Abstract: A metamaterial device exploiting parity-time symmetry to achieve ideal loss compensation. The metamaterial device includes metamaterials and metasurfaces that are engineered to respect space-time inversion symmetry, i.e., that are invariant after taking their mirror image and running time backwards. One such metamaterial device utilizes two resonators with loss and gain that exactly compensate each other thereby causing the metamaterial device to be invisible when excited from one side of the metamaterial device and reflective when excited from the other side of the metamaterial device. Furthermore, a metamaterial device may include an object covered by a portion of a metasurface with loss and another portion of the metasurface with gain, where the loss and gain exactly compensate each other. The first portion of the metasurface absorbs all of an incident wave, whereas, the second portion of the metasurface re-emits the incident wave.

Abstract: A nonlinear metasurface structure including a multi-quantum-well layer designed for a nonlinear response for a desired nonlinear optical process and an array of nanoantennas coupled to the intersubband transitions of the multi-quantum-well layer. Each nanoantenna in the array is designed to have electromagnetic resonances at or close to all input and output frequencies of a given nonlinear optical process. Nanoantennas allow efficient coupling of any incident and outgoing light polarizations to intersubband transitions. Nanoantennas may further provide significant field enhancement in the multi-quantum-well layer. As a result, the nonlinear metasurface structure can be designed to produce a highly nonlinear response for any polarization and angle of incidence of incoming and outgoing waves in a nonlinear optical process. Due to their very larger nonlinear response, efficient frequency conversion can be produced in these metasurfaces without the stringent phase-matching constraints of bulk nonlinear crystals.

Abstract: A non-reciprocal acoustic device that accomplishes non-reciprocity via linear or angular-momentum bias. The non-reciprocal acoustic device includes an azimuthally symmetric or planar acoustical cavity (e.g., ring cavity), where the cavity is biased by imposing a circular or linear motion of a gas, a fluid or a solid medium filling the cavity. Acoustic waveguides are connected to the cavity or the cavity is excited from the surrounding medium. A port of this device is excited with an acoustic wave. When the cavity is biased appropriately, the acoustic wave is transmitted to one of the other acoustic waveguides while no transmission of the acoustic wave occurs at the other acoustic waveguides. As a result, linear non-reciprocity is now realized in acoustics without distorting the input signal or requiring high input power or bulky devices.

Abstract: A non-reciprocal device incorporating metamaterials which exhibit non-reciprocity through angular momentum biasing. The metamaterial, such as a ring resonator, is angular-momentum biased. This is achieved by applying a suitable mechanical or spatio-temporal modulation to resonant inclusions of the metamaterial, thereby producing strong non-reciprocity. In this manner, non-reciprocity can be produced without requiring the use of large and bulky magnets to produce a static magnetic field. The metamaterials of the present invention can be realized by semiconducting and/or metallic materials which are widely used in integrated circuit technology, and therefore, contrary to magneto-optical materials, can be easily integrated into the non-reciprocal devices and large microwave or optical systems. The metamaterials of the present invention can be compact at various frequencies due to the enhanced wave-matter interaction in the constituent resonant inclusions.

Abstract: A non-reciprocal acoustic device that accomplishes non-reciprocity via linear or angular-momentum bias. The non-reciprocal acoustic device includes an azimuthally symmetric or planar acoustical cavity (e.g., ring cavity), where the cavity is biased by imposing a circular or linear motion of a gas, a fluid or a solid medium filling the cavity. Acoustic waveguides are connected to the cavity or the cavity is excited from the surrounding medium. A port of this device is excited with an acoustic wave. When the cavity is biased appropriately, the acoustic wave is transmitted to one of the other acoustic waveguides while no transmission of the acoustic wave occurs at the other acoustic waveguides. As a result, linear non-reciprocity is now realized in acoustics without distorting the input signal or requiring high input power or bulky devices.

Abstract: A communication system that reduces the mutual influence of antennas operating in similar or different frequency bands. The communication system includes a first and a second antenna operating in a first and a second frequency band, respectively, and placed in close proximity to each other. The first antenna is covered by a conformal mantle metasurface with anti-phase scattering properties thereby cancelling the scattering in the second frequency band. The conformal mantle metasurface consists of a patterned metallic sheet comprising slits both in an azimuthal and a vertical direction to reduce both vertical and horizontal polarization scattering. When the first antenna is a low-band dipole antenna and when the second antenna is a high-band dipole antenna, the conformal mantle metasurface reduces the low-band blockage without disrupting the performance of both antennas in terms of radiation pattern and impedance matching.

