EFFICIENT FREQUENCY-DOUBLING OF 1.5 MU-M FEMTOSECOND LASER-PULSES IN QUASI-PHASE-MATCHED OPTICAL FIBERS

Second-order nonlinear gratings in optical fibers have been produced f or efficient quasi-phase-matched frequency conversion around 1.5 mu m. Periodic poling was achieved by defining a patterned electrode on a D -shape fiber via standard lithography and applying high voltage (4-5 k V) at elevated temperature (270-280 degrees C). This fabrication techn ique has allowed us to produce gratings uniform over 7.5 cm, as indica ted by the shape and the bandwidth of the phase-matching curve. By fre quency doubling similar to 100 fs pulses in a grating similar to 4 cm long and with a period of 57.15 mu m, similar to 1.05 mW average power at 768 nm has been generated, with an average conversion efficiency s imilar to 1.2%. (C) 1998 American Institute of Physics.