Asymmetric transmission of terahertz radiation through a double grating

Abstract

We report on experimental evidence of unidirectional transmission of terahertz waves through a pair of metallic gratings with different periods. The gratings are optimized for a broadband transmission in one direction, accompanied with a high extinction rate in the opposite direction. In contrast to previous studies, we show that the zero-order nonreciprocity cannot be achieved. Nonetheless, we confirm that the structure can be used successfully as an asymmetric filter.

Experimental demonstration of deflection angle tuning in unidirectional fishnet metamaterials at millimeter-waves

“…4,5 In the limiting case, the backward transmission vanishes leading to the most interesting-unidirectional-regime. Different strategies have been proposed, including those based on higher diffraction orders, [6][7][8][9][10][11] polarization conversion, 12,13 and wave manipulation in prism-like structures. 14,15 For the first and second ones, asymmetry in transmission is achieved due to the use of different transmission channels that are open for each of the two opposite illumination directions at fixed frequency.…”

“…Asymmetric excitation of higher diffraction orders can be simply enabled in various volumetric and ultrathin structures by loading one of the interfaces with a grating-like structure. This strategy has successfully been realized in non-symmetric structures based on photonic crystals, [6][7][8][9]16 fishnet, 17 and multilayer metamaterials, 18 thin metallic gratings with slits, 10,19 and simple one-and twofraction gratings that contain Drude metals 7 or polar dielectrics. 20 Experimental results have been reported for acoustic, 9 microwave, 16,17 terahertz, 10 and optical 15,18 regimes.…”

One-way absorption of terahertz waves in rod-type and multilayer structures containing polar dielectrics

“…The known mechanisms include those inspired by diffractions [1,2,6,7] and polarization conversion [5,8,9]. The mechanisms realizable in the structures that (may) support surface waves should also be mentioned [10][11][12]. Clearly, full analogs of nonreciprocal effects cannot be achieved in the framework of these mechanisms [13].…”

Visible-frequency asymmetric transmission devices incorporating a hyperbolic metamaterial

“…A symmetric transmission using reciprocal electromagnetic devices has recently become a thriving research topic owing to potential applications in integrated photonic systems for communications and information processing [1][2][3][4][5][6][7][8][9][10][11][12] , such as, directionally-sensitive beam splitting 2,3 , multiplexing 4 and optical interconnection 7,8 . This Lorentz-reciprocal effect is characterized by the high contrast between forward and reverse transmission under illumination from anti-parallel directions.…”

“…Though reciprocal asymmetric transmission devices cannot be used for functions attainable only with non-reciprocal-active devices, such as optical isolation [13][14][15][16] , they have unique advantages such as small footprint, broad asymmetric transmission bandwidth and passive operation. Asymmetric transmission can be achieved through the use of artificial structures, such as, nonsymmetric gratings [2][3][4][5][6]11,12 , photonic crystals 7,8 and split-ring resonators 1,9,10 which break spatial inversion symmetry. Nevertheless, fabrication and alignment challenges associated with the intrinsic complexity of such approaches have not so far enabled structures with an efficient asymmetric transmission response at visible frequencies.…”