Abstract: There is provided an optical waveguide comprising: a periodic component comprising a plurality of material elements (101) arranged to receive radiation; and a plurality of tapered waveguides (103), wherein each material element is respectively coupled to a tapered waveguide which tapers outwardly from the material element. The device works as a broadband absorber.

Abstract: An electromagnetic invisibility cloaking device with a broadened cloaking bandwidth and/or a tunable frequency of operation. The cloaking device includes an object (e.g., antenna) and a metasurface (301) that conforms to the surface design of the object. The metasurface includes an array of metal cells (302A, . . . , 302Y), where each of the metal cells includes a circuit element (304) (e.g., active, passive, negative impedance converter element). The array of metal cells may be represented as an array of metal square patches, a mesh grid, horizontal or vertical conductive strips, or any arbitrary combination of unit cell patterns, where each opening, or a subset of them, in such an array includes an embedded circuit element. By incorporating the circuit elements in the conformal metasurface, the cloaking bandwidth is broadened and the frequency of operation is actively controlled and tuned.

Abstract: Circuits and circuit elements adapted to function at optical or infrared frequencies are made from plasmonic and/or nonplasmonic particles disposed on a substrate, where the plasmonic and nonplasmonic particles have respective dimensions substantially smaller than a wavelength of an applied optical or infrared signal. Such particles are deposited on a substrate in a variety of shapes and sizes from a variety of plasmonic and/or nonplasmonic materials so as to form resistors, capacitors, inductors and circuits made from combinations of these elements.

Abstract: A non-reciprocal device incorporating metamaterials which exhibit non-reciprocity through angular momentum biasing. The metamaterial, such as a ring resonator, is angular-momentum biased. This is achieved by applying a suitable mechanical or spatio-temporal modulation to resonant inclusions of the metamaterial, thereby producing strong non-reciprocity. In this manner, non-reciprocity can be produced without requiring the use of large and bulky magnets to produce a static magnetic field. The metamaterials of the present invention can be realized by semiconducting and/or metallic materials which are widely used in integrated circuit technology, and therefore, contrary to magneto-optical materials, can be easily integrated into the non-reciprocal devices and large microwave or optical systems. The metamaterials of the present invention can be compact at various frequencies due to the enhanced wave-matter interaction in the constituent resonant inclusions.

Abstract: Circuits and circuit elements adapted to function at optical or infrared frequencies are made from plasmonic and/or nonplasmonic particles disposed on a substrate, where the plasmonic and nonplasmonic particles have respective dimensions substantially smaller than a wavelength of an applied optical or infrared signal. Such particles are deposited on a substrate in a variety of shapes and sizes from a variety of plasmonic and/or nonplasmonic materials so as to form resistors, capacitors, inductors and circuits made from combinations of these elements.

Abstract: Waveguides and scattering devices are made from a pair of slabs, at least one slab being either an “epsilon-negative (ENG)” layer in which the real part of permittivity is assumed to be negative while its permeability has positive real part, or a “mu-negative (MNG)” layer that has the real part of its permeability negative but its permittivity has positive real part. The juxtaposition and pairing of such ENG and MNG slabs under certain conditions lead to some unusual features, such as resonance, complete tunneling, zero reflection and transparency. Such materials also may be configured to provide guided modes in a waveguide having special features such as mono-modality in thick waveguides and the presence of TE modes with no cut-off thickness in thin parallel-plate waveguides. Using equivalent transmission-line models, the conditions for the resonance, complete tunneling and transparency are described as well as the field behavior in these resonant paired structures.

Abstract: Waveguides and scattering devices are made from a pair of slabs, at least one slab being either an “epsilon-negative (ENG)” layer in which the real part of permittivity is assumed to be negative while its permeability has positive real part, or a “mu-negative (MNG)” layer that has the real part of its permeability negative but its permittivity has positive real part. The juxtaposition and pairing of such ENG and MNG slabs under certain conditions lead to some unusual features, such as resonance, complete tunneling, zero reflection and transparency. Such materials also may be configured to provide guided modes in a waveguide having special features such as mono-modality in thick waveguides and the presence of TE modes with no cut-off thickness in thin parallel-plate waveguides. Using equivalent transmission-line models, the conditions for the resonance, complete tunneling and transparency are described as well as the field behavior in these resonant paired structures.