10 low-noise holmium-doped fiber amplifier at 2095nm

We present our 10 W class CW holmium-doped fiber amplifier operating at a wavelength of 2095nm. With our monolithic, single-frequency, all-PM setup, we achieve a polarization extinction ratio of 26 dB, excellent beam quality M² =1.18, and no observable ASE for relative power levels of 60 dB. We demonstrate 10 W output power after the fiber-coupled isolator and more than 15 W without it. To the best of our knowledge, our system emits the highest output power of all published single-frequency, polarization-maintaining, single-mode holmium-doped fiber amplifiers. Our relative intensity noise (RIN) analysis shows excellent power stability characteristics for our currently free-running system. We present the results of our RIN analysis of our free-running system for frequencies from 10⁻³ Hz to 10⁴ Hz and, for example, we achieve a RIN of <10⁻⁵ Hz^−0.5 at a frequency of 100 Hz, demonstrating the suitability of our approach for achieving the highest power stabilities.