JPH11233867A - Pulse laser light generator - Google Patents

Abstract

(57) [Summary] To provide a pulse laser light generator capable of achieving a higher output with a shorter switching time while taking advantage of an AO-Q switch. In a conventional laser resonator including a semiconductor laser 1, an excitation optical system 2, a laser crystal 3, an AO-Q switch 4, and a laser output mirror 5, a Q switch is performed without changing a beam diameter in the laser crystal 3. In order to reduce only the beam diameter of the laser light inside 4, a pair of convex lens 9 and concave lens 10 are arranged between the laser crystal 3 and the Q switch 4 and between the Q switch 4 and the laser output mirror 5, respectively. I do.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse laser light generator.

[0002]

2. Description of the Related Art Conventionally, a Q switch has been used as an optical element for generating pulsed light in a pulsed laser light generator having a pulse time width of several ns to several tens of ns. This temporarily stops increasing the internal loss inside the laser resonator, thereby stopping the laser oscillation and growing the population inversion. Then, by rapidly reducing the internal loss of the laser resonator, the laser light is rapidly oscillated and energy stored in the laser medium is extracted as pulsed light.

There are roughly two types of Q switches. One is an AO-Q switch using an acousto-optic effect and an EO-Q switch using an electro-optic effect.

The AO-Q switch generates an ultrasonic wave in a material such as glass inserted into the laser resonator in a direction substantially perpendicular to the circulating light inside the resonator, thereby causing Bragg scattering. As a result, the circulating light inside the laser resonator cannot reciprocate, the laser oscillation is temporarily stopped, and the population inversion in the laser medium is accumulated. By instantaneously turning off the ultrasonic waves, pulsed laser oscillation is realized.

[0005] Ultrasonic waves are generated by attaching a piezo element to a material such as glass and applying an RF signal of about several tens Mhz thereto. The scattering efficiency by ultrasound is
Although the RF power is at most about 40%, it is enough to stop laser oscillation.

As a feature of the AO-Q switch, the device is simple and can oscillate pulses at repetition of several tens to several hundreds kHz. Also, the economic cost is low.

However, the switching time for turning on and off the AO-Q switch greatly depends on the time for the ultrasonic wave to cross the circulating light inside the resonator in the Q switch medium, and is about 54 ns at a laser beam diameter of 500 μm and a sound speed of 6000 m / s. turn into. In this specification, "beam diameter" indicates a beam diameter or a beam width in a designated direction unless otherwise specified. Since the pulse oscillation timing is advanced in the laser oscillator having a large gain, the laser oscillation occurs before the ultrasonic wave inside the Q switch completely disappears and the internal loss of the resonator becomes sufficiently small. Therefore, there is a disadvantage that the laser output is reduced due to the remaining internal loss.

In order to solve the disadvantage that the switching time is slow, a measure to reduce all the beam diameters inside the laser resonator can be considered. Then, Q
Although the beam diameter inside the switch can be reduced, the beam diameter in the laser medium also decreases at the same time. Considering the end-pumping method using the light of the semiconductor laser, the spot diameter of the excitation light is limited. Therefore, if the laser beam diameter is reduced to a certain degree or more, the pumping efficiency is reduced. Even if it is possible to reduce only the beam diameter while maintaining the pumping efficiency, the laser beam gain increases, so that the oscillation timing of the pulsed light is advanced, thereby canceling the effect.

On the other hand, the EO-Q switch is made of a crystal that causes an electro-optic effect, and plays a role of a quarter-wave plate or a half-wave plate by applying a voltage to the crystal. Inside the laser resonator, there is a polarizer such as a polarizing plate or a Brewster-cut laser crystal in addition to the EO-Q switch. For example, an EO-Q switch crystal
Consider a case where a quarter-wave plate plays a role in a state where a voltage is applied. Usually, when no voltage is applied to the EO-Q switch crystal, the polarized internal circulating light reciprocates.
The EO-Q switch crystal is arranged so that the polarization direction of the internal circulating light that has reciprocated once inside the laser resonator is rotated by 90 degrees when a voltage is applied. Then, the feedback in the laser medium is not applied, and the laser oscillation stops.
Therefore, the function of the Q switch is realized by turning on and off the voltage applied to the crystal.

