KR102356280B1 - pulse width stretcher and chirped pulse amplifier including the same - Google Patents

Abstract

The present invention discloses a pulse width expander and a chirped pulse amplification device comprising the same. The expander includes first and second multiple reflection mirrors, and a group delay dispersion block disposed between the first and second multiple reflection mirrors and refracting the pulsed laser beam to expand the pulse width of the pulsed laser beam. can do.

Description

Pulse width stretcher and chirped pulse amplifier including the same

The present invention relates to an optical amplification device, and more particularly, to a pulse width expander for expanding a pulse width of a pulsed laser beam, and a chirped pulse amplification device including the same.

In the mid-1980s, there was an important optical technological advance that overcomes the output power limit of the pulsed laser beam according to the damage threshold of the gain medium. This is the chirp pulse amplification technology. The chirped pulse amplification technique can provide a pulsed laser beam with an output power significantly higher than that of a general pulse amplification technique. A typical chirped pulse amplification device can generate a pulsed laser beam having a maximum output power of about 1 GW or less. On the other hand, the chirped pulse amplification apparatus can minimize the influence of the damage threshold of the optical medium by adjusting the pulse width of the pulsed laser beam. Accordingly, the chirped pulse amplifying apparatus may generate a pulsed laser beam having a maximum output power of about 1 TW or more.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pulse width expander having multiple passes of a pulsed laser beam.

Another object of the present invention is to provide a pulse width expander capable of maximizing space efficiency and a chirped pulse amplification apparatus including the same.

The present invention discloses a pulse width expander. The pulse width expander includes: a first multiple reflection mirror including a first large area mirror reflecting the pulsed laser beam and a first small area mirror in the first large area mirror; a second multiple reflection mirror including a second large-area mirror disposed to face the first large-area mirror and a second small-area mirror in the second large-area mirror; and a pulse group delay dispersion block disposed between the first multiple reflection mirror and the second multiple reflection mirror to expand the pulse width of the pulsed laser beam by refracting the pulsed laser beam.

A chirped pulse amplification apparatus according to an embodiment of the present invention includes an oscillator for generating a pulsed laser beam; a pulse width compressor disposed to be spaced apart from the oscillator and configured to compress a pulse width of the pulsed laser beam; a pulse amplifier disposed between the pulse width expander and the oscillator and amplifying the intensity of the pulsed laser beam; and a pulse width expander disposed between the pulse amplifier and the oscillator to expand the pulse width of the pulsed laser beam. Wherein the pulse width expander is:

a first multiple reflection mirror including a first large-area mirror reflecting the pulsed laser beam and a first small-area mirror in the first large-area mirror; a second multiple reflection mirror including a second large-area mirror disposed to face the first large-area mirror and a second small-area mirror in the second large-area mirror; and a pulse group delay dispersion block disposed between the first multiple reflection mirror and the second multiple reflection mirror and refracting the pulsed laser beam to expand a pulse width of the pulsed laser beam.

As described above, the pulse width expander according to an embodiment of the present invention includes a group delay dispersion block that expands the pulse width of the pulsed laser beam by refracting the pulsed laser beam reflected between the first and second multiple reflection mirrors. may include The group delay dispersion block may have multiple passes of the pulsed laser beam between the first and second multiple reflection mirrors. The first and second multiple reflection mirrors and the group delay dispersion block may maximize the spatial efficiency of the pulse width expander.

1 is a view showing a chirped pulse amplifying apparatus according to the concept of the present invention.
FIG. 2 is a diagram illustrating an example of the pulse oscillator of FIG. 1 .
3 and 4 are perspective and side views, respectively, showing an example of the pulse width expander of FIG. 1 .
5 is a perspective view and a side view illustrating an example of the pulse width expander of FIG. 1 ;
6 is a diagram illustrating an example of the pulse amplifier of FIG. 1 .
7 and 8 are perspective and side views, respectively, showing the pulse width compressor of FIG. 1 .

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Advantages and features of the present invention, and a method for achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments described herein, and may be embodied in different forms. Rather, the embodiments introduced herein are provided so that the disclosed content may be thorough and complete and the spirit of the present invention may be sufficiently conveyed to those skilled in the art, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout.

The terminology used herein is for the purpose of describing the embodiments and is not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, “comprises” and/or “comprising” means that a stated component, step, operation and/or element excludes the presence or addition of one or more other components, steps, operation and/or element. I never do that. Also, in the specification, chamber, thin film, and coating may be understood in general semiconductor and device terms. Since it is according to a preferred embodiment, reference signs provided in the order of description are not necessarily limited to the order.

