Enhancing dynamic extinction ratio of a fiber-based seed source

We report enhancing dynamic extinction ratio (DER) of a fiber-based seed source. The seed source consists of a waveguide Mach-Zenhder intensity modulator (MZIM) and a 1064 nm-wavelength continuous wave laser diode. The phase drift in MZIM is stabilized by a feed back bias control system. As a result we achieved a DER of 39 dB at 2 ns pulse duration and 200 kHz pulse repetition rate. The seed pulses were followed by an acoustic optical modulator (AOM) in order to enhance DER by a factor of 10⁵ and amplified by the fiber amplifier with a factor of 2×10⁴. We demonstrated the second harmonic generation (SHG) of the amplified pulses with a Periodically Poled Lithium Tantalate crystal (PPLT). As a result of DER enhancement a higher conversion efficiency of SHG was achieved when the AOM is working.