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-Graphene based plasmonic terahertz amplitude modulator operating above 100 MHz

D. S. Jessop1,a), S. J. Kindness1, L. Xiao2, P. Braeuninger-Weimer2, H. Lin3,b), Y. Ren1, C. X. Ren4, S. Hofmann2, J. A. Zeitler3, H. E. Beere1, D. A. Ritchie1 and R. Degl'Innocenti1,a)

a) Authors to whom correspondence should be addressed. Electronic addresses:dsj23@cam.ac.uk and rd448@cam.ac.uk.

b) Now at Department of Engineering, Lancaster University, Lancaster LA1 4YW, United Kingdom.

Appl. Phys. Lett. 108, 171101 (2016); http://dx.doi.org/10.1063/1.4947596

The terahertz (THz) region of the electromagnetic spectrum holds great potential in many fields of study, from spectroscopy to biomedical imaging, remote gas sensing, and high speed communication. To fully exploit this potential, fast optoelectronic devices such as amplitude and phase modulators must be developed. In this work, we present a room temperature external THz amplitude modulator based on plasmonic bow-tie antenna arrays with graphene. By applying a modulating bias to a back gate electrode, the conductivity of graphene is changed, which modifies the reflection characteristics of the incoming THz radiation. The broadband response of the device was characterized by using THz time-domain spectroscopy, and the modulation characteristics such as the modulation depth and cut-off frequency were investigated with a 2.0 THz single frequency emission quantum cascade laser. An optical modulation cut-off frequency of 105 ± 15 MHz is reported. The results agree well with a lumped element circuit model developed to describe the device.