Broadband and Efficient Femtosecond Second-Harmonic Generation With Temperature-Dependent Group Velocity Matching

In this paper, a method to achieve the simultaneous quasi-phased-matched and group-velocity-matched second harmonic (SH) generation for femtosecond pulses at 1550 nm band was proposed. Under the polarization configuration (e+e-o), group velocity can be matched by control of temperature. The described coupling equations were applied to MgO doped periodically poled lithium niobate crystal, and the temporal and spectral characteristics of interaction waves were investigated. The fractional time delay between the fundamental frequency wave and the SH wave is as a function of temperature and the input pulse duration, resulting in optimal conversion efficiency. Such method can be useful for the broadband and efficient ultrafast SH pulse generation and pulse compression applications.