Kerr Nonlinear Material Research Articles

Tunable Multi-switching in Plasmonic Waveguide with Kerr Nonlinear Resonator.

We propose a nanoplasmonic waveguide side-coupled with bright-dark-dark resonators in our paper. A multi-oscillator theory derived from the typical two-oscillator model, is established to describe spectral features as well as slow-light effects in bright-dark-dark structures, and confirmed by the finite-difference time domain (FDTD). That a typical plasmon induced transparency (PIT) turns to double PIT spectra is observed in this waveguide structure. At the same time, multi-switching effects with obvious double slow-light bands based on double PIT are also discovered in our proposed structure. What’s more, dynamically tuning the multi-switching is achieved by means of filling Fabry-Perot resonators with the Kerr nonlinear material Ag-BaO. These results may have applications in all-optical devices, moreover, the multi-oscillator theory may play a guiding role in designing plasmonic devices.

Form birefringence in Kerr media: analytical formulation and rigorous theory

Employing the first-order effective medium theory, we develop an analytical model that governs light propagation inside a form birefringent medium with isotropic dielectric Kerr nonlinear material. This analytical model is found to be in excellent agreement with the recently developed rigorous Fourier modal method for Kerr nonlinear material [J. Opt. Soc. Am. B31, 2371 (2014)JOSAAH0030-394110.1364/JOSAB.31.002371]. Theoretical results demonstrate that form birefringent linear gratings with Kerr nonlinear materials behave like uniaxial crystals. However, the magnitude of birefringence can be tuned with a change of the incident light intensity. This paves the way toward all-optical control of form birefringence by exploiting optical nonlinearities in subwavelength structures.

Dynamically tunable slow light based on plasmon induced transparency in disk resonators coupled MDM waveguide system

Ultrafast and low-power dynamically tunable single channel and multichannel slow light based on plasmon induced transparencies (PITs) in disk resonators coupled to a metal-dielectric-metal (MDM) waveguide system with a nonlinear optical Kerr medium is investigated both numerically and analytically. A coupled-mode theory (CMT) is introduced to analyze this dynamically tunable single channel slow light structure. Multichannel slow light is realized in this plasmonic waveguide structure based on a bright–dark mode coupling mechanism. In order to reduce the pump intensity and obtain ultrafast response time, the traditional nonlinear Kerr material is replaced by monolayer graphene. It is found that the magnitude of the single PIT window can be controlled between 0.08 and 0.48, while the corresponding group index is controlled between 14.5 and 2.0 by dynamically decreasing pump intensity from 11.7 to 4.4 MW cm−2. Moreover, the phase shift multiplication effect is found in this structure. This work paves a new way towards the realization of highly integrated optical circuits and networks, especially for wavelength-selective, all-optical storage and nonlinear devices.

Low-power and ultrafast all-optical tunable plasmon induced transparency in metal-dielectric-metal waveguide side-coupled Fabry-Perot resonators system

In this paper, low-power and ultrafast all-optical tunable plasmon induced transparency in metal-dielectric-metal (MDM) waveguide side-coupled Fabry-Perot (FP) resonators system with nonlinear optical Kerr medium is investigated both analytically and numerically. High tunability in transparency window magnitude and phase responses is obtained when nonlinear optical Kerr material is embedded in the MDM waveguide. In order to reduce the pump intensity, traditional nonlinear optical Kerr material is replaced by graphene. A shift of 64 nm in the central wavelength of the transparency window is achieved when the FP resonators are covered with monolayer graphene with pump intensity increasing from 9.2 to 10 MW/cm2. An ultrafast response time of the order of 1 ps is reached because of ultrafast carrier relaxation dynamics of graphene. This work not only paves the way towards the realization of on-chip integrated nanophotonic devices but also opens the possibility of the construction of ultrahigh-speed information processing chips based on plasmonic circuits.

