Skip to main content

Structured nonlinear Metamaterials for efficient generation and Active functional control of Radiation of THz light

Periodic Reporting for period 2 - SMART (Structured nonlinear Metamaterials for efficient generation and Active functional control of Radiation of THz light)

Reporting period: 2018-07-01 to 2019-12-31

The terahertz optical regime, covering the long wavelength end of the optical spectrum, has been for many years the least explored spectral regime. Recent interest in this regime has led to important emerging applications spanning many disciplines including medical, biological, materials sciences, communications, security, and basic sciences. However, advances in these emerging applications are held back by the lack of good and controllable terahertz light sources. This project is aimed at developing a new family of THz sources with unmatched functionality. The developed sources are based on nano-engineered nonlinear heterostructured metamaterials, man-made materials with artificial optical properties. In the project we work to study and design novel active metamaterials that efficiently emit THz light at broad range of frequencies, designed shapes and desired polarization, focus it directly from the emitter to a desired sample location and even actively steer and modify its radiation properties all-optically. Overall the aim of this research is to develop a unique family of THz light emitters that will lead to the, long sought for, leap in THz technology and will open the door to new applications and to new tools for advancing fundamental science.
The first part of the project was dedicated to build the experimental setup that allows to generate THz radiation from nonlinear metasurfaces and to characterize it. In addition, we developed the fabrication capabilities to allow us to fabricate mm-cm scale metasurfaces, which scale is essential to pursue the aims of SMART. We also developed the numerical skills to model the nonlinear interaction with the metasurfaces. We were able to experimentally demonstrate for the first time and study the THz emission from SMART nonlinear photonic crystals. This led to emission of few cycle THz pulses with engineered angular dispersion, which opens the door for development of new THz spectroscopy schemes, among other applications. We also showed that we can use the SMART concept for THz beam shaping and active control. We demonstrated generation of THz beam that cannot be demonstrated conventional mode conversion schemes. In addition, we introduced novel schemes for THz pulse shaping relying on direct space to time mapping by SMART metasurfaces. We also demonstrated new type of active nonlinear THz emitting lenses. These lenses generate broadband THz radiation and focus each generated frequency on a different focal point along the optical axis. We also studied the interaction in nonlinear THz waveguide configuration and showed the generated waveguides modes, and their spectral properties, can be controlled by the geometrical design of the nonlinear metasurface and waveguide configuration. This provided another novel promising platform for THz generation and manipulation. In addition, we also studied new ways to enhance, manipulate and control the nonlinear interaction on the metasurfaces. We found that collective interactions on the metasurface provide a promising path to significantly enhance the total nonlinear interaction, while showing interesting effects of slow light, induced transparencies and elimination of some nonlinear pathways.
In the next part of the project we focus our efforts to study better the physical mechanisms of THz emission from the nanostructures in order to be able to enhance the emission process to its limit and to find new ways to control it. In addition we will continue to demonstrate the potential of SMART THz emitters for generating designed THz wave forms.