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Thanks to their large sensitivity to electromagnetic fields, microelectromechanical systems are becoming attractive for applications in the THz band (0.1–10 THz). However, up to date all THz electromechanical systems couple electromagnetic fields to mechanical motion only through photothermal dissipative forces: such mechanism allows for sensitive detection but prevents applications that require coherent transfer of information. In this work, we present a THz electromechanical meta-atom where the coupling between an electromagnetic mode and the displacement of a metallic micro-beam is substantially controlled by a conservative Coulomb force due to charge oscillations in the nanometric-size capacitive part of the meta-atom. We present experiments, performed at room temperature, which allow distinguishing and precisely quantifying the contributions of conservative and dissipative forces in the operation of our electromechanical resonator. Our analysis shows that the Coulomb force becomes the dominant contribution of the total driving force for high-order mechanical modes. Such system paves the way for the realization of coherent THz to optical transducers and allows the realization of fundamental optomechanical systems in the THz frequency range.

Author(s): Daniele Palaferri [1]; Yanko Todorov [1]; Azzurra Bigioli [1]; Alireza Mottaghizadeh [1]; Djamal Gacemi [1]; Allegra Calabrese [1]; Angela Vasanelli [1]; Lianhe Li [2]; A. Giles Davies [2]; Edmund [...]

Room-temperature operation is essential for any optoelectronics technology that aims to provide low-cost, compact systems for widespread applications. A recent technological advance in this direction is bolometric detection for thermal imaging, which has achieved relatively high sensitivity and video rates (about 60 hertz) at room temperature. However, owing to thermally induced dark current, room-temperature operation is still a great challenge for semiconductor photodetectors targeting the wavelength band between 8 and 12 micrometres, and all relevant applications, such as imaging, environmental remote sensing and laser-based free-space communication, have been realized at low temperatures. For these devices, high sensitivity and high speed have never been compatible with high-temperature operation. Here we show that a long-wavelength (nine micrometres) infrared quantum-well photodetector fabricated from a metamaterial made of sub-wavelength metallic resonators exhibits strongly enhanced performance with respect to the state of the art up to room temperature. This occurs because the photonic collection area of each resonator is much larger than its electrical area, thus substantially reducing the dark current of the device. Furthermore, we show that our photonic architecture overcomes intrinsic limitations of the material, such as the drop of the electronic drift velocity with temperature, which constrains conventional geometries at cryogenic operation. Finally, the reduced physical area of the device and its increased responsivity allow us to take advantage of the intrinsic high-frequency response of the quantum detector at room temperature. By mixing the frequencies of two quantum-cascade lasers on the detector, which acts as a heterodyne receiver, we have measured a high-frequency signal, above four gigahertz (GHz). Therefore, these wide-band uncooled detectors could benefit technologies such as high-speed (gigabits per second) multichannel coherent data transfer and high-precision molecular spectroscopy. [ABSTRACT FROM AUTHOR]