Abstract-Negative free carrier absorption in terahertz quantum cascade lasers

C. Ndebeka-Bandou, M. Rösch, K. Ohtani, M. Beck, J. Faist

(Submitted on 28 Nov 2016)

https://arxiv.org/abs/1611.09269

We analyze the peculiar case where the free carrier absorption arising from LO phonon absorption-assisted transitions becomes negative and therefore turns into a gain source for quantum cascade lasers. Such an additional source of gain exists when the ratio between the electronic and the lattice temperatures is larger than one, a condition that is usually fulfilled in quantum cascade lasers. We find a gain of few cm−1's at 200K. We report the development of a terahertz quantum cascade laser operating in the negative free carrier absorption regime.

Abstract-A patch-array antenna single-mode low electrical dissipation continuous wave terahertz quantum cascade laser

L. Bosco1,a), C. Bonzon1, K. Ohtani1, M. Justen2, M. Beck1 and J. Faist1
http://scitation.aip.org/content/aip/journal/apl/109/20/10.1063/1.4967836
1 Institute for Quantum Electronics, ETH Zurich, Auguste-Piccard-Hof 1, 8093 Zurich, Switzerland
2 I. Institute of Physics, University of Cologne, Zulpicher Strasse 77, 50937 Cologne, Germany
a) Electronic mail: lbosco@phys.ethz.ch
Appl. Phys. Lett. 109, 201103 (2016); http://dx.doi.org/10.1063/1.4967836

We introduce a double metal terahertz quantum cascade laser meant for astrophysical heterodyne measurements. The laser ridge is embedded in benzocyclobutene, and the device exhibits single mode, continuous wave operation around 4.745 THz with a peak power of almost 1.8 mW at 10 K and a power consumption of ≈1.6 W. Moreover, thanks to the integration of a top metal contact with a patch array antenna for light out-coupling the beam of the emitted light has a low-divergence single-lobe profile and an FWHM of ≈30°.