The Michigan Engineer News Center

Chris Berry receives Paper Award at IMS 2013 for Research in Terahertz Technology

Berry's paper addresses important limitations such as low output power and poor power efficiency.| Short Read
EnlargeChris Berry

Chris Berry, a doctoral student in the Electrical Engineering program, received  Best Student Paper Award (3rd place) at the 2013 International Microwave Symposium for his paper Nanoscale Contact Electrodes for Significant Radiation Power Enhancement in Photoconductive Terahertz Emitters.

This paper presents a novel photoconductive terahertz emitter that achieves a dramatic increase in performance over current emitters. The improved performance results from the use of a plasmonic contact electrode configuration which enhances the optical-to-terahertz conversion efficiency by up to two orders of magnitude. This technique addresses the most important limitations of conventional photoconductive terahertz emitters, namely low output power and poor power efficiency. These limitations originate from the inherent tradeoff between high quantum efficiency and ultrafast operation of conventional photoconductors.

The key novelty in this work is the use of a plasmonic contact electrode configuration that accumulates a large number of photo-generated carriers in close proximity to the contact electrodes. This allows the photo-generated carriers to drift to the terahertz radiating antenna within a sub-picosecond timescale. In other words, the tradeoff between photoconductor ultrafast operation and high quantum efficiency is mitigated by spatial manipulation of the photo-generated carriers.

The paper was co-authored by Mohammed R. Hashemi, Mehmet Unlu, and his advisor, Prof. Mona Jarrahi.

Read more about this research and its applications in imaging (including medical imaging) and chemical detection.

Chris Berry
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The electrons absorb laser light and set up “momentum combs” (the hills) spanning the energy valleys within the material (the red line). When the electrons have an energy allowed by the quantum mechanical structure of the material—and also touch the edge of the valley—they emit light. This is why some teeth of the combs are bright and some are dark. By measuring the emitted light and precisely locating its source, the research mapped out the energy valleys in a 2D crystal of tungsten diselenide. Credit: Markus Borsch, Quantum Science Theory Lab, University of Michigan.

Mapping quantum structures with light to unlock their capabilities

Rather than installing new “2D” semiconductors in devices to see what they can do, this new method puts them through their paces with lasers and light detectors. | Medium Read