The characteristic of the EO-Q switch is that the switching time of the Q switch does not depend on the size of the beam diameter inside the Q switch, and is very high, about several ns. However, it is necessary to use a high on-off voltage of about 1 kV for this drive, and it is not often used for a high repetition laser, for example, a laser of about several tens to several hundreds kHz. It is also very difficult to reduce the size of the Q switch because a certain crystal size is required to generate the necessary electro-optic effect. Therefore, the EO-Q switch has been mainly used for a high-output and large-sized pulse laser device.

[0011]

The AO-Q switch used in the conventional pulse laser device has a high repetition rate of several tens of kHz to several hundreds of kHz, is small in size, has a low economic cost, and has an EO-switch. There is an advantage that a high voltage is not required unlike the Q switch. However, the switching time is as slow as several tens of ns, and the output of the high-gain laser is reduced.

The present invention realizes a laser resonator capable of providing a higher output than conventional ones by shortening the switching time while utilizing the advantages of the above-described AO-Q switch, and a pulsed laser light generator including the same. The purpose is to:

[0013]

In order to achieve the above object, according to a first aspect of the present invention, there are provided two reflecting surfaces, a laser medium disposed between the two reflecting surfaces, and acousto-optic by ultrasonic waves. A pulse laser generator having at least a Q switch utilizing the effect, and a beam for reducing the laser beam diameter in the propagation direction of the ultrasonic wave propagating inside the Q switch inside the Q switch inside the laser medium. Conversion means.

In the present invention, since the diameter of the laser beam in the traveling direction of the ultrasonic wave at least inside the Q switch only needs to be reduced, the laser beam diameter in all directions other than the traveling direction of the ultrasonic wave may be reduced at the same time. Absent.

Further, the beam converting means in the present invention comprises:
An optical system for reducing the diameter of the laser beam emitted from the laser medium may be obtained by providing between the two reflection surfaces of the pulsed laser generator, using a spherical or aspherical lens, or a cylindrical lens as the optical system. May be configured.

In addition, at least one of the two reflecting surfaces or at least one of the end surfaces of the members provided between the two reflecting surfaces is used as a beam converting means in the present invention. May be formed so as to be reduced, and their surface shape may be a spherical shape, an aspherical shape, or a shape such as a cylindrical lens.

In addition to the above, as a beam converting means in the present invention, at least one of two reflecting surfaces or at least one of end surfaces of members provided between the two reflecting surfaces has a laser beam diameter. An optical system formed so as to be reduced and configured to reduce the diameter of a beam emitted from the laser medium between the two reflecting surfaces may be used.

According to such a configuration, in the laser resonator between the two reflecting surfaces, the beam diameter of the laser light in the Q switch is reduced without changing the beam diameter in the laser medium. , The switching time of the AO-Q switch can be made faster than before, and a laser beam with a larger output can be obtained.

Further, a wavelength conversion means is added to the pulse laser light generator of the present invention to constitute a laser element, and a plurality of the laser elements are bundled to generate an ultraviolet pulse laser light capable of generating an ultraviolet pulse laser light. The device may be configured.

Further, in the projection exposure apparatus, the ultraviolet pulse laser light generator may be used as a light source.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a laser light generator according to an embodiment of the present invention will be described.

In this embodiment, a solid-state laser of an end face pumping type using a semiconductor laser will be described as an example. As shown in FIG. 2, the laser resonator of this embodiment includes a semiconductor laser 1 for excitation, an excitation optical system 2, a solid-state laser crystal 3, a convex lens 9,
It comprises a concave lens 10, an AO-Q switch 4, a concave lens 10, a convex lens 9, and a laser output mirror 5.

The laser resonator according to the present embodiment has a configuration in which the solid-state laser crystal 3 and the AO-Q switch 4 are internally provided, and the laser resonator is parallel to the traveling direction of the ultrasonic wave in the AO-Q switch 4. The laser beam diameter in the substantially parallel direction is AO-Q
In order to convert the shape of the laser beam so as to reduce the size inside the switch 4, a beam converting means including a convex lens 9 and a concave lens 10 is provided.

