Zhengping Wang

Power scaling of a continuous-wave (CW) bulk laser in the mid-infrared (Mid-IR) spectral region has been demonstrated employing a 2.5 at.% Er:CaF ₂ crystal slab with double-end-pumping configuration and tailored pump beam profile for better geometry matching. A maximum output power of 22.5 W is achieved at 2.8 μm, corresponding to a slope efficiency of 29.4%. The M ² -factor is 1.27 in the y -direction, compared to 10.29 in the x -direction. To the best of our knowledge, this presents the record power for end-pumped solid-state CW lasers in the 3-μm spectral range at room temperature. This work indicates that Er:CaF ₂ crystals with a low doping level are promising candidates for high-power laser emission in the Mid-IR region.

Continuous-wave vacuum-ultraviolet (VUV) radiation near 190–200 nm is highly desirable for high-resolution photoemission spectroscopy, precision spectroscopy, and semiconductor metrology, yet compact all-solid-state sources in this spectral region remain challenging due to the limited nonlinear materials and complex cascaded conversion schemes. Here, we propose a straightforward approach for achieving a VUV laser in the continuous-wave regime with only two-step nonlinear conversion processes. As a proof-of-principle study, we choose a visible Pr:YLF laser platform: the 522-nm ( ³ P ₁ → ³ H ₅ ) laser is at first intracavity frequency-doubled to 261 nm and subsequently sum-frequency mixed with the 721 nm ( ³ P ₀ → ³ F ₄ ) transition in β -BaB ₂ O ₄ (BBO), delivering milliwatt-level continuous-wave lasers at 192 nm. The proposed approach with two-step nonlinear-frequency up-conversions offers a markedly simplified path for compact, scalable continuous-wave VUV laser sources across the 190–200 nm spectral region.

Stimulated Raman scattering (SRS) with Raman crystals is widely recognized as an effective technical approach for achieving high-efficiency lasers at specific wavelengths. However, due to crystal size limitations, it is challenging to generate large-energy Raman lasers while simultaneously considering the laser damage threshold of optical components. To overcome this limitation, in this paper we describe the successful fabrication of a large-aperture barium nitrate Raman gain medium using the directional template growth technique. Employing this large-aperture Raman medium and a 532 nm pulse laser as the excitation source, a large-energy, high-efficiency yellow–orange waveband laser system was constructed. When injected with 886.7 mJ pump energy at 532 nm, the Raman laser achieved a maximum output energy of 556.2 mJ, corresponding to an optical-to-optical conversion efficiency of 62.7%. This represents a significant advancement in single-pulse energy for barium nitrate Raman lasers. Large-energy yellow–orange wavelength lasers have applications in the clinical treatment of skin diseases and microfluidic chip manufacturing.

This study proposes and experimentally verifies a method for generating tunable visible femtosecond lasers based on the cascaded nonlinear effects of a temperature-tuned lithium triborate (LiB ₃ O ₅ , LBO) crystal. A femtosecond laser with a central wavelength of 1030 nm was used as a single pump source. By precisely controlling the temperature of the LBO crystal to adjust its phase-matching conditions, the cascaded nonlinear processes of self-phase modulation and second-harmonic generation (SPM-SHG) were successfully excited, enabling efficient frequency conversion from the near-infrared (NIR) to the visible range in one step. Experimental results show that the system can achieve tunable visible laser output in the range of 428–515 nm, with a maximum conversion efficiency of 7.8% at 453 nm. This method of cascaded generation of SPM-SHG provides a high-performance solution for the convenient and rapid one-step generation of tunable visible lasers from the near-infrared and holds significant application prospects.

We report on a watt-level nanosecond 261-nm laser from an acousto-optically Q-switched visible Pr:YLF laser through intracavity second-harmonic generation (SHG). By implementing direct water-cooling for thermal management and an intracavity mirror for double-passing nonlinear crystal, a maximum average power of 1.03 W has been achieved at a repetition rate of 40 kHz, which, to the best of our knowledge, is the highest power ever reported from an intracavity-frequency-doubled pulsed, short-wave ultraviolet (UV-C) laser at 261 nm. Decreasing the repetition rate to 20 kHz, a single-pulse energy of 43.4 µJ can be obtained. This approach with a robust and simple structure demonstrates a promising way toward the direct generation of high-power UVC laser pulses.

