Using Terahertz Quantum Cascade Lasers as Amplifiers and Sources for Time-Domain Spectroscopy
Monday, May 9, 1065 Kemper Hall, 11:00am-12:00pm
Speaker: Dr. Nathan Jukam
Laboratoire Pierre Aigrain, Ecole Normale Supérieure
Host: Professor Rick Kiehl
Many products use electromagnetic radiation to improve our everyday lives and commercial products exist for almost every portion of the electromagnetic spectrum (from x-rays to radio waves). However, products that use terahertz radiation are lacking, even though there are many potential terahertz applications such as non-destructive testing, biological imaging, illicit substance detection, and high-speed wireless communication. The reason for this is the under- developed state of terahertz technology.
In this talk, I give a brief survey of terahertz sources and potential applications. I then proceed to discuss terahertz time-domain spectroscopy and quantum cascade lasers (QCLs) in more detail. Time-domain spectroscopy has permitted the development of terahertz applications such as pharmaceutical drug encapsulation testing1. However, time-domain systems often require an expensive regenerative amplified laser in order to increase the signal to noise ratio. As a result, potential applications are often limited to the laboratory. To address these problems, we recently introduced an amplifier for terahertz waves based on a QCL2. Our goal is to perform high-power time-domain spectroscopy by amplifying terahertz waves generated from low-power femtosecond lasers. Furthermore, by locking the QCL frequency to the repetition rate of a femtosecond laser, we show that QCLs can be used as sources for time-domain spectroscopy3.
 A.J. Fitzgerald et al. "Non-destructive analysis of tablet coating thickness using THz pulse imaging", Journal of Pharmaceutical Sciences 94, 177 (2005).
 N. Jukam et al. "THz amplifier based on gain switching in a quantum cascade laser", Nature Photonics 3, 715 (2009).
 D. Oustinov et al. "Phase seeding of a quantum cascade laser", Nature Communications 1, 69 (2010).
Nathan Jukam received the Ph.D. in physics from the University of California, Santa Barbara in 2006. He is currently employed as post-doctoral researcher at the Ecole Normale Supérieure (ENS) in Paris, France. At the ENS his research involves ultra-fast studies of quantum cascade lasers.