1 shows a chirped pulse amplifying device 10 according to the concept of the present invention.

Referring to FIG. 1 , the chirp pulse amplifying apparatus 10 may include a pulse oscillator 20 , a pulse width expander 30 , a pulse amplifier 40 , and a pulse width compressor 50 . The pulse oscillator 20 may generate the pulsed laser beam 100 . For example, the pulsed laser beam 100 may have about 10 ⁶ ultrashort pulses 102 per second. The pulse width expander 30 may expand the pulse width 104 of the pulsed laser beam 100 . The pulse width W may be defined as the time interval at which the intensity and/or amplitude is halved at the rise and fall times of the pulse 102 . The intensity of the pulse 102 may be varied in the pulse width expander 30 , the pulse amplifier 40 , and the pulse width compressor 50 . The pulse width expander 30 may expand the pulse width 104 for each wavelength band of the pulsed laser beam 100 . The intensity of the pulse 102 may be reduced. For example, the pulse width expander 30 may reduce the intensity of the pulsed laser beam 100 below a damage threshold of the second gain medium (46 of FIG. 6 ) of the pulse amplifier 40 . The pulse amplifier 40 may amplify the intensity of the pulsed laser beam 100 . The pulse width compressor 50 may compress the pulse width 104 of the pulsed laser beam 100 . For example, the intensity of the pulsed laser beam 100 in the pulse width compressor 50 may be increased to about 10 ⁵ to 10 ⁶ times or more than the intensity of the pulsed laser beam 100 in the pulse oscillator 20 . .

FIG. 2 shows an example of the pulse oscillator 20 of FIG. 1 .

Referring to FIG. 2 , the pulse oscillator 20 may include a first pump laser 21 , a first resonator 24 , a first chirped mirror 28 , and a first output mirror 29 . The first pump laser 21 may generate the first pump light 21a. The first pump light 21a may be provided to the first resonator 24 by the pump light focusing lens 22 . The first resonator 24 and the first chirped mirror 28 may generate the pulsed laser beam 100 from the pump light 21a. For example, the first resonator 24 may include first and second concave mirrors 23 , 25 , and a first gain medium 26 . The first and second concave mirrors 23 and 25 may reflect the pulsed laser beam 100 . Alternatively, the first and second concave mirrors 23 and 25 may amplify the intensity of the pulsed laser beam 100 . A first gain medium 26 may be disposed between the first and second concave mirrors 23 , 25 . The first gain medium 26 may oscillate the pulsed laser beam 100 . The first chirped mirror 28 may be disposed outside the extension of the first and second concave mirrors 23 , 25 and the first gain medium 26 . For example, the pulsed laser beam 100 may be transmitted between the second concave mirror 25 and the first chirped mirror 28 . The first chirped mirror 28 may generate a pulse 102 of the pulsed laser beam 100 . The first concave mirror 23 may provide the pulsed laser beam 100 to the first output mirror 29 . The first output mirror 29 may output the pulsed laser beam 100 to the pulse width expander 30 .

3 and 4 show an example of the pulse width expander 30 of FIG. 1 .

3 and 4 , the pulse width expander 30 may include a first multiple reflection mirror 32 , a second multiple reflection mirror 34 , and a group delay dispersion block 38 . The first and second multiple reflection mirrors 32 , 34 may reflect the pulsed laser beam 100 several times. The group delay dispersion block 38 may be disposed between the first and second multiple reflection mirrors 32 and 34 . The group delay dispersion block 38 may increase the pulse width 104 of the pulsed laser beam 100 .

The first and second multiple reflection mirrors 32 and 34 may be disposed to be spaced apart from each other. The first and second multiple reflection mirrors 32 and 34 may multiple reflect the pulsed laser beam 100 . For example, the first and second multiple reflection mirrors 32 and 34 may reflect the pulsed laser beam 100 about 24 times. “1” - “24” in Fig. 3 may correspond to reflection points of the pulsed laser beam 100. The distance between the first and second multiple reflection mirrors 32 and 34 is about 33.5 cm. The pulsed laser beam 100 may travel a distance of about 8 (24*33.5 cm) m The pulsed laser beam 100 may pass through the group delay dispersion block 38. Group delay dispersion Block 38 may have multiple passes 106 of pulsed laser beam 100. Multiple passes 106 may be spatially parallel without intersecting within group delay dispersion block 38. Multiple passes ( 106 may extend the transmission and/or refraction length of the pulsed laser beam 100 within the group delay dispersion block 38 without length extension of the group delay dispersion block 38. Thus, the first and the second multiple reflection mirrors 32 and 34 and the group delay dispersion block 38 may maximize the spatial efficiency of the pulse width expander 30 .

