Wavelength selective external resonator and beam combining system for dense wavelength beam combining laser

Patent metadata

Field	Value
Publication number	US-9905993-B2
Application number	US-201615054164-A
Country	US
Kind code	B2
Filing date	Feb 26, 2016
Priority date	Nov 22, 2013
Publication date	Feb 27, 2018
Grant date	Feb 27, 2018

Abstract

Wavelength-selective external resonators can be used to greatly increase the output brightness of dense wavelength beam combining (DWBC) system beams by stabilizing the wavelengths of the beams emitted by the individual emitters of the DWBC laser source. The present invention pertains to external resonant cavities that utilize thin-film filtering elements as wavelength-selective elements in external resonators. The present invention further pertains to particular embodiments that utilize thin-film filtering elements in DWBC systems as both output beam coupling elements and wavelength selective elements. The present invention provides advantages over the prior art that include decreased cost, increased fidelity of wavelength selection, and increased wall plug efficiency.

First claim

What is claimed is:

1. A beam wavelength stabilizing system comprising:
a laser source having a plurality of emitters that each emit a laser beam;
a reflective element;
a wavelength filtering element disposed between the laser source and the reflective element; and
a position-to angle transformation optic disposed between the laser source and the wavelength filtering element;
wherein each laser beam emitted by the plurality of emitters has a single wavelength,
wherein the position-to-angle transformation optic imparts, on each laser beam emitted by the plurality of emitters, a position-dependent angle of incidence with respect to the wavelength filtering element,
wherein the wavelength filtering element is configured to selectively transmit, towards the reflective element, only optical power corresponding to certain wavelength-angle of incidence pairs, and
wherein the reflective element reflects a portion of the optical power selectively transmitted by the wavelength filtering element back at the wavelength filtering element such that the portion of the optical power selectively transmitted by the wavelength filtering element interacts with the wavelength filtering element and is directed into the laser source as feedback.

2. The beam wavelength stabilization system of claim 1 , wherein the wavelength filtering element is a thin-film filtering element.

3. The beam wavelength stabilization system of claim 2 , wherein the thin-film filtering element is a thin-film etalon.

4. The beam wavelength stabilization system of claim 3 , wherein a thickness of the thin-film etalon is less than four times the wavelength corresponding to the shortest single wavelength emitted by the laser source.

5. The beam wavelength stabilization system of claim 3 , wherein the thin-film etalon comprises two parallel, reflective surfaces with reflectivity greater than or equal to 0.99.

6. The beam wavelength stabilization system of claim 3 , wherein the thin-film etalon comprises two reflective surfaces, the two surfaces having different values of reflectivity.

7. The beam wavelength stabilization system of claim 3 , wherein the thin-film etalon reflects a portion of the optical power corresponding to a wavelength at which the thin-film etalon is partially transmissive.

8. The beam wavelength stabilization system of claim 3 , further comprising:
a partially reflective surface positioned on the surface of the thin-film etalon.

9. The beam wavelength stabilization system of claim 3 further comprising:
a first high reflective element; and
a second position-to-angle transformation optic disposed between the thin-film etalon and the first high reflective element;
wherein the thin-film etalon transmits a portion of the optical power emitted by the laser source as a first feedback branch input and directs the first feedback branch input at the first high reflective element; and
wherein the second position-to-angle transformation optic collimates a plurality of component beams of the first feedback branch input.

10. The beam wavelength stabilization system of claim 3 , further comprising:
a second high reflective element; and
a position-to-angle transformation optic disposed between the thin-film etalon and the second high reflective element.

11. The beam wavelength stabilization system of claim 10 , wherein the thin-film notch filter reflects a portion of the optical power corresponding to a wavelength at which the thin-film notch filter is partially transmissive.

12. The beam wavelength stabilization system of claim 2 , wherein the thin-film filtering element is a thin-film notch filter.

13. The beam wavelength stabilization system of claim 12 , further comprising:
a first high reflective element
a second position-to-angle transformation optic disposed between the thin-film notch filter and the first high reflective element;
a second high reflective element; and
a third position-to-angle transformation optic disposed between the thin-film notch filter and the second high reflective element;
wherein the thin-film notch filter reflects a portion of the optical power emitted by the laser source as a first feedback branch input and directs the first feedback branch input at the first high reflective element; and
wherein the second position-to-angle transformation optic collimates a plurality of component beams of the first feedback branch input.

14. The beam combining system of claim 1 , wherein the thin-film filtering element comprises multiple pairs of reflective surfaces separated by a thickness.

15. A method for stabilizing the wavelengths of each of a plurality of beams, each beam emitted by a single emitter of a laser source comprising a plurality of emitters, the method comprising:
directing each of the plurality of beams at a reflective element through a position-to-angle transformation optic and a wavelength filtering element;
imparting, by the position-to-angle transformation optic on each of the plurality of beams, a position-dependent angle of incidence with respect to the wavelength filtering element;
selectively transmitting, by the wavelength filtering element, only optical power corresponding to certain wavelength-angle of incidence pairs; and
reflecting, by the reflective element, a portion of the optical power selectively transmitted by the wavelength filtering element back at the wavelength filtering element as a feedback component such that the feedback component interacts with the wavelength filtering element and is directed into the laser source as feedback.

16. A method for producing a combined output beam formed of components of a plurality of emitted beams, each emitted beam emitted by a single emitter in a laser source having a plurality of beam emitters, the method comprising:
directing each of the plurality of beams at a reflective element through a position-to-angle transformation optic and a wavelength filtering element;
imparting, by the position-to-angle transformation optic on each of the plurality of beams, a position-dependent angle of incidence with respect to the wavelength filtering element;
selectively transmitting, by the wavelength filtering element, only optical power corresponding to certain wavelength-angle of incidence pairs; and
reflecting, by the reflective element, a portion of the optical power selectively transmitted by the wavelength filtering element back at the wavelength filtering element as a feedback component such that the feedback component interacts with the wavelength filtering element and is directed into the laser source as feedback; and
directing, as an output component, a portion of the optical power of each of the plurality of emitted beams at a beam combining element arranged outside a wavelength stabilization system.

Assignees

• Trumpf Laser Gmbh

Inventors

• Huber Rudolf
• Zimer Hagen
• Killi Alexander
• Tillkorn Christoph
• Ried Steffen

Classifications

• G02B27/1006

  for splitting or combining different wavelengths (G02B27/1086, G02B27/141 take precedence) · CPC title

• H01S5/4062

  with an external cavity or using internal filters, e.g. Talbot filters · CPC title

• H01S5/141 Primary

  using a wavelength selective device, e.g. a grating or etalon (H01S5/146 takes precedence) · CPC title

• H01S5/4012

  Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms · CPC title

• H01S5/4087

  emitting more than one wavelength · CPC title