Use of volume Bragg gratings for the conditioning of laser emission characteristics
Apparatus and methods for altering one or more spectral, spatial, or temporal characteristics of a light-emitting device are disclosed. Generally, such apparatus may include a volume Bragg grating (VBG) element that receives input light generated by a light-emitting device, conditions one or more characteristics of the input light, and causes the light-emitting device to generate light having the one or more characteristics of the conditioned light.
1. Apparatus for altering a characteristic of a light-emitting device, the apparatus comprising:
a laser having a laser cavity and an emission spectrum; and
a light-conditioning element comprising a three-dimensional Bragg grating element having a holographic Bragg grating recorded therein,
wherein the light-conditioning element is adapted to receive laser light emitted by the laser, the emitted laser light having a first bandwidth, and
wherein the laser operates above threshold in the absence of the feedback and the Bragg grating is adapted to redirect a portion of the received laser light, the redirected portion of the received laser light having a second bandwidth that is narrower than the first bandwidth, such that the redirected portion of the received laser light is fed back optically into the laser cavity as a narrow wavelength seed that causes a narrowing of the emission spectrum of the laser.
2. Apparatus according to claim 1 , wherein the Bragg grating element is external to the laser cavity.
3. Apparatus according to claim 2 , wherein the light-conditioning element provides an external feedback to the laser cavity.
4. Apparatus according to claim 1 , wherein the Bragg grating element is disposed within the laser cavity.
5. Apparatus according to claim 4 , wherein the light-conditioning element is configured in a non-folding configuration.
6. Apparatus according to claim 5 , wherein the Bragg grating is a transmissive Bragg grating.
7. Apparatus according to claim 5 , wherein the Bragg grating element has an axial symmetry with respect to an optical axis of the laser cavity.
8. Apparatus according to claim 4 , wherein the light-conditioning element is adapted for use as an output coupler or high reflector of the laser.
9. Apparatus according to claim 8 , wherein the Bragg grating is a reflective Bragg grating.
10. Apparatus according to claim 9 , wherein the Bragg grating element has a clear aperture, and a reflectivity that varies smoothly as a function of position within the clear aperture.
11. Apparatus according to claim 10 , comprising a soft-aperture Bragg grating reflector.
12. Apparatus according to claim 1 , wherein the laser is one of a solid-state laser, a semiconductor laser diode, a gas laser, or an ion laser.
13. Apparatus according to claim 1 , further comprising a reflector that further redirects at least a portion of the light redirected by the Bragg grating.
14. Apparatus according to claim 13 , wherein the reflector is integrated into the Bragg grating element.
15. Apparatus according to claim 1 , wherein an optical power density incident upon an area of the Bragg grating element is at least about 40 W/cm 2 .
16. Apparatus according to claim 1 , wherein a total optical power incident upon a clear aperture of the Bragg grating element is at least about 20 W.
17. Apparatus according to claim 1 , wherein the laser is an edge-emitting broad-area multiple transverse mode laser diode device.
18. Apparatus according to claim 1 , wherein the laser has a front facet reflectivity of about 0.5-20%.
19. Apparatus for altering a characteristic of a light-emitting device, the apparatus comprising:
a light emitting device; and
a Bragg grating element comprising a three-dimensional bulk of optical recording material having a Bragg grating recorded therein, wherein the Bragg grating element receives input light from the light emitting device, redirects at least a portion of the received input light, conditions one or more characteristics of the redirected light, and causes the light-emitting device to generate light having the one or more characteristics of the conditioned light, and
wherein the Bragg grating element has a clear aperture and the Bragg grating has a period and peak wavelength that vary smoothly as a function of position within the clear aperture.
20. Apparatus according to claim 19 , wherein the Bragg grating element is an extra-cavity reflective Bragg grating element that provides an external feedback to the light-emitting device.
21. Apparatus according to claim 19 , wherein the Bragg grating element is an intra-cavity reflective Bragg grating element disposed within a cavity of the light-emitting device.
22. Apparatus according to claim 19 , wherein the Bragg grating element is a transverse chirp Bragg grating reflector.
23. Apparatus according to claim 19 , wherein the light emitting device has a natural coherence before the Bragg grating conditions the one or more characteristics of the redirected light, and a reduced coherence that is less than the natural coherence after the light-emitting device is caused to generate the light having the one or more characteristics of the conditioned light.
24. Apparatus for altering a characteristic of a light-emitting device, the apparatus comprising:
a light emitting device; and
a Bragg grating element comprising a three-dimensional bulk of optical recording material having a Bragg grating recorded therein, wherein the Bragg grating element receives input light from the light emitting device, redirects at least a portion of the received input light, conditions one or more characteristics of the redirected light, and causes the light-emitting device to generate light having the one or more characteristics of the conditioned light, and
wherein the Bragg grating has a period and peak wavelength that vary smoothly through the bulk of glass as a function of position along a direction of propagation of the input light.
25. Apparatus according to claim 24 , wherein the Bragg grating element is an extra-cavity reflective Bragg grating element that provides an external feedback to the light-emitting device.
26. Apparatus according to claim 24 , wherein the Bragg grating element is an intra-cavity reflective Bragg grating element disposed within a cavity of the light-emitting device.
27. Apparatus according to claim 24 , wherein the Bragg grating element is a longitudinal chirp Bragg grating reflector.
28. Apparatus according to claim 24 , wherein the light emitting device has a natural coherence before the Bragg grating conditions the one or more characteristics of the redirected light, and a reduced coherence that is less than the natural coherence after the light-emitting device is caused to generate the light having the one or more characteristics of the conditioned light.
29. A solid-state laser having a laser cavity and a gain medium, the laser comprising a three-dimensional, Bragg grating element having a continuous holographic Bragg grating recorded therein, wherein the Bragg grating comprises a plurality of grating planes distributed along an axis of the gain medium, and provides distributed feedback of reflected radiation along the axis of the gain medium.
30. The solid-state laser of claim 29 , wherein the Bragg grating element is also the gain medium.
31. The solid-state laser of claim 29 , wherein the gain medium is attached to the Bragg grating element.
32. The solid-state laser of claim 29 , wherein a resonator transverse mode is formed in free space.
33. The solid-state laser of claim 29 , further comprising a waveguide, wherein a resonator transverse mode is formed in the waveguide.