Diode-pumped Tm:YAP laser operating at 2.3†µm with enhanced performance through cascade lasing.

The laser diode (LD)-pumped Tm:YAP (a-cut, 3.5 at.%) laser generated a maximum ∼2.3 µm continuous wave (CW) laser output power of ∼3 W. The higher output power benefited from the positive effect of the cascade lasing (simultaneously operating on the 3H4 → 3H5 and 3F4 → 3H6 Tm3+ transition). It was the highest CW laser output power amongst the LD/Ti:Sapphire-CW-pumped ∼2.3 µm Tm3+-doped lasers reported so far. Under the cascade laser operation, the slope efficiency of the ∼2.3 µm laser emission versus the absorbed pump power increased from 13.0% to 21.4%.

A Study on the Surface Quality and Damage Properties of Single-Crystal Silicon Using Different Post-Treatment Processes.

Detecting subsurface defects in optical components has always been challenging. This study utilizes laser scattering and photothermal weak absorption techniques to detect surface and subsurface nano-damage precursors of single-crystal silicon components. Based on laser scattering and photothermal weak absorption techniques, we successfully establish the relationship between damage precursors and laser damage resistance. The photothermal absorption level is used as an important parameter to measure the damage resistance threshold of optical elements. Single-crystal silicon elements are processed and post-processed optimally. This research employs dry etching and wet etching techniques to effectively eliminate damage precursors from optical components. Additionally, detection techniques are utilized to comprehensively characterize these components, resulting in the successful identification of optimal damage precursor removal methods for various polishing types of single-crystal silicon components. Consequently, this method efficiently enhances the damage thresholds of optical components.

Cascade lasing at ∼2†µm and ∼2.3†µm in a diode-pumped Tm:YVO4 laser.

We report on the cascade continuous-wave operation of a diode-pumped Tm:YVO4 laser on the 3F4 → 3H6 (at ∼2 µm) and 3H4 → 3H5 (at ∼2.3 µm) Tm3+ transitions. Pumped with a fiber-coupled spatially multimode 794 nm AlGaAs laser diode, the 1.5 at.% Tm:YVO4 laser yielded a maximum total output power of 6.09 W with a slope efficiency of 35.7% out of which the 3H4 → 3H5 laser emission corresponded to 1.15 W at 2291-2295 and 2362-2371 nm with a slope efficiency of 7.9% and a laser threshold of 6.25 W.

Large-scale few-layered MoS2 as a saturable absorber for Q-switching operation at 2.3†µm.

In this Letter, the fabrication of large-scale (50.8 mm in diameter) few-layered MoS2 with physical vapor deposition on sapphire is described. Open-aperture Z-scan technology with a home-made excitation source at 2275 nm was applied to explore its nonlinear saturable absorption properties. The as-grown few-layered MoS2 membrane possessed a modulation depth of 17% and a saturable intensity of 1.185 MW cm-2. As a consequence, the deposited MoS2 membrane was exploited as a saturable absorber to realize a passively Q-switched Tm:YAP laser for the first time, to the best of our knowledge. Pulses as short as 316 ns were generated with a repetition rate of 228 kHz, corresponding to a peak power of 5.53 W. Results confirmed that the two-dimensional layered MoS2 could be beneficial for mid-infrared photonic applications.

Compact diode-pumped continuous wave and passively Q switched Tm:YAG laser at 2.33†µm.

Compact diode-pumped continuous wave (CW) and passively Q switched Tm:YAG lasers operating on the 3H4 → 3H5 transition are demonstrated. Using a 3.5-at.% Tm:YAG crystal, a maximum CW output power of 1.49 W is achieved at 2330 nm with a slope efficiency of 10.1%. The first Q switched operation of the mid-infrared Tm:YAG laser around 2.3 µm is realized with a few-atomic-layer MoS2 saturable absorber. Pulses as short as 150 ns are generated at a repetition rate of 190 kHz, corresponding to a pulse energy of 1.07 µJ. Tm:YAG is an attractive material for diode-pumped CW and pulsed mid-infrared lasers emitting around 2.3 µm.

Watt-level diode-pumped Tm:YVO4 laser at 2.3 µm.

In this Letter, a watt-level laser diode (LD)-pumped ∼2.3-µm (on the 3H4→3H5 quasi-four-level transition) laser is reported based on a 1.5 at.% a-cut Tm:YVO4 crystal. The maximum continuous wave (CW) output power obtained is 1.89 W and 1.11 W with the maximum slope efficiency of 13.6% and 7.3% (versus the absorbed pump power) for the 1% and 0.5% transmittance of the output coupler, respectively. To the best of our knowledge, the CW output power of 1.89 W we obtained is the highest CW output power amongst the LD-pumped ∼2.3-µm Tm3+-doped lasers.