Short-Wavelength, in-Band-Pumped Single- Frequency DBR Tm3+-Doped Germanate Fiber Laser at 1.7 μm

Based on several centimeters long heavily Tm3+-doped germanate fibers (TGFs) and in-band-pumped technique, a short-wavelength distribute Bragg reflector (DBR) single-frequency fiber laser (SFFL) emitting at $1.7~\mu \text{m}$ is investigated experimentally. A stable single-longitudinal-mode laser output with a signal-to-noise ratio of greater than 60 dB and an operation wavelength of 1727 nm is realized. The maximum output power of 12.4 mW and the slope efficiency of 4.81% for the absorbed pump power are obtained from a 1.8-cm-long TGF pumped by a 1610 nm fiber laser. The measured relative intensity-noise of the SFFL reaches to around −130 dB/Hz at frequencies of over 10 MHz and the laser linewidth is 8.6 kHz. To the best of our knowledge, this is the first demonstration of the DBR Tm3+-doped SFFL with an operation wavelength in $1.7~\mu \text{m}$ region. It is suitable for optical coherence tomography, methane gas detection and optical medical technology.