Dense Spectral Beam Combining with Volume Bragg Gratings in PTR Glass
UNIVERSITY OF CENTRAL FLORIDA ORLANDO SCHOOL OF OPTICS/CREOL
Pagination or Media Count:
An incoherent combination of laser radiation from multiple sources into a single near-diffraction-limited beam is an important problem of high power laser design. Energy brightness, but not spectral brightness, can be increased using spectral beam combining SBC. Initially, SBC was proposed on the basis of conventional surface gratings however, it was found later that volume Bragg gratings VBGs are more efficient for high density SBC with narrow separation between channels. Spectral beam combining by means of VBGs is based on the fact that diffraction efficiency at some wavelength offset from Bragg condition is zero. At this shifted wavelength, the second beam passes the grating without diffraction and is combined with a diffracted beam. Recently, a technique for high-efficiency VBG recording in photo-thermo-refractive PTR glass has been developed. While being photosensitive in the UV, PTR glass offers high transmittance in the near-IR and visible parts of spectrum, comparable to commercial optical glasses. Moreover, this glass has excellent mechanical properties and refractive index independent of temperature. These features of PTR glass enable VBGs in PTR glass to withstand high-power laser radiation, making them ideal elements for high-power SBC. Multi-kilowatt-power level for spectrally combined beams can be achieved by increasing spectral density of laser channels, i.e. decreasing spectral separation between them. The goal of this work is to explore high density SBC with PTR VBGs and determine limitations to channel density.
- Lasers and Masers