In this embodiment, as shown in FIG. 2, the beam converting means comprises a pair of convex lens 9 and concave lens 1.
0 between the laser crystal 3 and the AO-Q switch 4 and A
This is realized by disposing each between the OQ switch 4 and the laser output mirror 5. The shape and the number of optical elements for realizing the beam converting means according to the present invention are not limited to the example shown in FIG. 2, but may be, for example, a configuration realized by an optical system including one refractive optical element or diffractive optical element. Is also good.

As a comparative example of this embodiment, a laser light generator not having the features of the present invention will be described. A specific configuration example of the laser resonator of the comparative example will be described below.

FIG. 1 shows the configuration of a laser resonator in a comparative example. In FIG. 1, 3 is a solid-state laser crystal Nd:
Oscillation wavelength of about 1064 n with YVO ₄ (Nd concentration about 1%)
m, the thickness in the optical axis direction is 2 mm. Reference numeral 1 denotes a semiconductor laser for excitation, which is made of GaAlAs and has a center wavelength of 809 nm in accordance with the absorption of the solid-state laser crystal 3. The light-emitting surface is asymmetric and 500 μm × 1 μm. Reference numeral 2 denotes an excitation optical system including a spherical lens, a cylindrical lens, and the like. The excitation optical system 2 has a function of efficiently shaping the excitation light 6 from the semiconductor laser 1 into a circular shape and condensing it inside the laser crystal 3.

The end face 31 of the laser crystal 3 is coated so as to transmit the excitation light at a wavelength of 809 nm and reflect 100% of the laser light at 1064 nm. The other end face 32 has a wavelength of 1064 nm.
AR (Anti Reflection) coating is applied to this light.

Reference numeral 5 denotes a concave mirror having a radius of curvature of 1 m.
The end face 51 is provided with a partially reflective coating having a reflectivity of 70%, and the distance between the face 51 and the laser crystal end face 31 is 60 mm apart. The laser light circulates inside the resonator, and a part thereof is output as laser light 8.

Reference numeral 4 in the drawing denotes an AO-Q switch, and its thickness in the optical axis direction is 20 mm. The AO-Q switch 4 is located at the center of the laser resonator, so that the distance between the laser output mirror end face 51 and the AO-Q switch end face 42 is 20 mm. The material is fused quartz and the end faces 41, 4
2 has an AR for a laser beam having a wavelength of 1064 nm.
Coated. The AO-Q switch 4
This is a member for scattering the circulating light 7 inside the laser resonator to increase the internal loss of the laser resonator, or to transmit the laser light as it is to reduce the internal loss of the laser resonator. This A
The Q-switch pulse oscillation is realized by the change in the internal loss of the laser resonator given by the O-Q switch 4. The frequency of RF applied to the fused quartz is 80 MHz.

The radius of the beam in the laser cavity is given by ABC
It is obtained by solving the D matrix. Assuming that the mode inside the laser cavity is Gaussian of TEM00, the beam radii at the Q-switch end faces 41 and 42 are 276
μm, 278 μm, and the beam radius is almost equal to the end face inside the AO-Q switch 4. The beam radius at the end face 31 of the solid-state laser crystal is 275 μm, which also serves as a beam waist inside the resonator.

The switching time tr of the AO-Q switch
Is generally obtained by the following equation (1).

Tr = 1.3d / 2v (Equation 1) where d is the diameter of the laser beam, and v is the speed of the ultrasonic wave in the fused quartz at 5960 m / s. is there. Therefore,
The beam diameter at the Q switch 4 is 554 μm (= the end face 41,
By substituting the radius average value at 42 × 2) into Equation 1, the switching time is about 60 ns.

According to the above formula 1, if the beam diameter at the Q switch 4 is reduced, the switching time can be shortened. For example, in the case of FIG. 1, it is possible to reduce the radius of curvature of the output mirror. In addition,
In this specification, the term “beam diameter” refers to a beam diameter or a beam width in a specified direction unless otherwise specified.

However, since it is impossible to reduce the spot radius of the semiconductor laser 1 by about 250 μm or more without significantly reducing the pumping power, there is a limit to reducing the laser beam diameter further.

