S/S+-band tunable dual-wavelength thulium doped fluoride fiber laser

Abstract

A simple S/S+-band dual-wavelength thulium doped fluoride fiber laser (DWFL) with tunable channel spacing is demonstrated. The system utilizes a 24 channel arrayed waveguide grating to control the spacing between the two lasing wavelengths. The widest spacing that can obtained between two lasing wavelengths is 17.49 nm, while the narrowest is 0.75 nm. The cavity loss in the DWFL is controlled using two variable optical attenuators to equalize the power of the two lasing wavelengths. The DWFL has a maximum signal to noise ratio (SNR) of approximately 49.60 dB and good stability over long periods of operation, with only minor SNR fluctuations of less than 5.00 dB observed. The DWFL’s output also has side-mode suppression ratio (SMSR) of between 0.12 dB and 1.56 dB, indicating that there is little to no suppression of one wavelength over another, as well as a balanced power output that is highly desirable when used as reference or signal sources.