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abstract: A magnet less nonreciprocal metasurface (MNMs) exhibiting enhanced transmission is presented. The metasurface is constituted of a 2D periodic array of a stacked annular pair of slots loaded with semiconductor based unidirectional components sandwiching a dielectric slab spacer. The reflection and transmission dyadics of the metamaterial structure are computed using transmission line modeling with single layer annular slot impedance dyadic. A parametric study is conducted in terms of the spacer permittivity and thickness to achieve enhanced transmission. Possibility of designing total transmission or total reflection magnet less nonreciprocal metasurfaces is discussed.
author_names: Burak Gurlek

Christophe Caloz
title: Towards reflection less or total reflection magnet less nonreciprocal metasurface
venue: 2015 9th European Conference on Antennas and Propagation (EuCAP)
year: 2015

abstract: In this letter, we propose a magnet less nonreciprocal isolating system based on time varying metasurfaces. Two parallel time varying metasurfaces, one for frequency up conversion and one for down conversion by the same amount, are used for realizing a region of space where incident waves from opposite directions experience an opposite Doppler frequency shift. As a result, any device within this region becomes sensitive to the illumination direction, exhibiting a different scattering response from the opposite directions, and thus breaking reciprocity. Very importantly, thanks to the opposite frequency shift of the metasurfaces, the frequency of the transmitted electromagnetic field is the same as for the incident one. Here, we demonstrate this general approach by using a Bragg grating as the device between the time varying metasurfaces. The combined structure of the metasurfaces and the grating exhibits different transmission and reflection properties for opposite illumination direction, thereby realizing an isolator. More broadly, this letter presents a strategy for converting any conventional electromagnetic device to a nonreciprocal one by placing it between two time varying metasurfaces. This approach opens the door to several new nonreciprocal components based on thin and lightweight metasurfaces, which are simpler to realize compared to their volumetric counterparts.
author_names: Davide Ramaccia

Dimitrios L Sounas

Angelica Viola Marini

Alessandro Toscano

Filiberto Bilotti
title: Electromagnetic Isolation Induced by Time Varying Metasurfaces: Nonreciprocal Bragg Grating
venue: IEEE Antennas and Wireless Propagation Letters
year: 2020

abstract: AbstractNonreciprocal effects in light reflection by a medium moving along an interface are considered in a weakly relativistic approximation. It is found that nonreciprocal effects are anomalously large in the vicinity of the Brewster and the total internal reflection (TIR) angles when light is reflected by transparent moving media. These effects exceed considerably (by several orders of magnitude) the ratio of the velocity of the reflecting medium to the velocity of light b and can be proportional to $V_q \propto \Delta \sqrt n \sqrt n rather than to b under certain conditions. We show new possibilities for the creation a method for investigation of the structure of nonuniform flows with a very small spatial scale (less than one millimeter) This method is based on measurement of amplitude and phase nonreciprocities in light reflection by these flows.
author_names: Victor Ivanov

Mikhail A Novikov
title: Nonreciprocal effects in light reflection by a moving medium
year: 1995

abstract: A tunable multichannel nonreciprocal perfect absorber with the asymmetric metal photonic crystal hetero structure is theoretically proposed. By using the transfer matrix method, the linear and nonlinear properties of the absorber are investigated. An ultra narrow perfect absorption channel is realized in the linear case due to the impedance matching, and the channel number can be adjusted by changing the period of the photonic crystal. Bistable absorption and reflection are achieved in the nonlinear case due to the positive feedback between the metal nonlinear permittivity and the inner electric field, while the bistable thresholds can be altered by varying the incident light wavelength. Moreover, the absorber exhibits the intrinsic nonreciprocity in both absorption and reflection, and shows the polarization independent directional characteristics when the incident angle is less than 40deg.
author_names: Jun Zhou

Li Jin

Edwin Yue-Bun Pun
title: Tunable multichannel nonreciprocal perfect absorber based on resonant absorption
year: 2012

abstract: There is need for non reciprocal devices such as circulators and isolators. Although such devices are common at frequencies below 10 GHz, there is a lack of compact, low weight, devices at higher microwave frequencies. This paper examines the non reciprocal behavior associated with attenuated total reflection (ATR) for multi layered dielectric and magnetic structures. Non reciprocal behaviors produced by ATR have been explored for semi infinite magnetic materials. This paper focuses on ATR behavior with magnetic films of finite thickness, from thick layers of around 3 cm to thin layers of about 1 um. The results show significant non reciprocity even for magnetic layers less than 0.1 cm thick, with reflection loss differences of more than 30 dB between positive and negative signal propagation. Results are presented for yttrium iron garnet and M type barium hexagonal ferrites. The two materials allow nonreciprocal behavior at different frequencies, 5 20 GHz for the garnet and 45 80 GHz for the hexagonal fer.
author_names: Timothy J Fal

