Gallacher, K. et al. (2020) Design and simulation of losses in Ge/SiGe terahertz quantum cascade laser waveguides. Optics Express, 28(4), pp. 4786-4800. (doi: 10.1364/OE.384993)
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Abstract
The waveguide losses from a range of surface plasmon and double metal waveguides for Ge/Si1−xGex THz quantum cascade laser gain media are investigated at 4.79 THz (62.6 μm wavelength). Double metal waveguides demonstrate lower losses than surface plasmonic guiding with minimum losses for a 10 μm thick active gain region with silver metal of 21 cm−1 at 300 K reducing to 14.5 cm−1 at 10 K. Losses for silicon foundry compatible metals including Al and Cu are also provided for comparison and to provide a guide for gain requirements to enable lasers to be fabricated in commercial silicon foundries. To allow these losses to be calculated for a range of designs, the complex refractive index of a range of nominally undoped Si1−xGex with x = 0.7, 0.8 and 0.9 and doped Ge heterolayers were extracted from Fourier transform infrared spectroscopy measurements between 0.1 and 10 THz and from 300 K down to 10 K. The results demonstrate losses comparable to similar designs of GaAs/AlGaAs quantum cascade laser plasmon waveguides indicating that a gain threshold of 15.1 cm−1 and 23.8 cm−1 are required to produce a 4.79 THz Ge/SiGe THz laser at 10 K and 300 K, respectively, for 2 mm long double metal waveguide quantum cascade lasers with facet coatings.
| Item Type: | Articles |
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| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Paul, Professor Douglas and REW, Kirsty and Gallacher, Dr Kevin |
| Authors: | Gallacher, K., Ortolani, M., Rew, K., Ciano, C., Baldassarre, L., Virgillio, M., Scalari, G., Faist, J., Di Gaspare, L., De Seta, M., Capellini, G., Grange, T., Birner, S., and Paul, D.J. |
| College/School: | College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering |
| Journal Name: | Optics Express |
| Publisher: | Optical Society of America |
| ISSN: | 1094-4087 |
| ISSN (Online): | 1094-4087 |
| Copyright Holders: | Copyright © 2020 The Optical Society |
| First Published: | First published in Optics Express 28(4):4786-4800 |
| Publisher Policy: | Reproduced under a Creative Commons License |
| Data DOI: | 10.5525/gla.researchdata.950 |
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