Refractive index measurements of solid parahydrogen

Area of Science:

• Physics
• Materials Science
• Optics

Background:

• Solid para-hydrogen (p-H2) is a promising gain medium for stimulated Raman scattering due to its high number density and narrow Raman linewidth.
• Development of a continuous-wave (cw) solid hydrogen Raman laser requires precise knowledge of optical properties.

Purpose of the Study:

• To conduct the first measurements of the refractive index of solid para-hydrogen (p-H2) crystals.
• To investigate the refractive index across a wavelength range of 430-1100 nm.
• To understand the influence of crystal growth temperature on refractive index.

Main Methods:

• Measurement of the refractive index of solid p-H2 crystals.
• Stabilization of crystal temperature at 4.4 K.
• Wavelength range scanning from 430-1100 nm.
• Temperature variation studies up to 10 K.

Main Results:

• The refractive index of solid p-H2 was measured to be n(p-H2) = 1.130 ± 0.001 at 514 nm.
• A slight but significant dependence of refractive index on crystal growth temperature was observed.
• The refractive index remained stable when the crystal temperature was increased up to 10 K.
• Minimal variation of refractive index across the observed wavelength range and no significant birefringence were found.

Conclusions:

• The measured refractive index provides essential data for designing cw solid hydrogen Raman lasers.
• Understanding the temperature dependence of refractive index is critical for optimizing laser performance.
• Solid p-H2 exhibits suitable optical properties for advanced laser applications.