natalia litchinitser | SUNY: University at Buffalo (original) (raw)

Papers by natalia litchinitser

Optics Express, 2011

To date, magnetic and negative-index metamaterials at optical frequencies were realized on bulk s... more To date, magnetic and negative-index metamaterials at optical frequencies were realized on bulk substrates in the form of thin films with thicknesses on the order of, or less than, optical wavelengths. In this work, we design and experimentally demonstrate, for the first time, fiber-coupled magnetic metamaterials integrated on the transverse cross-section of an optical fiber. Such fiber-metamaterials integration may provide fundamentally new solutions for photonic-on-a-chip systems for sensing, subwavelength imaging, image processing, and biomedical applications.

Physical Review Letters, 2007

We discuss a novel kind of nonlinear coupler with one channel filled with a negative index materi... more We discuss a novel kind of nonlinear coupler with one channel filled with a negative index material (NIM). The opposite directionality of the phase velocity and the energy flow in the NIM channel facilitates an effective feedback mechanism that leads to optical bistability and gap soliton formation.

IEEE/OSA Journal of Lightwave Technology, 1997

We propose a transmission-based dispersion compensator employing an apodized, unchirped fiber Bra... more We propose a transmission-based dispersion compensator employing an apodized, unchirped fiber Bragg grating (FBG). A theoretical model for dispersion compensation in transmission based on the dispersive properties of the periodic structure is developed. A figure of merit is defined for optimization of the grating parameters for maximum recompression of dispersion-broadened optical pulses in long-haul communication systems. Numerical examples confirm that nearly perfect compensation with very low insertion losses can be achieved for many practical cases of interest.

Optics Letters, 2002

We propose a simple analytical theory for low-index core photonic bandgap optical waveguides base... more We propose a simple analytical theory for low-index core photonic bandgap optical waveguides based on an antiresonant ref lecting guidance mechanism. We identify a new regime of guidance in which the spectral properties of these structures are largely determined by the thickness of the high-index layers and the refractiveindex contrast and are not particularly sensitive to the period of the cladding layers. The attenuation properties are controlled by the number of high/low-index cladding layers. Numerical simulations with the beam propagation method confirm the predictions of the analytical model. We discuss the implications of the results for photonic bandgap fibers.

Optics Communications, 2010

We develop a theory to study stationary TM-type waves propagating in a nanostructured layer of 2D... more We develop a theory to study stationary TM-type waves propagating in a nanostructured layer of 2D nonlinear optical metamaterial or plasmonic device. It is assumed that the layer is inhomogeneous and contains non-linear isotropic elemental materials with non-linearity and loss mechanisms, including both linear and non-linear losses. While modeling of the non-linear propagation of the TE-type scalar waves is straightforward, the TM-type waves within the standard E-field formulations of non-linear optics cannot be treated in a purely scalar H-field context since an implicit equation for the non-linear dielectric functions should be resolved otherwise. A new formulation, which is built on the solution of the implicit equation for the non-linear dielectric function, is proposed. We use a general cubic non-linearity to illustrate all of the important features of the proposed approach. The general solution for scalar H-field waves is validated versus our previously tested particular cases, and important differences are shown between those cases and the general solution. These details, for example, include the link between linear and nonlinear loss mechanisms, and connection between the linear and non-linear dielectric functions. The proposed approach is used for modeling a non-linear focusing device with optically controlled isotropic Kerrtype non-linearity; the simulation results prove the predicted functioning of the device.

Physical Review E, 1999

We investigate theoretically properties of partially coherent solitons in optical nonlinear media... more We investigate theoretically properties of partially coherent solitons in optical nonlinear media with slow saturable nonlinearity. We have found numerically that such a medium can support spatial solitons which are asymmetric in shape and are composed of only a finite number of modes associated with the self-induced waveguide. It is shown that these asymmetric spatial solitons can propagate many diffraction lengths without changes, but that collisions change their shape and may split them apart.

Optics Express, 2003

We propose a simple physical model that predicts the optical properties of a class of microstruct... more We propose a simple physical model that predicts the optical properties of a class of microstructured waveguides consisting of high-index inclusions that surround a low-index core. On the basis of this model, it is found that a large regime exists where transmission minima are determined by the geometry of the individual high-index inclusions. The locations of these minima are found to be largely unaffected by the relative position of the inclusions. As a result of this insight the difficult problem of analyzing the properties of complex structures can be reduced to the much simpler problem of analyzing the properties of an individual high-index inclusion in the structure.

