@article{ozturk2015atomically,

title = {Atomically thin layers of B--N--C--O with tunable composition},

author = {Birol Ozturk and Andres de-Luna-Bugallo and Eugen Panaitescu and Ann N Chiaramonti and Fangze Liu and Anthony Vargas and Xueping Jiang and Neerav Kharche and Ozgur Yavuzcetin and Majed Alnaji and others},

year  = {2015},

date = {2015-01-01},

urldate = {2015-01-01},

journal = {Science advances},

volume = {1},

number = {6},

pages = {e1500094},

publisher = {American Association for the Advancement of Science},

keywords = {Metamaterials and Nanophotonics, Nanomaterials},

pubstate = {published},

tppubtype = {article}

}

@article{savo2011observation,

title = {Observation of slow-light in a metamaterials waveguide at microwave frequencies},

author = {Salvatore Savo and BDF Casse and Wentao Lu and Srinivas Sridhar},

year  = {2011},

date = {2011-01-01},

journal = {Applied Physics Letters},

volume = {98},

number = {17},

pages = {171907},

publisher = {American Institute of Physics},

abstract = {We report an experimental observation of slow-light in the GHz microwave regime utilizing the mechanism of the degeneracy of forward and backward waves in a planar waveguide consisting of a dielectric core cladded by single-negative metamaterial.



},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{ye2011tuning,

title = {Tuning the optical properties of metamaterials based on gold nanowire arrays embedded in alumina},

author = {Yong-Hong Ye and YJ Huang and WT Lu and BDF Casse and D Xiao and SP Bennett and D Heiman and L Menon and S Sridhar},

year  = {2011},

date = {2011-01-01},

journal = {Optical Materials},

volume = {33},

number = {11},

pages = {1667--1670},

publisher = {North-Holland},

abstract = {We fabricated a series of gold nanowires/alumina composite films with different wire lengths. Optical transmission measurements confirmed that the composite films exhibit transverse and longitudinal surface plasmon resonances. We show that the wavelength of the longitudinal resonance is sensitive to nanowire length, while that of the transverse resonance is not. The experimental results are in agreement with the modeled results based on the Maxwell Garnett effective medium theory. Moreover, the window for negative refraction of the samples can be tuned in synchronism with the longitudinal resonance by the nanowire length.},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{casse2011robust,

title = {Robust method to determine the resolution of a superlens by analyzing the near-field image of a two-slit object},

author = {BDF Casse and WT Lu and YJ Huang and S Sridhar},

year  = {2011},

date = {2011-01-01},

journal = {arXiv preprint arXiv:1105.0182},

abstract = {In the last decade, metamaterials-based superlenses, with a resolution below Abbe's diffraction limit, have emerged. To obtain a rough estimate of the resolution of such superlenses, imaging of two subwavelength slits, separated by a subwavelength gap textit{d} is typically performed. The resolution Δ of the lens corresponds to the minimum possible gap dmin for which a distinct image of the two slits can be resolved (Δ∼dmin). In this letter, we present a more quantitative estimate of the resolution of manufactured lenses by fitting analytical near-field image profiles, obtained from imaging a two-slit object with a theoretical negative-index lens of known resolution, to experimental data. We conclude the discussion by applying our analytical method to 3 case examples of superlensing from the literature. As shown, this method is particularly attractive for rapidly assessing the performance of fabricated superresolution lenses.},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{cassesuperresolution,

title = {Superresolution imaging and superfocusing with negative-index metamaterials},

