28 May 2024 | Ziwei Fan, Taeseung Hwang, Sam Lin, Yixin Chen & Zi Jing Wong
This study presents a novel pixelated directional micro-emitter that enables ultrabroadband, polarization-independent directional control of thermal radiation. The device, based on non-imaging optical principles, achieves efficient thermal emission control through etendue conservation, allowing for tunable angular control of thermal radiation. The micro-emitter demonstrates strong directionality in thermal emission, with a large emissivity contrast at different view angles. The device is used to create a pixelated infrared display, where information is only observable at certain directions, enabling thermal camouflage and secure infrared communication.
The micro-emitter is composed of parabolic reflectors with an underlying SU8-coated blackbody. By mapping thermal emission from a small area to a larger area on the micro-emitter's upper surface, the angular range of thermal emission is suppressed, resulting in directional control. The device's hexagonal pixel structure minimizes azimuthal anisotropy and allows for broadband, polarization-independent thermal emission over a wide wavelength range. The 15°-PDME exhibits directionally selective emission over an ultrawide wavelength range from 5 to 20 μm, with emissivity spectra for both polarizations matching closely.
The PDME was fabricated using two-photon polymerization 3D lithography and silver deposition. The device was characterized using Fourier-transform infrared spectroscopy and thermography, demonstrating strong directional selectivity and high emissivity. The PDME's ability to encode information into the viewing angle of infrared displays was further demonstrated through a pixelated display that can camouflage or replace information based on the viewing direction.
The PDME's properties, including high emissivity, narrow angular range, and ultrawide working wavelength range, make it a highly directional thermal radiator. The device has potential applications in radiative cooling, thermophotovoltaics, infrared spectroscopy, and thermal camouflage. The non-imaging approach to directional thermal radiation enhances the capabilities of these technologies, enabling efficient thermal energy transfer and secure communication. The study demonstrates the potential of pixelated non-imaging micro-optics for efficient thermal radiation control and infrared display applications.This study presents a novel pixelated directional micro-emitter that enables ultrabroadband, polarization-independent directional control of thermal radiation. The device, based on non-imaging optical principles, achieves efficient thermal emission control through etendue conservation, allowing for tunable angular control of thermal radiation. The micro-emitter demonstrates strong directionality in thermal emission, with a large emissivity contrast at different view angles. The device is used to create a pixelated infrared display, where information is only observable at certain directions, enabling thermal camouflage and secure infrared communication.
The micro-emitter is composed of parabolic reflectors with an underlying SU8-coated blackbody. By mapping thermal emission from a small area to a larger area on the micro-emitter's upper surface, the angular range of thermal emission is suppressed, resulting in directional control. The device's hexagonal pixel structure minimizes azimuthal anisotropy and allows for broadband, polarization-independent thermal emission over a wide wavelength range. The 15°-PDME exhibits directionally selective emission over an ultrawide wavelength range from 5 to 20 μm, with emissivity spectra for both polarizations matching closely.
The PDME was fabricated using two-photon polymerization 3D lithography and silver deposition. The device was characterized using Fourier-transform infrared spectroscopy and thermography, demonstrating strong directional selectivity and high emissivity. The PDME's ability to encode information into the viewing angle of infrared displays was further demonstrated through a pixelated display that can camouflage or replace information based on the viewing direction.
The PDME's properties, including high emissivity, narrow angular range, and ultrawide working wavelength range, make it a highly directional thermal radiator. The device has potential applications in radiative cooling, thermophotovoltaics, infrared spectroscopy, and thermal camouflage. The non-imaging approach to directional thermal radiation enhances the capabilities of these technologies, enabling efficient thermal energy transfer and secure communication. The study demonstrates the potential of pixelated non-imaging micro-optics for efficient thermal radiation control and infrared display applications.