Further, even if the spot diameter of the semiconductor laser can be reduced without losing the pump power, the gain of the laser increases because the pumping light density is improved, and as a result, the pulse oscillation timing is reduced. Be faster. Therefore, oscillation occurs when the internal loss of the resonator remains. Therefore, even if the switching time is shortened, the effect is offset.

The present invention has been made in view of the above points, and in one embodiment, is provided with a laser resonator having a configuration as shown in FIG. In the laser resonator of the present embodiment shown in FIG. 2, the semiconductor laser for excitation 1, the excitation optical system 2, and the excitation light 6 are the same as those in FIG.

The solid-state laser crystal 3 and the AO-Q switch 4 are substantially the same as those in FIG. However, the end face 31 of the solid-state laser crystal 3 is subjected to a convex processing with a radius of curvature of 1.21 m. Reference numeral 5 denotes a laser output mirror having a radius of curvature of 1.21 m. Coatings similar to those in FIG. 1 are applied to the laser crystal end faces 31 and 32 and the laser output mirror end face 51. The distance between the laser crystal end face 31 and the laser output mirror end face 51 is 60 mm, thereby forming a laser resonator. AO-Q switch 4
Is similar to FIG. 1 and is located at the center of the laser resonator.

Further, the thin convex lens 9 in FIG. 2 has a focal length of 20 mm, and the thin concave lens 10 has a focal length of 10 mm. The distance from the Q switch end faces 41 and 42 to the convex lens 9 is about 5 mm, and the distance between the convex lens 9 and the thin concave lens 10 is about 10 mm.

Let the radius of the laser beam in the laser resonator be A
By solving the BCD matrix, the end face 4 through which light passes from the solid-state laser crystal 3 in the AO-Q switch 4 is obtained.
The beam radius at 1, 42 is 130 μm. The beam radius at the end face 31 of the solid-state laser crystal is 257 μm, which is the same as in the comparative example of FIG.

FIG. 3 shows the profile of the beam diameter inside the resonator according to the present embodiment. The vertical line in the figure corresponds to the optical element or the end face of the optical element in FIG. Further, the beam diameter in the figure is plotted larger than the scale on the horizontal axis. As in the resonator of the comparative example, the beam diameter is almost equal between the inside of the Q switch and the end faces 41 and 42,
There is no problem if the beam diameter at the switch 4 is represented by the beam diameter at the end face.

According to such a resonator configuration, the beam diameter inside the laser crystal 3 and the overall length of the resonator are not changed.
The beam diameter inside the Q switch 4 can be reduced to about half of the beam diameter inside the laser crystal 3.

In this embodiment, since the same beam diameter as that of the laser resonator of the comparative example is realized inside the laser crystal 3, there is no change in the pulse oscillation timing. Further, the pulse time width of the pulse laser also depends on the resonator length of the laser resonator, but in the present embodiment, the same pulse time width as that of a conventional resonator can be realized because the resonator length does not change. .

Next, the effect when the switching time of the Q switch by the pulse laser light generator of the present embodiment is reduced to about half that of the comparative example will be described with reference to FIG.

FIG. 4 is a graph plotting the change over time in the internal loss of the laser in the laser resonator according to the present embodiment and the laser resonator in the comparative example. Here, the horizontal axis of the graph is time, and the vertical axis is the internal loss of the resonator. The time origin is the time when the switching of the AO-Q switch 4 is started, and the pulse oscillation timing is 30 ns after the start of the switching, although it depends on the gain of the laser and the like. In addition to the scattering by the AO-Q switch 4, the scattering inside the resonator and the loss in the laser crystal can be considered as the internal loss of the resonator, but it is ignored because it is smaller than the scattering by the AO-Q switch 4. I do.

As shown in FIG. 4, the change in the scattering efficiency of the AO-Q switch 4 can be approximated to be almost linear. For this reason, in the laser resonator of the comparative example, even when pulse oscillation occurs when the internal loss is 20%, oscillation occurs when the internal loss becomes almost zero according to the present embodiment.

