Multifunctional Nonvolatile Visible Light Regulator Using Chalcogenide Four-Layer Thin-Film Devices

Abstract

As a valuable tool for modulating light fields, conventional amplitude spatial light modulators face limitations, such as slow modulation speeds and mechanical issues. To address these challenges, we propose a novel four-layer thin-film structure composed of Ge₂Se₂Te₅ (GST225) sandwiched between two layers of ZnS:SiO₂ on a glass substrate. By tuning the thickness of the upper ZnS:SiO₂ layer, the amorphous device exhibits a color shift from purple to red in reflection, achieving full coverage of the visible spectrum. This innovative design simplifies structural coloring, making manufacturing more cost-effective and scalable. Additionally, phase changes can be induced via laser direct write using pulsed or continuous-wave lasers from both sides of the device without a reflective layer, enabling reconfigurability and multilevel adjustments. The GST225-based devices demonstrate a high reflectance contrast between their amorphous and crystallized states (from 2.35% to 19.7% at 658 nm) and significant CIE coordinate displacement exceeding 0.3, indicative of robust modulation capabilities. These features suggest potential as visible light regulators. The devices’ versatility is demonstrated through applying pixelated phase-change patterns in focusing, holography, and display. The phase change pattern can achieve a pixel size of 5 μm, comparable to commercial SLM, covering large areas of up to 3 mm × 3 mm. The underlying mechanisms of these multilevel phase changes are investigated using TEM and Raman techniques, offering insights into their microscopic properties. These advancements promise the devices’ significant applications in critical technologies like LiDAR, optical communication, and neural networks, addressing key challenges, such as slow modulation speeds and mechanical issues.