The first multi-reflection mirror 32 may include a first large-area mirror 31 and a first small-area mirror 33 . According to an example, the first large-area mirror 31 may include a concave mirror. The first large-area mirror 31 may have a radius of curvature of about 5 m. The first large-area mirror 31 may have a first side hole 31a. The first small-area mirror 33 may be disposed in the first large-area mirror 31 . The first small-area mirror 33 may be disposed in the first side hole 31a. For example, the first small-area mirror 33 may include a flat mirror. The pulsed laser beam 100 may pass through the first multiple reflection mirror 32 through the first side hole 31a.

The second multiple reflection mirror 34 may include a second large-area mirror 35 and a second small-area mirror 36 . According to an example, the second large-area mirror 35 may include a plane mirror. The second large-area mirror 35 may have a second side hole 35a. The second small-area mirror 36 may have a smaller area than the second large-area mirror 35 . The second small-area mirror 36 may be disposed in the second side hole 35a. For example, the second small area mirror 36 may include a flat plate mirror. The pulsed laser beam 100 may pass through the second multiple reflection mirror 34 through the second side hole 35a.

The group delay dispersion block 38 may be disposed between the first and second multiple reflection mirrors 32 and 34 . According to an example, the group delay dispersion block 38 may include a dielectric cylinder. The group delay dispersion block 38 may include silicon oxide. The group delay dispersion block 38 may have a positive group delay dispersion value for the pulsed laser beam 100 . For example, when the pulsed laser beam 100 passes through the group delay dispersion block 38 , the transmission time may vary for each wavelength band of the pulsed laser beam 100 . This is because the group delay dispersion block 38 has a different refractive index for each wavelength band of the pulsed laser beam 100 . The group delay dispersion block 38 may have group velocity dispersion of the wavelength of the pulsed laser beam 100 . A long wavelength of the pulsed laser beam 100 may extend to a front portion of the pulse 102 with respect to the time axis, and a short wavelength of the pulsed laser beam 100 may extend to a rear portion of the pulse 102 . Accordingly, the pulse width 104 can be extended over the entire wavelength band of the pulsed laser beam 100 .

라고 할 때, 각 주파수 성분의 펄스 레이저 빔(100)의 통과 소요 시간

은 다음과 같이 수학식 1로 표현될 수 있다.The group velocity dispersion may correspond to a phase change of the pulsed laser beam 100 in the group delay dispersion block 38 . The phase change of the pulsed laser beam 100 is a function of the frequency component of the pulsed laser beam 100

When , the time required for passage of the pulsed laser beam 100 of each frequency component

can be expressed by Equation 1 as follows.

는 펄스 레이저 빔(100)의 중심 주파수에 대하여 테일러(Taylor expansion)전개를 하면 다음과 같이 수학식 2로 표현될 수 있다.

can be expressed by Equation 2 as follows if Taylor expansion is performed with respect to the center frequency of the pulsed laser beam 100 .

) 펄스 레이저 빔(100)의 초기 위상으로서, 상기 펄스 레이저 빔(100)의 중심주파수의 절대위상일 수 있다. 두 번째 항(

)는 펄스 레이저 빔(100)의 군속도, 즉 중심 주파수의 펄스 레이저 빔(100)이 군지연 분산 블록(38)을 통과하는 소요 시간일 수 있다. 세 번째 항(

)은 펄스 레이저 빔(100)의 주파수에 따른

의 선형변화를 나타내는 항으로 군지연 분산(group delay dispersion, GDD) 값일 수 있다. 군지연 분산 값은 펄스 레이저 빔(100)의 주파수에 따른

의 선형변화에 비례할 수 있다. 예를 들어, 군지연 분산 값이 클수록

의 선형변화가 클 수 있다. 군지연 분산 블록(38)은 펄스 레이저 빔(100)의 군산지연분산 값을 결정할 수 있다. 펄스 레이저 빔(100)의 전체 군지연 분산은 군지연 분산 블록(38)의 군지연 분산 값과, 군지연 분산 블록(38) 내에서의 펄스 레이저 빔(100)의 진행 거리의 곱에 대응될 수 있다. 도시되지는 않았지만, 함수

