JP2011053489A - Laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser device that eliminates the need for alignment of respective members, and miniaturizes the device and performs high-speed delay. <P>SOLUTION: The laser device includes: a laser light generating part; an optical amplification part configured to amplify pulse light beams, respectively; and a wavelength conversion part configured to coaxially align the pulse light beams amplified by the optical amplification part, and also, make the pulse light beams enter a wavelength conversion optical element to perform wavelength conversion; wherein there is provided an optical path length adjusting part 60 including a rotary mirror 64 for reflecting and emitting the light in a direction different from the incident direction, a mirror rotating part 69 for rotating the rotary mirror 64, a second lens 65 for converting the light emitted from the rotary mirror 64 to collimated light, a transmission type diffraction grating 66 for transmitting the collimated light transmitted through the second lens 65 in the different direction, and a planar mirror 67 for reflecting the light transmitted through the transmission type diffraction grating 66 so that the light may advance in an opposite direction in the same optical path as the optical path of the collimated light. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a laser device that amplifies laser light in the infrared to visible region, converts the wavelength to laser light in the ultraviolet region, and outputs the laser light.

  In recent years, deep ultraviolet lasers have been actively developed for use in the field of semiconductor manufacturing equipment and the like. In particular, a 193 nm solid-state laser that combines an optical fiber amplifier and a wavelength conversion technology, which has advantages such as small size, high output, and no use of toxic gas, has been developed. As a laser device that outputs such a laser, a plurality of optical fiber amplifiers are used, and the fundamental wave amplified by each optical fiber amplifier is wavelength-converted by being incident on the wavelength conversion crystal, and 193 nm light is output. Is known (see, for example, Patent Document 1).

  In such a laser device, the pulse lights amplified by a plurality of fiber amplifiers are superimposed, but when a plurality of pulse lights are to be superimposed at the incident position of the light on the wavelength conversion crystal, the pulse generation timing is somehow used. The work which unites is necessary. Therefore, in general, a photodetector is arranged at the light incident position of the wavelength conversion crystal, and the timing is adjusted by adjusting the length of the fiber while observing an electric signal generated from the photodetector with an oscilloscope.

JP-A-2005-010402

  By the way, even if the timing is adjusted by adjusting the length of the fiber as described above, an error of about several mm may occur. For this reason, it is necessary to perform fine adjustment (hereinafter referred to as delay) to eliminate the error using an optical delay line described later. A conventional optical delay line 50 will be briefly described with reference to FIG. The optical delay line 50 includes a base 51, brackets 52a and 52b, and optical fiber attachment portions 53a and 53b. The optical fiber ends are attached to the optical fiber attachment portions 53a and 53b, respectively. By adjusting the distance between them, the optical path length can be adjusted to delay.

  However, when the conventional optical delay line 50 is used, some member needs to be swept to adjust the distance between the brackets 52a and 52b and the like when the delay is generated. Accordingly, since a physical space for the sweep is required, the sizes of the delay line main body and the entire apparatus are increased. In addition, it takes time to delay with sweeping, and the light is once taken out from the optical fiber, delayed between the brackets, and then incident on the optical fiber again. There was a problem of not becoming.

  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 that does not require alignment of each member, can be downsized, and can perform delay at high speed. To do.

  In order to achieve such an object, a laser device according to the present invention includes a pulsed light generating unit that generates pulsed light, a pulsed light divided into a first pulsed light and a second pulsed light. The optical amplifying unit to be amplified, and the first pulsed light and the second pulsed light amplified by the optical amplifying unit are coaxially overlapped and incident on the wavelength conversion optical element, and have a wavelength different from that of the first pulsed light and the second pulsed light. A wavelength converting unit that generates the light of the optical path, and an optical path length adjusting unit that is provided at a position where either the first pulsed light or the second pulsed light passes in the optical amplifying unit, and adjusts the optical path length of either of the lights. The optical path length adjustment unit has a reflection surface for entering any one of the lights, is rotatably supported in a direction perpendicular to the optical axis of the light, and makes the light incident on the reflection surface and the direction of incidence. Rotating mirror reflecting and emitting in different directions -, A mirror rotating unit that rotates the rotating mirror in a direction perpendicular to the optical axis, a lens that converts the light emitted by the rotating mirror into parallel light, and the optical axis of the parallel light that has passed through the lens It has a reflecting surface that faces in a different direction with respect to the optical axis, and extends in a direction perpendicular to the optical axis. And a light reflecting portion that reflects and emits the light so as to proceed to step (1).

