CAREER: On-Chip Terahertz Electronic Frequency Combs

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

Maintaining the exponential growth of electronic signal generation, sensing, and processing is essential to meet the new challenges of the upcoming era featuring ubiquitous sensors for healthcare, environment monitoring, autonomous vehicles/machines, etc. In particular, if the operating frequency of low-cost electronics can be extended into the terahertz (THz) regime, the unprecedented wide bandwidth will enable numerous new applications, such as non-ionizing imaging, molecular identification, high-resolution radar, and ultra-high-speed data link. Although in the past decade THz integrated circuits in silicon have improved remarkably in output power and efficiency, their reliance on high-quality-factor resonance makes the current THz sensors narrowband and fails to fully capitalize on the available broad spectrum for wide-range gas sensing and high-precision radar ranging. To break such a limit, this project investigates a new technique based on electronic THz frequency comb. Through parallel signal processing on the integrated circuit chip, gas sensor and imaging radar using the proposed technique will achieve significantly better spectral coverage and energy efficiency. This research effort will also be integrated with the principal investigator's educational career goal of promoting highly-interdisciplinary studies through the creation of new courses and engaging underrepresented and K-12 students through MIT's outreach programs. The objective of this proposal is to leverage the integration capability of the silicon semiconductor fabrication process and use THz frequency comb technique to distribute the signal-sensing load to an array of narrowband, precisely-controlled THz circuit units. It maintains high energy efficiency while covering a wide bandwidth in a scalable fashion. Sensors based on two types of THz frequency comb will be investigated under this program. First, a rotational-mode molecular sensor will be demonstrated using an evenly distributed frequency comb. The frequency comb will seamlessly cover more than 100 GHz of bandwidth and increase the spectral scanning speed of chip-scale THz spectrometer by a factor of 200. Through an on-chip frequency calibration technique, the spectrometer will scan the frequency spectrum with one-part-per-billion level frequency precision. Second, an imaging radar will be demonstrated using a non-uniform comb and compressive sensing. By quantizing the target distance with a set of nonlinearly distributed wavelengths and by using an error-correction algorithm, the radar can operate with low signal-to-noise ratio and low power consumption. The THz comb radar will also be integrated with a low-cost sensor array in a quasi-optical configuration, so that real-time 3D imaging with electronic scanning and fine resolution can be realized. Through these comprehensive studies, the program will establish the advantages of parallelism in chip-scale wide-band signal sensing and processing.