Abstract
Tunable and mode-locked laser operation near 2 µm based on different Tm-doped YAG ceramics, 4 at.% and 10 at.%, is demonstrated. Several designs of GaSb-based surface-quantum-well SESAMs are characterized and studied as saturable absorbers for mode-locking. Best mode-locking performance was achieved using an antireflection-coated near-surface quantum-well SESAM, resulting in a pulse duration of ~3 ps and ~150 mW average output power at 89 MHz. All mode-locked Tm:YAG ceramic lasers operated at 2012 nm, with over 133 nm demonstrated tuning for continuous-wave operation.
Highlights
Ultrashort pulse laser sources at 2 μm are of growing interest for the use as pump and seed sources in optical parametric systems operating in the mid-IR, for IR supercontinuum generation, and for time-resolved spectroscopy [1,2,3,4].The most popular lasers operating around 2 μm, both in continuous wave and pulsed mode, are based on the trivalent Tm and Ho ions [5]
We report passive mode-locking of different Tm:YAG transparent ceramics employing novel near-surface GaSb-based semiconductor saturable absorber mirrors (SESAM), setting a new record pulse duration for this intriguing laser material
For the first time to our knowledge, passive mode-locking is obtained for Tm:YAG at pulse durations as short as 2.5 ps
Summary
Ultrashort pulse laser sources at 2 μm are of growing interest for the use as pump and seed sources in optical parametric systems operating in the mid-IR, for IR supercontinuum generation, and for time-resolved spectroscopy [1,2,3,4]. Advanced growth and post-processing techniques, such as low-temperature growth [34], ions irradiation/implantation [35], or surface quantum wells (QWs) [36, 37] have to be applied for accelerating the absorption recovery of near-infrared SESAMs. In the mid-IR, GaSb offers a viable alternative to the previously discussed material systems. We report passive mode-locking of different Tm:YAG transparent ceramics employing novel near-surface GaSb-based SESAMs, setting a new record pulse duration for this intriguing laser material. Most of this improvement is due to the development of a new SESAM technology, which allows obtaining fast carrier relaxation without introduction of additional non-saturable losses at this challenging wavelength
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