Abstract

During the past years, there is a growing interest to thulium (Tm) lasers emitting in the short-wave infrared spectral range around 2.3 µm according to the ³H₄ → ³H₅ 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 µm emission, Tm³⁺-doped lithium yttrium fluoride (Tm:LiYF₄) attracts attention due to high thermal conductivity, low phonon energy leading to a weak non-radiative path from the upper laser level (³H₄) and broad emission spectra for polarized light. Soulard et al. reported on a passively mode-locked (ML) Tm:LiYF₄ 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:LiYF₄ laser while the output power was only 14.4 mW [2]. In the present work, we report on a GaSb-based SESAM ML Tm:LiYF₄ laser generating < 2 ps-long pulses at high average output powers owing to an original upconversion pumping scheme.

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