The purpose of this paper is to review the research progress in the realization of the organic–inorganic hybrid thin-film packaging of flexible organic electroluminescent devices using the PEALD (plasma-enhanced atomic layer deposition) and MLD (molecular layer deposition) techniques. Firstly, the importance and application prospect of organic electroluminescent devices in the field of flexible electronics are introduced. Subsequently, the principles, characteristics and applications of PEALD and MLD technologies in device packaging are described in detail. Then, the methods and process optimization strategies for the preparation of organic–inorganic hybrid thin-film encapsulation layers using PEALD and MLD technologies are reviewed. Further, the research results on the encapsulation effect, stability and reliability of organic–inorganic hybrid thin-film encapsulation layers in flexible organic electroluminescent devices are discussed. Finally, the current research progress is summarized, and the future research directions and development trends are prospected.

The refractive index of seawater is one of the essential parameters in ocean observation, so it is necessary to achieve high-precision seawater refractive index measurements. In this paper, we propose a method for measuring the refractive index of seawater, based on a position-sensitive detector (PSD). A theoretical model was established to depict the correlation between laser spot displacement and refractive index change, utilizing a combination of a position-sensitive detector and laser beam deflection principles. Based on this optical measurement method, a seawater refractive index measurement system was established. To effectively enhance the sensitivity of refractive index detection, a focusing lens was incorporated into the optical path of the measuring system, and simulations were conducted to investigate the impact of focal length on refractive index sensitivity. The calibration experiment of the measuring system was performed based on the relationship between the refractive index of seawater and underwater pressure (depth). By measuring laser spot displacement at different depths, changes in displacement, with respect to both refractive index and depth, were determined. The experimental results demonstrate that the system exhibits a sensitivity of $9.93\times {10}^{-9}\mathrm{R}\mathrm{I}\mathrm{U}$ (refractive index unit), and the refractive index deviation due to stability is calculated as $\pm 7.54\times {10}^{-9}\mathrm{R}\mathrm{I}\mathrm{U}$. Therefore, the feasibility of this highly sensitive measurement of seawater refractive index is verified. Since the sensitivity of the refractive index measurement of this measurement system is higher than the refractive index change caused by the wake of underwater vehicles, it can also be used in various applications for underwater vehicle wake measurement, as well as seawater refractive index measurement, such as the motion state monitoring of underwater navigation targets such as AUVs and ROVs.

A Tm:YAP laser with an output wavelength of 1989 nm was selected for the first time as the pump source of a Q-switched Ho:YAP laser. When the absorbed power was 30 W, an average power of 18.02 W with the pulse width of 104.2 ns acousto-optic (AO) Q-switched Ho:YAP laser was obtained at a repetition frequency of 10 kHz. The slope efficiency was 70.11%, and the optical-optical conversion efficiency was 43.03%. The output center wavelength was 2129.22 nm with the line width of 0.74 nm.

Tungsten oxide (WO₃) electrochromic devices are obtaining increasing interest due to their color change and thermal regulation. However, most previous work focuses on the absorption or transmission spectra of materials, rather than the optical parameters evolution in full spectrum in the electrochromic processes. Herein, we developed a systematic protocol of ex situ methods to clarify the evolutions of subtle structure changes, Raman vibration modes, and optical parameters of WO₃ thin films in electrochromic processes as stimulated by dosage-dependent Li⁺ insertion. We obtained the below information by ex situ spectroscopic ellipsometry. (1) Layer-by-layer Li⁺ embedding mechanism demonstrated by individual film thickness analysis. (2) The details of its optical leap in the Brillouin zone in the full spectral. (3) The optical constants varied with the Li⁺ insertion in the ultraviolet, visible, and near-infrared bands, demonstrating the potential for applications in chip fabrication, deep-sea exploration, and optical measurements. (4) Simulated angular modulation laws of WO₃ films for full spectra in different Li⁺ insertion states. This ex situ method to study the optical properties of electrochromic devices are important for monitoring phase transition kinetics, the analysis of optical leaps, and the study of ion diffusion mechanisms and the stoichiometry-dependent changes in optical constants over the full spectral. This work shows that electrochromic films in Li⁺ surface permeation can be applied in the field of zoom lenses, optical phase modulators, and other precision optical components. Our work provides a new solution for the development of zoom lenses and a new application scenario for the application of electrochromic devices.

The thermal effects model of slab crystal was established based on the practical operating conditions of the solid-state laser. To our knowledge, this is the first time to use the simulation software of COMSOL Multiphysics to investigate the thermal model of slab crystal with the complex boundary conditions in detail. And this is also the first time to use this theoretical method to a slab Tm:YLF laser. The results showed that thermal effects of Tm:YLF crystal were enhanced with the increase of the pump power. And the thermal effects increased sharply with the decrease of the size of the pump light along theY-axis or the increase of the crystal doping concentration. Thermal deformation which produced by thermal lens effect played a leading role of Tm:YLF crystal. Finally, under the premise of elevated the laser output efficiency and ameliorated thermal effects, the optimized parameters were chosen which were the pump size of omega(1)x omega(2)=1mm x 6mm and doping concentration of 2.5at.%.

By studying the theory of heat conduction, we established the transient heat conduction equation for a pulsed laser diode (LD) end pumped thulium doped laser. Combined with the actual working environment of a pulsed LD end pumped single-ended composite Tm:YAG rod, the expressions of transient temperature distribution and the time-varying thermal focal length were obtained by the integral transform method and the method of separation of variables. Under 240 mJ pump energy and repetition rates of 80, 90, and 100 Hz, thermal effects in the pulsed LD end pumped single-ended composite Tm:YAG rod were simulated, and the thermal lens focal length of the single-ended composite Tm:YAG rod was measured in experiments. The theoretical analysis was verified by the comparison between the theoretical results and the experimental results.