JP2002099011A - Laser beam generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate a short wavelength laser beam having good interferential quality at high output and highly repetitively. SOLUTION: A first laser beam L1 emitted from the first laser beam source 2 and a second pulse wave laser beam L2 emitted from the second laser beam source 3 are coaxially multiplexed by using a wavelength-selective mirror 4, which are then made incident on a light parametric amplifier 5 respectively as a seed light and a pump light. The first laser beam L1 amplified by the light parametric amplifier 5 is emitted as pulse wave. This first laser beam L1 is subjected to wavelength conversion a nonlinear optical wavelength conversion system 6, thereby, a forth laser beam L4, for example, of about 193 nm in wavelength is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam generator for converting a high-power pulse laser beam into a laser beam having a desired wavelength.

[0002]

2. Description of the Related Art Along with miniaturization of a semiconductor integrated circuit, a light source of an exposure apparatus used in a lithographic process and a light source of an inspection apparatus used for inspecting a circuit pattern have a very short wavelength. It is becoming.

According to the design rule of semiconductor integrated circuits in recent years, the line width has been reduced to about 0.18 μm. As a light source of an exposure apparatus for exposing such a fine circuit pattern, a wavelength of about 248 nm is used. KrF excimer lasers have been put to practical use and have been introduced into circuit pattern manufacturing processes.

In the future, when the miniaturization of the semiconductor integrated circuit is further advanced and, for example, a design rule with a line width of 0.13 μm or a design rule with a line width of 0.1 μm is applied, a light source of an exposure apparatus will be used. The wavelength is about 193n
It is expected that m ArF excimer lasers will be used.

Along with this, an inspection apparatus for inspecting a circuit pattern requires a light source having a similar short wavelength. In particular, in an inspection apparatus configured to inspect a circuit pattern by imaging an observation image of a laser microscope using a CCD camera, an average output is used as a laser light source for illuminating a circuit pattern to be inspected. Low,
There is a need for a laser light source with a high repetition frequency. In addition, as a laser light source used in such an inspection device,
It goes without saying that a highly reliable, compact and low maintenance cost is desired.

In order to realize the above-mentioned laser light source, efforts have been made to obtain a short-wavelength laser beam by wavelength conversion using a non-linear optical element by various methods, for example, as shown in FIG. (T. Ohtsuki, H. Kitano, H. Kawai, S. Owa, "Efficient 193
nm generation by eighth harmonics of Er ³⁺ -doped fi
beramplifier "Conference on Lasers and Electro-opt
ics 2000 (CLEO2000), postdeadline paper, paperCPD9 p
resented on May 11,2000, in SanFrancisco, CA.). The method shown in FIG.
A laser beam having a wavelength of about 1547 nm emitted from
A pulse wave is modulated by an optical modulator 102 using a lithium niobate crystal and then input to a fiber amplifier 103. The output light from the fiber amplifier 103 is wavelength-converted by a non-linear wavelength conversion unit 104 to obtain 1547n.
A laser beam having a wavelength corresponding to ８ of m and a wavelength of about 193 nm is obtained.

[0007]

The method shown in FIG. 4 as described above is widely used as an element for optical communication, and uses an optical element which can be easily incident thereon, and uses a laser beam having a wavelength of about 193 nm. It is an excellent technology that can be obtained efficiently. However, in this method, since the fiber amplifier 103 is used as an amplifier for amplifying the fundamental wave,
There is a limit in increasing the output of the fundamental wave due to the non-linearity inside the fiber amplifier 103, and this is a factor that hinders high output repetition or high output. There is also a problem that the coherence of the output light is impaired by the self-phase modulation of the fiber amplifier 103.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a laser light generator which generates laser light having high output, high repetition and good coherence. .

[0009]

A laser light generator according to the present invention comprises a first laser light source for emitting a first laser light serving as a seed light, and a second laser light of a pulse wave serving as a pump light. A second laser light source that emits light, and an optical system that coaxially multiplexes the first laser light emitted from the first laser light source and the second laser light emitted from the second laser light source And a first laser beam and a second laser beam coaxially multiplexed by the optical system are incident, and the wavelength of the first laser beam is λ1, and the wavelength of the second laser beam is λ2.
And λ3 due to the difference frequency mixing process of λ2 and λ1
Λ satisfying = 1 / {(1 / λ2) − (1 / λ1)}
3 is emitted, and the first laser light is emitted.
An optical parametric amplifier that amplifies the laser light and emits it as a pulse wave, and converts the wavelength of the first laser light that has been amplified by the optical parametric amplifier and emitted as a pulse wave to obtain a fourth laser light having a predetermined wavelength. And a non-linear wavelength converting means for generating.

