Highly efficient, single-pass, harmonic generator with round output beam

Patent metadata

Field	Value
Publication number	US-9912114-B2
Application number	US-201414209908-A
Country	US
Kind code	B2
Filing date	Mar 13, 2014
Priority date	Mar 14, 2013
Publication date	Mar 6, 2018
Grant date	Mar 6, 2018

Abstract

An extra cavity harmonic generator system may produce a round, non-astigmatic third harmonic output beam from a nominally round, non-astigmatic, diffraction limited input fundamental beam. The system may include a second harmonic generation crystal. An input fundamental beam size is expanded in a non-walkoff direction for the SHG crystal at the SHG crystal input face. A higher harmonic generation crystal has an output face oriented at an oblique angle of incidence in a non-walkoff direction for the HHG crystal such that an output higher harmonic beam size is contracted in this direction. Expansion of the input fundamental beam at the SHG crystal input face exceeds reduction of third harmonic beam at the HHG crystal output face.

First claim

What is claimed is:

1. An extra cavity harmonic generator system configured to produce a round, non-astigmatic third harmonic output beam from a nominally round, non-astigmatic, diffraction limited input fundamental beam, the system comprising:
a second harmonic generation (SHG) crystal having an input face oriented at an angle of incidence with respect to the input fundamental beam wherein the fundamental beam size is expanded in a non-walkoff direction for the SHG crystal at the input face, the SHG crystal being configured to generate a second harmonic beam from the input fundamental beam;
a third harmonic generation (THG) crystal having an output face oriented at an oblique angle of incidence in a non-walkoff direction for the THG crystal such that the third harmonic beam size is contracted in this direction, the THG crystal being configured to generate a third harmonic beam from the second harmonic beam and a residual fundamental beam from the SHG crystal;
wherein an expansion of the input fundamental beam at the input face of the SHG crystal exceeds a reduction of a third harmonic beam at the output face of the THG crystal.

2. The system of claim 1 , wherein the input face of the SHG crystal is oriented an oblique angle of incidence with respect to the fundamental input beam to expand the fundamental beam in the non-walkoff direction of the SHG crystal at the input face.

3. The system of claim 1 , wherein the output face of the THG crystal is oriented at less than a Brewster angle with respect to the third harmonic beam.

4. The system of claim 1 , wherein the third harmonic beam is angularly separated from the fundamental and second harmonic beams by an angle greater than an angular divergence of the beams.

5. The system of claim 1 , wherein an average power of the third harmonic beam is greater than about 30 W.

6. The system of claim 1 , wherein the input face of the SHG crystal is oriented within about 5 degrees of Brewster angle with respect to the input fundamental beam.

7. The system of claim 1 , wherein the output face of the THG crystal is oriented at a near-20 degree incident angle with respect to the residual fundamental and second harmonic beams where the residual fundamental and second harmonic beams are incident at the output face of the THG crystal.

8. The system of claim 1 , wherein the output face of the THG crystal is oriented at an incident angle with respect to the residual fundamental and second harmonic beams where the residual fundamental and second harmonic beams are incident at the output face of the THG crystal, wherein the incident angle is selected to optimize net efficiency of conversion of the fundamental beam to third harmonic radiation.

9. An extra cavity harmonic generator system configured to produce a round, non-astigmatic third harmonic output beam from a nominally round, non-astigmatic, diffraction limited input fundamental beam, the system comprising:
a second harmonic generation (SHG) crystal having an input face oriented at an angle of incidence with respect to the input fundamental beam wherein the fundamental beam size is expanded in a non-walkoff direction for the SHG crystal at the input face, the SHG crystal being configured to generate a second harmonic beam from the input fundamental beam;
one or more higher harmonic generation (HHG) crystals having an output face oriented at an oblique angle of incidence in a non-walkoff direction for at least one of the HHG crystals such that an output higher harmonic beam size is contracted in this direction, the one or more HHG crystals being configured to generate a higher harmonic beam from the second harmonic beam and a residual fundamental beam from the SHG crystal;
wherein an expansion of the input fundamental beam at the input face of the SHG crystal exceeds a reduction of a third harmonic beam at the output face of at least one of the one or more HHG crystals.

10. The system of claim 9 , wherein the one or more HHG crystals include a THG crystal configured to generate a third harmonic beam from the second harmonic beam and a first residual fundamental beam from the SHG crystal and a fourth (FHG) harmonic generation crystal configured to generate a fourth harmonic beam from the third harmonic beam and a second residual fundamental beam from the THG crystal.

11. The system of claim 9 , wherein the one or more HHG crystals include a nonlinear crystal configured to generate a fourth harmonic beam from the second harmonic beam.

Assignees

• Ipg Photonics Corp

Inventors

• Leonardo Manuel J
• Arbore Mark A
• Keaton Gregory L

Classifications

• H01S3/067

  Fibre lasers · CPC title

• H01S3/0092 Primary

  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) · CPC title

• H01S3/06754

  Fibre amplifiers (H01S3/06708 takes precedence) · CPC title

• H01S3/10084

  Frequency control by seeding · CPC title

• H01S3/1666

  borate, carbonate, arsenide · CPC title