Abstract-Amplitude Stabilization of a Terahertz Quantum Cascade Laser with an External Metamaterial Amplitude Modulator

B. Wei, S. J. Kindness, N. W. Almond, R. Wallis, Y. Wu, Y. Ren, P. Braeuninger-Weimer, S. Hofmann, H. E. Beere, D. A. Ritchie, and R. Degl'lnnocenti

https://www.osapublishing.org/abstract.cfm?uri=cleo_si-2018-STu4D.5&origin=search

Terahertz laser sources with stable power levels are requested for astronomical, communication and spectroscopic applications. Here we demonstrate the amplitude stabilization of a terahertz quantum cascade laser with a graphene loaded split-ring-resonator array. This integrated amplitude modulator operates at room temperature and is capable of actively modulating the quantum cascade laser power level and stabilizing the power output via a PID loop. The laser power fluctuation was reduced from 1.82% to 0.19% of the total power.

© 2018 The Author(s)

Abstract-Investigation of hollow cylindrical metal terahertz waveguides suitable for cryogenic environments

R. Wallis, R. Degl Innocenti, D. S. Jessop, O. Mitrofanov, C. M. Bledt, J. E. Melzer, J. A. Harrington, H. E. Beere, and D. A. Ritchie

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-26-30002

The field of terahertz (THz) waveguides continues to grow rapidly, with many being tailored to suit the specific demands of a particular final application. Here, we explore waveguides capable of enabling efficient and accurate power delivery within cryogenic environments (< 4 K). The performance of extruded hollow cylindrical metal waveguides made of un-annealed and annealed copper, as well as stainless steel, have been investigated for bore diameters between 1.75 - 4.6 mm, and at frequencies of 2.0, 2.85 and 3.4 THz, provided by a suitable selection of THz quantum cascade lasers. The annealed copper resulted in the lowest transmission losses, < 3 dB/m for a 4.6 mm diameter waveguide, along with 90° bending losses as low as ~2 dB for a bend radius of 15.9 mm. The observed trends in losses were subsequently analyzed and related to measured inner surface roughness parameters. These results provide a foundation for the development of a wide array of demanding low-temperature THz applications, and enabling the study of fundamental physics.

Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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Abstract-Efficient coupling of double-metal terahertz quantum cascade lasers to flexible dielectric-lined hollow metallic waveguides

R. Wallis, R. Degl’Iinnocenti, D. S. Jessop, Y. Ren, A. Klimont, Y. D. Shah, O. Mitrofanov, C. M. Bledt, J. E. Melzer, J. A. Harrington, H. E. Beere, and D. A. Ritchie
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-23-20-26276

The growth in terahertz frequency applications utilising the quantum cascade laser is hampered by a lack of targeted power delivery solutions over large distances (>100 mm). Here we demonstrate the efficient coupling of double-metal quantum cascade lasers into flexible polystyrene lined hollow metallic waveguides via the use of a hollow copper waveguide integrated into the laser mounting block. Our approach exhibits low divergence, Gaussian-like emission, which is robust to misalignment error, at distances > 550 mm, with a coupling efficiency from the hollow copper waveguide into the flexible waveguide > 90%. We also demonstrate the ability to nitrogen purge the flexible waveguide, increasing the power transmission by up to 20% at 2.85 THz, which paves the way for future fibre based terahertz sensing and spectroscopy applications.

© 2015 Optical Society of America

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