Low-noise, 2-W average power, 112-fs Kerr-lens mode-locked Ho:CALGO laser at 2.1†µm.

We report on an in-band pumped soft-aperture Kerr-lens mode-locked Ho3+-doped CaGdAlO4 (Ho:CALGO) bulk laser at 2.1 µm, generating 2 W of average power with 112 fs pulses at 91-MHz repetition rate. To the best of our knowledge, this is the highest average power from a 100-fs class mode-locked laser based on a Tm3+ or Ho3+ doped bulk material. We show that the laser has excellent noise properties, with an integrated relative intensity noise of 0.02% and a timing jitter of 950 fs (rms phase noise 0.543 mrad) in the integration interval from 10 Hz to 10 MHz of offset frequency. The demonstrated combination of high average power, short pulses, and low noise makes this an outstanding laser source for many applications at 2.1 µm.

8.7-W average power, in-band pumped femtosecond Ho:CALGO laser at 2.1 µm.

We report on an in-band pumped SESAM mode-locked Ho:CALGO bulk laser with a record-high average power of 8.7 W and an optical-to-optical efficiency of 38.2% at a central wavelength of 2.1 µm. At this power level, the bulk laser generates pulses with a duration of 369 fs at an 84.4-MHz repetition rate, corresponding to a pulse energy of 103 nJ and a peak power of 246 kW. To the best of our knowledge, this is the highest average power and pulse energy directly generated from a mode-locked bulk laser in the 2-3 µm wavelength region. Our current results indicate that Ho:CALGO is a competitive candidate for average power scaling of 2-µm femtosecond lasers.