JPH1117255A - Semiconductor excitation solid-state laser device and infrared laser device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor excitation solid-state laser device, in which the light excitation of the edge face of a solid laser medium can be efficiently attained by using a wide area semiconductor laser. SOLUTION: Beams from a semiconductor laser 1 having plural light emitting parts arranged with intervals along a prescribed direction are condensed through excitation optical systems 2-5 on the edge face of a solid laser medium 7, and laser excitation is operated by the light excitation of the solid laser medium 7. In this case, the excitation optical systems 2-5 are provided with a diffraction optical element 4 for dividing the beams from the plural light emitting parts of the semiconductor laser into plural beams, whose diffraction order is different along a direction optically corresponding to a prescribed direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser-excited solid-state laser device and an ultraviolet laser device using the same, and in particular, to excite an end face of a solid-state laser medium by a beam from a wide-area semiconductor laser having a plurality of light-emitting portions. The present invention relates to a semiconductor laser-excited solid-state laser device that oscillates laser light.

[0002]

2. Description of the Related Art In a semiconductor laser-excited solid-state laser device that excites an end face of a solid-state laser medium with a beam from a semiconductor laser, a semiconductor laser is driven through an excitation optical system including a spherical lens and a cylindrical lens in order to increase the excitation efficiency. A method of shaping a beam from a laser into a predetermined cross-sectional shape according to the mode shape of the solid-state laser resonator is used.
In this type of semiconductor laser-pumped solid-state laser device,
As an excitation semiconductor laser, a wide-area semiconductor laser capable of obtaining a high output is used, and this wide-area semiconductor laser has a plurality of light emitting units arranged at intervals. For example, in the case of a wide-area semiconductor laser having an output of 1 W to 5 W, its light emitting surface is formed by two to four elongated strip-shaped light emitting parts arranged in a line at intervals of several tens of μm along a predetermined direction. It is configured.

[0003]

In a conventional semiconductor laser-pumped solid-state laser device using a wide-area semiconductor laser configured as described above, the end face of the solid-state laser medium has two ends corresponding to the light-emitting surface of the semiconductor laser. One to four excitation light regions are formed in a line, and the intensity distribution of each excitation light region corresponds to the intensity distribution of each light emitting portion of the semiconductor laser. As a result, near the light intensity peak in each pumping light region, the pumping light density becomes too high to cause absorption saturation of the pumping light, and the absorption of the pumping light of the solid-state laser medium is reduced, so that the pumping efficiency is reduced. When a three-level solid-state laser medium is used, oscillation laser light is absorbed by the solid-state laser medium in a region where the excitation light intensity is low, such as a peripheral portion of each excitation light region, and the excitation efficiency is reduced.

A so-called fiber coupling method is known in which a beam from a semiconductor laser is focused on an end face of a solid-state laser medium via an optical fiber in a shape close to a Gaussian distribution. However, in the fiber coupling method, there is light loss in coupling from the semiconductor laser to the fiber, so that the improvement in the pumping efficiency is limited. In addition, coupling from a semiconductor laser to a fiber requires a complicated manufacturing process and is therefore expensive.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a semiconductor laser-pumped solid-state laser device that can efficiently pump an end face of a solid-state laser medium using a wide-area semiconductor laser. Aim. It is another object of the present invention to provide an ultraviolet laser device using the semiconductor laser-excited solid-state laser device of the present invention and having, for example, a sufficient output and low coherence as a light source of a semiconductor exposure device.

[0006]

In order to solve the above-mentioned problems, according to the present invention, there is provided an excitation optical system for exciting a beam from a semiconductor laser having a plurality of light-emitting portions arranged at intervals along a predetermined direction. Through the solid state laser medium,
In a semiconductor laser-pumped solid-state laser device that oscillates by optically pumping the solid-state laser medium, the pumping optical system transmits beams from a plurality of light emitting units of the semiconductor laser along a direction optically corresponding to the predetermined direction. A semiconductor laser-excited solid-state laser device having a diffractive optical element for splitting the beam into a plurality of beams having different diffraction orders.