  The light reflecting portion transmits the parallel light transmitted through the lens and emits the light in a different direction, and the light transmitted through the transmissive diffraction grating travels in the same optical path as the light in the opposite direction. However, as a reflection type diffraction grating having a large number of concave and convex surfaces, parallel light that has passed through the lens is incident on the concave and convex surfaces, and the same optical path as that of the parallel light is directed in the opposite direction. You may make it reflect and inject | emit so that it may progress to.

  According to the laser device of the present invention, the rotating mirror and the light reflecting unit are provided, the rotating mirror is rotated by the mirror rotating unit to change the optical path length, and the light reflecting unit reflects the light so as to pass through the same optical path. Therefore, alignment of each member becomes unnecessary, and the apparatus can be miniaturized and delayed at high speed.

It is a figure which shows schematic structure of the laser apparatus in this invention. It is a block diagram of the wavelength conversion part in the said laser apparatus. It is a figure which shows schematic structure of the conventional optical delay line. It is a figure which shows the optical path length adjustment part of 1st Embodiment in the said laser apparatus. It is a figure which shows the optical path length adjustment part of 2nd Embodiment in the said laser apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The light source device exemplified in this embodiment is an exposure apparatus for manufacturing semiconductor devices and various optical inspection apparatuses. It is used suitably for a laser treatment apparatus etc. A schematic configuration diagram of the laser device 1 is shown in FIG. 1. The laser device 1 divides a pulsed light generation unit 10 that generates pulsed light and a plurality of pulsed light generated by the pulsed light generation unit 10 in parallel. An optical amplifying unit 20 that amplifies and emits and a wavelength conversion unit 30 that generates a harmonic by sum frequency generation by superimposing a plurality of parallel amplified pulse lights on the same axis.

  The pulsed light generation unit 10 cuts out a laser light source 11 that generates laser light (also referred to as seed light) having a predetermined wavelength in the infrared to visible region and a part of the seed light generated by the laser light source 11. And an optical modulator 12 for outputting short pulse seed light (hereinafter referred to as “pulse seed light” for convenience). The laser light source 11 outputs seed light having a narrow wavelength and a single wavelength. As the laser light source 11, for example, a distributed feedback semiconductor that generates seed light having a single wavelength of 1.547 [μm] is used. A laser (DFB semiconductor laser) can be used. The DFB semiconductor laser can be oscillated CW or pulsed with an arbitrary intensity by controlling the waveform of the excitation current. In the laser device 1, seed light Ls having a single wavelength having a repetition frequency of 2 [MHz] and a pulse width of 1 to 2 [nsec] is generated.

  The optical modulator 12 cuts out part of the seed light Ls generated by the laser light source 11 in time, and emits the extracted pulse seed light to the optical amplification unit 20. As the optical modulator 12, for example, an electro-optic modulator (EOM) is used. The optical modulator 12 is synchronously controlled with the laser light source 11 by a control device (not shown), and has a pulse width of about 0.3 [nsec] from the seed light having a pulse width of 1 to 2 [nsec] emitted from the laser light source 11. The light pulse is cut out, and the cut out pulse seed light Lp is emitted to the optical amplifying unit 20.

The optical amplifying unit 20 includes an optical dividing unit 25 that branches the pulse seed light Lp emitted from the pulsed light generating unit 10 in parallel, and a plurality of fiber optical amplifiers 21 that amplify and emit the branched pulsed light, 22 and 23. In the present embodiment, the pulse seed light Lp emitted from the pulse light generator 10 is branched into three in parallel by the light splitter 25, and then the first, second, and third fiber optical amplifiers 21, 22, and 23 are used. Is incident on. The amplified light is amplified by the fiber optical amplifiers 21, 22, and 23, and the amplified light is output to the wavelength conversion unit 30. Hereinafter, the light amplified by the first fiber optical amplifier 21 is “first pulsed light La ₁ ”, the light amplified by the second fiber optical amplifier 22 is “second pulsed light La ₂ ”, and the third fiber optical amplifier. The light amplified by 23 is referred to as “third pulsed light La ₃ ”. As the first, second, and third fiber optical amplifiers 21, 22, and 23 that amplify infrared light having a wavelength of 1.5 [μm], for example, an erbium (Er) -doped fiber optical amplifier (EDFA) is used. ) Is used. When amplifying infrared light having a wavelength of 1.1 [μm], an yttrium (Yb) -doped fiber optical amplifier (YDFA) may be used.

