Shallow angle beam combining using a broad-band XeF laser

Experiments in which two xenon fluoride laser pump beams (353 nm) were crossed at an angle of 2.5 mrad in a 565-cm-long Raman amplifier containing high-pressure (10-atm) hydrogen are described. Bisecting the angle made by these two pump beams was a seed beam at the vibrational Stokes shifted wavelength of 414 nm. This seed beam was generated from a portion of the pump beam that was split off and brought to focus in a separate Raman seed generator. All three beam paths were adjusted so they arrived in the main Raman amplifier at the same time. For the 1.4-Å (FWHM) xenon fluoride pump radiation this required path offset precision to within 0.2 mm over many meters of optical path. The beam quality of the resulting amplified Stokes beam was determined through shearing interferometry techniques to be near the diffraction limit, whereas the pump beams had significant optical distortion