Design and Modeling of High Temperature Terahertz Quantum Cascade Lasers

Speaker: Ben Burnett
Affiliation: Ph.D. Candidate - UCLA

Abstract:  A leading candidate for a coherent source of terahertz radiation is the quantum cascade laser (QCL). In contrast to ordinary semiconductor lasers, QCLs operate entirely within the conduction band, via stimulated emission across subbands which can be spaced at energies chosen by design. The Restrahlen band in III-V semiconductors sets apart the distinct ranges of mid-IR and THz QCLs, which are also quite distinct in maturity; while mid-IR QCLs operate with watt-level power well above room temperature and have been commercialized, THz QCLs still do not operate above 200 K.

In this talk, I describe a density matrix-based formalism developed to describe transport over a wide array of QCL systems. The formalism is first used to test the highly exploratory concept of a terahertz quantum dot cascade laser (QDCL), where a means of treating strongly-coupled electron-phonon polarons is also put forward. Serious ramifications are predicted in the operating characteristics of QDCLs, leading to counterintuitive design strategies. Next, the density matrix formalism is extended for optical nonlinearities, to analyze the recent demonstration of THz difference frequency generation inside two-color mid-IR QCL active regions. This analysis reveals mechanisms that contribute significantly to the difference frequency susceptibility χ⁽²⁾ but are left out of the usual models, and suggests strategies for their exploitation.

Biography: Ben Burnett is currently a Ph.D. Candidate in the Electrical Engineering Department at UCLA, under the supervision of Professor Benjamin Williams. His research focus is on electron transport modeling of quantum cascade laser active regions.  He received his BS in 2010 from Boston University and his MS in 2012 from UCLA.

For more information, contact Prof. Benjamin Williams (bswilliams@ucla.edu)

Date/Time:
Date(s) - Jun 02, 2016
1:00 pm - 3:00 pm

Location:
E-IV Tesla Room #53-125
420 Westwood Plaza - 5th Flr., Los Angeles CA 90095