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Mid‐infrared (MIR) pulsed lasers operating at 2–5 µm have important applications in communication, sensing, and medicine. However, the lack of robust MIR saturable absorbers (SAs) remains a major obstacle. Here, a semiconductor material cadmium oxide (CdO) film with high laser‐induced damage threshold (800 nm, 134 mJ cm−2) and broadband saturable absorption (2.0–3.9 µm) is investigated. The effective tuning of the nonlinear optical response of CdO is demonstrated by adjusting the carrier concentration via a tungsten (W)‐doping scheme. The saturable absorption is improved and carrier relaxation process is accelerated after increasing the W‐dopant level. Based on these findings, the robust CdO‐SAs with customizable parameters are realized and Q‐switched lasers with decreasing pulse width from 372 to 254.3 ns are obtained at 2 µm. The design flexibility provided by CdO opens up a large parameter space that enables the continuous improvement of compact and high‐performance MIR ultrafast lasers. [ABSTRACT FROM AUTHOR]

• The performance degradation and compensation method of the beam-steering device based on liquid crystal polarization grating (LCPG) and liquid crystal adjustable half-wave plate (LCAHWP) is studied. • This beam-steering device can still work at a laser power density of 16 W/cm2 irradiation. • The laser tolerance of the device is higher than that of liquid crystal optical phased array (LCOPA) and liquid crystal micro-lens array (LCMLA). The effects of laser irradiation thermal deposition on the performance degradation of liquid crystal (LC) devices in high-power laser systems are extremely vital. In this study, the first-order beam-steering system (FBS) was developed using a passive liquid crystal polarization grating (LCPG) and liquid crystal adjustable wave-plate (LCAW). The LCPG was prepared by holographic exposure technology, and the LCAW was prepared using the standard LC cell preparation process. We investigated the influences of diffraction efficiency of FBS under a 1070-nm continuous-wave (CW) laser irradiation. The energy is concentrated in the −1st order at first. When the half-wave retardation was reached, all the energy is concentrated in the +1st order (∼97 %), and the beam is deflected. Once the phase retardation decreases below the half-wave retardation, the energy gradually reconcentrates in the −1st order. When the LCAW fails, the diffraction the energy is refocused to the −1st order by the LCPG. The results indicated that both thermal deposition and driving voltage reduce the phase retardation of the LCAW, generating a variation of energy between in ± 1 st orders. By reducing the driving voltage, this half-wave retardation can be recovered under a certain half-wave voltage and laser power density, and the diffraction efficiency of the +1st order can be compensated to ∼97 %. If the reduced phase retardation is not less than half-wave, the FBS can still be modulated in high-power continuous lasers. Our research provides a reference for the development of beam-steering technology based on LC materials in high-power laser systems. [ABSTRACT FROM AUTHOR]