  The wavelength conversion unit 30 includes a wavelength conversion optical element such as a nonlinear optical crystal or a periodically poled crystal, and a plurality of pulse lights emitted from the optical amplification unit 20 are coaxially overlapped and incident on the wavelength conversion optical element. And generate harmonics by sum frequency generation. As described above, there are various modes in the wavelength conversion optical system in which a plurality of pulse lights are coaxially overlapped to generate a harmonic by sum frequency generation. FIG. 2 shows the wavelength conversion unit 30 that converts the wavelength of the laser beam in the infrared region of the wavelength 1.5 [μm] into the laser beam in the ultraviolet region of the wavelength 193 [nm] corresponding to the eighth harmonic wave. While explaining. In FIG. 2, an ellipse on the optical path is a collimator lens or a condensing lens, and description thereof is omitted. In addition, the vertical arrow indicates P-polarized light, the dot in the circle indicates S-polarized light, the fundamental wave is represented by ω, and the nth harmonic wave is represented by nω.

The wavelength conversion unit 30 includes six wavelength conversion optical elements 31 to 36 and is configured by three optical paths. The first pulsed light La ₁ (fundamental wave) having a frequency ω that is amplified by the first fiber optical amplifier 21 and incident on the wavelength conversion unit 30 is wavelength-converted in the order of ω → 2ω → 3ω → 5ω. The second pulsed light La ₂ (fundamental wave) having the frequency ω amplified by the second fiber optical amplifier 22 and incident on the wavelength conversion unit 30 is wavelength-converted from ω → 2ω. Then, a 7th harmonic wave 7ω is generated by the sum frequency generation of the 5th harmonic wave of 5ω and the 2nd harmonic wave of 2ω, and the third pulsed light La having the frequency ω amplified by the 7th harmonic wave and the third fiber optical amplifier 23 is generated. _{3 The} 8th harmonic wave 8ω is generated by the sum frequency generation of (fundamental wave).

The P-polarized first pulsed light La ₁ emitted from the first fiber optical amplifier 21 and incident on the wavelength conversion unit 30 is condensed and incident on the wavelength conversion unit 30 to generate a double wave (2ω) of P-polarization. Let The generated second harmonic wave and the fundamental wave transmitted through the wavelength conversion optical element 31 are condensed and incident on the wavelength conversion optical element 32, and a third harmonic wave (3ω) of S-polarized light is generated by sum frequency generation. As the wavelength conversion optical elements 31 and 32, for example, a PPLN crystal, a PPKTP crystal, a PPSLT crystal, an LBO crystal, or the like can be used.

  The S-polarized third harmonic wave generated from the wavelength conversion optical element 32 and the P-polarized fundamental wave and the second harmonic wave transmitted through the wavelength conversion optical element 32 are transmitted through the second-wave plate 41 and only the second harmonic wave. To S-polarized light. As the second wave plate 41, for example, a wave plate made of a uniaxial crystal flat plate cut parallel to the optical axis of the crystal is used. The second harmonic wave converted to S-polarized light as described above and the third harmonic wave of S-polarized light generated from the wavelength conversion optical element 32 are condensed and incident on the wavelength conversion optical element 33, and 5 P-polarized light is generated by sum frequency generation. A double wave (5ω) is generated. As the wavelength conversion optical element 33 for generating the fifth harmonic wave, for example, an LBO crystal is used, but a BBO crystal, a CBO crystal, or the like can also be used. The fifth harmonic wave emitted from the wavelength conversion optical element 33 has an elliptical cross section due to the influence of walk-off. Therefore, the elliptical cross-sectional shape of the fifth harmonic wave is shaped into a circle by the two cylindrical lenses 42v and 42h provided behind the wavelength conversion optical element 33, and is incident on the dichroic mirror 43. Yes.

The P-polarized fundamental wave (second pulsed light La ₂ ) emitted from the second fiber optical amplifier 22 and incident on the wavelength conversion unit 30 is condensed and incident on the wavelength conversion optical element 34 and is doubled on the P-polarized light. (2ω) is generated. The second harmonic wave generated by the wavelength conversion optical element 34 enters the dichroic mirror 44. As the wavelength conversion optical element 34 for generating the second harmonic, for example, a PPLN crystal, an LBO crystal, a PPKTP crystal, a PPSLT crystal, or the like can be used.