According to a preferred aspect of the present invention, the excitation optical system includes a shaping optical system for shaping beams from a plurality of light emitting portions of the semiconductor laser into a parallel beam having a predetermined sectional shape as a whole. A phase grating for splitting the beam having passed through the shaping optical system into a plurality of beams having different diffraction orders, and a focusing optical system for collecting beams of each diffraction order split via the phase grating And Alternatively, the pumping optical system shapes the beams from the plurality of light emitting portions of the semiconductor laser as a whole into a beam having a predetermined cross-sectional shape, and collects the beams at a predetermined convergence angle toward the end face of the solid-state laser medium. And a phase grating for splitting a beam passing through the shaped condensing optical system into a plurality of beams having different diffraction orders.

According to another aspect of the present invention, there is provided a semiconductor laser-excited solid-state laser device according to the present invention, and a wavelength conversion device for converting the oscillation light from the semiconductor laser-excited solid-state laser device into ultraviolet light. Provided by arranging a plurality of laser units each having a plurality of laser units in parallel.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, a beam from a plurality of light emitting portions of a wide area semiconductor laser is diffracted along a predetermined direction by the action of a diffractive optical element such as a phase grating provided in an excitation optical system. The beam is divided into a plurality of beams of different orders. Therefore, the beam of each diffraction order diffracted along the predetermined direction by the phase grating reaches the end face of the solid-state laser medium along an optical path different from the zero-order light, and a predetermined amount of light from the excitation light region formed by the zero-order light. An excitation light region that is displaced along the direction is formed. Therefore, the maximum value of the excitation light intensity distribution of the present invention formed on the end face of the solid-state laser medium under the action of the phase grating is larger than the maximum value of the conventional excitation light intensity distribution formed without the action of the phase grating. Is substantially smaller, and the minimum value of the excitation light intensity distribution of the present invention is substantially larger than the minimum value of the conventional excitation light intensity distribution.

As described above, due to the action of the phase grating provided in the excitation optical system, the maximum value of the excitation light intensity distribution of the present invention is substantially smaller than the maximum value of the conventional excitation light intensity distribution. The minimum value of the excitation light intensity distribution of the present invention is substantially larger than the minimum value of the conventional excitation light intensity distribution. Therefore, in the present invention, it is possible to avoid a decrease in excitation efficiency due to absorption saturation due to a high peak light intensity seen in the conventional excitation light intensity distribution. In addition, even when a three-level solid-state laser medium is used, it is possible to avoid a decrease in pumping efficiency due to absorption of laser light at a valley of pumping light intensity, which is observed in a conventional pumping light intensity distribution. . As a result, in the present invention, a solid-state laser medium can be efficiently excited in a semiconductor laser-excited solid-state laser device using a wide-area semiconductor laser.

An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a view schematically showing a configuration of a semiconductor laser pumped solid-state laser device according to a first embodiment of the present invention. In FIG. 1, the z-axis is set in parallel with the optical axis AX of the excitation optical system of the apparatus, the x-axis is set in parallel with the plane of FIG. 1 in the plane perpendicular to the z-axis, and the y-axis is set perpendicular to the plane of FIG. I have.

The apparatus shown in FIG. 1 includes, as a pumping semiconductor laser (laser diode), a wide-area semiconductor laser 1 having four light-emitting portions arranged at intervals in the x direction. The laser beam emitted from the light emitting portion of the wide area semiconductor laser 1 has a fiber lens (or rod lens) 2 having a positive refractive power in the y direction and a non-refractive power in the x direction and a positive refractive power in the x direction in the y direction. A shaping optical system (2, comprising a cylindrical lens 3 having no refracting power)
3). Thus, the laser beam from the wide area semiconductor laser 1 is shaped into a parallel beam having a cross-sectional shape corresponding to the mode shape of the solid-state laser resonator described later by the operation of the shaping optical systems (2, 3).

The parallel beam shaped into a predetermined cross-sectional shape through the shaping optical system (2, 3) is passed through a phase grating 4 as a diffractive optical element to form a plurality of beams having different diffraction orders along the x direction. Is divided into The beams of the respective diffraction orders split via the phase grating 4 are condensed via a spherical lens 5 having a positive refractive power, and are focused on an end face 7 a of a laser crystal (solid laser medium) 7 in the solid laser resonator 6. Reach. As described above, the shaping optical system (2, 3), the phase grating 4, and the spherical lens 5 as a condensing optical system condense the beam from the wide area semiconductor laser 1 on the end face 7a of the laser crystal 7. An excitation optical system for forming an excitation light region is configured.

