1.2-ps SESAM Mode-Locked Tm:LiYF4 Laser at $2.31\ \mu \mathrm{m}$

During the past years, there is a growing interest to thulium (Tm) lasers emitting in the short-wave infrared spectral range around
$2.3\ \mu \mathrm{m}$
according to the
³
H4 →
³
H
5
electronic transition. Such emission is of practical importance for gas sensing, pollutant detection and non-invasive glucose blood measurements. Among the gain media suitable for
$2.3\ \mu \mathrm{m}$
emission,
$\text{Tm}^{3+}$
-doped lithium yttrium fluoride (Tm:LiYF
4
) attracts attention due to high thermal conductivity, low phonon energy leading to a weak non-radiative path from the upper laser level
$({{}^{3}\mathrm{H}}_{4})$
and broad emission spectra for polarized light. Soulard et al. reported on a passively mode-locked (ML) Tm:LiYF
4
laser generating 94-ps pulses at 2305.9 nm with an average output power of 165 mW at a pulse repetition rate of 100 MHz by using a commercial Semiconductor Saturable Absorber Mirror (SESAM) [1]. Canbaz et al. achieved shorter pulses (514 fs at 2303 nm) via Kerr-lens mode-locking of a Tm.LiYF
4
laser while the output power was only 14.4 mW [2]. In the present work, we report on a GaSb-based SESAM ML Tm:LiYF
4
laser generating < 2 ps-long pulses at high average output powers owing to an original upconversion pumping scheme.