Abstract

Molecular modulation in Raman media [1] has been shown to be an effective technique for frequency conversion of signals of arbitrary wavelength [2, 3]. The technique involves first inducing a coherent oscillation of the molecular population using intense pump and Stokes beams whose frequencies differ by the Raman transition frequency Ω. This "recording" step produces a travelling refractive index wave that (within the lifetime of the Raman coherence and provided phase-matching can be achieved) can be used to create a frequency-shifted version of a second "read-out" signal. Common approaches to achieving phase-matching and thus high conversion efficiencies employ crossed beam configurations in free space or higher order modes in fibres [2].

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