Abstract

Generation of broadband coherent radiation via Raman scattering in a focused H₂ gas cell has long been the topic of experimental and theoretical investigations. A broadband laser employing this technique has a number of useful applications including spectroscopy and remote sensing and imaging. Pure vibrational Raman generation can easily be obtained by operating at high pressures. However, the maximum gain for pure rotational Raman conversion is limited by the competing vibrational Raman scattering. Consequently, experiments designed to generate only rotational Raman spectra often generate unwanted vibrational lines. In addition, spectra containing combination lines, which result from rotational Stokes or antiStokes scattering off a Stokes vibrational line, also occur in this low pressure regime. Since the high order rotational Stokes shifted lines are only several nanometers from either vibrational Stokes lines or combination rotational/ vibrational lines, it is often difficult to determine whether the spectra were generated from pure rotational or combination rotational/ vibrational processes.

© 1993 Optical Society of America