author = {Bernard Didier F Casse and Srinivas Sridhar},

year  = {2010},

date = {2010-03-19},

abstract = {Developments in higher-resolution optics have often led to rapid scientific and technological progress in the life sciences and engineering. In 1873, Ernst Abbe showed1 that the spatial resolution of optical-imaging instruments is limited by diffraction because of the finite wavelength of light. Abbe’s diffraction-limit theory implies that the resolving power of optical components cannot be smaller than half the wavelength of the incident light. Nanoscale optical elements that can mold the flow of light offer the potential of entirely new modalities of superresolution imaging. With a vision to build superlenses capable of resolving subwavelength details, in the last decade the photonics community has focused on fabricating tiny metallic inclusions (or, closely related, plasmonic architectures) characterized by a negative index of refraction. 2 Unfortunately, such metamaterials suffer from material losses enhanced by resonances, leading to a degradation of functionality. Instead, our group has demonstrated successful performance of highly functional nanostructured metamaterials in ‘low-loss’ dielectric platforms such as metal-dielectric composites and III-V semiconductors (composed of indium phosphide/indium gallium arsenide phosphide: InP/InGaAsP). We recently reported the experimental realization of superresolution imaging with a low-loss 3D nanolens, 3 comprised of gold nanowires embedded in nanoporous alumina: see Figure 1 (right). This 3D nanolens, manufactured using a combination of bottom-up self-assembly and electrochemical process, transmits subwavelength details down to= 4 (: Wavelength) and over a significant distance of more than …},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{casse2010super,

title = {Super-resolution imaging using a three-dimensional metamaterials nanolens},

author = {BDF Casse and WT Lu and YJ Huang and E Gultepe and L Menon and S Sridhar},

year  = {2010},

date = {2010-01-01},

journal = {Applied Physics Letters},

volume = {96},

number = {2},

pages = {023114},

publisher = {American Institute of Physics},

abstract = {Super-resolution imaging beyond Abbe’s diffraction limit can be achieved by utilizing an optical medium or “metamaterial” that can either amplify or transport the decaying near-field evanescent waves that carry subwavelength features of objects. Earlier approaches at optical frequencies mostly utilized the amplification of evanescent waves in thin metallic films or metal-dielectric multilayers, but were restricted to very small thicknesses (⪡λ, wavelength) and accordingly short object-image distances, due to losses in the material. Here, we present an experimental demonstration of super-resolution imaging by a low-loss three-dimensional metamaterial nanolens consisting of aligned gold nanowires embedded in a porous alumina matrix. This composite medium possesses strongly anisotropic optical properties with negative permittivity in the nanowire axis direction, which enables the transport of both far-field and near-field components with low-loss over significant distances (>6λ), and over a broad spectral range. We demonstrate the imaging of large objects, having subwavelength features, with a resolution of at least λ/4 at near-infrared wavelengths. The results are in good agreement with a theoretical model of wave propagation in anisotropic media.

The authors would like to thank M. G. Silveirinha, D. Heiman, J. Sokoloff, and F. Camino for useful discussions and comments. This work was financially supported by the Air Force Research Laboratories, Hanscom through Grant No. FA8718-06-C-0045 and NSF through Grant No. PHY-0457002. The work was also performed in part at the Kostas Center at Northeastern University and the Center for Nanoscale Systems, a member of NNIN, which is supported by the National Science Foundation under NSF Award No. ECS-0335765. Research carried out in part at the Center for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886.},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{lu2010storing,

title = {Storing light in active optical waveguides with single-negative materials},

author = {WT Lu and YJ Huang and BDF Casse and RK Banyal and S Sridhar},

year  = {2010},

date = {2010-01-01},

journal = {Applied Physics Letters},

volume = {96},

number = {21},

pages = {211112},

publisher = {American Institute of Physics},

abstract = {We show that a nonresonant planar waveguide consisting of conventional dielectric cladded with single-negative materials supports degenerate propagating modes for which the group velocity and total energy flow can be zero if the media are lossless. Absorptive losses will destroy the zero-group velocity condition for real frequency/complex wave vector modes.