Optics Communications, 2011

We propose a novel optofluidic biosensor in which detection is based on a shift in the transmissi... more We propose a novel optofluidic biosensor in which detection is based on a shift in the transmission spectrum due to the contrast in refractive index between the carrier fluid and the target biomaterial. The sensor can function using focused illumination without the need for fiber or waveguide coupled input/output signals. We study the spectral response of the sensor using 2D full-wave time-harmonic field analysis and perform parametric analysis of detection sensitivity as a function of material and device parameters. Our analysis demonstrates that detectible shifts in the transmission spectrum can be achieved with nanoscale accumulation of biomaterial within the sensor. We show that the transmission minima and detection sensitivity can be estimated using analytical expressions based on a 1D antiresonant waveguide model.

Optics Letters, 2009

This document has been made available through Purdue e-Pubs, a service of the Purdue University L... more This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu for additional information.

Journal of The Optical Society of America B-optical Physics, 2006

We derive equations modeling the resonant interaction of electric and magnetic components of ligh... more We derive equations modeling the resonant interaction of electric and magnetic components of light fields with metal nanostructures. This paired resonance was recently shown to produce negative refractive index. The model equations are a generalization of the well-known Maxwell-Lorentz model. We demonstrate that in the case of nonlinear polarization and linear magnetization, these equations are equivalent to a system of equations describing the resonant interaction of light with plasmonic oscillations in metal nanospheres. A family of solitary wave solutions is found that is similar to pulses associated with self-induced transparency in the framework of the Maxwell-Bloch model. The evolution of incident optical pulses is studied numerically, as are the collision dynamics of the solitary waves. These simulations reveal that the collision dynamics vary from near perfectly elastic to highly radiative, depending on the relative phase of the initial pulses.

IEEE/OSA Journal of Lightwave Technology, 1997

Numerical analysis of the dispersion-compensating properties of fiber Bragg gratings (FBG's) in b... more Numerical analysis of the dispersion-compensating properties of fiber Bragg gratings (FBG's) in both reflective and transmissive modes is presented. First, the sensitivity of chirped, reflective gratings to the grating chirp parameter, index modulation, and grating length is examined, showing that apodization provides lower sensitivity to variations in these parameters. Second, we introduce a new transmissive geometry for grating-based dispersion compensation that utilizes the dispersive properties of a uniform Bragg grating in transmission.

Optics Letters, 2010

We investigate the effect of anomalous field enhancement in metamaterials where the effective ref... more We investigate the effect of anomalous field enhancement in metamaterials where the effective refractive index gradually changes from positive to negative values, i.e. transition metamaterials. We demonstrate that considerable field enhancement can be achieved in lossy optical transition metamaterials that have electromagnetic material properties obtained from experimental data. The field enhancement factor is found to be polarization-dependent and largely determined by the material parameters and the width of the transition layer.

IEEE/OSA Journal of Lightwave Technology, 1998

Fiber gratings operating in the transmission mode can provide high dispersion at wavelengths clos... more Fiber gratings operating in the transmission mode can provide high dispersion at wavelengths close to the Bragg resonance. When multiple gratings are cascaded for wavelength division multiplexing (WDM) applications, the net dispersion between the stop bands of any two consecutive gratings is significantly modified. We discuss the dispersion characteristics of such cascaded fiber gratings and propose a dispersion compensator for simultaneous compensation of group-velocity dispersion (GVD) for multiple channels of a WDM lightwave system. We also discuss the impact of the dispersion possessed by cascaded gratings on grating based add-drop multiplexers.

Applied Optics, 1998

We demonstrate experimentally the compression of optical pulses, spectrally broadened by self-pha... more We demonstrate experimentally the compression of optical pulses, spectrally broadened by self-phase modulation occurring in the rod of a mode-locked Q-switched YLF laser, with an unchirped, apodized fiber Bragg grating in transmission. The compression is due to the strong dispersion of the Bragg grating at frequencies close to the edge of the photonic bandgap, in the passband, where the transmission is high. With the systems investigated, an 80-ps pulse, which is spectrally broadened, owing to self-phase modulation, with a peak nonlinear phase shift of ⌬⌽ ϭ 7, is compressed to approximately 15 ps, in good agreement with theory and numerical simulations. The results demonstrate that photonic bandgap structures are promising devices for efficient pulse compression.