The S-polarized fundamental wave (third pulsed light La ₃ ) emitted from the third fiber optical amplifier 23 is incident on the dichroic mirror 44 without undergoing wavelength conversion. The dichroic mirror 44 is configured to transmit light in the fundamental wavelength band and reflect light in the second harmonic wavelength band. The dichroic mirror 44 and the dichroic mirror 44 transmit the S-polarized fundamental wave transmitted through the dichroic mirror 44. The second polarized wave of the P-polarized light reflected by the laser beam is superimposed on the same axis and is incident on the dichroic mirror 43. The dichroic mirror 43 is configured to transmit light in the wavelength band of the fundamental wave and the second harmonic wave and reflect light in the wavelength band of the fifth harmonic wave. The fundamental wave of S polarization transmitted through the dichroic mirror 43. The second harmonic wave of P-polarized light and the fifth harmonic wave of P-polarized light reflected by the dichroic mirror 43 are coaxially superimposed and incident on the wavelength conversion optical element 35.

  In the wavelength conversion optical element 35, sum frequency generation is performed by P-polarized second harmonic (2ω) and P-polarized fifth harmonic (5ω), and seventh harmonic (7ω) is generated. As the wavelength conversion optical element 35 for generating the seventh harmonic wave, for example, a CLBO crystal is used. The 7th harmonic wave (7ω) of the S-polarized light generated from the wavelength conversion optical element 35 and the fundamental wave (ω) of the S-polarized light transmitted through the wavelength conversion optical element 35 are incident on the wavelength conversion optical element 36 and are generated by sum frequency generation. P-polarized eighth harmonic (8ω) is generated. As the wavelength conversion optical element 36 for generating the eighth harmonic wave, for example, a CLBO crystal is used. The light output from the wavelength conversion optical element 36 includes a fundamental wave, a second harmonic wave, and the like transmitted through the wavelength conversion optical element 36 in addition to the above eighth harmonic wave. However, the dichroic mirror, the polarization beam splitter, and the prism are included. Etc. can be separated and removed.

  As described above, the laser light in the infrared region having the wavelength of 1.547 [μm] output from the optical amplifying unit 20 is sequentially wavelength-converted by the wavelength converting unit 30, and the wavelength converting unit 30 outputs the ultraviolet light having the wavelength of 193 [nm]. The laser beam Lv in the area is output. Thus, the fifth harmonic, the second harmonic, and the fundamental wave are superimposed on the same axis by the dichroic mirror 43, and the sum frequency generation of the fifth harmonic and the second harmonic is generated in the wavelength conversion optical element 35 for generating the seventh harmonic. The sum frequency generation of the seventh harmonic and the fundamental wave is performed in the wavelength converting optical element 36 for generating the harmonic. Note that the configuration of the wavelength conversion unit 30 is not limited to the above-described configuration. For example, the configuration disclosed in Japanese Patent Application Laid-Open No. 2004-86193 and International Publication No. 2005-116751 are all related to the present applicant. The configuration disclosed in the above can be applied.

  By the way, as described above, the first, second, and third fiber optical amplifiers 21, 22, and 23 respectively output pulsed light. These pulsed light are incident on the wavelength conversion unit 30 (for example, It is superimposed at position A or B) in FIG. It is necessary to adjust the timing of each pulsed light so as not to reduce the efficiency of wavelength conversion at the time of superposition, but as this method, a photodetector (photoelectric conversion element) is positioned at position A or B in FIG. ) And adjusting the length of the fiber while observing the waveform of the electric signal output from the photodetector with an oscilloscope. At this time, the adjustment of the fiber length in the first, second, and third fiber optical amplifiers 21, 22, and 23 may cause an error of about several millimeters. In this case, it is necessary to perform a delay). The optical delay line is upstream or downstream of any of the first, second, and third fiber optical amplifiers 21, 22, and 23 (for example, any one of positions A, B, C, and D in FIG. 1). It is possible to perform a delay mechanically or electrically by installing it in

  A typical optical delay line 50 is shown in FIG. As shown in FIG. 3, the optical delay line 50 includes a base 51, brackets 52a and 52b, and optical fiber mounting portions 53a and 53b. The brackets 52a and 52b are respectively located above the base 51. , And is supported in a movable state only in one direction (the left-right direction in FIG. 3). The optical fiber attachment portions 53a and 53b are configured such that end portions of the optical fibers can be attached to the brackets 52a and 52b, respectively, and light can be propagated from the optical fiber attached to the bracket 52a to the optical fiber attached to the bracket 52b. . Further, the delay can be performed by sweeping the bracket 52a and the bracket 52b and adjusting the distance therebetween.