는 3차 분산(third order dispersion), 내지 N차 분산을 포함할 수 있다. 군지연 분산 값이 계산되면, 3차 분산 내지 N차 분산은 펄스 레이저 빔(100)의 군속도 변화에 거의 영향을 주지 않을 수 있다.first term (

) As an initial phase of the pulsed laser beam 100 , it may be an absolute phase of a center frequency of the pulsed laser beam 100 . second term (

) may be the group velocity of the pulsed laser beam 100 , that is, the time required for the pulsed laser beam 100 of the center frequency to pass through the group delay dispersion block 38 . third term (

) according to the frequency of the pulsed laser beam 100

As a term representing a linear change in , it may be a group delay dispersion (GDD) value. The group delay dispersion value depends on the frequency of the pulsed laser beam 100 .

can be proportional to the linear change in For example, the larger the group delay variance value, the more

The linear change of can be large. The group delay dispersion block 38 may determine the group delay dispersion value of the pulsed laser beam 100 . The total group delay dispersion of the pulsed laser beam 100 corresponds to the product of the group delay dispersion value of the group delay dispersion block 38 and the traveling distance of the pulsed laser beam 100 in the group delay dispersion block 38. can Although not shown, the function

may include third order dispersion, to Nth order dispersion. When the group delay dispersion value is calculated, the 3rd order dispersion to the Nth order dispersion may have little effect on the group velocity change of the pulsed laser beam 100 .

)은 수학식 3으로부터 계산될 수 있고, 군지연 분산 값(GDD)과 입력 펄스폭(

)의 변수로 나타내어 진다. Meanwhile, the pulse 102 of the pulsed laser beam 100 may have a bell-shaped Gaussian distribution. The pulse width of the pulsed laser beam 100 extended by the group delay dispersion block 38 (

) can be calculated from Equation 3, the group delay dispersion value (GDD) and the input pulse width (

) as a variable.

)은 불확정성의 원리에 따라

에 대응될 수 있다.

는 펄스 레이저 빔(100)의 중심 파장일 수 있다. c는 빛의 속도(3×10⁸ m/s)일 수 있다.

는 펄스 레이저 빔(100)의 파장의 반치 폭(Full Width Half Maximum)일 수 있다. 확장되는 펄스 폭(

)은 펄스 레이저 빔(100)의 중심 파장(

)과, 반치 폭(

)에 의해 계산될 수 있다. 예를 들어, 중심파장(

)이 800 nm이고, 반치 폭(

)이 100 nm인 펄스 레이저 빔(100)가 군지연 분산 블록(38)을 8m를 통과하면, 펄스 레이저 빔(100)의 펄스 폭(104)은 약 388 ps(피코초)로 확장될 수 있다. 따라서, 펄스 폭 확장기(30)는 군지연 분산 블록(38)의 다중 패스(106)를 이용하여 펄스 폭(104)을 효과적으로 확장시킬 수 있다. input pulse width (

) according to the uncertainty principle

can correspond to

may be the center wavelength of the pulsed laser beam 100 . c may be the speed of light (3×10 ⁸ m/s).

may be the full width half maximum of the wavelength of the pulsed laser beam 100 . Extended pulse width (

) is the central wavelength of the pulsed laser beam 100 (

) and half width (

) can be calculated by For example, the central wavelength (

) is 800 nm, and the half width (

When the pulsed laser beam 100 of 100 nm passes through the group delay dispersion block 38 for 8 m, the pulse width 104 of the pulsed laser beam 100 can be extended to about 388 ps (picoseconds). . Accordingly, the pulse width expander 30 can effectively extend the pulse width 104 by using the multiple passes 106 of the group delay dispersion block 38 .

5 shows an example of the pulse width expander 30 of FIG. 1 .

Referring to FIG. 5 , the first multi-reflection mirror 32 may include a plurality of first small-area mirrors 33 . The second multi-reflection mirror 34 may include a plurality of second small-area mirrors 35 . The first and second large-area mirrors 31 and 35 and the group delay dispersion block 38 may have the same configuration as in FIG. 3 .

)이 800 nm이고, 반치 폭(

)이 100 nm인 펄스 레이저 빔(100)이 군지연 분산 블록(38)을 24m를 통과하면, 펄스 레이저 빔(100)의 펄스 폭(104)은 약 1,164 ps로 확장될 수 있다.For example, the first and second multiple reflection mirrors 32 and 34 of the pulse width expander 30 may reflect the pulsed laser beam 100 about 70 times. “1” to “70” may correspond to reflection points of the pulsed laser beam 100 . The pulsed laser beam 100 may pass through the group delay dispersion block 38 72 times. The pulsed laser beam 100 may pass through about 24 (72 * 33.5 cm) m in the group delay dispersion block 38 . center wavelength (

) is 800 nm, and the half width (

) of 100 nm, when the pulsed laser beam 100 passes through the group delay dispersion block 38 24m, the pulse width 104 of the pulsed laser beam 100 can be extended to about 1,164 ps.

