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Proceedings Paper

Mechanically robust cylindrical metal terahertz waveguides for cryogenic applications
Author(s): Robert Wallis; Riccardo Degl'Innocenti; Oleg Mitrofanov; Joanna Waldie; Carlos M. Bledt; Jeffrey E. Melzer; James A. Harrington; Harvey E. Beere; David A. Ritchie
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Paper Abstract

As the ambition behind THz quantum cascade laser based applications continues to grow, abandoning free-space optics in favor of waveguided systems promises major improvements in targeted, easy to align, and robust radiation delivery. This is especially true in cryogenic environments, where illumination is traditionally challenging. Although the field of THz waveguides is rapidly developing, most designs have limitations in terms of mechanical stability at low temperatures, and are costly and complicated to fabricate to lengths > 1 m. In this work, we investigate readily available cylindrical metal waveguides which are suitable for effective power delivery in cryogenic environments, and explore the optimal dimensions and materials available. The materials chosen were extruded un-annealed and annealed copper, as well as stainless steel, with bore diameters of 1.75, 2.5, and 4.6 mm. Measurements were performed at three different frequencies, 2.0, 2.85 and 3.2 THz, with optimal transmission losses <3 dB/m demonstrated at 2.0 THz. Additionally, novel optical couplers are also presented and characterised, with the ability to change the beam path by 90° with a coupling loss of just 2.2 dB whilst maintaining mode quality, or thermally isolate sections of waveguide with a coupling loss as low as 0.5 dB. The work presented here builds on previous work1, and forms a comprehensive investigation of cryogenically compatible THz waveguides and optical couplers, paving the way for a new generation of systems to utilize THz QCLs for a host of low-temperature investigations.

Paper Details

Date Published: 24 February 2017
PDF: 9 pages
Proc. SPIE 10103, Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications X, 1010307 (24 February 2017); doi: 10.1117/12.2250530
Show Author Affiliations
Robert Wallis, Univ. of Cambridge (United Kingdom)
Riccardo Degl'Innocenti, Univ. of Cambridge (United Kingdom)
Oleg Mitrofanov, Univ. College London (United Kingdom)
Joanna Waldie, Univ. of Cambridge (United Kingdom)
Carlos M. Bledt, Rutgers, The State Univ. of New Jersey (United States)
Jeffrey E. Melzer, Rutgers, The State Univ. of New Jersey (United States)
James A. Harrington, Rutgers, The State Univ. of New Jersey (United States)
Harvey E. Beere, Univ. of Cambridge (United Kingdom)
David A. Ritchie, Univ. of Cambridge (United Kingdom)


Published in SPIE Proceedings Vol. 10103:
Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications X
Laurence P. Sadwick; Tianxin Yang, Editor(s)

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