VUV Generation in Improved Nonlinear Photonic Crystal Structure of α-strontium Tetraborate

Orthorhombic strontium tetraborate is one of a few nonlinear optical materials feasible for generation of radiation in the range below 150 nm. Possibility of efficient nonlinear optical generation in strontium tetraborate depends on existence of spontaneously grown domain structures in this non-ferroelectric crystal. Present Letter reports investigation of improved domain (nonlinear photonic crystal) structure the reciprocal superlattice vector of which demonstrates increase in the vacuum ultraviolet range upon the generated wavelength decrease. Vacuum ultraviolet generation tunable from 200 to 162 nm with the efficiency above 10 –4 is achieved with the employment of starting femtosecond laser of the lowest power class.