Background-reduced spectral peak generation using a nonlinear loop mirror with a gas cell

Spectral peaking in an optical fiber is a useful phenomenon for comb mode filtering and wavelength standards. However, for highly sensitive spectroscopic applications, it is important to suppress the pedestal components. Here we propose and demonstrate pedestal-suppressed spectral peak generation using a nonlinear fiber loop mirror with a molecular gas cell. The physical mechanism and fundamental properties were investigated numerically, and the output characteristics were examined experimentally. Almost background-free spectral peaks were generated successfully in the 1.65-mu m wavelength range using a CH4 gas cell. The maximum signal to-background ratio was more than 30 dB. Stable operation without any feedback control was achieved. It is expected that the proposed method is useful for highly sensitive spectroscopic applications.(c) 2023 Optica Publishing Group