1.6-W self-referenced frequency comb at 2.06 mu m using a Ho:YLF multipass amplifier

A high-power optical frequency comb at 2.06 mu m has been generated using a Ho:YLF multipass amplifier seeded by the long wavelength supercontinuum tail of an octave-spanning Er: fiber comb source. The Ho:YLF amplifier showed a net gain larger than 30 dB from 2048 to 2068 nm, allowing the generation of a 20 nm bandwidth comb with a mode spacing of 100 MHz and a power per mode ranging from 20 to 370 mu W. In the time domain, the amplified comb corresponds to a pulse train with 1.6 W total power and 508 fs transform-limited pulse duration. Using a self-referencing f - 2f interferometer and a phase-locking loop, spectral narrowing of the offset frequency down to less than 17 Hz has been achieved. (c) 2011 Optical Society of America