Parallel Laser Printing of a Thermal Emission Pattern in a Phase‐Change Thin Film Cavity for Infrared Camouflage and Security

Abstract

Abstract Engineering the thermal emission of a material in the long‐wavelength infrared (IR) range is applicable to a wide variety of fields, including IR‐adaptive camouflage, information encryption, radiative cooling, energy‐saving windows, and personal thermal management. Although many different materials or structures have been proposed for these purposes, the position‐selective dynamic control of their thermal emission remains a significant challenge. Herein, a laser printing method is presented to spatially tune the thermal emission of a Ge 2 Sb 2 Te 5 (GST) planar cavity formed on a metal back reflector. Crystallization‐induced emission patterns are directly recorded into an amorphous GST film (400 nm thick) in a layer‐by‐layer fashion, where the crystallization of each layer is patterned using a spatially modulated pulsed laser beam. The proposed parallel laser printing method can produce gradient emission patterns as well as stepwise patterns, enabling the emissivity at a specific position to be tuned from 0.26 to 0.8. This provides a promising platform for IR‐adaptive camouflage, which is demonstrated with emissivity‐modulated GST emitters. This study also shows that laser‐printed emission patterns can be effectively utilized for security applications such as anti‐forgery.