Towards Universality of Terahertz Electromagnetic Synthesis and Sensing with Chip-scale Systems

Abstract

The THz spectrum, wedged between microwave and infrared, can foster future ultra-high-speed wireless networks, and high-resolution sensing and imaging for the next generation of autonomous systems. The current technology landscape in this spectrum is relatively unexplored compared to its adjacent spectra. The last decade has significant efforts across the electronics-photonics domain focusing on chip-scale platforms which can synthesize and sense THz fields. While proofs-of-concepts have been demonstrated to harness this spectrum, a key challenge for enabling versatile technology in a complex environment is to incorporate programmability and adaptability that can be leveraged with machine intelligence for an end-to-end system. This has been a major challenge because the devices are operating near or beyond their cut-off frequencies.

In this thesis, we focus on design approaches that enables a universality in THz signal synthesis and detection with reconfigurability across spectrum, spatial field configuration and polarization. The key idea is that the wavelengths of THz signals approach the chip dimensions ($\sim$mm), we enter a region where new radiating and scattering structures can be integrated with a billion active devices in the same substrate. This creates a new design space that allows programmable sub-wavelength synthesis, manipulation, and detection. This leads to new sensing architectures and functionalities evolved through a different design approach.

We demonstrate a THz spectrum sensing architecture that can estimate incident spectrum through direct near-fields measurement and estimation algorithms, eliminating the need for the conventional complex receiver architectures. We demonstrate the first single-chip source-free THz spectroscope across 40GHz-990GHz.

Through such sub-wavelength sensing, we can add local active field perturbations to program sensor properties to incident field. This leads to an optimization-based design approach where we can map optimal sensor properties to a digital reconfiguration space. We demonstrate the design techniques and the trade-off space experimentally in a single-chip THz sensor with reconfigurability across 100GHz-1000GHz, incident angle and polarization.

On the synthesis side, we demonstrate a programmable THz source which can shape the radiated signal time-evolution dynamically. In addition, we also show that these multi-port EM/systems interfaces lead to new reconfigurable properties for spectrally-agile millimeter-wave array elements with pattern, polarization, and spatial diversity.