  However, the general optical delay line 50 has the following problems I to III. I: Since a physical distance difference corresponding to the delay amount is required, the size of the optical delay line main body increases and the size of the laser device 1 itself also increases. II: In order to generate a delay, it is necessary to sweep some parts such as the brackets 52a and 52b. In order to generate a large delay amount, a large sweep amount is required, and as a result, the time required for the delay becomes long. III: Since the configuration is such that the pulsed light is extracted from the optical fiber into the space, given a delay, and then incident on the optical fiber again, it is necessary to accurately align each component. Hereinafter, two embodiments (the first embodiment and the second embodiment) for solving the problems I to III will be described.

  First, in the first embodiment, an optical path length adjustment unit 60 is used instead of the optical delay line 50. Similar to the optical delay line 50, the optical path length adjustment unit 60 can be installed on either the upstream side or the downstream side of any of the first, second, and third fiber optical amplifiers 21, 22, and 23. As shown in FIG. 4, a circulator 62, a first lens 63, a rotating mirror 64, a second lens 65, a transmission diffraction grating 66, a plane mirror 67, and a mirror rotating unit 69 are provided. Has been. Note that a straight line or a curve provided between the members shown in FIG. 4 and FIG. 5 described later indicates an optical path, and the optical path of the light reflected by the rotating mirror 64 changes with the rotation of the rotating mirror 64 (later FIG. 4 shows the optical paths changed by the rotation of the rotating mirror 64 as A, A ′, and A ″, respectively.

  The circulator 62 is an optical component called a three-port circulator having three ports (ports 1, 2, and 3), and light incident on the port 1 is emitted from the port 2 as shown in FIG. The light that has entered the port 2 is emitted from the port 3. When the optical path length adjustment unit 60 is provided on the upstream side (position C or position D in FIG. 1) of the first, second, and third fiber optical amplifiers 21, 22, and 23, the optical path length adjustment unit 60 is divided by the light dividing unit 25. The light incident on the port 1 and then emitted from the port 3 is emitted toward the first, second, and third fiber optical amplifiers 21, 22, and 23. When the optical path length adjusting unit 60 is provided on the downstream side (position A or position B in FIG. 1) of the first, second, and third fiber optical amplifiers 21, 22, and 23, the first and second The light amplified by the third fiber optical amplifiers 21, 22, and 23 is incident on the port 1, and then the light emitted from the port 3 is emitted toward the wavelength conversion unit 30.

  The first lens 63 is provided at a position where light emitted from the port 2 of the circulator 62 is collected, and a rotary mirror 64 is provided so that the reflection surface is located at the focal position of the collected light. Further, the light transmitted through the first lens 63 is emitted into the space. The rotating mirror 64 is supported by the mirror rotating unit 69 so as to be rotatable about an axis extending in a direction perpendicular to the optical axis of the light collected by the first lens 63, and is collected by the first lens 63. The light that has been reflected and reflected by the rotating mirror 64 is bent, for example, 90 degrees and emitted toward the second lens 65. Note that the optical path of the light reflected by the rotating mirror 64 is changed, for example, from the optical path A to the optical path A ′ shown in FIG. 4 by rotating the rotating mirror 64 by the mirror rotating unit 69 or from the optical path A to the optical path. A ″ can be changed to A ″, and the incident positions of light of the second lens 65 and the transmissive diffraction grating 66, which will be described in detail later, are also changed as A, A ′, A ″, for example. As a result, the length of the optical path can be changed depending on the rotation angle of the rotary mirror 64.

  The second lens 65 transmits the light reflected by the rotating mirror 64 and then emits the light toward the transmissive diffraction grating 66. The transmissive diffraction grating 66 is configured to transmit and emit incident light in a direction different from the traveling direction (for example, a direction bent 90 degrees with respect to the traveling direction). As shown in FIG. 4, the plane mirror 67 is provided so that the reflection surface thereof is orthogonal to the optical axis of the light emitted from the transmissive diffraction grating 66. Therefore, the light emitted from the transmission type diffraction grating 66 and reflected by the plane mirror 67 passes through the same optical path as before being reflected, and as shown in FIG. 4, the transmission type diffraction grating 66, the second lens 65, The light enters the port 2 of the circulator 62 via the rotating mirror 64 and the first lens 63. The light incident on the port 2 is emitted toward the first, second, and third fiber optical amplifiers 21, 22, and 23 or the wavelength conversion unit 30 as described above. In the above description, the plane mirror 67 reflects the light emitted from the transmissive diffraction grating 66. However, the present invention is not limited to this. The incident light travels along the same path as that path. Any member that reflects the light (for example, a mirror array) can be substituted for the plane mirror 67.