},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{lu2010slow,

title = {Slow light, open-cavity formation, and large longitudinal electric field on a slab waveguide made of indefinite permittivity metamaterials},

author = {WT Lu and S Sridhar},

year  = {2010},

date = {2010-01-01},

journal = {Physical Review A},

volume = {82},

number = {1},

pages = {013811},

publisher = {APS},

abstract = {The optical properties of slab waveguides made of indefinite permittivity (

ɛ

) materials (IEMs) are considered. In this medium, the real part of the transverse permittivity is negative while that of the longitudinal permittivity is positive. At any given frequency, the IEM waveguide supports an infinite number of transverse magnetic (TM) eigenmodes. For a slab waveguide with a fixed thickness, at most only one TM mode is forward wave. The remainder are backward waves which can have a very large phase index. At a critical thickness, the waveguide supports degenerate forward- and backward-wave modes with zero group velocity if loss is absent. Above the critical thickness, the waveguide supports complex-conjugate decay modes instead of propagating modes. The presence of loss in IEMs will lift the TM mode degeneracy, resulting in modes with finite group velocity. A feasible realization is proposed. The performance of the IEM waveguide is analyzed and possible applications are discussed, which are supported by numerical calculations. These slab waveguides can be used to make optical delay lines in optical buffers to slow down and trap light, to form open cavities, to generate strong longitudinal electric fields, and as phase shifters in optical integrated circuits. Although the presence of loss will hinder these applications, gain can be introduced to compensate the loss and enhance the performance.},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{reynoso2010th,

title = {TH-D-201C-08: Multi-Modal MRI SPECT and CT Imaging of Theranostic Nanoplatforms},

author = {F Reynoso and E Gultepe and A Jhaveri and P Kulkarni and B Gershman and C Ferris and R Campbell and M Harisinghani and S Sridhar},

year  = {2010},

date = {2010-01-01},

journal = {Medical Physics},

volume = {37},

number = {6Part8},

pages = {3470--3470},

publisher = {American Association of Physicists in Medicine},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{casse2010superresolution,

title = {Superresolution Imaging Using a 3D Nanolens Made Up of Bulk Nanowires Metamaterials},

author = {Bernard Didier Frederic Casse and Wentao Lu and Yongjian Huang and Evin Gultepe and Latika Menon and Srinivas Sridhar},

year  = {2010},

date = {2010-01-01},

journal = {Bulletin of the American Physical Society},

volume = {55},

publisher = {APS},

abstract = {Superresolution Imaging Using a 3D Nanolens Made Up of Bulk

Nanowires Metamaterials1 BERNARD DIDIER FREDERIC CASSE, WENTAO LU, YONGJIAN HUANG, EVIN GULTEPE, LATIKA MENON, SRINIVAS

SRIDHAR, Northeastern University — We report superresolution imaging of large

objects, having sub-λ features, over significant distances (>> λ, wavelength) with

a resolution well below the diffraction limit in optics, using a metallic nanolens.

The metallic nanolens is composed of high aspect ratio gold nanowires embedded

in disordered porous alumina template matrix. This composite medium possesses

strongly anisotropic optical properties with negative permittivity in the nanowire

axis direction, which enables negative refraction, and transports both far-field and

near-field components with minimal distortions and with very lowattenuations. The

long-distance image transport mechanism is not based on resonances of materials parameters and thus the subwavelength imaging occurs with low loss (Figure-of-merit

(FOM) = Re(n)/Im(n) ∼ 12 (much higher than existing metamaterials)) and in

a broad spectral range. This nanolens not only exhibits superior optical properties

over existing metamaterials-based lenses, but can also be manufactured in large scale

(mm size), thereby offering significant potential for applications in optical storage

devices, nanolithography and biomedical imaging.

1This work was financially supported by the AFRL, Hanscom through grant no.

