Abstract-Broadband all-electronically tunable MEMS terahertz quantum cascade lasers

Ningren Han, Alexander de Geofroy, David P. Burghoff, Chun Wang I. Chan, Alan Wei Min Lee, John L. Reno, and Qing Hu  »View Author 

Optics Letters, Vol. 39, Issue 12, pp. 3480-3483 (2014)
http://dx.doi.org/10.1364/OL.39.003480

http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-39-12-3480

In this work, we demonstrate all-electronically tunable terahertz quantum cascade lasers (THz QCLs) with MEMS tuner structures. A two-stage MEMS tuner device is fabricated by a commercial open-foundry process performed by the company MEMSCAP. This provides an inexpensive, rapid, and reliable approach for MEMS tuner fabrication for THz QCLs with a high-precision alignment scheme. In order to electronically actuate the MEMS tuner device, an open-loop cryogenic piezo nanopositioning stage is integrated with the device chip. Our experimental result shows that at least 240 GHz of single-mode continuous electronic tuning can be achieved in cryogenic environments (∼4  K) without mode hopping. This provides an important step toward realizing turn-key bench-top tunable THz coherent sources for spectroscopic and coherent tomography applications.

© 2014 Optical Society of America

Abstract-Tall-barrier terahertz quantum cascade lasers

Chun Wang I. Chan, Qing Hu, John L. Reno,
http://apl.aip.org/resource/1/applab/v103/i15/p151117_s1?isAuthorized=no
A terahertz quantum cascade laser is presented in which selectively placed pure AlAs barriers are used to reduce parasitic leakage currents to the conduction band continuum. The design is demonstrated to have improved temperature performance over a regrowth of the current T_max ∼ 200 K record holder (181 K vs. 175 K). Strangely, it fails to lase below ∼70 K, which we attribute to negative differential resistance (NDR) prior to threshold. A subsequent design using only AlAs barriers failed to lase, the reason for which we posit to be either early NDR or excessive interface roughness scattering.

© 2013 AIP Publishing LLC