In this laser light generator, a first laser light serving as seed light is emitted from the first laser light source, and a second laser light of a pulse wave serving as pump light is emitted from the second laser light source. Is emitted. The first laser light serving as the seed light and the second laser light of the pulse wave serving as the pump light are multiplexed coaxially by the optical system and then input to the optical parametric amplifier.

When an optical parametric amplifier receives a first laser beam as a seed beam and a second laser beam as a pump beam, the second laser beam and the first laser beam are mixed by a difference frequency mixing process. A third laser beam having a difference frequency of light is emitted. In addition, the optical parametric amplifier includes a first optical parametric amplifier that has entered the optical parametric amplifier as seed light.
Is amplified. At this time, since the second laser light incident on the optical parametric amplifier as the pump light is a pulse wave, the amplified first laser light is emitted from the optical parametric amplifier as a pulse wave.

The first laser light amplified by the optical parametric amplifier and emitted as a pulse wave is subjected to wavelength conversion by nonlinear wavelength conversion means. Thereby, the fourth laser light of a predetermined wavelength, for example, the wavelength λ of the first laser light
A fourth laser beam having a wavelength λ4 corresponding to ８ of 1 will be generated.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of a laser light generator to which the present invention is applied. The laser light generator 1 shown in FIG.
Is a first laser light source 2 that emits a first laser light L1.
And a second laser light source 3 that emits a second laser light L2
, A wavelength selective mirror 4, an optical parametric amplifier (OPA) 5, and a nonlinear wavelength conversion optical system 6.

The first laser light source 2 is, for example, a DFB semiconductor laser or the like, and emits a continuous wave laser light having a wavelength of about 1547 nm and having good coherence as the first laser light L1. Here, the first laser light L1 is incident on the optical parametric amplifier 5 as seed light.
The good coherence of the first laser light L1 emitted from the first laser light source 2 is based on the finally obtained fourth laser light L1 described later.
Laser light L4 (the eighth harmonic of the first laser light L1;
When the wavelength of the first laser light L1 is about 1547 nm, it has an effect on the coherence of the laser light having a wavelength of about 193 nm). Here, the DFB semiconductor laser used as the first laser light source 2 has an output of about 20 mW, for example, and can be easily obtained as an element for optical communication.

The first laser light source 2 may emit a pulsed laser light as the first laser light L1. In this case, it is possible to increase the peak power of the first laser light L1 to be incident on the optical parametric amplifier 5 as the seed light, but the second laser light L2, which is a pulse wave, will be described later.
It is necessary to match the timing.

The second laser light source 3 is composed of, for example, a semiconductor laser-pumped Nd: YVO ₄ laser and has a wavelength of about 1 nm.
The laser light of the pulse wave of 064 nm is converted into the second laser light L2.
And emitted. Here, the second laser light L2 is incident on the optical parametric amplifier 5 as pump light. The second laser light source 3 is provided, for example, in a laser resonator and has an external timing signal generator FG.
The Q switch operation is performed in response to a trigger from the signal from. That is, the second laser light source 3 is formed by the Q switch element driven by the timing signal generator FG.
It typically has an average power of a few watts level, for example, 5 W, for example, 10 watts from the timing signal generator FG.
A pulse wave laser beam having a repetition frequency of 100 kHz by a rectangular wave signal of 0 kHz is converted into a second laser beam L2.
And emitted. Therefore, the second laser light L2
Is about 50 microjoules.

Nd: Y excited by a semiconductor laser as described above
The VO ₄ laser and the like have been sufficiently developed from the past, and can be easily obtained or manufactured. In addition, if such a solid-state laser excited by a semiconductor laser is used as the second laser light source 3, the second laser light L2 can be efficiently emitted and the second laser light source 3 can be miniaturized. , A longer life is realized.

