# US 2014/0192829 A1 · Multi-crystal frequency tripler for third harmonic conversion

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- Number: US 2014/0192829 A1
- Document ID: US20140192829A1
- Status: Published application
- Kind: A1
- Application number: 13/884,598
- Filed: 2011-11-08
- Published: 2014-07-10
- Earliest claimed: 2010-11-09
- Inventors: Mark K. Henesian; Amber L. Bullington; Kenneth R. Manes; Mary L. Spaeth; Robert Deri; Chris A. Ebbers
- Web page: https://patentgrep.com/patent/US20140192829A1

## CPC

- G02F 1/3532: {Arrangements of plural nonlinear devices for generating multi-colour light beams, e.g. arrangements of SHG, SFG, OPO devices for generating RGB light beams}
- G02F 1/353: {Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams}
- G02F 1/3551: {Crystals}
- H01S 3/109: Frequency multiplication, e.g. harmonic generation
- G02F 1/3507: {Arrangements comprising two or more nonlinear optical devices}
- G02F 1/354: {Third or higher harmonic generation}
- H01S 3/0092: {Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity (nonlinear frequency conversion per se G02F1/35)}
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- 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

## Abstract

An optical system includes a laser source operable to output a laser beam at a fundamental wavelength and a frequency conversion system. The frequency conversion system includes a frequency doubler module including a first plurality of nonlinear optical crystals and a frequency polarization tripler module including a second plurality of nonlinear optical crystals. The optical system also includes a control system coupled to the frequency conversion system and a diagnostics system coupled to the frequency conversion system.

## Claims

### Claim 1

A frequency conversion system comprising:
a frequency doubler module disposed along a beam path and comprising a first plurality of non-linear crystals; and
a frequency tripler module disposed along the beam path and comprising a second plurality of non-linear crystals.

### Claim 2 (depends on 1)

The frequency conversion system of claim 1 wherein:
a first crystal of the first plurality of non-linear crystals is detuned by a first angle and a second crystal of the first plurality of non-linear crystals is detuned by a second angle; and
a first crystal of the second plurality of non-linear crystals is detuned by a third angle and a second crystal of the second plurality of non-linear crystals is detuned by a fourth angle.

### Claim 3 (depends on 2)

The frequency conversion system of claim 2 wherein:
the first angle is measured between a direction of beam propagation and an optic axis of the first crystal of the first plurality of non-linear crystals in a first direction; and
the second angle is measured between the direction of beam propagation and the optic axis of the second crystal of the first plurality of non-linear crystals in a second direction opposite to the first direction.

### Claim 4 (depends on 3)

The frequency conversion system of claim 3 wherein the first angle is a positive angle and the second angle is a negative angle.

### Claim 5 (depends on 2)

The frequency conversion system of claim 2 wherein:
the third angle is measured between a direction of beam propagation and an optic axis of the first crystal of the second plurality of non-linear crystals in a first direction; and
the fourth angle is measured between the direction of beam propagation and the optic axis of the second crystal of the second plurality of non-linear crystals in a second direction opposite to the first direction.

### Claim 6 (depends on 5)

The frequency conversion system of claim 5 wherein the third angle is a positive angle and the fourth angle is a negative angle.

### Claim 7 (depends on 1)

The frequency conversion system of claim 1 further comprising a continuous random phase plate disposed along the beam path between the frequency doubler module and the frequency tripler module.

### Claim 8 (depends on 1)

The frequency conversion system of claim 1 wherein:
the frequency doubler module is operable to receive a 1ω beam and output a portion of the 1ω beam and a 2ω beam; and
the frequency tripler module is operable to receive the 1ω beam and the 2ω beam and to output a 3ω beam.

### Claim 9 (depends on 1)

The frequency conversion system of claim 1 wherein the first plurality of non-linear crystals comprises at least two type I crystals.

### Claim 10 (depends on 1)

The frequency conversion system of claim 1 wherein the first plurality of non-linear crystals comprises at least two type II crystals.

### Claim 11 (depends on 1)

The frequency conversion system of claim 1 wherein the second plurality of non-linear crystals comprise a set of type II crystals.

### Claim 12 (depends on 11)

The frequency conversion system of claim 11 wherein the set of type II crystals comprises three crystals.

### Claim 13 (depends on 1)

The frequency conversion system of claim 1 wherein the first plurality of non-linear crystals comprises DKDP and the second plurality of non-linear crystals comprise DKDP.

### Claim 14 (depends on 1)

The frequency conversion system of claim 1 further comprising a polarization rotator.

### Claim 15 (depends on 14)

The frequency conversion system of claim 14 wherein the polarization rotator comprises a DKDP half-wave plate.

