Opt Express. 2018 Feb 19;26(4):3814-3827. doi: 10.1364/OE.26.003814.

Silver-based surface plasmon waveguide for terahertz quantum cascade lasers.

Optics express

Y J Han, L H Li, J Zhu, A Valavanis, J R Freeman, L Chen, M Rosamond, P Dean, A G Davies, E H Linfield

PMID: 29475360 DOI: 10.1364/OE.26.003814

Abstract

Terahertz-frequency quantum cascade lasers (THz QCLs) based on ridge waveguides incorporating silver waveguide layers have been investigated theoretically and experimentally, and compared with traditional gold-based devices. The threshold gain associated with silver-, gold- and copper-based devices, and the effects of titanium adhesion layers and top contact layers, in both surface-plasmon and double-metal waveguide geometries, have been analysed. Our simulations show that silver-based waveguides yield lower losses for THz QCLs across all practical operating temperatures and frequencies. Experimentally, QCLs with silver-based surface-plasmon waveguides were found to exhibit higher operating temperatures and higher output powers compared to those with identical but gold-based waveguides. Specifically, for a three-well resonant phonon active region with a scaled oscillator strength of 0.43 and doping density of 6.83 × 10

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• Journal Article