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Abstract
We numerically demonstrate narrowband thermal emission with unity emissivity peak in the near-infrared range by critically coupling a flat tungsten surface with guided resonances of a dielectric photonic crystal slab. The tungsten surface is separated from the photonic crystal slab by a vacuum gap. The structure possesses significant tunability for both the center frequency and the linewidth of the thermal emission band. Moreover, the tungsten surface, being un-structured, should exhibit enhanced thermal stability at elevated temperature as compared to tungsten nanostructures.
Highlights
Conventional thermal light emitting sources, such as the sun or the filament of an incandescent light bulb, typically generate broadband and incoherent electromagnetic radiations [1]
In this paper, using the rigorous coupled wave analysis [29], we numerically demonstrate the control of thermal emissivity from a flat tungsten surface, by critical coupling to a dielectric photonic crystal guided resonance in the near field
We place the silicon carbide (SiC) photonic crystal slab as discussed above, with a period of 1μm and a grating depth of 0.04μm, on top of a flat tungsten surface separated by a vacuum gap (Fig. 1(a))
Summary
Conventional thermal light emitting sources, such as the sun or the filament of an incandescent light bulb, typically generate broadband and incoherent electromagnetic radiations [1]. The emission property of all these structures to the normal direction can all be understood in terms of a single resonance coupling to an input/output port For these structures peak unity emissivity is achieved by satisfying the critical coupling condition. The field is located somewhat away from the tungsten region, resulting in a smaller intrinsic loss rate and a narrower linewidth For such a Fabry-Perot mode, the intrinsic linewidth is controlled by the absorption coefficient for light normally incident from vacuum onto the flat tungsten surface, which is a constant at a given resonant frequency. At a given vacuum gap size, which largely fixes the intrinsic loss rate of the resonance, one can achieve critical coupling by adjusting the geometric parameters of the photonic crystal slab which control the external loss rate.
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