Frequency doubling of picosecond pulses in periodically poled D-shape silica fibre

D-shape silica fibres have been periodically poled at an elevated temperature by applying high voltage via a patterned electrode deposited on the plane side. The resulting nonlinear grating of 25 μm period, uniform over the whole 1.8 cm length, has been used for quasi-phase-matched second harmonic generation. With a mode-locked laser as a fundamental source, blue powers up to ~76 μW have been generated at ~422 nm with an average conversion efficiency of ~0.22%