Benjamin Williams at UCLA presents talk" Next generation terahertz sources: quantum cascade lasers and active metamaterials"

Benjamin Williams

UCLA, Electrical Engineering Department

what
when	Sep 19, 2012 from 01:00 PM to 02:30 PM
where	Engr. IV Bldg., Shannon Room 54-134
contact name	Prof. Ben Williams

Abstract

The terahertz frequency range (roughly 0.3-10 THz, or wavelengths of 30-1000 μm) remains one of the least developed regions of electromagnetic spectrum. Compared to the neighboring microwave/mm-wave or infrared spectral ranges it remains challenging to manipulate, to detect, and particularly to generate THz radiation. However, the location of the terahertz range offers unique opportunities for hybrid devices, as photonic techniques for achieving gain (i.e. stimulated emission and lasing) can be combined with lower-frequency circuit and antenna techniques for waveguiding and radiation control. In the past decade, the terahertz quantum cascade (QC) laser has emerged as a promising and flexible source of THz continuous-wave radiation with milliwatt power in the 2-5 THz range. However challenges remain in issues of output power, beam quality, operating temperature, and frequency tunability.

In this talk, I will discuss our efforts to address these challenges for THz sources using novel material and electromagnetic approaches. Using the THz QC-laser gain material as a foundation, we have introduced the concept of active composite right/left handed (CRLH) THz metamaterial waveguides. By loading sub-wavelength transmission-line laser waveguides with additional inductive and capacitive circuit elements, we can engineer the waveguide dispersion to enable new functionality, such as laser antennas for beam-steering and shaping and efficient out-coupling of THz radiation. We have demonstrated proof-of-concept devices including passive CRLH metamaterial waveguides, and active QC-laser metamaterial leaky-wave antennas. I will also discuss the prospects for novel THz laser devices based upon metamaterial waveguides, including widely tunable THz sources, and integrated THz laser phased arrays.

Biography

Benjamin Williams is an Assistant Professor of Electrical Engineering at the University of California, Los Angeles. He received the Ph.D. degree from the Massachusetts Institute of Technology, Cambridge, Massachusetts in 2003 in Electrical Engineering and Computer Science, and was a Postdoctoral Associate at the Research Laboratory of Electronics at MIT from 2003-2006. His research interests include quantum cascade lasers, intersubband and intersublevel devices in semiconductor nanostructures, and terahertz metamaterials and sub-wavelength plasmonics. He is the recipient of the DARPA Young Faculty Award (2008) and the NSF CAREER award (2012).