6 shows an example of the pulse amplifier 40 of FIG.

Referring to FIG. 6 , the pulse amplifier 40 may include second pump lasers 41 , first mirrors 42 , and a second resonator 44 . The second pump lasers 41 may be disposed on both sides of the first mirrors 42 and the second resonator 44 . The second pump lasers 41 may generate the second pump light 41a. The first mirrors 42 may provide the second pump light 41a to the second resonator 44 . The frequency of the pulsed pumping light 41b may be a frequency that is well absorbed by the second of these media 46 . The second resonator 44 may amplify the intensity of the pulsed laser beam 100 . According to one example, the second resonator 44 may include first mirrors 43 , second mirrors 45 , and a second gain medium 46 . The first mirrors 43 and the second mirrors 45 may be disposed to face each other. A second gain medium 46 may be disposed between the first mirrors 43 and the second mirrors 45 . The second gain medium 46 may include the same material as the first gain medium 26 . Whenever the pulsed laser beam 100 passes through the second gain medium 46 , the intensity of the pulsed laser beam 100 may gradually increase. On the other hand, the pulse width 104 of the pulsed laser beam 100 in the pulse width expander 30 and the pulse amplifier 40 may be the same.

7 and 8 show the pulse width compressor 50 of FIG. 1 .

3, 4, 7, and 8 , the pulse width compressor 50 may include third and fourth multiple reflection mirrors 52 and 54 . The third and fourth multiple reflection mirrors 52 and 54 may be disposed to face each other. According to an example, the third and fourth multiple reflection mirrors 52 and 54 may include group delay dispersion mirrors that reflect the pulsed laser beam 100 . The third and fourth multiple reflection mirrors 52 and 54 are the third and fourth multiple reflection mirrors 52 and 54 are the group delay dispersion values of the group delay dispersion block 38 with respect to the pulsed laser beam 100 . It may have a group delay variance value opposite to . For example, the third and fourth multiple reflection mirrors 52 and 54 may have negative group delay dispersion values.

According to one example, each of the third and fourth multiple reflection mirrors 52 , 54 may include low refractive dielectric layers 62 and high refractive dielectric layers 64 . The low refractive dielectric layers 62 may have the same refractive index as the group delay dispersion block 38 . The low refractive dielectric layers 62 may include silicon oxide (SiO ₂ ) having a refractive index of about 1.4. High refractive dielectric layers 64 may be disposed between low refractive dielectric layers 62 . The high refractive dielectric layers 64 may have a higher refractive index than the refractive index of the low refractive dielectric layers 62 . The high refractive dielectric layers 64 may include titanium oxide (TiO ₂ ) having a refractive index of about 1.9. The thicknesses of the low refractive dielectric layers 62 and the high refractive dielectric layers 64 may be different from each other. For example, the low refractive dielectric layers 62 may have a thickness of about 1/4 of the wavelength of the pulsed laser beam 100 . The high refractive dielectric layers 64 may have a thickness of about 1/2 the wavelength of the pulsed laser beam 100 . When the pulsed laser beam 100 has a wavelength of about 800 nm, the low refractive dielectric layers 62 may have a thickness of about 200 nm, and the high refractive dielectric layer 64 may have a thickness of about 400 nm.

The third multi-reflection mirror 52 may include a third large-area mirror 51 and third small-area mirrors 53 . According to an example, the third large-area mirror 51 may include a concave mirror. The third large-area mirror 51 may have the same radius of curvature as the first large-area mirror 31 . The third large-area mirror 51 may have a third hole 51a. The third small-area mirrors 53 may be disposed in the third large-area mirror 51 . The third small-area mirrors 53 may be fixed in the third hole 51a.

The fourth multiple reflection mirror 54 may include a fourth large-area mirror 55 and fourth small-area mirrors 56 . According to an example, the fourth large-area mirror 55 may include a flat mirror. The fourth large-area mirror 55 may have a fourth hole. The fourth small-area mirrors 56 may be disposed in the fourth large-area mirror 55 . The fourth small-area mirrors 56 may be fixed in the fourth hole 55a.

