Vladimir Kuzmiak

Waveguide structures with antisymmetric gain/loss profile

Waveguide structures with an antisymmetric gain/loss profile were studied more than a decade ago as benchmark tests for beam propagation methods. These structures attracted renewed interest, recently e.g. as photonic analogues of quantum mechanical structures with parity-time symmetry breaking. In this paper, properties of both weakly and strongly guiding two-mode waveguides and directional couplers with balanced loss and gain are described. Rather unusual power transmission in such structures is demonstrated by using numerical methods. We found that the interface between media with balanced loss and gain supports propagation of confined unattenuated TM polarized surface wave and we have shown that its properties are consistent with the prediction of a simple analytical model.

One-way EM waveguide formed at the interface between metal and uniformly magnetized two-dimensional photonic crystal fabricated from magneto-optic material

We have demonstrated numerically that a waveguide formed by the interface of a metal and uniformly magnetized twodimensional photonic crystal fabricated from a transparent dielectric magneto-optic (MO) material possesses a one-way frequency range where only a forward propagating surface plasmon polariton (SPP) mode is allowed to propagate. In contrast to an analogous waveguide proposed by Yu1 the non-reciprocity at the interface is introduced by the MO properties of the photonic crystal material and not by applying an unrealistically high static magnetic field (up to 1 T) on metal described by free-electron Drude form of the dielectric function. The considered magnetic material is Bismuth Iron Garnet (BIG, Bi3Fe5O12), a ferrimagnetic oxide which may be easily magnetically saturated by fields of the order of tens of mT. Therefore, this configuration allows to achieve sizable one-way bandwidth by using significantly smaller values of the external magnetic field which makes such a waveguide favorable for design of diode-like elements in optical integrated circuits. By using a novel MO aperiodic Fourier Modal Method (MO a-FMM) to calculate the band structure of this magneto-plasmonic photonic crystal waveguide we have proven the existence of one-way SPP bands within the optical wavelength.To investigate transport properties of the structures within this frequency range we have implemented two finite-difference time-domain (FDTD) methods, namely ADE2 and that based on Z-transforms3 that allow calculating the propagation of EM waves through media with full tensorial magneto-optic permittivity. We provide numerical evidence confirming suppression of disorder-induced backscattering in the one-way waveguide.

Modified nonreciprocal waveguide formed at the interface between plasmonic metal and uniformly magnetized two-dimensional photonic crystal fabricated from magneto-optic material

We have demonstrated numerically that the interface of a metal and uniformly magnetized two-dimensional photonic crystal fabricated from a transparent dielectric magneto-optic (MO) material possesses a one-way frequency range where only a forward propagating surface plasmon polariton (SPP) mode is allowed to propagate. The nonreciprocity at the interface is introduced by the MO properties of the photonic crystal that is fabricated from Bismuth Iron Garnet (BIG, Bi3Fe5O12), a ferrimagnetic oxide which may be easily magnetically saturated by fields of the order of tens of mT. Therefore, this configuration allows to achieve sizable one-way bandwidth by using significantly smaller values of the external magnetic field than an analogous waveguide proposed by Yu1 which makes such a waveguide favorable for design of diode-like elements in optical integrated circuits. By using simple analytical model we have determined one-way frequency range which is consistent with the results obtained previously by using a MO aperiodic Fourier Modal Method (MO a-FMM). To investigate transport properties of the structures within this frequency range we have implemented finite-difference time-domain(FDTD) method, that allows calculating the propagation of EM waves through media with full tensorial magneto-optic permittivity. We examined the unidirectional transport properties of the proposed one-way waveguide and studied how the nonreciprocity depends on boundary conditions, for instance, by placing a perfect conducting mirror at the end of one-way waveguide.

Nonreciprocal waveguiding structures for THz region based on InSb

We have studied theoretically and numerically surface magnetoplasmons in three types of THz guiding structures, namely, InSb/dielectric planar boundary, InSb/air/metal planar waveguide, and symmetric InSb/air/InSb planar waveguide, in the presence of an external magnetic field. We consider the Voigt magneto-optic configuration in which these structures provide a frequency range where only one propagation direction is allowed to support one-way propagation of the surface plasmon polariton, due to nonreciprocity of the structures. To study the dispersion properties associated with unidirectional propagation of magnetoplasmons in finite-size nanostructured waveguides, we have developed an efficient two-dimensional numerical technique based on the magneto-optic aperiodic rigorous coupled-wave analysis. We have shown that the one-way bandwidth can be controlled by an external magnetic field and by the permittivity and thickness of the dielectric guiding layer. To enable numerical simulation, we have utilized the configuration in which the magnetized section of a waveguide is along the direction of propagation sandwiched by the identical waveguide segments without a magnetic field. We have also shown that the one-way bandwidth can be controlled by an external magnetic field and by the permittivity and thickness of the dielectric guiding layer.