  In the optical path length adjustment unit 60 configured as described above, the light incident on the first lens 63 is reflected by the planar mirror 67 after the optical path is bent by the rotating mirror 64 and the transmission diffraction grating 66, and The optical path is bent in the same manner as described above by the transmissive diffraction grating 66 and the rotating mirror 64, and is then incident again on the first lens 63, so that the optical path is bent four times in total. Then, by rotating the rotating mirror 64 before and after the optical path is bent, the optical path can be changed as indicated by A, A ′, A ″ in FIG. 4. Accordingly, only the rotating mirror 64 is rotated. This makes it possible to change the length of the optical path, and the delay can be performed at a higher speed and the time can be shortened as compared with the conventional optical delay line 50 that changes the length of the optical path by sweeping. Therefore, the above problem II can be solved.

  In addition, the light emitted from the first lens 63 passes through the rotating mirror 64, the second lens 65, the transmissive diffraction grating 66, and the plane mirror 67 until the light enters the first lens 63 again for a total of four times. Since it is bent, a large delay amount can be generated even if the rotating mirror 64 is slightly rotated. Therefore, a physical distance difference corresponding to the delay amount is not required, and the optical delay line main body and the laser device 1 itself can be reduced in size, and the problem I can be solved. Further, in the optical path length adjusting unit 60, it is not necessary to sweep any parts, and a delay can be generated only by rotating the rotating mirror 64. Therefore, it is not necessary to align each part as in the optical delay line 50. The above problem III can be solved.

  In the second embodiment, an optical path length adjustment unit 70 as shown in FIG. 5 is used instead of the optical path length adjustment unit 60 of the first embodiment. Similar to the optical path length adjusting unit 60, the optical path length adjusting unit 70 can be installed on either the upstream side or the downstream side of any of the first, second, and third fiber optical amplifiers 21, 22, and 23. As shown in FIG. 5, the circulator 72, the first lens 73, the rotating mirror 74, the second lens 75, the reflective diffraction grating 76, and the rotation driving mechanism 79 are configured. . Since the optical path of the light reflected by the rotating mirror 74 is changed by the rotation of the rotating mirror 74 (described later in detail), the optical paths changed by the rotation of the rotating mirror 74 are denoted by B, B ′, B ″ in FIG. It shows.

  The circulator 72, the first lens 73, the rotating mirror 74, the second lens 75, and the rotation driving mechanism 79 are respectively the circulator 62, the first lens 63, the rotating mirror 64, the second lens 65, and the mirror rotating unit of the first embodiment. Since the configuration and function are the same as those of 69, their detailed description is omitted. The second lens 75 is provided so that the light reflected by the rotary mirror 74 is transmitted and then emitted toward the reflective diffraction grating 76. The reflective diffraction grating 76 has a fine uneven surface, and is provided so that the uneven surface is opposed to the optical path of the light transmitted through the second lens 75. Therefore, the light emitted from the second lens 75 is incident on the reflective diffraction grating 76, passes through the same optical path as the incident light path, and is reflected and emitted from the reflective diffraction grating 76. As shown in FIG. 5, the light emitted from the reflective diffraction grating 76 is incident on the port 2 of the circulator 72 through the second lens 75, the rotating mirror 74, and the first lens 73, and the first, second, The light is emitted toward the third fiber optical amplifiers 21, 22, 23 or the wavelength conversion optical system.

  In the optical path length adjustment unit 70 configured as described above, the light emitted from the first lens 73 is reflected by the reflective diffraction grating 76 after the optical path is bent by the rotating mirror 74, and again by the rotating mirror 74. After the optical path is bent, it enters the first lens 73 again, and the optical path is bent twice in total. The optical path can be changed to B, B ′, B ″ in FIG. 5 by the rotation of the rotating mirror 74. Accordingly, the length of the optical path can be increased only by rotating the rotating mirror 74. As in the first embodiment, the delay can be performed at a higher speed and the time can be shortened as in the first embodiment, so that the problem II is solved. Can do.