In this work, Ti₃CN powder was successfully synthesized using Ti₃AlCN as a precursor. Both materials were processed into nanosheets via liquid-phase exfoliation. Using the open- and closed-aperture Z-scan technique, we conducted the first comparative study of the broadband nonlinear absorption properties of Ti₃AlCN and Ti₃CN nanosheets, covering the spectrum from deep ultraviolet (DUV) to near-infrared (NIR) wavelengths. The results revealed that both nanosheets exhibit notably higher two-photon absorption coefficients in the DUV band, indicating their significant potential as optical limiting materials for short-waveband applications. Also, the band gap structure of the nanosheets was analyzed using density functional theory. This comparative study underscores the significant potential and value of both Ti₃AlCN and Ti₃CN nanosheets for broadband nonlinear applications.

By optimizing a laser crystal and resonator structure, we obtained a series of the best experimental results of Pr³⁺-doped solid-state lasers, including a 10.8 W continuous-wave (CW) laser, a 5.29 W acousto-optical (AO) Q-switched laser, and a 6.03 W AO Q-switched, intracavity frequency-doubled laser. With a 0.1 at.%, 18 mm Pr:YLF crystal as the laser medium, when the absorbed pump power was 23 W, a maximum CW output power of 10.8 W was achieved at 640 nm, with a slope efficiency of 56.6%. The laser output exhibited excellent beam quality (M_x²=1.26, M_y²=1.22) and remarkable power stability (RMS = 0.16%). For AO Q-switched pulse laser operation at 640 nm, a maximum average output power of 5.29 W was achieved at a repetition rate of 40 kHz. When the repetition rate was 10 kHz, a maximum single pulse energy of 342 μJ was realized. With a (θ = 90°, ϕ = 53.6°)-oriented, 10 mm LBO crystal as the nonlinear optical medium, the AO Q-switched, intracavity frequency-doubled ultraviolet (UV) laser properties at 320 nm were researched at different repetition rates. The highest average output power of 6.03 W was obtained at a repetition rate of 40 kHz, the largest single pulse energy of 333 μJ and the highest peak power of 6.05 kW were achieved at a repetition rate of 10 kHz. The laser output also exhibited excellent beam quality (M_x², M_y²<1.3) and power stability (RMS < 1%). The high quality, compact 10 W visible laser at 640 nm, and 6 W UV laser at 320 nm, will be very favorable for many practical applications, like biomedical, micro-nano processing, and generating sources for shorter wavelength deep UV lasers.

Two-dimensional (2D) transition metal carbides (MXenes), known for their unique properties, have ignited a surge of extensive interdisciplinary research. However, the broadband nonlinear absorption properties of MXenes have rarely been explored in prior studies, particularly in the deep ultraviolet region. Furthermore, the nonlinear optical properties of the precursor MAX phase are often overlooked. In this study, we synthesized a 2D V₂C multilayer MXene by selectively etching aluminum from V₂AlC. The broadband nonlinear optical behaviors of both V₂AlC and V₂C nanosheets were investigated using open aperture and closed aperture Z-scan techniques, spanning a wide range from the deep ultraviolet to near-infrared wavelengths. Additionally, we employed density functional theory (DFT) calculations to determine the energy band structures. The results reveal that both V₂AlC and V₂C nanosheets exhibit excellent optical limiting properties in the deep ultraviolet range, along with a significantly larger nonlinear refractive index in the visible spectrum. These findings underscore the importance of V₂AlC and V₂C nanosheets as promising materials for optical limiting applications, thereby broadening their potential applications in nonlinear optics.

Potassium dihydrogen phosphate (KH₂PO₄, KDP) family crystals are the only nonlinear optical materials that can satisfy the aperture requirement of the inertial confinement fusion (ICF) laser driver. As a major ultraviolet (UV) generation scheme in service, the type-II phase-matched (PM) third harmonic generation (THG) performance of KDP and DKDP crystals is critical to ICF equipment. All the time, the largest efforts from all aspects have been made to achieve the highest output energy, conversion efficiency, and anti-damage ability. For this purpose, an effective route is developed and analyzed in this paper, i.e. substantial elevating the operation temperature of KDP and DKDP crystals. When the crystal temperature was set at 130 °C, the THG energy, conversion efficiency, and laser-induced damage threshold (LIDT) were increased by 11.9%-16.5%, 5.3%-5.4%, 17.1%-24.5% for KDP crystals, and 4.2%-7.6%, 4.2%-6.6%, 14.2%-26.5% for DKDP crystals, respectively. Variable-temperature Z-scan tests reveal that increasing the temperature of KDP-like crystals effectively suppresses the two-photon absorption effect of the crystals and thus improves their UV frequency conversion performance. This research offers a valuable technique for the future development of ultraviolet, deep-ultraviolet lasers in ICF facilities.