# US 8,542,713 B2 · Enhanced optical pumping of materials exhibiting polarization-dependent absorption

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- Number: US 8,542,713 B2
- Document ID: US8542713B2
- Status: Granted
- Kind: B2
- Application number: 10/857,642
- Filed: 2004-05-28
- Published: 2004-12-23
- Granted: 2013-09-24
- Earliest claimed: 2003-05-30
- Assignees: Coherent Kaiserslautern GmbH
- Applicants: Achim Nebel; Ralf Knappe; Louis McDonagh
- Inventors: Achim Nebel; Ralf Knappe; Louis McDonagh
- Web page: https://patentgrep.com/patent/US8542713B2

## CPC

- H01S 3/09415: {the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping}
- H01S 3/1611: {neodymium}
- H01S 3/1673: {YVO4 [YVO]}
- 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 optically pumped laser oscillator or amplifier including a laser head including a gain medium exhibiting polarization-dependent absorption along two crystallographic axes and a pump source producing a pump beam. The medium's absorption coefficients along both of the crystallographic axes are equal or the difference between the absorption coefficients relative to the lowest absorption coefficients is reduced at least by a factor of two compared to the same relative difference between the two absorption coefficients at the medium's absorption peaks. In some embodiments, the gain medium is a crystal, e.g., a Neodymium-doped Vanadate (Nd:YVO4) crystal, greater than 15 mm. In various embodiments, the optically pumped laser oscillator or amplifier includes two pump sources producing two pump beams.

## Claims

### Claim 1

An optically pumped laser oscillator or amplifier, comprising:
a laser head including a gain medium exhibiting polarization-dependent absorption along two crystallographic axes, wherein the gain medium is a Neodymium-doped Vanadate (Nd:YVO4) crystal; and
a pump source producing pump light having a center wavelength of 888±2 nm.

### Claim 2 (depends on 1)

The oscillator or amplifier of claim 1, wherein the pump light is emitted by at least one laser diode and delivered to the gain medium through a non-polarization-maintaining device.

### Claim 3 (depends on 1)

The oscillator or amplifier of claim 1, wherein the pump light is emitted by laser diodes whose beams are combined by means of polarizing elements.

### Claim 4 (depends on 1)

The oscillator or amplifier of claim 1, wherein the gain medium is end-pumped, the pump and laser radiations traveling through the crystal with close to parallel directions.

### Claim 5 (depends on 1)

The oscillator or amplifier of claim 1, wherein the Neodymium-doped Vanadate (Nd:YVO4) crystal is longer than 15 mm.

### Claim 6

A method comprising:
operating a pump laser to generate pump light having a center wavelength of 888±2 nm; and
pumping the pump light into a laser medium having polarization-dependent absorption along two crystallographic axes, the laser medium being a Neodymium-doped Vanadate (Nd:YVO4) crystal.

### Claim 7 (depends on 6)

The method of claim 6, wherein the pump light is emitted by laser diodes and delivered to a gain medium through a non-polarization-maintaining device.

### Claim 8 (depends on 6)

The method of claim 6, wherein the pump light is emitted by laser diodes whose beams are combined by means of polarizing elements.

### Claim 9 (depends on 6)

The method of claim 6, wherein the gain medium is end-pumped, the pump and laser radiations traveling through the crystal with close to parallel directions.

### Claim 10 (depends on 6)

The method of claim 6, wherein the Neodymium-doped Vanadate (Nd:YVO4) crystal is longer than 15 mm.