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|a Gan, Yuner
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|a Mirzaei, Behnam
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|a van der Poel, Sebastiaan
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|a Silva, Jose RG
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|a Finkel, Matvey
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|a Eggens, Martin
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|a Ridder, Marcel
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|a Khalatpour, Ali
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|a Hu, Qing
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|a van der Tak, Floris
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|a Gao, Jian-Rong
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|a 39 THz spatial filter based on a back-to-back Si-lens system
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|b The Optical Society,
|c 2022-06-29T17:43:53Z.
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|z Get fulltext
|u https://hdl.handle.net/1721.1/143595
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|a © 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement. 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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|a Article
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|t 10.1364/OE.410446
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|t Optics Express
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