Highlight in Nature Photonics
Terahertz quantum cascade lasers operating up to about 200 K with optimized oscillator strength and improved injection tunneling
By: S. Fathololoumi, E. Dupont, C.W.I. Chan, Z.R. Wasilewski, S.R. Laframboise, D. Ban, A. Matyas, C. Jirauschek, Q. Hu, and H. C. Liu
Our co-authored paper about terahertz quantum cascade lasers has been highlighted in Nature Photonics.
A new temperature performance record of 199.5 K for terahertzquantum cascade lasers is achieved by optimizing the lasing transition oscil-lator strength of the resonant phonon based three-well design.
The optimumoscillator strength of 0.58 was found to be larger than that of the previousrecord (0.41) by Kumar etal.[Appl. Phys. Lett. 94, 131105 (2009)].
The choice of tunneling barrier thicknesses was determined with a simplifieddensity matrix model, which converged towards higher tunneling couplingstrengths than previously explored and nearly perfect alignment of the statesacross the injection and extraction barriers at the design electric field.
At8 K, the device showed a threshold current density of 1 kA/cm2, with apeak output power of∼38 mW, and lasing frequency blue-shifting from2.6 THz to 2.85 THz with increasing bias.
The wavelength blue-shifted to3.22 THz closer to the maximum operating temperature of 199.5 K, whichcorresponds to∼1.28 ̄hω/κB.
The voltage dependence of laser frequency isrelated to the Stark effect of two intersubband transitions and is comparedwith the simulated gain spectra obtained by a Monte Carlo approach.