  Further, as in the first embodiment, the physical distance difference corresponding to the delay amount is not necessary, and the entire apparatus can be reduced in size, so that the problem I can be solved. Further, since it is not necessary to sweep parts and a delay can be generated only by rotating the rotary mirror 74, the above problem III can be solved for the same reason as in the first embodiment.

  Further, in the optical path length adjusting unit 70 of the second embodiment, unlike the transmission diffraction grating 66 of the first embodiment, a reflection type reflection diffraction grating 76 is used, and the reflection type diffraction grating 76 itself reflects light. Therefore, the number of times the optical path is bent is less than in the first embodiment, and the delay speed is inferior to that in the first embodiment. However, since it is not necessary to provide a plane mirror and the number of parts can be reduced as compared with the first embodiment, the second embodiment is more advantageous in terms of downsizing the entire apparatus. In the second embodiment, the example in which the reflection type diffraction grating 76 reflects light has been described. However, the present invention is not limited to the reflection type diffraction grating 76, and the incident light travels along the same path as that path. A reflection type diffraction grating 76 can be used as long as it is a member that reflects light (for example, a mirror array).

  As described above, in each of the above-described embodiments, by providing a diffraction grating and a rotating mirror, and rotating the rotating mirror to change the length of the optical path, it is possible to perform a delay at a high speed compared to a conventional delay line, Further, since a mechanism for sweeping parts is not necessary, the apparatus can be reduced in size.

  In each of the above-described embodiments, the example in which the optical path length adjusting unit 60 or 70 according to the present invention is applied to an optical system of a 193 nm solid-state laser has been described. However, the application range of the present invention is limited to this. In other words, the present invention can be applied to all optical systems using an optical delay line.

La ₁ 1st pulse light La ₂ 2nd pulse light 1 Laser apparatus 10 Pulse light generation part 20 Optical amplification part 30 Wavelength conversion part 60 Optical path length adjustment part (1st Embodiment) 64 Rotating mirror (1st Embodiment)
65 Second lens (lens, first embodiment)
66 Transmission diffraction grating 67 Plane mirror (mirror)
69 Mirror rotating unit (first embodiment) 70 Optical path length adjusting unit (second embodiment)
74 Rotating mirror (second embodiment)
75 Second lens (lens, second embodiment)
76 Reflective diffraction grating 79 Mirror rotating part (second embodiment)

Claims (3)

A pulsed light generator for generating pulsed light;
An optical amplification unit that divides the pulsed light into a first pulsed light and a second pulsed light, and amplifies each of the divided lights;
The first pulsed light and the second pulsed light amplified by the optical amplification unit are superimposed on the same axis and incident on a wavelength conversion optical element to generate light having a wavelength different from that of the first pulsed light and the second pulsed light. A wavelength converter to be
An optical path length adjustment unit that adjusts an optical path length of any one of the light beams provided at a position where either the first pulsed light or the second pulsed light passes in the optical amplification unit;
The optical path length adjusting unit is
It has a reflecting surface on which any one of the light is incident, and is supported so as to be rotatable in a direction perpendicular to the optical axis of the light. The light is incident on the reflecting surface and reflected in a direction different from the incident direction. And with a rotating mirror to be ejected,
A mirror rotating unit that rotates the rotating mirror in a direction perpendicular to the optical axis;
A lens that converts light emitted by the rotating mirror into parallel light and transmits the parallel light;
The reflective surface is provided so as to face different directions with respect to the optical axis of the parallel light transmitted through the lens and extends in a direction perpendicular to the optical axis, and the parallel light transmitted through the lens is reflected on the reflective surface. And a light reflecting section that reflects and emits the light so as to travel in the opposite direction along the same optical path as that of the parallel light.   The light reflecting portion transmits the parallel light transmitted through the lens and emits it in a different direction, and the light transmitted through the transmissive diffraction grating travels in the same optical path as the light in the opposite direction. The laser apparatus according to claim 1, further comprising a mirror that reflects the light.   The light reflecting portion is a reflection type diffraction grating having a large number of concave and convex surfaces, and reflects the parallel light transmitted through the lens so that the parallel light enters the concave and convex surface and travels in the same direction as the optical path of the parallel light in the opposite direction. The laser device according to claim 1, wherein the laser device is emitted.

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