Abstract
Incandescent sources such as hot membranes and globars are widely used for mid-infrared spectroscopic applications. The emission properties of these sources can be tailored by means of resonant metasurfaces: control of the spectrum, polarization, and directivity have been reported. For detection or communication applications, fast temperature modulation is desirable but is still a challenge due to thermal inertia. Reducing thermal inertia can be achieved using nanoscale structures at the expense of a low absorption and emission cross-section. Here, we introduce a metasurface that combines nanoscale heaters to ensure fast thermal response and nanophotonic resonances to provide large monochromatic and polarized emissivity. The metasurface is based on platinum and silicon nitride and can sustain high temperatures. We report a peak emissivity of 0.8 and an operation up to 20 MHz, six orders of magnitude faster than commercially available hot membranes.
Highlights
Incandescent sources such as hot membranes and globars are widely used for mid-infrared spectroscopic applications
The mid-wavelength infrared (MWIR) absorption spectrum is a material fingerprint so that MWIR spectroscopy plays a key role in many applications[1] such as chemical analysis, astrophysics, gas sensing, or security
Thermal emission by hot electrons has been observed in the visible[29,30,31] using metallic nanostructures and in the nearinfrared (NIR)[32,33,34] using graphene. This process is potentially ultrafast as the electrons thermalize by interaction with phonons in the substrate on a picosecond time scale. Due to their small emitting area, the power emitted in the MWIR by these sources is too low to be detected
Summary
Incandescent sources such as hot membranes and globars are widely used for mid-infrared spectroscopic applications. Thermal emission by hot electrons has been observed in the visible[29,30,31] using metallic nanostructures and in the nearinfrared (NIR)[32,33,34] using graphene This process is potentially ultrafast as the electrons thermalize by interaction with phonons in the substrate on a picosecond time scale. Modulation of MWIR emission by hot electrons in large quantum wells[35] has been observed up to 500 kHz. Other emitters have been reported where the electrons are in equilibrium with phonons so that the time response is governed by heat diffusion and no longer by electron-photon interaction. By using a small hot volume deposited with a good thermal contact on a cold substrate which behaves as a thermal sink, it is possible to ensure a fast thermal relaxation[36,37,38,39]
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