Random quasi-phase-matched nonlinear optical conversion of supercontinuum to the ultraviolet

Conversion of fs supercontinuum to the ultraviolet (UV) range from 260 to 305 nm in nonlinear photonic crystal of strontium tetraborate is obtained. Spectral shape of generated UV radiation is governed by the shape of supercontinuum spectrum, focusing conditions and phase mismatch in the material of nonlinear photonic crystal. Maximum integral UV power of 2.6 μW was obtained in the case of weaker focusing, and peaks with the spectral width 1–3 nm dominate in the spectrum. Using tight focusing, broadband radiation in the range 265–300 nm was obtained.