Optical frequency conversion by a rotating molecular wave plate

We demonstrate efficient four-wave mixing in low-pressure molecular deuteri um without the need for phase matching. We use two laser fields with opposi te circular polarizations to produce a strong excitation of a rovibrational transition at a frequency of 3167 cm(-1). The coherent molecular motion, i n turn, modulates a third laser field (also circularly polarized) and resul ts in highly efficient single-sideband conversion. (C) 2001 Optical Society of America.