A Single-Frequency Linearly Polarized Fiber Laser Using a Newly Developed Heavily Tm³⁺-Doped Germanate Glass Fiber at 1.95 μm

A compact linearly polarized, low?noise, narrow-linewidth, single-frequency fiber laser at 1950 nm is demonstrated. This compact fiber laser is based on a 21-mm-long homemade Tm³⁺-doped germanate glass fiber. Over 100-mW stable continuous-wave single transverse and longitudinal mode lasing at 1950 nm are achieved. The measured relative intensity noise is less than -135 dB/Hz at frequencies over 5 MHz. The signal-to-noise ratio of the laser is larger than 72 dB, and the laser linewidth is less than 6 kHz, while the obtained linear polarization extinction ratio is higher than 22 dB.