# US 2021/0242649 A1 · Laser system

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- Number: US 2021/0242649 A1
- Document ID: US20210242649A1
- Status: Published application
- Kind: A1
- Application number: 17/237,471
- Filed: 2021-04-22
- Published: 2021-08-05
- Earliest claimed: 2017-01-26
- Assignees: Gigaphoton Inc.
- Applicants: Gigaphoton Inc.
- Inventors: Takashi ONOSE
- Web page: https://patentgrep.com/patent/US20210242649A1

## CPC

- H01S 3/0085: {Modulating the output, i.e. the laser beam is modulated outside the laser cavity}
- H01S 3/2375: {Hybrid lasers (H01S3/07 takes precedence)}
- G02B 27/0983: {being curved}
- G02B 27/10: Beam splitting or combining systems (polarising systems G02B27/28; mixing and splitting light signals using optical waveguides G02B6/28; {beam shaping, e.g. changing the cross-sectional area, by dividing or superposing multiple light beams G02B27/0905})
- G02B 27/141: {using dichroic mirrors}
- G02B 27/48: Laser speckle optics
- G03F 7/70025: {by lasers}
- H01S 3/0057: {Temporal shaping, e.g. pulse compression, frequency chirping (soliton generation and propagation G02F1/3513, H01S3/063 and H01S3/108)}
- H01S 3/10: Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S 3/1003: {tunable optical elements, e.g. acousto-optic filters, tunable gratings}
- H01S 3/2308: {Amplifier arrangements, e.g. MOPA}
- H01S 5/005: {Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping (H01S5/026, H01S5/18388 take precedence)}
- H01S 3/005: {Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping (shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B)}
- H01S 3/0071: {Beam steering, e.g. whereby a mirror outside the cavity is present to change the beam direction}
- H01S 3/10053: {Phase control}
- H01S 3/2251: {ArF, i.e. argon fluoride is comprised for lasing around 193 nm}
- H01S 3/2333: {Double-pass amplifiers}
- H01S 3/2366: {comprising a gas as the active medium (H01S3/10092, H01S3/2383 take precedence)}
- H01S 2301/08: Generation of pulses with special temporal shape or frequency spectrum
- H01S 2301/20: Lasers with a special output beam profile or cross-section, e.g. non-Gaussian
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G)

## Abstract

A laser system including: A. a laser apparatus configured to output a pulse laser beam; B. an optical pulse stretcher including a delay optical path for expanding a pulse width of the pulse laser beam; and C. a phase optical element included in the delay optical path and having a function of spatially and randomly shifting a phase of the pulse laser beam. The phase optical element includes a plurality of types of cells providing different amounts of phase shift to the pulse laser beam and arranged irregularly in any direction.

## Claims

### Claim 1

An optical pulse stretcher that expands a pulse width of a pulse laser beam, the optical pulse stretcher comprising:
a delay optical system including a plurality of mirrors;
a beam splitter that divides the pulse laser beam into a first pulse laser beam that does not circulate through the delay optical system and a second pulse laser beam that circulates through the delay optical system; and
a phase optical element that is included in the delay optical system and changes speckle distribution of the second pulse laser beam such that the speckle distribution of the second pulse laser beam is different from speckle distribution of the first pulse laser beam,
the beam splitter dividing the second pulse laser beam having circulated through the delay optical system into a third pulse laser beam that does not circulate through the delay optical system and a fourth pulse laser beam that circulates through the delay optical system, and
the first pulse laser beam being combined with the third pulse laser beam.

### Claim 2 (depends on 1)

The optical pulse stretcher according to claim 1, wherein:
the phase optical element changes speckle distribution of the fourth pulse laser beam such that the speckle distribution of the fourth pulse laser beam is different from the speckle distribution of the second pulse laser beam,
the beam splitter divides the fourth pulse laser beam having circulated through the delay optical system into a fifth pulse laser beam that does not circulate through the delay optical system and a sixth pulse laser beam that circulates through the delay optical system, and
the first pulse laser beam being combined with the third pulse laser beam and the fifth pulse laser beam.

### Claim 3 (depends on 2)

The optical pulse stretcher according to claim 2, wherein:
the phase optical element includes a plurality of types of cells that shifts a phase of the pulse laser beam, provides different amounts of phase shift and are arranged irregularly in any dimensions, and
an amount of deviation between optical axes of the second and fourth pulse laser beams is larger than a size of the cell.

### Claim 4 (depends on 1)

The optical pulse stretcher according to claim 1, wherein
the phase optical element has a function of spatially and randomly shifting a phase of the pulse laser beam.

### Claim 5 (depends on 1)

The optical pulse stretcher according to claim 1, wherein:
the phase optical element includes a transmission type optical element, and
the speckle distribution of the second pulse laser beam is changed after the second pulse laser beam is transmitted through the phase optical element.

### Claim 6 (depends on 1)

The optical pulse stretcher according to claim 1, wherein
the phase optical element includes a reflection type optical element, and
the speckle distribution of the second pulse laser beam is changed after the second pulse laser beam is reflected by the phase optical element.

### Claim 7 (depends on 1)

The optical pulse stretcher according to claim 1, wherein
the phase optical element is arranged on an optical path of a beam collimated in an optical path of the delay optical system.

### Claim 8

A laser system comprising:
a laser apparatus;
an optical pulse stretcher that expands a pulse width of a pulse laser beam output from the laser apparatus; and
an amplifier that amplifies the pulse laser beam, the pulse width of the pulse laser beam having been expanded by the optical pulse stretcher,
the optical pulse stretcher comprising:
a delay optical system including a plurality of mirrors;
a beam splitter that divides the pulse laser beam into a first pulse laser beam that does not circulate through the delay optical system and a second pulse laser beam that circulates through the delay optical system; and
a phase optical element that is included in the delay optical system and changes speckle distribution of the second pulse laser beam such that the speckle distribution of the second pulse laser beam is different from speckle distribution of the first pulse laser beam,
the beam splitter dividing the second pulse laser beam having circulated through the delay optical system into a third pulse laser beam that does not circulate through the delay optical system and a fourth pulse laser beam that circulates through the delay optical system, and
the first pulse laser beam being combined with the third pulse laser beam.

### Claim 9 (depends on 8)

The laser system according to claim 8, wherein
the laser system includes the laser apparatus that is a solid-state laser apparatus or an excimer laser apparatus as a master oscillator.

### Claim 10 (depends on 8)

The laser system according to claim 8, wherein
the amplifier is an excimer laser apparatus.