Robert E Camley
title: Non reciprocal devices using attenuated total reflection and thin film magnetic layered structures
year: 2011

abstract: Impedance matched ferrite loaded waveguide nonreciprocal phase shifters are designed using the method of field expansion into eigenmodes, which includes higher order mode interaction between the step discontinuities. Computer optimized Ku band ferrite stepped design examples, of 45deg and 90deg nonreciprocal differential phase shifts, attain typically about 2deg phase error and less than 25 dB input reflection within a bandwidth of about 5 percent. Compact designs are achieved by thicker uniform ferrite slabs with dielectric transformer sections at each end. The theory is verified by comparison with available results from measurements and other methods.
author_names: Jason Uher

Fritz Arndt

Jens Bornemann
title: Field Theory Design of Ferrite Loaded Waveguide Nonreciprocal Phase Shifters with Multisection Ferrite Or Dielectric Slab Impedance Transformers
year: 1987

abstract: A stable phase demodulation system for diaphragm based acoustic sensors is reported. The system is based on a modified fiber optic Sagnac interferometer with a stable quadrature phase bias, which is independent of the parameters of the sensor head. The phase bias is achieved passively by introducing a nonreciprocal frequency shift between the counter propagating waves, avoiding the use of complicated active servo control. A 100 nm thick graphite diaphragm based acoustic sensor interrogated by the proposed demodulation system demonstrated a minimum detectable pressure level of ~450 uPa/Hz(1/2) and an output signal stability of less than 0.35 dB over an 8 hour period. The system may be useful as a universal phase demodulation unit for diaphragm based acoustic sensors as well as other sensors operating in a reflection mode.
author_names: Jun Ma

Yongqin Yu

Wei Jin
title: Demodulation of diaphragm based acoustic sensor using Sagnac interferometer with stable phase bias.
venue: Optics express
year: 2015

abstract: There is experimental evide nce t hat VLF signa ls propagating from west to east suffer less attenuation than from east to west. Earlier work t reating t he case of nonreciprocal propagation along t he magnetic equator is extended in latitude. T he nonreciprocity sh own by I I RII for highly oblique propagation a long t he magnetic equator p ersists when t he refl ection point moves towards a magnetic pole, but at the pole itself II RII i reciprocal. To a first approximatio n .L R.L is reciprocal at a ll magnetic lati tudes. The conversion coe fficients II a.L, .L a ll are greater for east to west propagation than for propagation in t h e opposite di rect io n, except at a magnetic pole where they are equal.
author_names: Douglass D Crombie
title: Reflection from a sharply bounded ionosphere for VLF propagation Perpendicular to the magnetic meridian
year: 1961

abstract: Theories of integration and dependence approach the phenomenon of international interdependence from opposite sides of the spectrum of relations between nations. Integration emphasizes voluntarism in the study of relations characterized by more or less symmetric interdependence, joint participation, and mutual benefits. Dependence, on the other hand, is concerned with asymmetric interdependence and the nonreciprocal reliance this engenders, with emphasis on coercion. These two streams of theorizing share a predilection for a unidirectional focus as they analyze the process by which integration or domination is achieved and maintained. The unidirectional focus in integration theory has been, in part, a reflection of the initial optimism and commitment toward integration in West Europe. Moreover, it was sustained by the concept of spillover, the core of functionalist integration thinking, which attributed a high degree of automaticity to the process of integration once underway. If it was optimism that gave integration theory its unidirectional, quasi automatic orientation, it was the inherent pessimism of dependency analysts concerning the ability of peripheral countries to overcome the domestic dislocations stemming from integration into the global capitalist system which has given dependency theory its highly deterministic outlook. It cannot adequately explain periodic efforts by peripheral states to change the nature of their ties with metropole countries. To be sure, not all works on integration and dependence have adopted a unidirectional, highly deterministic framework. Pioneering
author_names: Michael B Dolan

Brian W Tomlin

Harald von Riekhoff
title: Integration and Autonomy in Canada United States Relations, 1963 1972
year: 1982

abstract: It is known that it is impossible to construct certain types of n ports for which too many design contraints are required. For instance, a lossless, reciprocal three port cannot be completely matched. The paper is mainly concerned with n ports that provide an equal power split. Scattering matrices are derived which provide for maximum power transfer for the two limiting cases of zero absorption loss and zero reflection at the input ports. It is shown that the first of these cases corresponds to an absolute maximum power transfer and that no other division of the over all loss into reflection and absorption loss will yield better results. For matched inputs, it is shown that the optimum transmission can always be improved by going from a reciprocal to a nonreciprocal n port. While no matched, reciprocal three ports (providing an equal power split from all ports) can be built with less than 50 per cent loss, an equivalent nonreciprocal device can have losses as low as 33 1/3 per cent. Similar results are given for n ports in general.
author_names: Harry Gruenberg
title: Some Optimum Properties of n Ports
year: 1961