SOULMAN · Sound-Light Manipulation in the Terahertz

The interaction of electromagnetic radiation with the mechanical vibrations of solids affects and determines many different physical phenomena. At the microscopic level, scattering of light with phonon excitations is a well known process exploited in semiconductor devices like Raman amplifiers and acousto-optic modulators. At the macroscopic scale, the interaction is mediated by the radiation pressure and is raising considerable interest as a way to excite and control mechanical oscillators, allowing, for instance, the refrigeration of a macroscopic object near the quantum limit.This rich physics has been mostly developed in the visible or near-infrared spectral ranges. The progress of quantum cascade technologies now offers a new device platform where to explore concepts for the reciprocal manipulation of light and vibrations with unprecedented possibilities. The accessible THz spectrum is in fact particularly intriguing. The wavevector of the electromagnetic field can be tuned to that of the vibration, be it a phonon or the oscillating mode of a macroscopic object, enhancing selectivity and strength of the interaction. The low radiation frequency then makes it technically feasible to optically couple mechanical elements at distances much smaller than the wavelength, allowing, for instance, to exploit optical forces between surface plasmon modes atop metallic membranes. Lastly, it is foreseeable to include mechanical oscillators within the laser cavities, thereby creating new laser dynamics driven by the radiation pressure, and developing opto-mechanical effects in an active device where they can be studied, and eventually controlled, through the laser emission.SouL Man aims at establishing the field of THz opto-mechanics, relying on quantum cascade lasers for investigating phenomena and concepts available in this spectral range and in optically active systems, as wells as at using this knowledge to implement innovative device functionalities and applications.