Cascaded sum frequency generation of ultraviolet laser radiation at 228 nm based on stimulated Raman adiabatic passage

Abstract

A cascaded sum frequency generation (SFG) conversion scheme based on the stimulated Raman adiabatic passage (STIRAP) technique is proposed for generating an ultraviolet laser radiation at 228 nm. The conversion involves two simultaneous SFG processes, in which the signal laser radiation is converted to ultraviolet laser radiation through a negligible intermediate laser radiation. Dark state expressions and adiabatic conditions are given. Numerical simulations demonstrate the efficient conversion processes in a nonlinear LaBGeO5 (LBGO) crystal, and the effects of the coupling modulation function, pump laser intensity, and temperature on the quantum conversion efficiency are investigated. Tunable output of ultraviolet laser radiation in the 210–250 nm range is achieved by varying the signal or pump laser radiation wavelength while maintaining other input parameters. The large amount of optical data obtained in this work will contribute to the generation of deep ultraviolet laser sources based on nonlinear cascaded frequency conversion.