Tunable femtosecond frequency doubling in random domain structure of strontium tetraborate

Efficient tunable femtosecond phase-matched noncollinear second-harmonic generation in randomized nonlinear photonic crystal of strontium tetraborate is obtained. Spatial spectrum of nonlinear photonic structure is not flat but enables tuning of the harmonic frequency in the range from 355 to 460 nm. The narrowing of the bandwidth of second harmonic is found to be of order of 10-20%.