Comparative Analysis of Relative Intensity Noise in DBR Single-Frequency Fiber Lasers with Different Output Power

Single-frequency fiber lasers (SFFLs) are essential for applications such as gravitational wave detection, high-precision spectroscopy, and inertial confinement fusion, requiring narrow linewidth, low noise, and high output power. Here, we present a comparative study of 1 μm waveband distributed Bragg reflector (DBR) SFFLs with varying cavity parameters. Numerically, we investigate the effects of key cavity parameters on laser performance by plotting contour maps of output power versus grating reflectivity and lasing wavelength. We also simulate intensity noise transfer functions from pump fluctuations. Increasing pump power shifts the relaxation oscillation peak to higher frequency and reduces its amplitude, which originates from the higher intracavity photon density that speeds up the damping of perturbations. Experimentally, we construct two lasers using 6.5 mm and 10.5 mm YDFs spliced between FBG pairs. These lasers employ low-reflectivity FBGs centered at 1053 nm and 1064 nm, with reflectivities of 74% and 55%, respectively. The corresponding maximum output powers are 29.7 mW and 197 mW. The 1053 nm SFFL exhibits a relative intensity noise (RIN) of −102 dBc/Hz at 2.07 MHz, a linewidth of 12.52 kHz, and a mode-hop-free tuning range of 0.64 nm. Although increasing the pump power suppresses the relaxation oscillation peak, it broadens the linewidth due to laser phase noise degradation caused by pump noise-induced temperature fluctuations in the gain fiber. For SFFLs, the output powers should be selected according to the specific application, as a higher output power inherently leads to a broader linewidth. These insights are essential for optimizing such lasers and underscore their strong potential for future applications.