Highly efficient frequency conversion of near-IR pulses into mid-IR range via boosted vibrational SRS in hydrogen and deuterium

摘要

Summary form only given. The main features of vibrational SRS in hydrogen and deuterium pumped by laser pulses between 1.5-2 /spl mu/m are low nonlinearity and high diffraction losses caused by a large Stokes wavelength equal to 3-12 /spl mu/m. This process is complicated by competition with SBS and backward rotational SRS, and optical breakdown at high intensity can be a significant problem. All these above factors lead to a multifold increase of the SRS threshold. As a result, the conversion efficiency of a repetitively pulsed pump mid-IR system of moderate pulse energy of a dozen millijoules is very low. To increase the efficiency and obtain conditions under which the SRS in deuterium and hydrogen can provide a real coherent source suitable for many applications, we propose to excite a phonon grating using two auxiliary "booster" pumps. The difference in frequencies of these pulses must coincide with the Raman frequency of the gas used.