Surface waves at the interface with an antisymmetric gain/loss profile

We studied properties of strongly guiding two‐mode waveguides with antisymmetric gain/loss profile which constitute photonic analogues of quantum mechanical structures with parity‐time symmetry breaking. For both TE and TM polarizations, the dependences of effective indices of the guided modes vs. gain/loss coefficient exhibit a degenerate critical point that defines two regimes with profoundly different behavior. In addition, we have shown that the interface between the two media supports propagation of a strongly confined non‐attenuated TM polarized surface wave. We examined the properties of the surface wave obtained by both the modal and FDTD method and discuss the differences between the results obtained by both techniques as both the material and geometrical parameters are varied.

Controlling flow of light in the one-way EM waveguide

By using a generalized finite-difference time-domain (FDTD) method which allows to study the propagation of electromagnetic (EM) waves through media with tensor magneto-optic permittivity we studied transport properties of the one-way waveguide consisting of the interface between a metal and uniformly magnetized 2D photonic crystal fabricated from a transparent dielectric magneto-optic (MO) material. Specifically, we examined how the one-way functionality is affected in the presence of a time-dependent external magnetic field. By evaluating Fourier transform of the energy density we inspected the field patterns observed. We have shown that the harmonic modulation of the magnetic field gives rise to a discrete spectrum of both the localized and the propagating modes. The results obtained by using Fourier analysis of field distribution which indicate existence of new and interesting features may lead to new ways to dynamically control and manipulate the surface plasmon-polariton waves that can be employed in design of active devices.

Low energy acoustic plasmons in one-way EM waveguide formed at the interface between metal and two-dimensional photonic crystal

It has been shown recently that a low-energy collective excitation mode that can be found on bare metal surfaces has acoustic(linear) dispersion and arises due to the coexistence of a partially occupied quazi-2D surface state band with the underlying 3D bulk continuum. Since acoustic dispersion allows the confinement of light on small surface areas in a broad frequency range, it becomes relevant for variety of photonics applications. We demonstrate that collective acoustic excitations can be employed in unidirectional waveguide formed by the interface of a metal and 2D photonic crystal where only a forward propagating surface acoustic plasmon mode is allowed to propagate. To describe acoustic plasmons we employed a simplified model based on the effective 2D dielectric function in which 3D bulk electron continuum is taken into account in terms of 2D Fourier transform of the screened interaction term. To investigate transport properties of the structures within this frequency range we used finite-difference time-domain (FDTD) method that allows calculating the propagation of EM waves through media with full tensorial magnetooptic permittivity. By using numerical simulation we have shown that implementing surface acoustic plasmons offers a possibility to operate such a one-way waveguide structure in the terahertz frequency range.

Transport properties of MOPhC/metal one‐way waveguide

We have demonstrated numerically that the interface between metal and uniformly magnetized 2D photonic crystal(PC) fabricated from a transparent dielectric magneto‐optic(MO) material possesses a one‐way frequency range where only a forward propagating surface plasmon polariton mode is allowed to propagate. By using a simple theoretical model we have shown that nonreciprocity is introduced by the MO properties of the PC. Transport properties of the structures within this frequency range have been investigated by FDTD method which enables to calculating propagation of EM waves through media with full tensorial MO permittivity. We found that in the presence of a time‐dependent external magnetic field interesting features associated with the redistribution of the EM field appear.

Front Matter: Volume 8070

This PDF file contains the front matter associated with SPIE Proceedings Volume 8070, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

Photonic waveguiding structures with loss and gain

Passive real-world waveguiding structures are inevitably lossy, and some of them, such as plasmonic waveguides, exhibit even very strong attenuation. Losses can be compensated by including active components with gain. In this paper we discuss properties of waveguiding structures with generally complex dielectric permittivity distributed across their cross-section. In particular, we focus on the existence of modes that exhibit balance between loss and gain and that can propagate unattenuated provided the suitable conditions are satisfied. Specifically, we examine power transmission in the structures with a balance of loss and gain supporting lossless propagation of two modes. We demonstrate that when both modes are excited simultaneously, the total transmitted power is not conserved as the modes propagate along the waveguide. We also show that even if one of the modes propagates with gain, the maximum attainable transmitted power is strongly influenced by back-reflections from the interface with the passive output waveguide. We also discuss the conditions for the existence of an un-attenuated propagation of a confined surface mode supported by the gain/loss nature of these photonic structures.