Journal of The Optical Society of America B-optical Physics, 2009

Metamaterials constitute a new area of science that is expanding our fundamental understanding of... more Metamaterials constitute a new area of science that is expanding our fundamental understanding of the behavior of the propagation of electromagnetic waves and their interactions, and providing new solutions for a wide range of applications from optical communications and defense to biological imaging. In this brief review, we focus on recent progress in theoretical, numerical, and experimental studies of linear and nonlinear optical properties of negative index materials and in the emerging field of transformation optics.

Optics Express, 2004

Microstructured optical fibers with the low refractive index core surrounded by high refractive i... more Microstructured optical fibers with the low refractive index core surrounded by high refractive index cylindrical inclusions reveal several intriguing properties. Firstly, there is a guiding regime in which the fibers' confinement loss is strongly dependent of wavelength. In this regime, the positions of loss maxima are largely determined by the individual properties of high index inclusions rather than their position and number. Secondly, the spectra of these fibers can be tuned by changing the refractive index of the inclusions. In this paper we review transmission properties of these fibers and discuss their potential applications for designing tunable photonic devices.

Journal of The Optical Society of America B-optical Physics, 2001

We study spatiotemporal instabilities in a bulk medium with Kerr-type nonlinearity and a volume B... more We study spatiotemporal instabilities in a bulk medium with Kerr-type nonlinearity and a volume Bragg grating along the direction of wave propagation. The continuous-wave beam propagation is unstable in such a periodic structure because of an interplay among grating-induced dispersion, diffraction, and nonlinear phase modulation. A linear stability analysis of the nonlinear coupled-mode equations predicts parameters for which novel self-pulsations that occur in both time and space can be observed experimentally.

IEEE/OSA Journal of Lightwave Technology, 1998

Fiber gratings operating in the transmission mode can provide high dispersion at wavelengths clos... more Fiber gratings operating in the transmission mode can provide high dispersion at wavelengths close to the Bragg resonance. When multiple gratings are cascaded for wavelength division multiplexing (WDM) applications, the net dispersion between the stop bands of any two consecutive gratings is significantly modified. We discuss the dispersion characteristics of such cascaded fiber gratings and propose a dispersion compensator for simultaneous compensation of group-velocity dispersion (GVD) for multiple channels of a WDM lightwave system. We also discuss the impact of the dispersion possessed by cascaded gratings on grating based add-drop multiplexers.

IEEE Journal of Selected Topics in Quantum Electronics, 2010

Optics Express, 2011

To date, magnetic and negative-index metamaterials at optical frequencies were realized on bulk s... more To date, magnetic and negative-index metamaterials at optical frequencies were realized on bulk substrates in the form of thin films with thicknesses on the order of, or less than, optical wavelengths. In this work, we design and experimentally demonstrate, for the first time, fiber-coupled magnetic metamaterials integrated on the transverse cross-section of an optical fiber. Such fiber-metamaterials integration may provide fundamentally new solutions for photonic-on-a-chip systems for sensing, subwavelength imaging, image processing, and biomedical applications.

Physical Review Letters, 2007

We discuss a novel kind of nonlinear coupler with one channel filled with a negative index materi... more We discuss a novel kind of nonlinear coupler with one channel filled with a negative index material (NIM). The opposite directionality of the phase velocity and the energy flow in the NIM channel facilitates an effective feedback mechanism that leads to optical bistability and gap soliton formation.

IEEE/OSA Journal of Lightwave Technology, 1997

We propose a transmission-based dispersion compensator employing an apodized, unchirped fiber Bra... more We propose a transmission-based dispersion compensator employing an apodized, unchirped fiber Bragg grating (FBG). A theoretical model for dispersion compensation in transmission based on the dispersive properties of the periodic structure is developed. A figure of merit is defined for optimization of the grating parameters for maximum recompression of dispersion-broadened optical pulses in long-haul communication systems. Numerical examples confirm that nearly perfect compensation with very low insertion losses can be achieved for many practical cases of interest.

Optics Letters, 2002

We propose a simple analytical theory for low-index core photonic bandgap optical waveguides base... more We propose a simple analytical theory for low-index core photonic bandgap optical waveguides based on an antiresonant ref lecting guidance mechanism. We identify a new regime of guidance in which the spectral properties of these structures are largely determined by the thickness of the high-index layers and the refractiveindex contrast and are not particularly sensitive to the period of the cladding layers. The attenuation properties are controlled by the number of high/low-index cladding layers. Numerical simulations with the beam propagation method confirm the predictions of the analytical model. We discuss the implications of the results for photonic bandgap fibers.