In the second laser light source 3 as described above, it is technically possible to reduce the width of each optical pulse to, for example, 10 ns or less by appropriately designing a laser such as a resonator parameter. Here, for the sake of simplicity, it is assumed that the width of each optical pulse is 2.5 ns. At this time, the peak power of the pulse is about 20 kW. If a higher peak power is desired, the second laser light source 3
May be configured by combining a laser oscillator that oscillates the second laser light L2 and a laser amplifier corresponding to the wavelength of the second laser light L2.

The wavelength-selective mirror 4 coaxially multiplexes the first laser light L1 emitted from the first laser light source 2 and the second laser light L2 emitted from the second laser light source 3. The optical path of the first laser beam L1 and the optical path of the second laser beam L2 intersect each other. This wavelength-selective mirror 4 transmits, for example, approximately 100% of the first laser light L1 having a wavelength of about 1547 nm and has a wavelength of about 1047 nm.
The optical design is such that the second laser light L2 of 64 nm is reflected almost 100%. Then, the first laser light L1 transmitted through the wavelength-selective mirror 4 enters the optical parametric amplifier 5 as seed light, and the second laser light L2 reflected by the wavelength-selective mirror 4 is used as pump light. The light enters the parametric amplifier 5.

The optical parametric amplifier 5 is made of a non-linear optical material and comprises a first laser light L1 and a second laser light L.
2 satisfies the phase matching or quasi-phase matching by natural birefringence. That is, when the wavelength of the first laser light L1 as the seed light is λ1 and the wavelength of the second laser light L2 as the pump light is λ2, the optical parametric amplifier 5 has a difference frequency between λ2 and λ1. By the mixing process, λ3 = 1 / ｛(1 / λ
2) The third laser light L3 having the wavelength λ3 satisfying-(1 / λ1)｝ is emitted as idler light.
For example, as described above, the wavelength λ1 of the first laser light L1 incident on the optical parametric amplifier 5 as the seed light is used.
Is about 1547 nm, and the wavelength λ2 of the second laser beam L2 incident on the optical parametric amplifier 5 as the pump light is about 1064 nm, the wavelength λ3 becomes about 34 in the process of generating the difference frequency in the optical parametric amplifier 5.
The third laser light L3 having a wavelength of 07 nm is generated as idler light.

Here, in the process of generating the difference frequency, it is noted that the input light of one of the longer wavelengths (lower frequency) is amplified, and the first laser light L1 of the wavelength λ1 is amplified. This difference frequency process functions as an amplifier. Further, considering that this optical parametric amplification occurs only when the second laser light L2, which is the pump light, is incident, the first laser light L1 incident as seed light into the optical parametric amplifier 5 is a continuous wave. Even so, the first laser light L1 amplified in the process of generating the difference frequency in the optical parametric amplifier 5 is emitted from the optical parametric amplifier 5 as a pulse wave having a high peak value. The spectrum of each optical pulse of the first laser beam L1 amplified by the optical parametric amplifier 5 and emitted as a pulse wave is the spectrum of the first laser beam L1 incident on the optical parametric amplifier 5 as seed light. This is reflected, and in the example described above, the coherence is high at a single frequency.

In the optical parametric amplification, the energy of photons of the second laser light L2, which is pump light, is divided into the first laser light L1, which is seed light, and the third laser light L3, which is idler light. Because it is a process, in theory,
The number of photons of the first laser light L1 emitted from the optical parametric amplifier 5 is the same as the number of photons of the second laser light L2 which is incident on the optical parametric amplifier 5 as the pump light at the maximum. The wavelength λ of the second laser light L2 as the pump light
2 is 1064 nm and the wavelength λ1 of the first laser light as the seed light is 1547 nm, the peak value is 20 k
For a W pulse, the first with a maximum output of 14 kW
Will be obtained.

In order to perform the above-described efficient conversion, it is necessary to use a material having high optical nonlinearity as the optical parametric amplifier 5. By using lithium tantalate or the like as the optical parametric amplifier 5, it is possible to sufficiently achieve the above efficient conversion.

When the second laser light source 3 emits a laser beam having an extremely high peak power, for example, in addition to the above periodically poled lithium niobate and lithium tantalate, for example, LBO ( LiB
₃ O ₅ ), BBO (β-BaB ₂ O ₄ ), KTP (KTiO
A nonlinear optical crystal satisfying the phase matching condition by natural birefringence such as PO ₄ ) may be used as the optical parametric amplifier 5.

