Femtosecond optical pulse generation using quasi-velocity-matched electrooptic phase modulator

Ultrashort optical pulses in the femtosecond range were generated from a continuous-wave (CW) narrow linewidth laser by using the chirping compression method with a highly efficient electrooptic phase modulator. Before the femtosecond pulse generation, a high modulation index electrooptic modulator specially designed was fabricated by employing the quasi-velocity-matching. In the pulse generation experiment, the electrooptic modulator and a grating pair as a negative group delay dispersion element were used for a 514.5-nm CW Ar laser. As a result, the sideband spectrum of 2.0 THz full-width half-maximum (FWHM) was produced and 560-fs optical pulses with 16.25-GHz repetition rate was successfully obtained. For this electrooptic pulse compression method is applicable to the negative group delay dispersion element as well as the positive group delay dispersion.