Chirped bragg grating elements
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. A Bragg grating element comprising a photorefractive material having a holographic Bragg grating recorded therein, said holographic Bragg grating having a grating period that varies continuously as a function of position along an axis of the Bragg grating element, said Bragg grating defining an entrance aperture and an exit aperture, wherein the entrance aperture and exit aperture coincide.
2. The Bragg grating element of claim 1 , wherein the Bragg grating has a longitudinal axis, and the grating period varies as a function of position along the longitudinal axis.
3. The Bragg grating element of claim 2 , wherein the grating period varies as a periodic function of position along the longitudinal axis.
4. The Bragg grating element of claim 2 , wherein the grating period varies linearly as a function of position along the longitudinal axis.
5. The Bragg grating element of claim 2 , wherein the longitudinal axis is an axis along which light received by the Bragg grating is transmitted through the Bragg grating element.
6. The Bragg grating element of claim 1 , wherein the Bragg grating element has a longitudinal axis, and the grating period varies as a function of position along an axis that is transverse to the longitudinal axis.
7. The Bragg grating element of claim 6 , wherein the grating period varies as a periodic function of position along the transverse axis.
8. The Bragg grating element of claim 6 , wherein the grating period varies linearly as a function of position along the transverse axis.
9. The Bragg grating element of claim 6 , wherein the longitudinal axis is an axis along which light received by the Bragg grating is transmitted through the Bragg grating element.
10. The Bragg grating element of claim 1 , wherein the Bragg grating has a Gaussian reflectivity profile.
11. The Bragg grating element of claim 1 , wherein the Bragg grating has a super-Gaussian reflectivity profile.
12. The Bragg grating element of claim 1 , wherein the Bragg grating has an axially symmetric reflectivity profile.
13. A three-dimensional optical element having a Bragg grating recorded therein, said Bragg grating having a reflectivity profile that varies continuously as a function of position within the optical element, said Bragg grating defining an entrance aperture and an exit aperture, wherein the entrance aperture and exit aperture coincide.
14. The optical element of claim 13 , wherein the reflectivity profile is a linear function of position within the optical element.
15. The optical element of claim 13 , wherein the reflectivity profile is a Gaussian reflectivity profile.
16. The optical element of claim 13 , wherein the reflectivity profile is a super-Gaussian reflectivity profile.
17. The optical element of claim 13 , wherein the reflectivity profile is an axially symmetric reflectivity profile.
18. The optical element of claim 13 , wherein the Bragg grating is a holographic Bragg grating recorded on a photorefractive material.
19. The Bragg grating element of claim 1 , wherein the photorefractive material is a photorefractive glass.
20. The optical element of claim 13 , wherein the Bragg grating is recorded in a three-dimensional bulk of photorefractive glass.