As described above, the internal loss of the resonator at the time of pulsed laser oscillation was caused by the ultrasonic waves remaining in the AO-Q switch 4 even after the ultrasonic source was stopped. Is reduced in the propagation direction of the ultrasonic wave, so that the time during which the internal loss of the resonator changes (for example, FIG.
The time required for the internal loss of the resonator to become zero as shown by (2) is shortened, and the output of the pulse laser light oscillating with respect to the output of the pump light can be increased. Further, even if the pulse oscillation timing is earlier than that in the present embodiment, the pulse oscillation occurs when the internal loss is one half of that in the laser resonator of the comparative example, so that the effect of improving the output power exists. .

The present invention is also realized by other embodiments as described below.

For example, in the embodiment of FIG. 2, instead of processing the end face 31 of the solid-state laser crystal 3 by a lens,
A concave mirror having the same radius of curvature as the laser output mirror 5 and having the same coating as the solid-state laser crystal end face 31 may be provided. At this time, both end faces of the laser crystal 3 are flat, and an AR coating is applied to light having a wavelength of 1064 nm. With such a configuration, as in the embodiment of FIG. 2, only the beam diameter inside the AO-Q switch 4 can be reduced, and the same effect can be expected.

In the embodiment of FIG. 2, the thin convex lens 9 and the thin concave lens 10 inserted into the resonator may be replaced with a thin convex cylindrical lens and a thin concave cylindrical lens, respectively. AO-
Ultrasonic waves inside the Q-switch travel only in one direction perpendicular to the optical axis. Therefore, if only the beam diameter in this direction is reduced, the same effect as the embodiment of FIG. 2 can be expected.

In the embodiment shown in FIG. 2, instead of processing the end face 31 of the solid-state laser crystal 3 into a lens, the end face 31 of the solid-state laser crystal 3 has the same radius of curvature as that of the laser output mirror 5, and has the same coating concave face as the solid-state laser crystal end face 31. A mirror is arranged, and both end faces of the solid-state laser crystal 3 are flat, and the concave mirror is coated with an AR coating for light having a wavelength of 1064 nm. Further, instead of the thin convex lens 9, the curvature of the laser crystal end face 32 and the curvature of both end faces of the laser output mirror 5 are respectively changed to provide a lens function. In addition, instead of the thin concave lens 10, the end face 41 of the AO-Q switch 4,
The curvature of the end surface of each may be changed so as to have a lens function. Also, only some of these may be implemented. With such a configuration, similarly to the embodiment of FIG. 2, only the beam diameter inside the Q switch can be reduced, and the same effect can be expected. And
The loss inside the resonator is smaller than when a lens is inserted, and an improvement in power can be expected.

Further, in the above-described embodiment in which the end surface of the optical element has a lens function, the thin convex cylindrical lens processing is performed so as to replace the lens function of the thin convex lens 9 and the thin concave lens 10 inserted inside the resonator. , Thin concave cylindrical lens processing, laser crystal end face 32, laser output mirror end face, Q switch end face 4
It may be configured to apply to the end faces of 1, 42 respectively.
Also, only some of these may be implemented.

Next, one embodiment of a pulsed laser light generating apparatus having the laser resonator of the present invention will be described with reference to FIG.

The pulse laser light generator of this embodiment is
As shown in FIG. 5, it is composed of a total of 100 laser elements of 10 × 10. Each laser element has a laser light generating unit 1 for generating long-wavelength light of visible light or infrared light.
00 and a wavelength converter 104 for converting the generated laser light into ultraviolet light.

The laser light generator 100 includes a semiconductor laser 101 for excitation, an optical fiber 102, a solid laser medium 3, a convex lens 9, a concave lens 10, and an AO-Q shown in FIG.
A laser resonator 103 including a switch 4 and a laser output mirror 5 is provided.

The wavelength conversion unit 104 includes a nonlinear optical crystal for converting a wavelength, for example, a nonlinear optical crystal for converting to a second harmonic and a nonlinear optical crystal for converting to a fourth harmonic.

The cross-sectional dimension of each laser element except for the semiconductor laser 101 is, for example, about 5 mm × 5 mm. Further, here, a configuration in which 100 laser elements are combined is taken as an example, but the number of laser elements is not limited to this.