The first laser beam L1 emitted from the optical parametric amplifier 5 at a peak power of 14 kW
Has a pulse width slightly smaller than the second laser light L2 which is typically a pump light, but when a material having high optical nonlinearity is used as the optical parametric amplifier 5,
These pulse widths can be considered sufficiently close. Therefore, the wavelength λ1 of the first laser light L1 is about 1
At 547 nm, the pulse energy is 35 microjoules. The repetition frequency of the first laser light L1 emitted from the optical parametric amplifier 5 is:
Since it becomes the same as the second laser light L2 which is the pump light,
In the example described above, the repetition frequency of the first laser light L1 emitted from the optical parametric amplifier 5 is 10
0 kHz, and the average power is 3.5 W.

As described above, the optical parametric amplifier 5
The first laser light L1 amplified by the above and emitted from the optical parametric amplifier 5 as a high-output, high-repetition pulse wave enters the nonlinear wavelength conversion optical system 6.

The non-linear wavelength conversion optical system 6 receives the first incident light.
The wavelength conversion is performed on the laser light L1 to generate a fourth laser light L4 having a predetermined wavelength λ4. Here, the first laser light L having a wavelength λ1 of about 1547 nm
Nonlinear wavelength configured to perform wavelength conversion on 1 (fundamental wave) to generate a fourth laser beam L4 having a wavelength λ4 of about 193 nm, which is the eighth harmonic of the first laser beam L1. The conversion optical system 6 will be specifically described with reference to an example.

The nonlinear wavelength conversion optical system 6 includes, for example, as shown in FIG. 2, a first nonlinear optical crystal (SHG) 11 for generating a second harmonic of the first laser beam L1 incident as a fundamental wave. A second nonlinear optical crystal (4HG) 12 for generating a fourth harmonic of the first laser light L1, and a third nonlinear optical crystal (8HG) for generating an eighth harmonic of the first laser light L1 The optical crystals 11, 12, and 13 are arranged in-line.

As the first nonlinear optical crystal 11, for example, LBO (LiB ₃ O ₅ ) or the like is used. The wavelength λ1 is about 1547 nm inside the first nonlinear optical crystal 11.
When the first laser light L1 is incident as a fundamental wave, the first laser light L1, which is the fundamental wave, passes through an optical path in the first nonlinear optical crystal 11 where the phase matching condition is satisfied. A laser beam having a wavelength of about 774 nm, which is the second harmonic of the first laser beam L1, is generated and emitted to the outside of the first nonlinear optical crystal 11 together with the first laser beam L1. Then, the first laser light L1 emitted to the outside of the first nonlinear optical crystal 11 and the laser light that is the second harmonic of the first laser light L1 are then converted to the second nonlinear optical crystal 11 will be incident inside.

As the second nonlinear optical crystal 12, for example, LBO (LiB ₃ O ₅ ) is used. Inside the second nonlinear optical crystal 12, the second laser beam L1
When a higher harmonic wave (wavelength: about 774 nm) is incident, the second laser wave passes through an optical path in the second nonlinear optical crystal 12 where the phase matching condition is satisfied.
A laser beam having a wavelength of about 387 nm, which is the fourth harmonic, is generated, and the first laser beam L1 and the first laser beam L1
Is emitted to the outside of the second nonlinear optical crystal 12 together with the second harmonic. Then, the first laser light L1 emitted to the outside of the second nonlinear optical crystal 12, the second harmonic of the first laser light L1, and the fourth harmonic of the first laser light L1
The harmonic will then enter the interior of the third nonlinear optical crystal 13.

As the third nonlinear optical crystal 13, for example, SBBO (Sr ₂ Be ₂ B ₂ O ₇ ) is used. Inside the third nonlinear optical crystal 13, a first laser beam L
When the first fourth harmonic (wavelength: about 387 nm) enters, the fourth harmonic passes through the optical path in the third nonlinear optical crystal 13 where the phase matching condition is satisfied. A laser beam having a wavelength of about 193 nm, which is the eighth harmonic of the first laser beam L1, the first laser beam L
The light is emitted outside the third nonlinear optical crystal 13 together with the first second harmonic and the fourth harmonic of the first laser light L1.

