In2S3 nanoflakes-based saturable absorber for multi-state soliton generation

Abstract

Attributing to their excellent photoelectric properties, metal sulfides are potential alternatives for femtosecond photonics. Here, indium sulfide nanoflakes are employed as saturable absorbers. The morphology and chemical composition of In2S3 nanoflakes are characterized. An In2S3 nanoflakes-based SA is fabricated by the method of evanescent light deposition with modulation depth of 2.7 % and saturable intensity of 5 MW/cm2. Stable mode locking with central wavelength of 1530 nm, 3 dB bandwidth of 4.9 nm, pulse duration of 733 fs and fundamental repetition rate of 8.18 MHz is obtained. By carefully adjusting of polarization controller and pumping power, harmonic mode locking with repetition rate of 538 MHz could be achieved. By changing the length of single mode fiber and altering the angle of PC, harmonic soliton molecules centered at 1560 nm are generated with spectral modulation period of 1.3 nm and pulse interval of 4.96 ps. The multi-state soliton generation of the laser confirms the excellent nonlinear absorption characteristics of In2S3 in the communication band, which could be expected to enable more practical instrumentations for spectroscopy, optical sensing and optoelectronics, etc.