At this time, the zero-order light transmitted as it is without being diffracted by the phase grating 4 is, as shown in FIG. 2B, four excitation lights along the x direction on the end face 7a of the laser crystal 7. Form an area. The position and intensity distribution of each excitation light region on the end face 7 a of the laser crystal 7 optically correspond to the position and intensity distribution of each light emitting unit of the wide area semiconductor laser 1. On the other hand, x
The beam of each diffraction order diffracted along the direction reaches the end face 7a of the laser crystal 7 along an optical path different from the 0th-order light, and is located along the x-direction from the excitation light region formed by the 0th-order light. A shifted excitation light region is formed.

Therefore, in the first embodiment, the maximum value of the excitation light intensity distribution formed on the end face of the laser crystal 7 under the action of the phase grating 4 is, as shown in FIG. It becomes substantially smaller than the maximum value of the conventional excitation light intensity distribution formed without being affected. The minimum value of the excitation light intensity distribution formed in the first embodiment is substantially larger than the minimum value of the conventional excitation light intensity distribution. Further, the characteristics of the phase grating 4 and the spherical lens 5
By setting the characteristics of the laser crystal 7 as described later, it is possible to obtain a laser beam 7 having a substantially uniform intensity distribution on the end face of the laser crystal 7.
One excitation light region can be formed.

Thus, the laser crystal 7 whose end face is pumped by the pump light from the wide area semiconductor laser 1 emits light having a predetermined wavelength unique to the laser crystal 7. Light generated from the laser crystal 7 is incident on a concave reflecting mirror 8 constituting an output coupler. The concave surface of the concave reflecting mirror 8 is provided with a coating that reflects most (for example, 95%) of the light generated from the laser crystal 7. Therefore, most of the generated light is reflected by the concave reflecting mirror 8 and enters the laser crystal 7. The end face 7a of the laser crystal 7 on the excitation light incident side has
A wavelength-selective coating having a high transmittance to the excitation light and a high reflectance to the generated light is provided. Thus, the end face 7a of the laser crystal 7 and the concave reflecting mirror 8
A laser resonator is formed between the first and second concave surfaces, and laser oscillation occurs. A part of the oscillation light inside the laser resonator is output as oscillation laser light via the concave reflecting mirror 8.

Hereinafter, the characteristics of the phase grating 4 and the characteristics of the spherical lens 5 necessary for forming an excitation light region having a substantially uniform intensity distribution on the end face of the laser crystal 7 will be described based on specific numerical examples. explain. First, it is assumed that the phase modulation amplitude t (x) of the phase grating 4 has a period Λ _{0 in the} x direction and is represented by the following equation (1) as a periodic function of the modulation depth m. t (x) = exp {j (m / 2) sin (2πx / { ₀ )} (1)

In this case, the diffraction efficiency I for light of the diffraction order q
_q (m) is represented by the following equation (2).

(Equation 1) Here, J _q is a Bessel function of the first kind of order q.

In this numerical example, the modulation depth m of the phase grating 4 is set to m = 2.9 so that the light intensity of the zero-order light and the light intensity of the ± first-order diffracted light are substantially equal. In this case, the diffraction efficiency for the zero-order light is I ₀ = 0.291, the diffraction efficiency for the ± _first -order diffraction light is I ₁ = 0.303, and the diffraction efficiency for the ± second-order diffraction light is I ₂ = 0. 048, and the diffraction efficiency for diffracted light of higher order (q ≧ 3, q ≦ −3) than ± 2 order is I
_q <1.1 × 10 ⁻⁴ .

Incidentally, the phase modulation in the phase grating 4 is performed by the refractive index modulation of the element or equivalently by the optical distance modulation by the surface relief. Then, assuming that the refractive index modulation of the element is Δn, a relationship expressed by the following equation (3) is established between the modulation depth m of the phase grating 4 and the refractive index modulation Δn. m = k ₀ Δnd (3) Here, k ₀ is the wave number of the incident excitation light (2π / λ ₀ : λ ₀ is the wavelength of the incident excitation light), and d is the thickness of the phase grating 4.

