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Harmonic Frequency Combs of Quantum Cascade Lasers: Origin, Control, and Prospective Applications


Harmonic Frequency Combs of Quantum Cascade Lasers: Origin, Control, and Prospective Applications

Hosted By: Applied Spectroscopy Technical Group

29 May 2018, 10:00 - 11:00

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Multimode behavior in semiconductor lasers is a complex and intriguing topic. When and why the second mode will start lasing? How do the different modes compete and interact? Such questions are not only fascinating from the perspective of fundamental laser science but also crucial in terms of related applications. A number of mechanisms can affect the gain experienced by the first lasing mode giving origin to multimode operation, including spatial hole burning, spectral hole burning and population pulsations. Some of these phenomena play a central role in the operation of quantum cascade lasers (QCLs), unipolar semiconductor lasers characterized by an ultra-fast gain recovery dynamics and strong nonlinear interactions among the optical modes, making these lasers an ideal platform for the observation of different multimode regimes.

Coherent instabilities triggering the onset of multimode operation in QCLs have been widely studied in the last decade. Recently, a novel multimode regime in QCLs — the harmonic state — was discovered. This new laser state is characterized by modes separated by several free spectral ranges of the cavity, being fundamentally different from conventional dense multimode states of QCLs, where adjacent cavity modes are populated. Moreover, the spacing among the modes of the harmonic state was shown to be uniform, by extreme accuracy, proving its nature of optical frequency comb. The ability of the laser to distribute its optical power among few, powerful modes separated by many free spectral ranges (as opposed to many, weaker adjacent cavity modes) has opened previously unforeseen possibilities for QCLs.

In this webinar, Dr. Marco Piccardo will discuss prospects for microwave and terahertz generation, the possibility of mid-infrared pulse generation, and broadband spectroscopy. Dr. Piccardo is a postdoctoral research fellow at Harvard University in the group of Prof. Federico Capasso, one of the inventors of quantum cascade lasers.



Dr. Marco Piccardo, Harvard University

Dr. Marco Piccardo is a postdoctoral research fellow in the Capasso Group at Harvard University. He obtained his bachelor’s in Physics from Universita’ degli Studi di Torino, his master’s in Physics from Ecole Normale Superieure and Ecole Polytechnique, and his Ph.D. in Physics from Ecole Polytechnique advised by Prof. C. Weisbuch and Dr. J. Peretti. His awards include the Young Physicist Award "G. F. Bassani" of the Italian Physical Society, and the Université Paris-Saclay’s PhD Award "Innovative Materials and Applications". His research is oriented towards the physics of optoelectronic devices, his interests include in particular quantum cascade lasers, optical frequency combs, and microwave photonics.