Second-harmonic generation in thermally poled twin-hole fiber using nanosecond and femtosecond laser pulses

This paper investigates the second-harmonic generation (SHG) in poled twin-hole fiber. Both a Q-switched YAG laser and a femtosecond fiber laser are used as fundamental sources. The characteristics of SHG in the poled twin-hole fiber is studied, and the direction of nonlinearity and phase matching between fundamental and SH waves are discussed.