Therefore, as an example, the wavelength of the incident pump light (ie, the oscillation wavelength of the wide area semiconductor laser 1)
Is λ ₀ = 800 nm, and the thickness of the phase grating 4 is d = 1 mm
In order to set the modulation depth of the phase grating 4 to m = 2.9, a phase grating having a refractive index modulation Δn having a value represented by the following equation (4) may be used. . Δn = m / (k ₀ d) = mλ ₀ /(2πd)=3.7×10 ⁻⁴ (4)

The following equation (5) holds between the period Λ ₀ of the phase grating 4 and the diffraction angle θ ₁ of ± 1st-order diffracted light. Λ ₀ = λ ₀ / sin θ ₁ (5) Therefore, ± 1st-order diffracted light of the laser crystal 7 is shifted from the position where the 0th-order light is focused on the end face of the laser crystal 7 by the spherical lens 5 having the focal length f. The position where light is condensed on the end face is shifted by the distance δx in the x direction, and the shift amount δx is given by the following equation (6). δx = f tan θ ₁ ≒ f sin θ ₁ (6)

Thus, from equations (5) and (6),
Between the period Λ ₀ of the phase grating 4 and the deviation δx of ± 1st-order diffracted light with respect to the 0th-order light on the end face of the laser crystal 7,
It can be seen that the relationship shown in the following equation (7) is approximately established. Λ ₀ ≒ λ ₀ f / δx (7) In this numerical example, as described above, the light intensity of the zero-order light and ± 1
The light intensity of the second-order diffracted light is almost equal to the higher order (2
, 3rd,...) Are set to be very small.

Therefore, when the interval (center distance in the x direction) between the excitation light regions formed by the zero-order light on the end face of the laser crystal 7 is, for example, 90 μm, the laser beam is shifted so that the shift amount δx becomes 30 μm. By superimposing the 0th-order light and the ± 1st-order diffracted light on the end face of the crystal 7, an excitation light region having a substantially uniform intensity distribution can be formed. In addition, referring to the equation (7), the shift amount δ
It can be seen that in order to set x to be 30 μm, for example, the focal length of the spherical lens 5 should be set to f = 15 mm, and the period of the phase grating 4 should be set to Λ ₀ = 40 μm.

FIGS. 2A and 2B are diagrams for explaining the effect of the present invention in a numerical example of the first embodiment. FIG. 2A shows an excitation light intensity distribution in a numerical example of the first embodiment having the phase grating 4. (B) shows the excitation light intensity distribution of the conventional example without the phase grating 4, and (c) shows the comparison between the excitation light intensity distribution of the numerical example at y = 0 and the excitation light intensity distribution of the conventional example. Is shown. As shown in FIG. 2B, the phase grating 4
In the conventional example without the above, the interval (center-to-center distance in the x direction) between the respective excitation light regions formed on the end face of the laser crystal 7 is about 90 μm. Therefore, in the numerical example of the first embodiment corresponding to the conventional example, the interval between the respective excitation light regions formed by the zero-order light on the end face of the laser crystal 7 is 90 μm.

In FIG. 2B, the distribution shape of the excitation light region was obtained by approximating the intensity distribution of each excitation light region with a Gaussian distribution from experimental data using a commercially available wide area semiconductor laser. Things. Thus, FIG.
As shown by the solid line in (b) and the dashed line in (c), in the conventional example without the phase grating 4, four excitation light regions having a Gaussian intensity distribution on the end face of the laser crystal 7 are arranged in the x direction. Formed side by side. However, in the numerical example of the first embodiment including the phase grating 4, the 0th-order light and the ± 1st-order diffracted light are adjusted so that the shift amount δx on the end face of the laser crystal 7 becomes 30 μm by the action of the phase grating 4. Are superimposed. As a result, as shown by the solid line in FIG. 2A and the solid line in FIG. 2C, one excitation light region having an almost uniform intensity distribution and extending in the x direction is formed on the end face of the laser crystal 7. Can be.

