Quantum cascade laser pumped molecular laser: widely tunable THz sources from 200 GHz to > 1 THz

Federico Capasso
John A. Paulson School of Engineering and Applied Sciences
Harvard University

The terahertz region of the electromagnetic spectrum has been the least utilized owing to inadequacies of available sources. We introduce a compact, widely frequency-tunable, extremely bright source of terahertz radiation: a gas-phase molecular laser based on rotational population inversions optically pumped by a quantum cascade laser. By identifying the essential parameters that determine the suitability of a molecule for a terahertz laser, almost any rotational transition of almost any molecular gas can be made to lase. Nitrous oxide is used to illustrate the broad tunability over 37 lines spanning 0.251 to 0.955 terahertz, each with kilohertz linewidths. Our analysis shows that laser lines spanning more than 1 terahertz with powers greater than 1 milliwatt are possible from many molecular gases pumped by quantum cascade lasers.

Collaborators: Harvard: Paul Chevalier, Arman Armizhan, Marco Piccardo
MIT: Fan Wang, Steven G. Johnson; Duke University: Henry O. Everitt

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