GaSe -assisted microfiber autocorrelator for characterizing ultrashort optical pulses

Recent advances in laser technology demand more-effective measurement of ultrashort optical pulses in fiber optics and nanophotonics devices. Here we propose an in-fiber strategy to characterize ultrashort pulses by incorporating a gallium selenide-assisted microfiber, as a frequency-doubling block, in an all-fiber interferometer. Pulses to be retrieved were first split into the two arms of the interferometer and then overlapped, exciting the interferometric autocorrelated second harmonic in the microfiber due to high second-order nonlinearity of gallium selenide. In the experiment, the autocorrelator shows high accuracy in measuring 7.13-ps, 1239-fs, and 683-fs pulses. In comparison with a commercial frequency-resolved optical gating, the relative errors are only 1.53%, 3.74%, and 6.86%, respectively. Moreover, by attenuation of the incident laser of one arm of the interferometer, the measured peak-to-background ratio was less than the conventional theoretical value. The proposed autocorrelator could be very compatible with current systems for future applications of in-fiber or on-chip ultrafast optical technology.