As described above, the maximum value of the excitation light intensity distribution of the first embodiment is substantially smaller than the maximum value of the conventional excitation light intensity distribution by the action of the phase grating 4 provided in the excitation optical system. That is, the minimum value of the excitation light intensity distribution of the first embodiment is substantially larger than the minimum value of the conventional excitation light intensity distribution. Also, according to the numerical example of the first embodiment, the laser crystal 7
An excitation light region having a substantially uniform intensity distribution can be formed on the end face of. Therefore, in the first embodiment, it is possible to avoid a decrease in excitation efficiency due to absorption saturation due to a high peak light intensity observed in the conventional excitation light intensity distribution. Further, even when a three-level solid-state laser medium is used, it is possible to avoid a decrease in the pumping efficiency due to the absorption of the laser beam at the valley of the pumping light intensity, which is observed in the conventional pumping light intensity distribution. As a result, in the first embodiment,
In a semiconductor laser pumped solid-state laser device using the wide area semiconductor laser 1, the end face of the laser crystal 7 can be efficiently pumped.

FIG. 3 is a diagram schematically showing the configuration of a semiconductor laser pumped solid-state laser device according to a second embodiment of the present invention. The second embodiment has a configuration similar to that of the first embodiment. However, in the first embodiment, the parallel beam passing through the phase grating 4 is focused by the spherical lens 5, whereas in the second embodiment, the beam focused at a predetermined convergence angle is incident on the phase grating 4. The only difference is that the spherical lens 5 is omitted and the spherical lens 5 is omitted. Therefore, in FIG.
Elements having functions similar to those of the first embodiment shown in FIG. 1 are denoted by the same reference numerals as in FIG. Hereinafter, the second embodiment will be described by focusing on the differences from the first embodiment.

The device shown in FIG. 3 has a wide-area semiconductor laser 1 having four light-emitting portions arranged at intervals in the x-direction as in the first embodiment, as a semiconductor laser for excitation. The laser beam emitted from the light emitting portion of the wide area semiconductor laser 1 has a positive refractive power in the y direction and a non-refractive power in the x direction with a fiber lens (or rod lens) 12 having a positive refractive power in the x direction and a non-refractive power in the y direction. A shaped condensing optical system (1) composed of a cylindrical lens 13 having a refractive power.
2, 13). Thus, the shaped condensing optical system (1)
2, 13), the wide area semiconductor laser 1
Is shaped into a beam having a cross-sectional shape corresponding to the mode shape of the solid-state laser resonator and condensing at a predetermined convergence angle.

A beam having a predetermined cross-sectional shape via a shaped condensing optical system (12, 13) and shaped so as to be condensed at a predetermined convergence angle passes through a phase grating 4 along the x direction. And is split into a plurality of beams having different diffraction orders. The beams of the respective diffraction orders split via the phase grating 4 reach an end face 7 a of a laser crystal 7 built in the solid-state laser resonator 6. At this time, also in the second embodiment, the zero-order light transmitted as it is without being diffracted by the phase grating 4 forms four excitation light regions along the x direction on the end face of the laser crystal 7. The position and intensity distribution of each excitation light region on the end face of the laser crystal 7 optically correspond to the position and intensity distribution of each light emitting unit of the wide area semiconductor laser 1.

On the other hand, the beam of each diffraction order diffracted along the x direction by the phase grating 4 reaches the end face of the laser crystal 7 along an optical path different from the zero-order light, and is excited by the zero-order light. An excitation light region that is displaced along the x direction from the light region is formed. Therefore, also in the second embodiment,
The maximum value of the excitation light intensity distribution formed on the end face of the laser crystal 7 under the action of the phase grating 4 is substantially smaller than the maximum value of the conventional excitation light intensity distribution, and the minimum value of the excitation light intensity distribution is It is substantially larger than the conventional minimum value of the excitation light intensity distribution.