Optics Communications, 2010

We develop a theory to study stationary TM-type waves propagating in a nanostructured layer of 2D... more We develop a theory to study stationary TM-type waves propagating in a nanostructured layer of 2D nonlinear optical metamaterial or plasmonic device. It is assumed that the layer is inhomogeneous and contains non-linear isotropic elemental materials with non-linearity and loss mechanisms, including both linear and non-linear losses. While modeling of the non-linear propagation of the TE-type scalar waves is straightforward, the TM-type waves within the standard E-field formulations of non-linear optics cannot be treated in a purely scalar H-field context since an implicit equation for the non-linear dielectric functions should be resolved otherwise. A new formulation, which is built on the solution of the implicit equation for the non-linear dielectric function, is proposed. We use a general cubic non-linearity to illustrate all of the important features of the proposed approach. The general solution for scalar H-field waves is validated versus our previously tested particular cases, and important differences are shown between those cases and the general solution. These details, for example, include the link between linear and nonlinear loss mechanisms, and connection between the linear and non-linear dielectric functions. The proposed approach is used for modeling a non-linear focusing device with optically controlled isotropic Kerrtype non-linearity; the simulation results prove the predicted functioning of the device.

Physical Review E, 1999

We investigate theoretically properties of partially coherent solitons in optical nonlinear media... more We investigate theoretically properties of partially coherent solitons in optical nonlinear media with slow saturable nonlinearity. We have found numerically that such a medium can support spatial solitons which are asymmetric in shape and are composed of only a finite number of modes associated with the self-induced waveguide. It is shown that these asymmetric spatial solitons can propagate many diffraction lengths without changes, but that collisions change their shape and may split them apart.

Optics Express, 2003

We propose a simple physical model that predicts the optical properties of a class of microstruct... more We propose a simple physical model that predicts the optical properties of a class of microstructured waveguides consisting of high-index inclusions that surround a low-index core. On the basis of this model, it is found that a large regime exists where transmission minima are determined by the geometry of the individual high-index inclusions. The locations of these minima are found to be largely unaffected by the relative position of the inclusions. As a result of this insight the difficult problem of analyzing the properties of complex structures can be reduced to the much simpler problem of analyzing the properties of an individual high-index inclusion in the structure.

Optics Communications, 2011

We propose a novel optofluidic biosensor in which detection is based on a shift in the transmissi... more We propose a novel optofluidic biosensor in which detection is based on a shift in the transmission spectrum due to the contrast in refractive index between the carrier fluid and the target biomaterial. The sensor can function using focused illumination without the need for fiber or waveguide coupled input/output signals. We study the spectral response of the sensor using 2D full-wave time-harmonic field analysis and perform parametric analysis of detection sensitivity as a function of material and device parameters. Our analysis demonstrates that detectible shifts in the transmission spectrum can be achieved with nanoscale accumulation of biomaterial within the sensor. We show that the transmission minima and detection sensitivity can be estimated using analytical expressions based on a 1D antiresonant waveguide model.

Optics Letters, 2009

This document has been made available through Purdue e-Pubs, a service of the Purdue University L... more This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu for additional information.

Journal of The Optical Society of America B-optical Physics, 2006

We derive equations modeling the resonant interaction of electric and magnetic components of ligh... more We derive equations modeling the resonant interaction of electric and magnetic components of light fields with metal nanostructures. This paired resonance was recently shown to produce negative refractive index. The model equations are a generalization of the well-known Maxwell-Lorentz model. We demonstrate that in the case of nonlinear polarization and linear magnetization, these equations are equivalent to a system of equations describing the resonant interaction of light with plasmonic oscillations in metal nanospheres. A family of solitary wave solutions is found that is similar to pulses associated with self-induced transparency in the framework of the Maxwell-Bloch model. The evolution of incident optical pulses is studied numerically, as are the collision dynamics of the solitary waves. These simulations reveal that the collision dynamics vary from near perfectly elastic to highly radiative, depending on the relative phase of the initial pulses.

IEEE/OSA Journal of Lightwave Technology, 1997

Numerical analysis of the dispersion-compensating properties of fiber Bragg gratings (FBG's) in b... more Numerical analysis of the dispersion-compensating properties of fiber Bragg gratings (FBG's) in both reflective and transmissive modes is presented. First, the sensitivity of chirped, reflective gratings to the grating chirp parameter, index modulation, and grating length is examined, showing that apodization provides lower sensitivity to variations in these parameters. Second, we introduce a new transmissive geometry for grating-based dispersion compensation that utilizes the dispersive properties of a uniform Bragg grating in transmission.

