Generation of broadband frequency-variable laser comb allowing full-frequency sweep in the near-infrared region

Abstract

We succeeded in developing a broadband-frequency-variable laser comb with a mode spacing of 12.5 GHz in the near-infrared region. We found that the spectrum of optical pump pulses can be frequency shifted over the mode spacing frequency by a single-sideband (SSB) optical modulator involving the amplitude and phase. Optical heterodyne measurement showed that the frequency shift of the optical pump pulses was precisely consistent with the modulation frequency applied to the SSB modulator with an accuracy of 20 kHz. The pump pulses were amplified and compressed to enhance the peak intensity. Finally, the frequency-shifted pump pulses launched into highly nonlinear fibers and generated a frequency-shifted laser comb. The precise frequency shift of pump pulses induced a simultaneous frequency shift of all modes of the laser comb. As a result, we succeeded in fast frequency sweeping of the laser comb over a full spectral range of 1080 to 1750 nm. This full-wavelength tuning implies that laser light of arbitrary and accurate wavelength can be obtained over the comb bandwidth.