Further, also in the second embodiment, similarly to the numerical example of the first embodiment, by setting the characteristics and arrangement of the phase grating 4 appropriately, an almost uniform surface on the end face of the laser crystal 7 can be obtained. An excitation light region having an intensity distribution can be formed. That is, in the first embodiment, the characteristics of the phase grating 4 and the focal length f of the spherical lens 5 are appropriately set, but in the second embodiment, the optical axis AX between the phase grating 4 and the end face 7a of the laser crystal 7 is set. By appropriately setting the distance L along and the characteristics of the phase grating 4, it is possible to form an excitation light region having a substantially uniform intensity distribution on the end face of the laser crystal 7.

In the numerical example of the first embodiment, an excitation light region having a substantially uniform intensity distribution is formed on the end face of the laser crystal. However, the action and effect of the present invention can be obtained only by substantially reducing the maximum value of the excitation light intensity distribution and substantially increasing the minimum value of the excitation light intensity distribution by the action of the phase grating. Not even. In the first and second embodiments described above, the present invention has been described by taking as an example the case where the excitation light is focused on the end face of the solid-state laser medium on the excitation light incidence side. However, if the focus position of the excitation light is any position in the solid-state laser medium, the function and effect of the present invention can be obtained. In general, a position where the solid-state laser output becomes almost maximum is selected as a focus position of the excitation light.

Further, in the above-described first and second embodiments, the present invention is described by taking as an example a wide area semiconductor laser having four light emitting portions arranged along one direction. However, even for a wide-area semiconductor laser having light-emitting portions arranged in an array along two directions, a diffractive optical element (for example, two The operation and effect of the present invention can be obtained by using a phase grating. In the present invention, it goes without saying that the number of light emitting units of the wide area semiconductor laser is not limited at all.

FIG. 4 is a perspective view schematically showing a configuration of an embodiment of an ultraviolet laser device using the semiconductor laser pumped solid-state laser device of the present invention. This embodiment is an example in which the device of the present invention is applied to a semiconductor laser-excited solid-state laser device of an ultraviolet laser light source disclosed in Japanese Patent Application Laid-Open No. 8-334803 filed by the present applicant. As shown in FIG. 4, the ultraviolet laser device 20 according to the present embodiment includes 100 laser units 23 arranged in parallel vertically and horizontally.
Each laser unit 23 has a semiconductor laser-excited solid-state laser device 21 and a wavelength conversion device 22 for converting the oscillation laser light from the laser device 21 into ultraviolet laser light. As the semiconductor laser pumped solid-state laser device 21,
For example, the semiconductor laser-excited solid-state laser device according to the above-described first or second embodiment can be used.

In this embodiment, the solid-state laser medium of the semiconductor laser-excited solid-state laser device 21 is, for example, Nd: YV
O ₄ (Yttrium Vanadate doped with Nd) can be used. In this case, the laser medium (ie, Nd: Y
A laser diode having a wavelength of 1064 nm can be oscillated from the semiconductor laser-excited solid-state laser device 21 using a laser diode that supplies excitation light of about 809 nm according to the absorption spectrum of VO ₄ ). The 1064 nm visible laser light oscillated from the semiconductor laser-excited solid-state laser device 21 is wavelength-converted through, for example, a wavelength converter 22 having a fifth harmonic generation action, and is converted into an ultraviolet laser light having a wavelength of 213 nm. Output from the unit 23. Note that the wavelength converter 22 is disclosed in
As shown in Japanese Patent No. 34803, a combination of a nonlinear optical crystal as the second harmonic generation means and a nonlinear optical crystal as the sum frequency generation means can be used.

In the ultraviolet laser device 20 of the present embodiment, even if the output of the ultraviolet laser light from each laser unit 23 is small, a required number (100 in this embodiment)
), The output of the finally obtained ultraviolet laser light can be increased. Further, in the ultraviolet laser device 20 of the present embodiment, since the ultraviolet laser light output from the plurality of laser units 23 arranged in parallel is synthesized, the spatial coherence of the finally obtained ultraviolet laser light is reduced. Can be lower. As a result, in the present embodiment, for example, an ultraviolet laser device having a sufficient output and low coherence as a light source of a semiconductor exposure apparatus can be realized.