FA8718-06-C-0045 and the NSF through grant no. PHY-0457002.},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{casse2009imaging,

title = {Imaging with subwavelength resolution by a generalized superlens at infrared wavelengths},

author = {BDF Casse and WT Lu and RK Banyal and YJ Huang and S Selvarasah and MR Dokmeci and CH Perry and S Sridhar},

year  = {2009},

date = {2009-01-01},

journal = {Optics letters},

volume = {34},

number = {13},

pages = {1994--1996},

publisher = {Optical Society of America},

abstract = {We demonstrate experimentally negative refraction by a photonic crystal prism and imaging of a point source by a photonic crystal slab at 1.5 μm wavelength. The photonic crystal structures were nanofabricated in a InGaAsP/InP heterostructure platform, and optical characterization was performed using a near-field scanning optical microscope. By designing a suitable lens surface termination, an image spot size of 0.12λ^2 was achieved, demonstrating superlens imaging with subwavelength resolution well below Abbe's diffraction limit (0.5λ^2).},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{lu2009slow,

title = {Slow microwave waveguide made of negative permeability metamaterials},

author = {Wentao T Lu and Savatore Savo and Didier B F Casse and Srinivas Sridhar},

year  = {2009},

date = {2009-01-01},

journal = {Microwave and Optical Technology Letters},

volume = {51},

number = {11},

pages = {2705--2709},

publisher = {Wiley Subscription Services, Inc., A Wiley Company Hoboken},

abstract = {The framework for designing a slow light waveguide structure which operates in the GHz and up to THz frequencies is outlined. The design for the structure consists of a dielectric core layer cladded with negative permeability metamaterials. The parameter space for the metamaterial has been identified for the waveguide to stop light and the negative permeability is achieved by split‐ring resonator (SRR) metallic elements. A prototype structure operating at 8.5 GHz is proposed. Numerical simulations of electromagnetic waves interacting with SRRs have been performed to extract scattering parameters and a parameter retrieval method has been used to verify the designed window for negative permeability. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2705–2709, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24727},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{lu2009slowb,

title = {Slow light, open cavity formation, and large longitudinal electric field on slab waveguide made of indefinite-index metamaterials},

author = {WT Lu and S Sridhar},

year  = {2009},

date = {2009-01-01},

journal = {arXiv preprint arXiv:0902.4482},

abstract = {There is a strong interest in slow light structures and devices [1–10]. This is driven by the need for optical buffers and optical memory in optical integrated circuits and other applications. In order to have small group velocity, various methods have been exploited to engineer material and structural dispersions, such as electromagnetic induced transparency [11], coupled resonant structures [5, 12], and optical nonlinearity [3]. Tsakmakidis et al [6] proposed a new scheme to realize trapped rainbow by using negative-index metamaterials. This slow light waveguide requires its core layer to be made of double negative metamaterial (DNM) whose permittivity and permeability are both negative. It is quite a challenge to realize DNMs with very low loss [13] since even moderate loss will destroy the zero group velocity mode [14, 15]. Strictly speaking, when loss is present as is inevitable in passive systems, stop light is impossible. However, gain may be introduced to compensate loss and makes zero group velocity possible [16]. In this paper we consider planar waveguide made of the so-called indefinite-index media [17–20] whose permittivity and/or the permeability tensors are indefinite matrices. For an indefinite-index metamaterial (IIM), the dispersion is hyperbolic for one polarization and elliptical for the other. Negative refraction, superlens imaging, and hyperlens focusing [21, 22] can be realized by using IIMs. Nanowire waveguide made of IIM has been considered by Huang et al [23]. These indefinite-index waveguides can support both forward-and backwardwave modes. High phase index can be obtained for these guided modes. These waveguides …},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{lu2008electronic,

title = {Electronic structure: Wide-band, narrow-band, and strongly correlated systems-Superlens imaging theory for anisotropic nanostructured metamaterials with broadband all-angle negative refraction},

author = {WT Lu and S Sridhar},

year  = {2008},

date = {2008-01-01},

journal = {Physical Review B Condensed Matter And Materials Physics},

volume = {78},

number = {23},

pages = {233101},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{lu2008superlens,

title = {Superlens imaging theory for anisotropic nanostructured metamaterials with broadband all-angle negative refraction},

author = {WT Lu and S Sridhar},

year  = {2008},

date = {2008-01-01},

journal = {Physical Review B},

volume = {77},

number = {23},

pages = {233101},

publisher = {APS},

abstract = {We show that a metamaterial consisting of aligned metallic nanowires in a dielectric matrix has strongly anisotropic optical properties. For long wavelngths, the longitudinal SPR, the material exhibits positive transverse permittivity and negative longitudinal permittivity, relative to the nanowires axis, enabling the achievement of broadband all-angle negative refraction and superlens imaging. An imaging theory of superlens made of these media is established. High performance systems made with Au, Ag, or Al nanowires in nanoporous templates are designed and predicted to work from the infrared up to ultraviolet frequencies.



