Abstract
AbstractPlasmons in heavily doped semiconductor layers are optically active excitations with sharp resonances in the 5–15 μm wavelength region set by the doping level and the effective mass. Here, we demonstrate that volume plasmons can form in doped layers of widths of hundreds of nanometers, without the need of potential barrier for electronic confinement. Their strong interaction with light makes them perfect absorbers and therefore suitable for incandescent emission. Moreover, by injecting microwave current in the doped layer, we can modulate the temperature of the electron gas. We have fabricated devices for high frequency thermal emission and measured incandescent emission up to 50 MHz, limited by the cutoff of our detector. The frequency-dependent thermal emission is very well reproduced by our theoretical model that let us envision a frequency cutoff in the tens of GHz.
Highlights
Plasmons are collective excitations of electron gas that concentrate the interaction with light
We have exploited the peculiar quantum properties of plasmons confined in semiconductor layers to demonstrate perfect absorption and dynamic modulation of thermal emission up to 50 MHz in the mid-infrared frequency range
When they are confined in a layer with thickness smaller than the plasma wavelength, confined plasmons are optically active and display absorption resonances, known as Berreman modes, with a quality factor in the order of 20 at low internal angle of light propagation
Summary
Plasmons are collective excitations of electron gas that concentrate the interaction with light In metals, they have been studied for more than a century as volume and surface plasmons and have sparked fundamental semiclassical theories that we are still using to determine the high frequency conductivity and the upper limit of transparency (the plasma frequency) of many metals and highly doped semiconductors. The study and the understanding of these properties are of major interest today and go under the name of quantum plasmonics [9] Another challenge that is actively studied in this field is the generation of infrared radiation by thermally excited plasmons [10,11,12]. The modulation of the current injected in the doped layer induces fast temperature variations of the electron gas In this configuration, we were able to modulate the thermal emission up to 50 MHz, the highest frequency response of our detector
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