The correlated Stokes-anti-Stokes Raman scattering mediated by phonons was introduced in 1977 by Klyshko. In the last two decades, it has been broadly studied experimentally, including results on diamond, graphene and transparent liquid. The theoretical description of non-resonant Stokes-anti-Stokes pair production was shown to be formally similar to the BCS theory of superconductivity, raising attention to the study of pair production as a function of the Raman shift. Intriguingly, the pair production efficiency is not symmetric with respect to the positive versus negative detuning from phonon resonance, a result that was shown for a 180fs pulsed laser, and that remains without a theoretical explanation. Here we show the asymmetry is persistent in diamond measured with lasers of different pulse widths (180 fs and 5 ps) and different wavelengths (633 nm versus 785 nm).
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