[0038]

As described above, according to the semiconductor laser-excited solid-state laser device of the present invention, the maximum value of the excitation light intensity distribution is substantially reduced by the action of the phase grating provided in the excitation optical system. Therefore, it is possible to avoid a decrease in the excitation efficiency due to the absorption saturation due to the high peak light intensity. In addition, since the minimum value of the excitation light intensity distribution can be substantially increased, even when a three-level solid-state laser medium is used, the excitation efficiency caused by the absorption of the laser light at the excitation light intensity valley can be improved. Can be avoided. As a result, according to the present invention, in a semiconductor laser-excited solid-state laser device using a wide-area semiconductor laser, the end face of the solid-state laser medium can be efficiently excited.
Further, according to the present invention, an expensive fiber coupling is not required, so that a semiconductor laser-excited solid-state laser device which is advantageous in terms of cost can be realized.

Further, by arranging a plurality of laser units having the semiconductor laser-excited solid-state laser device of the present invention and a wavelength conversion device for wavelength-converting oscillation light from the laser device into ultraviolet light, a plurality of laser units are arranged in parallel. A laser device can be configured. In this case, when the ultraviolet laser light output from each laser unit is combined, the output of the finally obtained ultraviolet laser light can be increased and the spatial coherence can be reduced. As a result, the ultraviolet laser device of the present invention can supply an ultraviolet laser beam having sufficient output and low coherence as a light source of a semiconductor exposure apparatus, for example.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a configuration of a semiconductor laser pumped solid-state laser device according to a first embodiment of the present invention.

FIGS. 2A and 2B are diagrams illustrating an effect of the present invention in a numerical example of the first embodiment, and FIG. 2A illustrates an excitation light intensity distribution in a numerical example of the first embodiment including the phase grating 4; (b) shows the excitation light intensity distribution of the conventional example without the phase grating 4, and (c) shows the comparison between the excitation light intensity distribution of the numerical example at y = 0 and the excitation light intensity distribution of the conventional example. .

FIG. 3 is a diagram schematically showing a configuration of a semiconductor laser pumped solid-state laser device according to a second embodiment of the present invention.

FIG. 4 is a perspective view schematically showing a configuration of an embodiment according to an ultraviolet laser device using the semiconductor laser pumped solid-state laser device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wide-area semiconductor laser 2, 12 Fiber lens (or rod lens) 3, 13 Cylindrical lens 4 Phase grating 5 Spherical lens 6 Solid-state laser resonator 7 Laser crystal 8 Concave reflector 20 Ultraviolet laser device 21 Semiconductor laser-excited solid-state laser device 22 Wavelength converter 23 Laser unit

Claims (4)

[Claims] 1. A laser beam from a semiconductor laser having a plurality of light-emitting portions arranged at intervals along a predetermined direction is condensed into a solid-state laser medium via an excitation optical system, and the solid-state laser medium is optically pumped. A semiconductor laser-excited solid-state laser device that oscillates a laser beam by performing a laser beam oscillation from the plurality of light-emitting units of the semiconductor laser along a direction optically corresponding to the predetermined direction. 1. A semiconductor laser-excited solid-state laser device, comprising: a diffractive optical element for splitting a laser beam. 2. An excitation optical system, comprising: a shaping optical system for shaping beams from a plurality of light emitting units of the semiconductor laser into a parallel beam having a predetermined cross-sectional shape as a whole; and the shaping optical system. A phase grating for splitting the split beam into a plurality of beams having different diffraction orders, and a focusing optical system for collecting the beams of the respective diffraction orders split via the phase grating. The solid-state laser device excited by a semiconductor laser according to claim 1. 3. The excitation optical system, wherein the beam from the plurality of light-emitting portions of the semiconductor laser is shaped into a beam having a predetermined cross-sectional shape as a whole, and a predetermined convergence angle toward an end face of the solid-state laser medium. A shaped condensing optical system for condensing the light beam by a light source; and a phase grating for splitting a beam passing through the shaped condensing light optical system into a plurality of beams having different diffraction orders. 22. A solid-state laser device excited by the semiconductor laser according to the above. 4. A semiconductor laser-excited solid-state laser device according to claim 1, and a wavelength converter for converting oscillation light from the semiconductor laser-excited solid-state laser device into ultraviolet light. An ultraviolet laser device comprising: a plurality of laser units each having the device.