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 light emitting device having an emission spectrum and defining a fast axis and a slow axis thereof; and
a three-dimensional reflective Bragg grating element that is adapted to receive light emitted from the light-emitting device, the emitted light having a first bandwidth, wherein the Bragg grating comprises a plurality of flat Bragg grating planes,
wherein the Bragg grating is adapted to redirect only a portion of the received light, the redirected portion having a second bandwidth that is narrower than the first bandwidth, such that the redirected portion is fed back directly into the light-emitting device as a narrow-wavelength seed that causes a narrowing of the emission spectrum of the light-emitting device, and
wherein the Bragg grating element is positioned to receive the light emitted from the light emitting device in the absence, between the light emitting device and the Bragg grating element, of any optics that collimates or reduces divergence along either the fast axis or the slow axis of the light emitting device.
2. Apparatus according to claim 1 , wherein the Bragg grating element has a thickness in the range of about 0.1 mm to about 3.0 mm.
3. Apparatus according to claim 1 , wherein the Bragg grating element is positioned at distance in front of the laser, the distance being in a range from about 0 mm to about 5 mm.