Tm/Ho co-doped pulsed fiber laser with low spectral and temporal noise

Abstract

A Tm/Ho co-doped mode-locked soliton fiber laser design is presented with stable and low noise single-pulsing operation at a repetition rate of 135.2 MHz and a transform limited pulse duration of 375 fs. The fiber laser is directly core pumped at a wavelength of 790 nm. In single-pulsing operation, the fiber laser is centered at a wavelength of 1983 nm and can be continuously tuned over an 8 nm bandwidth. The fiber laser consists of a linear cavity which allows scaling of the repetition rate further by reducing the cavity length and utilizing the high pump absorption at 790 nm and efficient absorption/emission dynamics without photodarkening. In addition, co-doping with Tm/Ho increases the efficiency of the lasing with enhanced cross-relaxation rates. Stable mode-locked operation with reduced ripples in the optical spectrum and high signal-to-background ratios in the RF spectrum is observed. A low relative intensity noise with an rms fluctuation level of 0.13 % (frequency interval of 10 Hz to 1 MHz) and a low phase noise with a timing jitter of 20 fs (frequency range of 100 Hz to 1 MHz) characterizes the mode-locked laser.