As described above, the nonlinear wavelength conversion optical system 6 sequentially performs the nonlinear wavelength conversion using each of the optical crystals 11, 12, and 13 so that the first wavelength having the wavelength λ1 of about 1547 nm is obtained.
The wavelength λ4, which is the eighth harmonic of the laser beam L1 of FIG.
The third laser beam L4 of 3 nm is generated.

The configuration of the nonlinear wavelength conversion optical system 6 is as follows.
The configuration is not limited to the above example, and any configuration may be used as long as it can appropriately perform wavelength conversion on the first laser beam L1 incident as a fundamental wave. For example, as shown in FIG. 3, the nonlinear wavelength conversion optical system 6 includes a fourth nonlinear optical crystal (SHG) 14 that generates a second harmonic of the first laser beam L1 incident as a fundamental wave, Fifth nonlinear optical crystal (3HG) 15 for generating the third harmonic of the first laser light L1, and sixth nonlinear optical crystal (4HG) for generating the fourth harmonic of the first laser light L1
16, a seventh nonlinear optical crystal (7HG) 17 for generating the seventh harmonic of the first laser light L1, and an eighth nonlinear optical crystal (7HG) for generating the eighth harmonic of the first laser light L1 ( 8HG) 18 and each of these optical crystals 14, 1
5, 16, 17, and 18 may be arranged inline.

In the nonlinear wavelength conversion optical system 6 shown in FIG. 3, as the fourth nonlinear optical crystal 14, for example, L
BO (LiB ₃ O ₅ ) or the like is used. When a first laser beam L1 having a wavelength λ1 of about 1547 nm is incident as a fundamental wave into the fourth nonlinear optical crystal 14, the first laser beam L1 as the fundamental wave is transmitted to the fourth nonlinear optical crystal 1.
In the process of passing through the optical path satisfying the phase matching condition inside 4, a laser beam having a wavelength of about 774 nm, which is the second harmonic of the first laser beam L1, is generated, and the first laser beam L1
At the same time, the light is emitted outside the fourth nonlinear optical crystal 14. Then, the first laser light L1 emitted to the outside of the fourth nonlinear optical crystal 14 and the laser light that is the second harmonic of the first laser light L1 are then converted to the fifth nonlinear optical crystal 14. 15 will be incident.

As the fifth nonlinear optical crystal 15, for example, LBO (LiB ₃ O ₅ ) or the like is used. When the first laser light L1 and the second harmonic (wavelength: about 774 nm) of the first laser light L1 enter the inside of the fifth nonlinear optical crystal 15, during the sum frequency mixing process of these lights, The wavelength of the third harmonic of the first laser beam L1 is about 516n.
m laser light is generated and emitted to the outside of the fifth nonlinear optical crystal 15 together with the first laser light L1 and the second harmonic of the first laser light L1. Then, the first laser light L1, the second harmonic of the first laser light L1, and the third harmonic of the first laser light L1 emitted to the outside of the fifth nonlinear optical crystal 15 are: The light enters the sixth nonlinear optical crystal 16.

As the sixth nonlinear optical crystal 16, for example, LBO (LiB ₃ O ₅ ) is used. Inside the sixth nonlinear optical crystal 16, the second laser light L1
When a higher harmonic wave (wavelength: about 774 nm) is incident, the second laser wave passes through the optical path in the sixth nonlinear optical crystal 16 where the phase matching condition is satisfied.
Laser light having a wavelength of about 387 nm, which is the fourth harmonic of the first laser light L1, the second laser light L1
Along with the third harmonic of the first laser beam L1,
Is emitted to the outside of the nonlinear optical crystal 16.
Then, the first laser light L1, the second harmonic of the first laser light L1, the third harmonic of the first laser light L1, and the first laser light emitted to the outside of the sixth nonlinear optical crystal 16. The fourth harmonic of the light L1 is then transmitted to the seventh nonlinear optical crystal 17
Will be incident on the inside.

