The metrology and transduction of quantum level sub-terahertz and terahertz waves is a prerequisite for future applications in quantum sciences, sensing, metrology or high speed control of light.
By using nonlinearities in state-of-the-art hybrid silicon-organic and lithium niobate circuits we custom-tailor the detection and emission of terahertz radiation.
By studying these miniaturized devices, we want to understand several questions:
- what opportunities lie behind metrology and transduction of quantum level electric fields that oscillate at frequencies up to the terahertz, especially if the measurement happens on temporal and spatial scales that are shorter than one single cycle of their oscillation?
- what are the limits for achieving such measurement precision (in time, space and amplitude) in practical nano-engineered devices deployed at large scales?
So far, most demonstrations of dynamic control of metasurfaces make use of mechanical strain in the substrate, immersion of the metasurface in liquid crystals, or, more recently, thermal tuning of the refractive index of the substrate. All these approaches are an essential first step towards continuous control of the functionality of a metasurface. However, they suffer from inherently slow speed, exhibit hysteretic behavior, and have a limited number of switching cycles. Electro-optic polymers have been recently integrated into plasmonic structures and shown to change their refractive index upon an applied bias up to terahertz speeds and no hysteresis.
Coherent exchange of energy is a prerequisite for any interface that can transform and encode quantum information. As a consequence, coherent time-resolved read-out thereof is essential to detect phase-sensitive information. One example can be formulated for optics. Most quantum optics experiments nowadays involve the detection of single quanta of light – photons – at detectors that are sensitive to their energy, hence frequency. Typically, such detectors have response times that are not able to resolve the temporal profile of the photon wavepacket. Complementary insight can be gained instead by measuring the electric field on quantum states of light with a resolution shorter than one cycle of oscillation, both in time and in space. At terahertz frequecies, electro-optic sampling is a powerful technique that provides the necessary resolution and sensitivity to perform electric field measurements on quantum states of light.