The metasurface optomechanical modulator is a device designed to modulate the amplitude, phase and polarization of a beam of electromagnetic radiation, independently, or simultaneously, according to prescribed paths in the parameter space (for example, as regards polarization, paths on the Poincaré sphere). The concept of our device can be applied to the entire spectrum of electromagnetic waves: from radio frequency, to microwaves (GHz), to millimeter waves (THz), to far and near infrared radiation, and to visible light. The device has as its main element a metasurface, which consists of a set of elements, dielectric or metallic, with dimensions smaller than the wavelength of the radiation that they must handle, arranged on a plane (typically, a dielectric surface or a membrane). From the radiation point of view, the metasurface acts as an anomalous interface, so the ordinary Fresnel relations for amplitude and phase of the reflected / transmitted radiation are replaced by values that can be defined ad hoc during the device design phase.
Our technology leverages on the concept of metasurface. A metasurface is an "engineered surface" capable of responding to very specific requirements of optical/photonic design (reflection coefficient, birefringence, achromaticity...). In other words, metasurfaces are components whose functionality is established "by design" and not "by material". For example, it is possible to produce variable delay plates without using liquid crystals (thus avoiding the need for a confinement cell), or polarizers without resorting to rare solids in their monocrystalline form (for example, calcite). Typical optical metasurfaces are in fact made of silicon by means of large-scale electronic microfabrication technologies. Our modulation technology allows to overcome the typical speed limits of liquid crystal devices (~1MHz compared to ~10 KHz) and to reduce the dimensions typical of electro-optical devices (~0.1 mm vs ~10 mm).
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