fundamental laser beam based on the detection value of the optical output monitor unit;
The plurality of optical amplifiers are respectively configured to amplify the fundamental laser light input from the laser light source by supplying excitation light output from the excitation light source to an optical amplification medium,
The control unit is configured to output only the pumping light output supplied to the optical amplifier for amplifying the fundamental laser light having the largest number of wavelength conversions in the wavelength conversion unit among the plurality of optical amplifiers. A laser device, wherein the intensity of the fundamental wave laser beam is controlled by controlling based on a detection value of the light output monitor unit.   2. The laser device according to claim 1, wherein the predetermined harmonic laser beam is ultraviolet light having a wavelength of 200 nm or less.   3. The laser device according to claim 1, wherein the wavelength conversion optical element is used in a temperature rising state heated to a predetermined temperature by a temperature adjustment unit in the wavelength conversion unit. The optical amplifier is composed of a plurality of stages in which a plurality of the optical amplification media are connected in series,
The control unit controls only the pumping light output supplied to the final stage optical amplifying medium among the plurality of optical amplifying media based on a detection value of the optical output monitoring unit. The laser apparatus in any one of -3.

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