3.9 THz spatial filter based on a back-to-back Si-lens system

Journal article (2020)

Authors

Y. Gan SRON–Netherlands Institute for Space Research, Rijksuniversiteit Groningen
B. Mirzaei SRON–Netherlands Institute for Space Research, ImPhys/Optics - AS
S. van der Poel QN/van der Zant Lab - AS , Kavli institute of nanoscience Delft
J. R.G. Silva SRON–Netherlands Institute for Space Research, Rijksuniversiteit Groningen
M. Finkel SRON–Netherlands Institute for Space Research
Martin Eggens SRON–Netherlands Institute for Space Research
M.L. Ridder SRON–Netherlands Institute for Space Research
A. Khalatpour Massachusetts Institute of Technology
J.R. Gao SRON–Netherlands Institute for Space Research, ImPhys/Optics - AS
More Authors... External organisation
Research Group
ImPhys/Optics (AS) (TU Delft)
Copyright: © 2020 Y. Gan, B. Mirzaei, S. van der Poel, Jose R.G. Silva, M. Finkel, Martin Eggens, M.L. Ridder, Ali Khalatpour, J.R. Gao, More Authors
DOI: https://doi.org/10.1364/OE.410446
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Published Date

2020

Language

English

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Faculty

Applied Sciences

Department

ImPhys/Imaging Physics

Research Group

ImPhys/Optics

Abstract

We present a terahertz spatial filter consisting of two back-to-back (B2B) mounted elliptical silicon lenses and an opening aperture defined on a thin gold layer between the lenses. The beam filtering efficiency of the B2B lens system is investigated by simulation and experiment. Using a unidirectional antenna coupled 3rd-order distributed feedback (DFB) quantum cascade laser (QCL) at 3.86 THz as the source, the B2B lens system shows 72% transmissivity experimentally with a fundamental Gaussian mode as the input, in reasonably good agreement with the simulated value of 80%. With a proper aperture size, the B2B lens system is capable of filtering the non-Gaussian beam from the QCL to a nearly fundamental Gaussian beam, where Gaussicity increases from 74% to 99%, and achieves a transmissivity larger than 30%. Thus, this approach is proven to be an effective beam shaping technique for QCLs, making them to be suitable local oscillators in the terahertz range with a Gaussian beam. Besides, the B2B lens system is applicable to a wide frequency range if the wavelength dependent part is properly scaled.

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