},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{huang2008nanowire,

title = {Nanowire waveguide made from extremely anisotropic metamaterials},

author = {YJ Huang and WT Lu and S Sridhar},

year  = {2008},

date = {2008-01-01},

journal = {Physical Review A},

volume = {77},

number = {6},

pages = {063836},

publisher = {APS},

abstract = {Exact solutions are obtained for all the modes of wave propagation along an anisotropic cylindrical waveguide. Closed-form expressions for the energy flow on the waveguide are also derived. For extremely anisotropic waveguide where the transverse permittivity is negative while the longitudinal permittivity is positive, only transverse magnetic (TM) and hybrid modes will propagate on the waveguide. At any given frequency the waveguide supports an infinite number of eigenmodes. Among the TM modes, at most only one mode is forward wave. The rest of them are backward waves which can have very large effective index. At a critical radius, the waveguide supports degenerate forward- and backward-wave modes with zero group velocity. These waveguides can be used as phase shifters and filters, and as optical buffers to slow down and trap light.



},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{menon2008negative,

title = {Negative index metamaterials based on metal-dielectric nanocomposites for imaging applications},

author = {L Menon and WT Lu and AL Friedman and SP Bennett and D Heiman and S Sridhar},

year  = {2008},

date = {2008-01-01},

journal = {Applied Physics Letters},

volume = {93},

number = {12},

pages = {123117},

publisher = {American Institute of Physics},

abstract = {Negative index metamaterials are demonstrated based on metal-dielectric nanocomposites prepared using a versatile bottom-up nanofabrication approach. The method involves the incorporation of vertically aligned metal nanowires such as Au and Ag inside dielectric aluminum oxide nanotemplates. Optical absorbance measurements show resonance peaks corresponding to the transverse and longitudinal surface plasmon modes. A quantitative model based on effective medium theory is in excellent agreement with experimental data, and points to specific composite configurations and wavelength regimes where such structures can have applications as negative refraction media for imaging.},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{casse2008nano,

title = {Nano-optical microlens with ultrashort focal length using negative refraction},

author = {BDF Casse and WT Lu and YJ Huang and S Sridhar},

year  = {2008},

date = {2008-01-01},

journal = {Applied Physics Letters},

volume = {93},

number = {5},

pages = {053111},

publisher = {American Institute of Physics},

abstract = {We have experimentally realized an ultrashort focal length planoconcave microlens in an InP/InGaAsP semiconductor two-dimensional photonic crystal with negative index of refraction n = -0.7. At wavelength 1.5 microns, the lens exhibits ultrashort focal lengths of 12 microns (~ 8x wanelength) and numerical aperture close to unity. The focused beam has a near diffraction-limited spot size of 1.05 microns (~ 0.68 wavelength) at full width at half maximum. The negative refractive index and focusing properties of the microlens are confirmed by 2D finite-difference time-domain simulations. Such ultrarefractive negative-index nano-optical microlenses can be integrated into existing emiconductor heterostructure platforms for next-generation optoelectronic applications.



