Random quasi-phase-matched conversion of broadband radiation in a nonlinear photonic crystal

Radiation in the range 187.5-215 nm was generated via random quasi-phase-matched frequency doubling of femtosecond laser pulses in nonlinear photonic crystals of strontium tetraborate. A broad spectrum of fundamental radiation favors the probing of the nonlinear photonic crystal band structure. The red shift of the band structure upon the fundamental wave-vector rotation was observed. No principal limitations of the tuning range at its shorter wavelength boundary from the nonlinear photonic crystal (NPC) material are found. Calculation shows that the NPC structure enables enhancement of nonlinear generation in the vacuum ultraviolet.