### Claim 16 (depends on 1)

The frequency conversion system of claim 1 wherein at least one of the frequency doubler module or the frequency tripler module comprises a set of three non-linear optical crystals, wherein a thickness of a first crystal of the set of three non-linear optical crystals is less than a thickness of a second crystal of the set of three non-linear optical crystals.

### Claim 17

A method of generating frequency converted light, the method comprising:
providing an input beam characterized by a fundamental wavelength;
frequency converting a portion of the input beam to a doubled beam characterized by a doubled wavelength half the fundamental wavelength, wherein frequency converting the input beam comprises transmitting the input beam through a first plurality of non-linear optical crystals and outputting the doubled beam and another portion of the input beam; and
frequency converting the doubled beam and the another portion of the input beam to a tripled beam characterized by a tripled wavelength two thirds the doubled wavelength, wherein frequency converting the doubled beam and the remaining portion of the input beam comprises transmitting the doubled beam light and the remaining portion of the input beam through a second plurality of non-linear optical crystals and outputting the tripled beam.

### Claim 18 (depends on 17)

The method of claim 17 wherein frequency converting a portion of the input beam to a doubled beam comprises:
detuning a first crystal of the first plurality of non-linear optical crystals by a first angle; and
detuning a second crystal of the first plurality of non-linear optical crystals by a second angle.

### Claim 19 (depends on 18)

The method of claim 18 wherein:
the first angle is measured between a direction of beam propagation and an optic axis of the first crystal in a first direction; and
the second angle is measured between the direction of beam propagation and the optic axis of the second crystal in a second direction opposite to the first direction.

### Claim 20 (depends on 19)

The method of claim 19 wherein the first angle is a positive angle and the second angle is a negative angle.

### Claim 21 (depends on 17)

The method of claim 17 wherein frequency converting the doubled beam and the remaining portion of the input beam to the tripled beam comprises:
detuning a first crystal of the second plurality of non-linear optical crystals by a third angle; and
detuning a second crystal of the second plurality of non-linear optical crystals by a fourth angle.

### Claim 22 (depends on 21)

The method of claim 21 wherein:
the third angle is measured between a direction of beam propagation and an optic axis of the first crystal in a first direction; and
the fourth angle is measured between the direction of beam propagation and the optic axis of the second crystal in a second direction opposite to the first direction.

### Claim 23 (depends on 22)

The method of claim 22 wherein the third angle is a positive angle and the fourth angle is a negative angle.

### Claim 24 (depends on 17)

The method of claim 17 wherein the first plurality of non-linear crystals comprise a set of two or more type I crystals.

### Claim 25 (depends on 17)

The method of claim 17 wherein the first plurality of non-linear crystals comprise a set of two or more type II crystals.

### Claim 26 (depends on 17)

The method of claim 17 wherein the second plurality of non-linear crystals comprise a set of two or more type II crystals.

### Claim 27 (depends on 17)

The method of claim 17 wherein the first plurality of non-linear crystals comprises DKDP and the second plurality of non-linear crystals comprise DKDP.

### Claim 28 (depends on 17)

The method of claim 17 further comprising rotating the polarization of at least the doubled beam and the remaining portion of the input beam or the tripled beam.

### Claim 29

An optical system comprising:
a laser source operable to output a laser beam at a fundamental wavelength;
a frequency conversion system including:
a frequency doubler module including a first plurality of nonlinear optical crystals; and
a frequency tripler module including a second plurality of nonlinear optical crystals;
a control system coupled to the frequency conversion system; and
a diagnostics system coupled to the frequency conversion system.

### Claim 30 (depends on 29)

The optical system of claim 29 wherein the frequency doubler module further comprises a first plurality of rotation stages, each of the first plurality of rotation stages being operable to rotate one of the first plurality of nonlinear optical crystals.

### Claim 31 (depends on 29)

The optical system of claim 29 wherein the frequency tripler module further comprises a second plurality of rotation stages, each of the second plurality of rotation stages being operable to rotate one of the second plurality of nonlinear optical crystals.

### Claim 32 (depends on 29)

The optical system of claim 29 wherein the frequency conversion system further comprises a CPP plate disposed between the frequency doubler module and the frequency tripler module.

### Claim 33 (depends on 29)

The optical system of claim 29 wherein first plurality of nonlinear optical crystals comprise DKDP crystals and the second plurality of nonlinear optical crystals comprise DKDP crystals.

### Claim 34 (depends on 29)

The optical system of claim 29 wherein the frequency conversion system further comprises a half wave plate optically upstream of the frequency doubler module.