As the seventh nonlinear optical crystal 17, for example, BBO (β-BaB ₂ O ₄ ) or the like is used. This seventh
Inside the nonlinear optical crystal 17, the third harmonic (wavelength: about 516 nm) of the first laser light L 1 and the first laser light L 1
When the first fourth harmonic (wavelength: about 387 nm) is incident, the first laser light L
A laser light having a wavelength of about 221 nm, which is the seventh harmonic of 1, is generated, and the first laser light L1, the second harmonic of the first laser light L1, the third harmonic of the first laser light L1, The light is emitted outside the seventh nonlinear optical crystal 17 together with the fourth harmonic of the first laser light L1. Then, the first laser light L emitted to the outside of the seventh nonlinear optical crystal 17
1, the second harmonic of the first laser light L1, the third harmonic of the first laser light L1, the fourth harmonic of the first laser light L1,
Next, the seventh harmonic of the first laser light L <b> 1 enters the inside of the eighth nonlinear optical crystal 18.

As the eighth nonlinear optical crystal 18, for example, CLBO (CsLiB ₆ O ₁₀ ) is used. Inside the eighth nonlinear optical crystal 18, the first laser light L
1 (wavelength: about 1547 nm) and the first laser light L1
When the seventh harmonic (wavelength: about 221 nm) is incident on the first laser light L1 in the sum frequency mixing process of these lights.
A laser beam having a wavelength of about 193 nm, which is the eighth harmonic of the first laser light L1, the second laser light L1
Along with the harmonic, the third harmonic of the first laser light L1, the fourth harmonic of the first laser light L1, and the seventh harmonic of the first laser light L1, they are located outside the eighth nonlinear optical crystal 18. It will be emitted.

In the nonlinear wavelength conversion optical system 6 shown in FIG. 3, each of the optical crystals 14, 15, 16, 1
By sequentially performing the nonlinear wavelength conversion using the wavelengths 7 and 18, a fourth laser light L4 having a wavelength λ4 of about 193 nm, which is the eighth harmonic of the first laser light L1 having a wavelength λ1 of about 1547 nm, is generated. Like that.

In the laser light generator 1 to which the present invention is applied, as described above, the first laser light L
1 is subjected to wavelength conversion by the nonlinear wavelength conversion optical system 6 to generate, for example, a fourth laser beam L4 having a wavelength λ4 of about 193 nm. Since the light L1 has a high peak power, it is possible to obtain extremely high conversion efficiency with a simple configuration.

That is, the conversion efficiency in non-linear wavelength conversion using a pulse laser beam as a fundamental wave depends on the peak power of the pulse laser beam, as described in T. Ohtsuki, H. Kitano, HK
awai, S.Owa, "Efficient 193 nm generation by eighth
harmonics of Er ³⁺ -doped fiber amplifier "Conferenc
e on Lasers and Electro-optics 2000 (CLEO2000), pos
tdeadline paper, paperCPD9 presented on May 11,200
0, in San Francisco, CA. "
When a 7-nm pulse laser beam (fundamental wave) is wavelength-converted to generate an eighth harmonic having a wavelength of about 193 nm, if the peak power of the fundamental wave is 23 kW, a conversion efficiency of as much as 7% can be obtained. It is reported that a conversion efficiency of 1% can be obtained when the peak power of the fundamental wave is 10 kW.

In the laser light generating apparatus 1 to which the present invention is applied, as described above, the first laser light L1 of the pulse wave emitted from the optical parametric amplifier 5 and incident on the nonlinear wavelength conversion optical system 6 as a fundamental wave. Is, for example, 14
Since the peak power of kW is expected, if the conversion efficiency of 1% is expected when the peak power of the fundamental wave is 14 kW, the fourth laser with the output of 35 mW is output by the laser light generator 1 to which the present invention is applied. It is possible to generate light L4 (wavelength λ4 is about 193 nm).

Further, in the laser light generator 1 to which the present invention is applied, the first laser light L1 is amplified by the optical parametric amplifier 5 without self-phase modulation, so that the coherence is reduced in the amplification process. Without being impaired, the finally obtained fourth laser light L4 can also be light having high coherence. Therefore, the fourth laser light L4 generated from the laser light generating device 1 does not easily generate chromatic aberration even when it is incident on an objective lens having a large numerical aperture, and has a high repetition frequency. It is easy to remove and is very suitable as illumination light in a laser microscope or a semiconductor inspection device using this laser microscope.

