Using Terahertz Quantum Cascade Lasers as Amplifiers and Sources for Time-Domain Spectroscopy

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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.

[1] A.J. Fitzgerald et al. "Non-destructive analysis of tablet coating thickness using THz pulse imaging", Journal of Pharmaceutical Sciences 94, 177 (2005).

[2] N. Jukam et al. "THz amplifier based on gain switching in a quantum cascade laser", Nature Photonics 3, 715 (2009).

[3] D. Oustinov et al. "Phase seeding of a quantum cascade laser", Nature Communications 1, 69 (2010).


Dr. Nathan JukamNathan 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.