Refractive index measurements of solid parahydrogen

Solid para-H₂ is a promising gain medium for stimulated Raman scattering, due to its high number density and narrow Raman linewidth. In preparation for the design of a cw solid hydrogen Raman laser, we have made the first measurements, to our knowledge, of the index of refraction of a solid para-H2 crystal, in the wavelength range of 430-1100nm. For a crystal stabilized at 4:4K, this refractive index is measured to be n_p-H2 = 1.130 ± 0:001 at 514nm. A slight, but significant, dependence on the final crystal-growth temperature is observed, with higher n_{p-H 2} at higher crystal-growth temperatures. Once a crystal is grown, it can be heated up to 10 K with no change in n_p-H2 . The refractive index varies only slightly over the observed wavelength range, and no significant birefringence was observed.