Optics Letters, 2010

We investigate the effect of anomalous field enhancement in metamaterials where the effective ref... more We investigate the effect of anomalous field enhancement in metamaterials where the effective refractive index gradually changes from positive to negative values, i.e. transition metamaterials. We demonstrate that considerable field enhancement can be achieved in lossy optical transition metamaterials that have electromagnetic material properties obtained from experimental data. The field enhancement factor is found to be polarization-dependent and largely determined by the material parameters and the width of the transition layer.

IEEE/OSA Journal of Lightwave Technology, 1998

Fiber gratings operating in the transmission mode can provide high dispersion at wavelengths clos... more Fiber gratings operating in the transmission mode can provide high dispersion at wavelengths close to the Bragg resonance. When multiple gratings are cascaded for wavelength division multiplexing (WDM) applications, the net dispersion between the stop bands of any two consecutive gratings is significantly modified. We discuss the dispersion characteristics of such cascaded fiber gratings and propose a dispersion compensator for simultaneous compensation of group-velocity dispersion (GVD) for multiple channels of a WDM lightwave system. We also discuss the impact of the dispersion possessed by cascaded gratings on grating based add-drop multiplexers.

Applied Optics, 1998

We demonstrate experimentally the compression of optical pulses, spectrally broadened by self-pha... more We demonstrate experimentally the compression of optical pulses, spectrally broadened by self-phase modulation occurring in the rod of a mode-locked Q-switched YLF laser, with an unchirped, apodized fiber Bragg grating in transmission. The compression is due to the strong dispersion of the Bragg grating at frequencies close to the edge of the photonic bandgap, in the passband, where the transmission is high. With the systems investigated, an 80-ps pulse, which is spectrally broadened, owing to self-phase modulation, with a peak nonlinear phase shift of ⌬⌽ ϭ 7, is compressed to approximately 15 ps, in good agreement with theory and numerical simulations. The results demonstrate that photonic bandgap structures are promising devices for efficient pulse compression.

Journal of The Optical Society of America B-optical Physics, 2009

Metamaterials constitute a new area of science that is expanding our fundamental understanding of... more Metamaterials constitute a new area of science that is expanding our fundamental understanding of the behavior of the propagation of electromagnetic waves and their interactions, and providing new solutions for a wide range of applications from optical communications and defense to biological imaging. In this brief review, we focus on recent progress in theoretical, numerical, and experimental studies of linear and nonlinear optical properties of negative index materials and in the emerging field of transformation optics.

Optics Express, 2004

Microstructured optical fibers with the low refractive index core surrounded by high refractive i... more Microstructured optical fibers with the low refractive index core surrounded by high refractive index cylindrical inclusions reveal several intriguing properties. Firstly, there is a guiding regime in which the fibers' confinement loss is strongly dependent of wavelength. In this regime, the positions of loss maxima are largely determined by the individual properties of high index inclusions rather than their position and number. Secondly, the spectra of these fibers can be tuned by changing the refractive index of the inclusions. In this paper we review transmission properties of these fibers and discuss their potential applications for designing tunable photonic devices.

Journal of The Optical Society of America B-optical Physics, 2001

We study spatiotemporal instabilities in a bulk medium with Kerr-type nonlinearity and a volume B... more We study spatiotemporal instabilities in a bulk medium with Kerr-type nonlinearity and a volume Bragg grating along the direction of wave propagation. The continuous-wave beam propagation is unstable in such a periodic structure because of an interplay among grating-induced dispersion, diffraction, and nonlinear phase modulation. A linear stability analysis of the nonlinear coupled-mode equations predicts parameters for which novel self-pulsations that occur in both time and space can be observed experimentally.

IEEE/OSA Journal of Lightwave Technology, 1998

Fiber gratings operating in the transmission mode can provide high dispersion at wavelengths clos... more Fiber gratings operating in the transmission mode can provide high dispersion at wavelengths close to the Bragg resonance. When multiple gratings are cascaded for wavelength division multiplexing (WDM) applications, the net dispersion between the stop bands of any two consecutive gratings is significantly modified. We discuss the dispersion characteristics of such cascaded fiber gratings and propose a dispersion compensator for simultaneous compensation of group-velocity dispersion (GVD) for multiple channels of a WDM lightwave system. We also discuss the impact of the dispersion possessed by cascaded gratings on grating based add-drop multiplexers.

IEEE Journal of Selected Topics in Quantum Electronics, 2010