},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{gultepe2008large,

title = {Large scale 3D vertical assembly of single-wall carbon nanotubes at ambient temperatures},

author = {Evin Gultepe and Dattatri Nagesha and Bernard Didier Frederic Casse and Selvapraba Selvarasah and Ahmed Busnaina and Srinivas Sridhar},

year  = {2008},

date = {2008-01-01},

journal = {Nanotechnology},

volume = {19},

number = {45},

pages = {455309},

publisher = {IOP Publishing},

abstract = {We demonstrate three-dimensional directed assembly of single-wall carbon nanotubes (SWNT) into porous alumina nanotemplates on silicon substrates by means of electrophoresis and dielectrophoresis at ambient temperatures. Assembled SWNT provided an interconnection between the surface and base of the nanotemplate. I–V measurements clearly show that the connection between silicon and SWNT is established inside the templates. This technique is particularly useful for large scale, rapid, 3D assembly of SWNT over centimeter square areas under mild conditions for nanoscale electronics applications.},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{casse2008nanoengineering,

title = {Nanoengineering of a negative-index binary-staircase lens for the optics regime},

author = {Bernard Didier F Casse and Ravinder K Banyal and WT Lu and YJ Huang and Selvapraba Selvarasah and M Dokmeci and Srinivas Sridhar},

year  = {2008},

date = {2008-01-01},

journal = {Applied Physics Letters},

volume = {92},

number = {24},

pages = {243122},

publisher = {American Institute of Physics},

abstract = {We show that a binary-staircase optical element can be engineered to exhibit an effective negative index of refraction, thereby expanding the range of optical properties theoretically available for future optoelectronic devices. The mechanism for achieving a negative-index lens is based on exploiting the periodicity of the surface corrugation. By designing and nanofabricating a planoconcave binary-staircase lens in the InP/InGaAsP platform, we have experimentally demonstrated at 1.55 micrometers that such negative-index concave lenses can focus plane waves. The beam propagation in the lens was studied experimentally and was in excellent agreement with the three-dimensional finite-difference time-domain numerical simulations.



},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{huang2007alternative,

title = {Alternative approach to all-angle negative refraction in two-dimensional photonic crystals},

author = {YJ Huang and WT Lu and S Sridhar},

year  = {2007},

date = {2007-01-01},

journal = {Physical Review A},

volume = {76},

number = {1},

pages = {013824},

publisher = {APS},

abstract = {We show that with an appropriate surface modification, a slab of photonic crystal can be made to allow wave transmission within the photonic band gap. Furthermore, negative refraction and all-angle negative refraction (AANR) can be achieved by this surface modification in frequency windows that were not realized before in two-dimensional photonic crystals [C. Luo et al., Phys. Rev. B 65, 201104 (2002)]. This approach to AANR leads to different applications in flat lens imaging. Previous flat lens using photonic crystals requires object-image distance u+ v less than or equal to the lens thickness d, u+ v∼ d. Our approach can be used to design a flat lens with u+ v= σ d with σ≫ 1, thus being able to image large and/or far away objects. Our results are confirmed by finite-difference time-domain simulations.},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{lu2007new,

title = {A new mechanism for negative refraction and focusing using selective diffraction from surface corrugation},

author = {WT Lu and YJ Huang and P Vodo and RK Banyal and CH Perry and S Sridhar},

year  = {2007},

date = {2007-01-01},

journal = {Optics express},

volume = {15},

number = {15},

pages = {9166--9175},

publisher = {Optical Society of America},

abstract = {Refraction at a smooth interface is accompanied by momentum transfer normal to the interface. We show that corrugating an initially smooth, totally reflecting, non-metallic interface provides a momentum kick parallel to the surface, which can be used to refract light negatively or positively. This new mechanism of negative refraction is demonstrated by visible light and microwave experiments on grisms (grating-prisms). Single-beam all-angle-negative-refraction is achieved by incorporating a surface grating on a flat multilayered material. This negative refraction mechanism is used to create a new optical device, a grating lens. A planoconcave grating lens is demonstrated to focus plane microwaves to a point image. These results show that customized surface engineering can be usedto achieve negative refraction even though the bulk material has positive refractive index. The surface periodicity provides a tunable parameter to control beam propagation leading to novel optical and microwave devices.



