用于红外激光防护的高开关率VO2薄膜

采用反应离子束溅射和后退火处理技术在石英玻璃基底上制备了具有纳米粒子的二氧化钒(VO₂)薄膜. 该薄膜具有半导体-金属相变特性,在3 μm处的开关率达到76.6%。 热致相变实验结果给出了准确的最佳退火温度为465 ℃. 仿真、热致相变和光致相变实验都显示VO₂薄膜在红外波段具有很高的光学开关特性. 光电池防护实验结果显示VO₂薄膜将硅光电池的抗干扰能力提升了2.6倍, 证明了VO₂在激光防护中的适用性. 采用连续可调节系统研究得到VO₂在室温条件下的相变阈值功率密度为4.35 W/cm², 损伤阈值功率密度为404 W/cm²。 低相变阈值和高损伤阈值都进一步证明VO₂薄膜适用于激光防护系统。本实验制备的VO₂薄膜在光开关、光电存储器、智能窗等方面也具有广泛的应用价值.

Infrared laser protection of multi-wavelength with high optical switching efficiency VO2 film

Vanadium dioxide (VO₂) film with nanoparticles is fabricated by reactive ion beam deposition (RIBD) technology and post-annealing method on a quartz glass substrate. RIBD can enhance the damage threshold of VO₂ film and reduce its scattering at insulator-state. And post-annealing can eliminate the structure defects and residual stress. VO₂ film exhibits first-order and reversible metal-to-insulator (MIT) phase transition at a temperature of 68 ℃. It also exhibits photo-induced MIT, in which process a metal-like phase of monoclinic VO₂ appears. With many surprising features in heat-induced and photo-induced MIT processes, VO₂ film turn to satisfy all the characteristics needed for a laser protection system. The thickness of VO₂ film used in these experiments and simulations is about 100 nm. The double-frequency He-Ne laser at a wavelength of 3 μm is used to perform the experiment of heat-induced MIT, with a temperature controlling system. The exact optimal annealing temperature is demonstrated to be 465 ℃, as the sample annealing at this temperature shows the sharpest transition properties and unmixed VO₂ phase peaks in X-ray diffraction pattern. Drude and Drude-Lorentz dispersion models are taken to analyze the dielectric constant of VO₂. Then, the complex refractive index is calculated for simulation. Simulations with the TFCale software show that the transmissions at high temperature and low temperature have high contrasts in the infrared range. MIT experiments at multi-wavelength, which cover heat-induced and photo-induced MIT phase transition, are performed to investigate the applicability of VO₂ film in multi-wavelength laser protection for both continuous wave and pulsed lasers Thus the excellent performance of VO₂ film for laser protection is roundly verified. The laser protection experiments on silicon photocell exhibit that the VO₂ film enhances the anti-jamming capability of photocell system by about 2.6 times, demonstrating the applicability of VO₂ film to laser protection system. The power density of MIT transition threshold of VO₂ film with a thickness of 100 nm is 4.35 W/cm² at room temperature, which is investigated with a continuous wave laser at a wavelength of 1.08 μm with a continuous tunable system. In addition, atomic force microscope is used to observe the film surfaces, which are irradiated by lasers with different power densities for different times The experimental results demonstrate that the power density damage threshold of VO₂ film becomes very high (404 W/cm²). The low MIT transition threshold and high damage threshold of VO₂ film further demonstrate its applicability as a key role for a laser protection system. With the high switching efficiency ratio and high damage threshold, VO₂ thin film can be used in optical switch, smart windows and photoelectric device.