Low-power frequency conversion through parametric interaction and cascaded processes in a N-(4-nitrophenyl)-l-prolinol crystal Original Research Article

Crystals of N-(4-nitrophenyl)-l-prolinol (NPP) of large size and of high optical quality are grown in methanol solution starting from toluene nucleated seeds. Measurements are conducted on a 2.8 mm thick specimen obtained by cleaving a thick slice parallel to the (101) plane. This type of cut allows access to the dominant phase-matching orientation, including the noncritical one. We exploit the high second-order susceptibility of NPP to produce various frequency conversion processes (second harmonic, parametric generation and nearly-degenerate wavelength conversion through cascading) at a very low input intensity. In particular, frequency conversion of a signal pulse (from 1.16 to 1.14 μm) under the action of a pump pulse (at 1.15 μm) with unit gain is obtained with a pump intensity as low as 9 MW/cm2, while parametric generation from quantum noise, with 10% conversion efficiency, is obtained in a single pass of the pump pulse focussed to an intensity around 108 W/cm2.