The pulsed laser beam 100 may pass through the third hole 51a and be reflected by the fourth large-area mirror 55 . Alternatively, the pulsed laser beam 100 may pass through the fourth hole 55a after being reflected by the third small-area mirror 53 .

)이 약 100nm인 펄스 레이저 빔(100)의 펄스 폭(104)은 약 -42ps로 압축될 수 있다. For example, when the pulsed laser beam 100 has a wavelength of about 800 nm, the third and fourth large-area mirrors 51 and 55 and the third and fourth small-area mirrors 53 and 56 . Each time it is reflected, it may have a group delay dispersion value of about -2,000 fs ² . The third and fourth large-area mirrors 51 and 55 and the third and fourth small-area mirrors 53 and 56 may reflect the pulsed laser beam 100 about 70 times. The third and fourth large-area mirrors 51 and 55 and the third and fourth small-area mirrors 53 and 56 have a pulse width 104 of the pulsed laser beam 100 of -144,000 fs ² in total. It can be compressed to a group delay variance value. half width (

) of about 100 nm, the pulse width 104 of the pulsed laser beam 100 can be compressed to about -42 ps.

In the above, embodiments of the present invention have been described with reference to the accompanying drawings, but those of ordinary skill in the art to which the present invention pertains will implement the present invention in other specific forms without changing the technical spirit or essential features. It can be understood that Therefore, it should be understood that the embodiments and application examples described above are illustrative in all respects and not restrictive.

Claims (14)

delete delete delete delete delete an oscillator that generates a pulsed laser beam;
a pulse width compressor that is spaced apart from the oscillator and compresses a pulse width of the pulsed laser beam;
a pulse amplifier disposed between the pulse width expander and the oscillator and amplifying the intensity of the pulsed laser beam; and
a pulse width expander disposed between the pulse amplifier and the oscillator to expand the pulse width of the pulsed laser beam;
The pulse width expander is:
a first multiple reflection mirror including a first large-area mirror reflecting the pulsed laser beam and a first small-area mirror in the first large-area mirror;
a second multiple reflection mirror including a second large-area mirror disposed to face the first large-area mirror and a second small-area mirror in the second large-area mirror; and
a pulse group delay dispersion block disposed between the first multiple reflection mirror and the second multiple reflection mirror and refracting the pulsed laser beam to expand a pulse width of the pulsed laser beam;
The pulse width compressor comprises:
a third multiple reflection mirror reflecting the pulsed laser beam; and
a fourth multiple reflection mirror disposed opposite to the third multiple reflection mirror and reflecting the pulsed laser beam to the third multiple reflection mirror;
and the third and fourth multiple reflection mirrors include group delay dispersion mirrors having a group delay dispersion value opposite to a group delay dispersion value of the group delay dispersion block. delete 7. The method of claim 6,
The group delay dispersion block includes a dielectric cylinder,
Each of the third and fourth multi-reflecting mirrors comprises:
low refractive dielectric layers having the same refractive index as that of the dielectric cylinder; and
and high refractive dielectric layers disposed between the low refractive dielectric layers and having a refractive index greater than the refractive index of the low refractive dielectric layers. 9. The method of claim 8,
wherein the low refractive dielectric layer comprises silicon oxide;
wherein the high refractive dielectric layer includes titanium oxide. 7. The method of claim 6,
The third multi-reflecting mirror comprises:
a third large-area mirror; and
a third small-area mirror disposed within the three large-area mirrors;
The fourth multi-reflecting mirror comprises:
a fourth large-area mirror opposite to the third large-area mirror; and
and a fourth small-area mirror disposed within the fourth large-area mirror. 7. The method of claim 6,
The third and fourth large-area mirrors fix the third and fourth small-area mirrors, and have third and fourth holes through which the pulsed laser beam passes, respectively. 7. The method of claim 6,
wherein the first and second multiple reflection mirrors include metal mirrors. 7. The method of claim 6,
The pulse oscillator is:
a first pump laser generating a first pump light;
a first resonator for generating the pulsed laser beam from the first pump light; and
A chirped mirror for chirping the pulsed laser beam,
The first resonator includes:
a plurality of concave mirrors; and
and a first gain medium disposed between the concave mirrors. 14. The method of claim 13,
The pulse amplifier comprises:
a second pump laser generating a second pump light; and
A second resonator resonating the pump laser beam with the second pump light to amplify the intensity of the pump laser beam,
The second resonator includes:
a plurality of mirrors; and
and a second gain medium disposed between the mirrors and made of the same material as the first gain medium.

Images