Terahertz nanodevices for photonic integrated circuits

Over the past decades, Terahertz (THz) systems development has taken a major step forward together with laser-based technologies for the generation and detection of THz signals. Optoelectronic generation of continuous-wave THz signals relies on mixing two optical signals oscillating in a high-speed photoconductive antenna, for which the photocurrent depends on the incident optical power. The capability to operate THz fields in passive devices can be combined smoothly with photonic integrated circuit (PIC) technologies to enable photonic chips with enhanced THz efficiency. There are still many open questions about implementation and improvement to reduce equipment size, noise, alignment efforts, electrical and optical power consumption, and to increase the system flexibility. In this manuscript, we introduce a new THz system platform based on photonic integrated circuits and micro-structured photoconductive antennas that will increase the integration by reducing the footprint of THz spectrometers by more than 3 orders of magnitude. Additionally, a new integrated lens-antenna consisting of a Fresnel zone plate is designed and implemented for a nanocontact based THz photomixer. The new design replaces the standard conventional bulky silicon lens, which normally no THz photomixer can avoid. THz measurements showed a comparable behavior with the Fresnel zone plate to that of the conventional bulky silicon lens, demonstrating its readiness for photonic integrated circuits-based THz systems. This integration platform will represent a technological jump from currently bulky equipment and devices to extremely flexible, portable, and energy efficient THz systems-on-chip, at much lower costs.