},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{huang2007part,

title = {PART B-Quantum optics, physics of lasers, nonlinear optics, classical optics-Alternative approach to all-angle negative refraction in two-dimensional photonic crystals},

author = {YJ Huang and WT Lu and S Sridhar},

year  = {2007},

date = {2007-01-01},

journal = {Physical Review-Section A-Atomic Molecular and Optical Physics},

volume = {76},

number = {1},

pages = {13824--13824},

publisher = {New York, NY: Published by the American Physical Society through the~…},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{banyal2007nanophotonic,

title = {Nanophotonic structures for Negative Refraction at NIR and VIS},

author = {Ravinder Banyal and BDF Casse and Plarenta Vodo and WT Lu and Srinivas Sridhar},

year  = {2007},

date = {2007-01-01},

journal = {APS},

pages = {X38--007},

abstract = {Nanophotonic structures were fabricated for negative index refraction at NIR and VIS frequencies. Structures include prisms and flat lenses fabricated in Si using nanolithography. Refraction and imaging experiments were carried out at NIR and VIS. Natural divergence of laser beam, collimation and guiding of the light within the device structures are also discussed.},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{huang2007new,

title = {New approach to all-angle-negative-refraction in two-dimensional photonic crystals},

author = {YJ Huang and WT Lu and S Sridhar},

year  = {2007},

date = {2007-01-01},

journal = {APS},

pages = {S38--002},

abstract = {We show that with an appropriate surface modification, a slab of photonic crystal can be made to allow wave transmission within the photonic band gap. Furthermore, negative refraction and all-angle negative refraction _AANR_ can be achieved by this surface modification in frequency windows that were not realized before in two-dimensional photonic crystals _C. Luo et al., Phys. Rev. B 65, 201104 _2002__. This approach to AANR leads to different applications in flat lens imaging. Previous flat lens using photonic crystals requires object-image distance u + v less than or equal to the lens thickness d, u + v = σd. Our approach can be used to design a flat lens with large σ, thus being able to image large and/or far away objects. Our results are confirmed by finite-difference time-domain simulations.



},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{vodo2006negative,

title = {Negative refraction and plano-concave lens focusing in one-dimensional photonic crystals},

author = {P Vodo and WT Lu and Y Huang and S Sridhar},

year  = {2006},

date = {2006-01-01},

journal = {Applied physics letters},

volume = {89},

number = {8},

pages = {084104},

publisher = {American Institute of Physics},

abstract = {Negative refraction is demonstrated in one-dimensional _1D_ dielectric photonic crystals _PCs_ at microwave frequencies. Focusing by plano-concave lens made of 1D PCs due to negative refraction is also demonstrated. The frequency-dependent negative refractive indices, calculated from the experimental data, match very well with those determined from band structure calculations. The easy fabrication of one-dimensional photonic crystals may open the door for future applications.



},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{vodo2005focusing,

title = {Focusing by planoconcave lens using negative refraction},

author = {Plarenta Vodo and PV Parimi and WT Lu and Srinivas Sridhar},

year  = {2005},

date = {2005-01-01},

journal = {Applied Physics Letters},

volume = {86},

number = {20},

pages = {201108},

publisher = {American Institute of Physics},

abstract = {We demonstrate focusing of a plane microwave by a planoconcave lens fabricated from a photonic crystal having a negative refractive index and left-handed electromagnetic properties. An inverse experiment, in which a plane wave is produced from a source placed at the focal point of the lens, is also reported. A frequency-dependent negative refractive index, n(ω) < 0 is obtained for the lens from the experimental data which match well with that determined from band structure calculations.



},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{lu2005flat,

title = {Flat lens without optical axis: Theory of imaging},

author = {Wentao T Lu and Srinivas Sridhar},

year  = {2005},

date = {2005-01-01},

journal = {Optics express},

volume = {13},

number = {26},

pages = {10673--10680},

publisher = {Optical Society of America},

abstract = {We derive a general theory for imaging by a flat lens without optical axis. We show that the condition for imaging requires a material having elliptic dispersion relations with negative group refraction. This medium is characterized by two intrinsic parameters σ and κ. Imaging can be achieved with both negative and positive wave vector refraction if σ is a positive constant. The Veselago-Pendry lens is a special case with σ = 1 and κ = 0. A general law of refraction for anisotropic media is revealed. Realizations of the imaging conditions using anisotropic media and inhomogeneous media, particularly photonic crystals, are discussed. Numerical examples of imaging and requirements for sub-wavelength imaging are also presented.