In this embodiment, the excitation light from the semiconductor laser 101 is transmitted through the optical fiber 102 to the laser resonator 1.
03, and excites the laser crystal 3 (see FIG. 2).
Note that, instead of using the optical fiber 102, the light may be condensed by the excitation optical system 2 and guided to the laser resonator 103 as in the embodiment of FIG. 2 described above.

The laser resonator 103 has a built-in Q switch 4 based on the acousto-optic effect, and has a wavelength of 1064 nm.
Of pulsed light. Since the pulsed light output from the laser resonator 103 has a large peak output, highly efficient wavelength conversion is performed.

Assuming that the fundamental wave emitted from the laser resonator 103 is 1064 nm, the first nonlinear optical crystal (for example, KTP: chemical formula KTiOPO ₄ ) has a wavelength of 532 nm.
And a second nonlinear optical crystal (eg, BB
O: chemical formula BaB ₂ O ₄ ), which is converted into a fourth harmonic of 266 nm ultraviolet light. Further, the BBO crystal generates a sum frequency of a fundamental wave and a fourth harmonic, and can generate 213 nm ultraviolet light. In addition, the wavelength of the fundamental wave emitted from the laser resonator is set to 772 nm, and the first nonlinear optical crystal (for example, LBO: chemical formula LiB ₃ O ₅ ) has a wavelength of 386 nm.
Alternatively, the second nonlinear optical crystal (for example, SBBO: chemical formula Sr ₂ Be ₂ B ₂ O ₇ ) may convert the light into a 193 nm ultraviolet light of the fourth harmonic. In order to further increase the wavelength conversion efficiency, a condensing lens may be provided to condense laser light and then pass the light through the nonlinear optical crystal.

According to the configuration of the present embodiment, by bundling a plurality of laser elements having the above-described configuration, it is possible to add light outputs to achieve high output, and to output light from independent laser elements. Thus, temporal and spatial coherence can be reduced, and the wavelength band can be narrowed by controlling each laser element.

Further, by bundling a plurality of laser elements, it is not necessary to increase the output from each laser element.
For this reason, by reducing the load on the nonlinear optical crystal of the wavelength conversion unit 104, the deterioration can be minimized, and the life of the device can be prolonged. Further, since each laser element is provided independently so as to be exchangeable, only the deteriorated laser element can be exchanged. In this way, maintenance becomes easier.

Next, an embodiment of a projection exposure apparatus using the pulse laser beam generator of the embodiment shown in FIG. 5 as a light source will be described with reference to FIG.

As shown in FIG. 6, the projection exposure apparatus according to the present embodiment comprises a laser light source 61 comprising a pulse laser light generator capable of generating the ultraviolet pulse laser light shown in FIG. A rotating diffuser 62 for diffusing the light emitted from 61, a reflector 64 for irradiating the light from the laser light source 61 to a lower fly-eye lens (or integrator lens) 65, and a fly-eye lens 65. An illumination lens system 66, a mask support 671 for placing a mask 67 on which an exposure pattern is drawn, and an objective lens for imaging the pattern drawn on the mask 67 on a semiconductor substrate (or wafer) 691 68 and a moving stage 692 for mounting the substrate 691. Then, the rotating diffusion plate 62
Can be rotated by a diffuser rotating device (not shown). The moving stage 692 includes a moving stage support 693 for supporting the moving stage 692, a stage driving unit 695 for driving the moving stage,
It can be moved by a transmission member 694 for transmitting the power generated by the stage driving section 695 to the moving stage support section 693.

In this projection exposure apparatus, a beam emitted from a laser light source 61 is applied to a rotating diffusion plate 62 to diffuse the beam. When the diffuser rotates and the beam position on the diffuser changes, the intensity distribution and phase distribution of the diffused light change. As a result, speckles generated during irradiation of the mask pattern are constantly changed and averaged during the exposure time, thereby causing an adverse effect of speckles (illuminance unevenness).
Is removed. The number of the diffusion plates may be two in order to completely remove speckles. In that case, one may be a fixed diffusion plate. Both may be moved in different directions.

