We report a high average power actively $Q$-switched (AQS) orthogonal polarization dual-wavelength Nd:YLF laser at 1047 and 1053 nm. The gain-to-loss balance of dual wavelengths was realized via an uncoated quartz etalon. A maximum continuous wave (CW) output power of 14.2 W was obtained under the incident pump power of 41.7 W, corresponding to an optical-to-optical conversion efficiency of 34.1% and a slope efficiency of 38.3%. Active $Q$-switching was accomplished by inserting an acousto-optic modulator in the cavity. Under the incident pump power of 40 W, this setup delivered a maximum average output power of 10 W at the pulse repetition frequency (PRF) of 30 kHz and the largest pulse energy of 3.4 mJ at the PRF of 1 kHz, respectively. To the best of our knowledge, these are the highest average output powers for both CW and AQS orthogonally polarized dual-wavelength lasers based on laser crystals.

A compact dual-wavelength passively Q-switched green laser by intra-cavity frequency doubling of a Yb:YAG/Cr⁴⁺:YAG/YAG composite crystal was demonstrated for the first time to our best knowledge. The maximum green laser output power of 1.0 W was obtained under the pump power of 9.7 W, and the corresponding slope efficiency is 15.2%. The shortest pulse width, largest pulse energy, and highest peak power were achieved to be 5.54 ns, 246.1μJ, and 40.76 KW, respectively. Dual-wavelength laser oscillation simultaneously at 515 nm and 524.5 nm has been achieved. This passively Q-switched dual-wavelength green laser can be used as a laser source for Terahertz generation.

The use of ${\mathrm{Nd}}^{3+}$ codoping for sensitizing the ${\mathrm{Ho}}^{3+}$ ion and enhancing the $\sim 3.9\mathrm{\mu m}$ emission from ${\mathrm{Ho}}^{3+}\text{:}{}^5{\mathrm{I}}_5\to {}^5{\mathrm{I}}_6$ was investigated in the ${\mathrm{PbF}}_2$ crystal for the first time, to the best of our knowledge. The $\sim 3.9\mathrm{\mu m}$ fluorescence emission properties and energy transfer mechanism of the as-grown crystals were investigated. The results show that the ${\mathrm{Nd}}^{3+}$ ion can act as a sensitizer to the ${\mathrm{Ho}}^{3+}$ ion, providing an efficient excitation channel, making the ${\mathrm{Ho}}^{3+}/{\mathrm{Nd}}^{3+}\text{:}{\mathrm{PbF}}_2$ crystal propitious to be pumped by commercialized InGaAs laser diodes (LDs). Moreover, an enhanced $\sim 3.9\mathrm{\mu m}$ emission was obtained in the ${\mathrm{Ho}}^{3+}/{\mathrm{Nd}}^{3+}\text{:}{\mathrm{PbF}}_2$ crystal due to the codoping of ${\mathrm{Nd}}^{3+}$ ions, leading to an efficient energy transfer from a lower laser level of ${\mathrm{Ho}}^{3+}\text{:}{}^5{\mathrm{I}}_6$ to ${\mathrm{Nd}}^{3+}\text{:}{}^4{\mathrm{I}}_{15/2}$, while having little influence on the higher laser level of ${\mathrm{Ho}}^{3+}\text{:}{}^5{\mathrm{I}}_5$. These advantageous spectroscopic characteristics indicate that the ${\mathrm{Ho}}^{3+}/{\mathrm{Nd}}^{3+}\text{:}{\mathrm{PbF}}_2$ crystal might have potential application in $\sim 3.9\mathrm{\mu m}$ mid-infrared lasers under a conventional 808 nm LD pump.

Rabi oscillation has been proven to be one of the cornerstones of quantum mechanics, triggering substantial investigations in different disciplines and various important applications both in the classical and quantum regimes. So far, two independent classes of wave states in the Rabi oscillations have been revealed as spin waves and orbital waves, while a Rabi wave state simultaneously merging the spin and orbital angular momentum has remained elusive. Here we report on the experimental and theoretical observation and control of spin–orbit-coupled Rabi oscillations in the higher-order regime of light. We constitute a pseudo spin-1/2 formalism and optically synthesize a magnetization vector through light-crystal interaction. We observe simultaneous oscillations of these ingredients in weak and strong coupling regimes, which are effectively controlled by a beam-dependent synthetic magnetic field. We introduce an electrically tunable platform, allowing fine control of transition between different oscillatory modes, resulting in an emission of orbital-angular-momentum beams with tunable topological structures. Our results constitute a general framework to explore spin–orbit couplings in the higher-order regime, offering routes to manipulating the spin and orbital angular momentum in three and four dimensions. The close analogy with the Pauli equation in quantum mechanics, nonlinear optics, etc., implies that the demonstrated concept can be readily generalized to different disciplines.

A single-longitudinal-mode crystalline Raman laser in the 1.7 µm wave band was reported for the first time, to the best of our knowledge. The Y V O 4 Raman laser, which was intracavity-pumped by an actively Q -switched 1314 nm Nd:YLF laser, demonstrated the cascaded Stokes oscillation at 1715 nm. By inserting an etalon in the fundamental resonator, linewidth narrowing and power scaling of the second-Stokes laser were realized based on the spatial-hole-burning-free Raman gain. With an optimal pulse repetition frequency of 4 kHz, the maximum single-longitudinal-mode average output power of 1.8 W was acquired with the spectrum linewidth of ∼ 340 M H z . Further increasing the incident pump power, the second-Stokes laser transitioned to multimode regime, and the maximum average output power reached 2.7 W with the peak power as high as ∼ 380 k W .

We demonstrated a narrowband eye-safe intracavity Raman laser by incorporating a fused silica etalon into the fundamental resonator. The KGd(WO₄)₂ (KGW) Raman laser was pumped by an actively Q-switched Nd:YLF laser at 1314 nm. Thanks to the KGW bi-axial properties, two distinct eye-safe Raman lasers operating at 1461 and 1490 nm were obtained separately by rotation of the KGW crystal. At an optimized pulse repetition frequency of 4 kHz, the maximum average output powers of 3.6 and 4.0 W were achieved with the peak powers up to approximately 330 and 480 kW, respectively. The eye-safe Stokes emissions were narrow linewidth (∼0.05 nm FWHM; measurement limited) and near diffraction limited (M ² < 1.4). The powerful narrowband eye-safe Raman lasers are of interest for applications as diverse as laser range finding, scanning lidar and remote sensing.