A nano-photonic filter for near infrared radiative heater

Infrared (IR) radiative heating is a highly desirable method for heating as compared to convective heating due to the unprecedented control of radiative energy transfer, leading to a significant increase in energy efficiency. The greatest challenge however with IR radiative heating is its low penetration depth due to the strong IR absorption by the water content in the substance to be heated. Near IR (NIR) heating can circumvent this problem as it has greater penetration depths. The proposed nano-photonic design for NIR filter (or effective selective emitter) has transmissivity of more than 70% in NIR and less than 15% in both visible and IR wavelengths as opposed to currently available IR heaters, which have high emissivity across all wavelengths. This NIR filter can be applied to any radiative heating source to transform it into a NIR radiative heater. We demonstrate this with a simple prototype by applying it in front of tungsten-based incandescent lamp where significant reduction in white glow (glare) was observed. Potential application of this NIR filter would be in heating in both building and industrial sectors where the ability to provide localized heating could lead to significant energy savings. In addition, NIR selective emitters can be applied for power generation by supplying thermophotovoltaics (TPV) with photons at the right wavelengths, which will increase the efficiency of TPV.