The diffused light is made into a substantially parallel beam state by the lens 63 and then enters the fly-eye lens 65.
In the fly-eye lens 65, the beam intensity is made uniform, and a mask (or reticle) 67 is illuminated by an illumination lens system 66 including a plurality of lenses.

The illuminated circuit pattern on the mask 67 is reduced and projected by a projection lens 68 onto a semiconductor substrate (or wafer) 691 at a predetermined magnification (1 to 1/5). The substrate 691 is placed on a moving stage 692, and by providing a moving mechanism for moving the mask 67 to the mask supporting portion 671 by step-and-repeat by moving the stage, and moving in synchronization with the mask. Scan exposure is performed.

According to the projection exposure apparatus of the present embodiment,
Since gas exchange and window exchange, which are required in the excimer laser, are not required, throughput in semiconductor manufacturing can be improved. In addition, the light source itself further increases the output of the laser light emitted from each laser element as described above, so that the exposure time to the wafer can be shortened. This also improves the throughput in semiconductor manufacturing.

[0068]

As described above, according to the present invention,
Even with the AO-Q switch, higher-speed switching than before can be performed, and a high-output pulsed laser light output can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an example of a pulse laser resonator using an AO-Q switch according to the related art.

FIG. 2 is an explanatory diagram showing a configuration of an embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating a configuration of a main part of the embodiment of FIG. 2;

FIG. 4 is an explanatory diagram showing the relationship between internal loss and time for explaining the effect of the present invention.

FIG. 5 is a perspective view showing a configuration of an embodiment of an ultraviolet laser light source according to the present invention.

FIG. 6 is an explanatory diagram showing a configuration of an embodiment of a projection exposure apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 2 ... Excitation optical system, 3 ... Laser crystal Nd: YVO4 (Nd concentration about 1%), 31, 32 ... Laser crystal end face, 4 ... AO-Q switch, 41, 42 ... Q switch end face, 5 ... Laser output mirror, 51 ... Laser output mirror end face, 6 ... Excitation light (wavelength 809 nm), 7 ... Laser cavity internal circulation light (wavelength 1064 nm), 8 ... Laser light (wavelength 1064 nm), 9 ... Thin convex lens, 10 ... Thin wall concave lens.

Claims (8)

[Claims] A pulse laser generator including at least two reflecting surfaces and a Q switch utilizing an acousto-optic effect of a laser medium and ultrasonic waves disposed between the two reflecting surfaces; and the Q switch. A pulsed laser light generator, comprising: a beam converting means for reducing a laser beam diameter in a propagation direction of an ultrasonic wave propagating inside the Q switch inside the laser medium as compared with the inside of the laser medium. 2. An optical system for reducing a diameter of the laser beam emitted from the laser medium.
The pulse laser light generator according to claim 1, wherein the pulse laser light generator is provided between two reflection surfaces of the pulse laser generator. 3. The pulse laser beam generator according to claim 2, wherein said optical system is constituted by using a spherical or aspherical lens. 4. The pulse laser light generator according to claim 2, wherein said optical system is constituted by using a cylindrical lens. 5. The beam conversion means according to claim 1, wherein at least one of the two reflecting surfaces or at least one of the end surfaces of the members provided between the two reflecting surfaces has the laser beam diameter. The pulse laser light generator according to claim 1, wherein the pulse laser light generator is formed so as to be reduced. 6. A surface of at least one of the two reflecting surfaces,
6. The pulse laser light generator according to claim 5, wherein at least one of the end faces of the member provided between the two reflection surfaces has a spherical or aspherical shape. 7. At least one of the two reflecting surfaces,
6. The pulse laser beam generator according to claim 5, wherein at least one of the end faces of the member provided between the two reflecting surfaces has a shape similar to a cylindrical lens. 8. The beam conversion means according to claim 1, wherein at least one of said two reflection surfaces or at least one of end surfaces of members provided between said two reflection surfaces reduces said laser beam diameter. 2. The pulse laser light generator according to claim 1, further comprising an optical system formed to reduce the diameter of a beam emitted from the laser medium between the two reflecting surfaces.