Picosecond pulse generation of blue light by frequency doubling of a GaAlAs laser diode is reported. High power pulse generation is realized by incorporating gain switching of a laser diode having saturable absorber and frequency doubling in a proton-exchanged MgO:LiNbO3 waveguide. The laser diode having longer saturable absorber can produce optical pulses with higher peak power and narrower pulsewidth. Rate equation analysis verifies these experimental results. It also indicates that there exists an optimum length of saturable absorber for a given current pulse. The proton-exchanged waveguide efficiently frequency-doubles the gain-switched laser diode oscillating in multilongitudinal modes in the ÄŒerenkov radiation scheme. The spectral bandwidth of second harmonic generation for the waveguide is evaluated at about 20 nm. This is wide enough to frequency-double all the multilongitudinal modes of the gain-switched laser diode. Blue light pulse of 7.88 mW maximum peak power and 28.7 ps pulse width is obtained for 1.23 W peak pulse of the laser diode.
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