[0045]

According to the laser light generator of the present invention, the first laser light serving as seed light and the second laser light of pulse wave serving as pump light are made to enter the optical parametric amplifier. Since the first laser light amplified by the optical parametric amplifier and emitted as a pulse wave is subjected to non-linear wavelength conversion to obtain a fourth laser light of a predetermined wavelength, interference occurs with high output and high repetition. A good laser beam can be generated.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a laser light generator to which the present invention is applied.

FIG. 2 is a diagram illustrating an example of a nonlinear wavelength conversion optical system provided in the laser light generator.

FIG. 3 is a diagram showing another example of the nonlinear wavelength conversion optical system provided in the laser light generator.

FIG. 4 is a diagram for explaining a conventional method of obtaining a short-wavelength laser beam by wavelength conversion using a nonlinear optical element.

[Explanation of symbols]

Reference Signs List 1 laser light generator, 2 first laser light source, 3
Second laser light source, 4 wavelength selective mirror, 5 optical parametric amplifier, 6 nonlinear wavelength conversion optical system

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H01S 3/094 H01S 5/12 3/11 H01L 21/30 515B 5/12 H01S 3/094 SF term (reference) 2H097 AA13 BA10 CA13 CA17 EA01 LA10 2K002 AA07 AB12 AB30 BA02 CA03 DA01 EA30 HA20 HA21 5F046 CA03 CA10 CB27 5F072 AB02 GG05 HH07 MM03 PP07 SS06 YY09 5F073 AA64 BA09 EA29

Claims (13)

[Claims] A first laser light source that emits a first laser light serving as a seed light; a second laser light source that emits a second laser light of a pulse wave serving as a pump light; An optical system for coaxially multiplexing the first laser light emitted from the laser light source and the second laser light emitted from the second laser light source; and a first optical system coaxially multiplexed by the optical system. When the wavelength of the first laser beam is λ1 and the wavelength of the second laser beam is λ2, λ3 = 2 is obtained by the difference frequency mixing process of λ2 and λ1. 1 /
An optical parametric amplifier that emits a third laser beam having a wavelength λ3 that satisfies {(1 / λ2) − (1 / λ1)}, amplifies the first laser beam, and emits it as a pulse wave; Non-linear wavelength conversion means for converting the wavelength of a first laser beam amplified by a parametric amplifier and emitted as a pulse wave to generate a fourth laser beam of a predetermined wavelength. . 2. The non-linear wavelength converting means converts the wavelength of the first laser light amplified by the optical parametric amplifier and emitted as a pulse wave, and converts the wavelength into 1/8 of λ1.
The laser light generator according to claim 1, wherein a fourth laser light having a wavelength λ4 corresponding to the following is generated. 3. The wavelength λ1 of the first laser beam is about 15
47 nm, and the wavelength λ4 of the fourth laser light is about 1
3. The laser beam generator according to claim 2, wherein the wavelength is 93 nm. 4. The laser light generator according to claim 1, wherein said first laser light source comprises a semiconductor laser. 5. The laser light generator according to claim 4, wherein said first laser light source comprises a semiconductor laser for emitting a continuous wave first laser light. 6. The wavelength λ2 of the second laser light is about 10
2. The laser beam generator according to claim 1, wherein the wavelength is 64 nm. 7. The laser light generator according to claim 1, wherein said second laser light source is a solid-state laser excited by a semiconductor laser. 8. The Q laser, wherein the second laser light source is provided in a laser resonator and driven by an external signal generator.
2. The laser light generator according to claim 1, wherein the switch element emits a pulsed laser light. 9. The laser light generating apparatus according to claim 7, wherein said second laser light source is excited by a continuous wave semiconductor laser and operates at a pulse repetition frequency of 10 kHz or more. 10. The laser light generator according to claim 1, wherein the wavelength λ3 of the third laser light emitted from the optical parametric amplifier is about 3407 nm. 11. The laser light generator according to claim 1, wherein said optical parametric amplifier is made of periodically poled lithium niobate or lithium tantalate. 12. The laser light generator according to claim 1, wherein said optical parametric amplifier is made of a nonlinear optical crystal satisfying a phase matching condition by natural birefringence. 13. The laser light generating apparatus according to claim 7, wherein said second laser light source is a combination of a laser oscillator having a wavelength of λ2 and a laser amplifier having a wavelength of λ2.