},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{di2005slow,

title = {Slow microwaves in left-handed materials},

author = {E Di Gennaro and PV Parimi and WT Lu and S Sridhar and JS Derov and B Turchinetz},

year  = {2005},

date = {2005-01-01},

journal = {Physical Review B},

volume = {72},

number = {3},

pages = {033110},

publisher = {APS},

abstract = {Remarkably slow propagation of microwaves in two different classes of left-handed materials LHM�s is reported from microwave-pulse and continuous-wave transmission measurements. Microwave dispersion in a composite LHM made of split-ring resonators and wire strips reveals group velocity vg ~ c/50, where c is the free-space light velocity. Photonic crystals PhCs made of dielectric Al2O3 rods reveal vg ~ c/10. Group delay dispersion of both the composite LHM and PhCs determined from the experiment is in complete agreement with that obtained from theory. The slow group velocities are quantitatively described by the strong dispersion observed in these materials.



},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{parimi2004negative,

title = {Negative refraction and left-handed electromagnetism in microwave photonic crystals},

author = {PV Parimi and WT Lu and P Vodo and J Sokoloff and JS Derov and S Sridhar},

year  = {2004},

date = {2004-01-01},

journal = {Physical review letters},

volume = {92},

number = {12},

pages = {127401},

publisher = {APS},

abstract = {We demonstrate the negative refraction of microwaves in a metallic photonic crystal prism. The spectral response of the photonic crystal prism, which manifests both positive and negative refraction, is in complete agreement with band-structure calculations and numerical simulations. The validity of Snell’s law with a negative refractive index is confirmed experimentally and theoretically. The negative refraction observed corresponds to left-handed electromagnetism that arises due to the dispersion characteristics of waves in a periodic medium. This mechanism for negative refraction is different from that in metamaterials.},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{vodo2004negative,

title = {Negative Refraction experiments in Photonic Crystal prisms},

author = {Plarenta Vodo and Patanjali V Parimi and Wentao T Lu and Emiliano Di Gennaro and Srinivas Sridhar},

year  = {2004},

date = {2004-01-01},

journal = {APS},

volume = {2004},

pages = {S19--008},

abstract = {We have experimentally demonstrated negative refraction in metallic photonic crystal (PC) prisms [1]. The refracted fields in the parallel plate waveguide (PPW) are measured by an automated dipole antenna, which scans the desired area, while the free space (FS) measurements, performed in a anechoic chamber, are measured by a rectangular X-band horn that swings in an arc in far field area. Both TE and TM excitation modes are used in FS experiments. Numerical calculations of the band structure and equi-frequency surface simulations are used to determine frequency regions of negative refraction of the triangular lattice PC. Angle of refraction determined by theoretical simulations and experimental results, are in exceptional good agreement, yielding the negative refraction index. FS and PPW refraction experimental results agree remarkably with simulations. 1. "Negative Refraction and Left-handed electromagnetism in Microwave Photonic Crystals", P.V Parimi, W.T Lu, P.Vodo J. Sokoloff and S.Sridhar, cond-mat/0306109 (2003)},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

@article{lu2004refraction,

title = {Refraction of electromagnetic energy for wave packets incident on a negative-index medium is always negative},

author = {WT Lu and JB Sokoloff and S Sridhar},

year  = {2004},

date = {2004-01-01},

journal = {Physical Review E},

volume = {69},

number = {2},

pages = {026604},

publisher = {APS},

abstract = {We analyze refraction of electromagnetic wave packets on passing from an isotropic positive to an isotropic negative-refractive-index medium. We definitively show that in all cases the energy is always refracted negatively. For localized wave packets, the group refraction is also always negative},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}