Ultrafast and Low-power Dynamically Tunable Plasmon Induced Transparencies in Compact Aperture-Coupled Rectangular Resonators

In this paper, ultrafast and low-power dynamically tunable single and multiple plasmon-induced transparencies in ultracompact rectangular resonators aperture-coupled metal-dielectric-metal (MDM) waveguide system with nonlinear optical Kerr medium is investigated both analytically and numerically. Multiple PITs are realized in this plasmonic waveguide structure based on bright-dark mode coupling mechanism. High tunability in transparency window magnitude, phase shift, and group index is obtained when nonlinear optical Kerr material is embedded in the MDM waveguide. In order to reduce the pump intensity, traditional nonlinear optical Kerr material is replaced by graphene. A shift of 45 nm in the central wavelength of the single transparency window is achieved when the rectangular resonators are covered by monolayer graphene with pump intensity increasing from 6.7 to 7.5 MW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Calculated results show that whole structure is ultracompact with the footprint of <;0.5 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and an ultrafast response time of the order of 1 ps can be reached.

Widely tunable SPP bandgap in a nonlinear metal-insulator-metal waveguide.

In this article, we propose a novel kind of widely tunable surface plasmon polaritons (SPP) bandgap in a Kerr nonlinear metal-insulator-metal waveguide. By two identical gratings, the pump beam is coupled to two opposing SPP waves, which interfere with each other and results in SPP standing wave in the region between the two gratings. The refractive index of the Kerr nonlinear material is then periodically modulated by the SPP standing wave, and a SPP bandgap is formed. The position of the SPP bandgap can be tuned from 1.4 μm to 1.75 μm by adjusting the pump wavelength, and the relationship between the transmittance contrast of the bandgap and the pump power is also studied. Comparing with existing methods that directly modulate the refractive index (RI) or the width of the waveguide, in our work, the periodic modulation of the RI comes from the interference of the pump light, which can greatly simplify the fabrication. This work may find applications in the design of novel nonlinear devices for future all-optical integrated circuits.

Engineering optical bistability in a multimaterial loop metasurface

The performance of a multimaterial loop (MML) metasurface integrated with Kerr nonlinear material as the dielectric spacer layer is investigated comprehensively with the finite-difference time-domain method. Optical bistability is obtained by exciting the metasurface with a saw-tooth profile for its amplitude. Based on effects of coupling between the plasmonic loops on the performance of the MML metasurface, it is shown that there is a trade-off between the required input intensity for switching and the extinction ratio of the two states of the switch. Two distinct designs are proposed where in the second design, which has lower coupling, the extinction ratio is increased by a factor of 2 while the required intensity for switching is 13 times higher than that of the first design.

Low-power optical switching with Kerr nonlinear material in two-dimensional photonic crystal nanocavity

We investigate numerically optical bistability in direct-coupled cavity–waveguide photonic crystal system using the finite-difference time-domain method. The quality factor of the cavity is optimized by engineering the geometrical parameters. Numerical results indicate that the threshold power of optical bistability can be reduced greatly due to the increased quality factor.

Enhanced optical bistability with film-coupled plasmonic nanocubes

Colloidally synthesized nanocubes strongly coupled to conducting films hold great promise for enhancing different nonlinear optical processes. They exhibit a robust and sensitive scattering response that can be easily controlled by their geometrical and material parameters. Strong local field enhancement is generated at the gap regions between the nanocubes and the metallic film. We show that strong optical bistability and all-optical switching behavior can be obtained by loading these nanogaps with Kerr nonlinear materials. Relatively low input intensities are required to obtain these nonlinear effects. The proposed design can lead to efficient, low-power, and ultrafast all-optical memories and scattering nanoswitches.

Tunable multiple all-optical switch based on multi-nanoresonator-coupled waveguide systems containing Kerr material

By using a 2-D finite difference time domain and transfer matrix method, we have theoretically and numerically analyzed the optical transmission characteristics of optical waveguide coupling to ring cavity array. The simulation results reveal that the dual-ring cavity waveguide configuration with Kerr nonlinear material can act as a double channel all-optical switch. The contrast ratio of the two switch channels is 16.6dB and 10.37dB, respectively. We also designed a bidirectional all-optical switch based on two parallel waveguides coupled to ring cavity structure. In addition, multi-channel optical switches are achieved by increasing the number of cavity. The designed all optical switching models will be helpful to dynamic control of light in photonic circuits.

Spontaneous symmetry breaking in a double-defect nonlinear grating

We study spontaneous symmetry breaking in localized modes trapped by a pair of defects embedded in a Bragg grating written in a Kerr-nonlinear material. While the system has two symmetric modes at low energies, the nonlinearity renders one of these unstable in favor of an asymmetric mode emerging at sufficiently high energies. Using a simple semianalytic model, we explain this transition as originating from the degeneracy between a state in a grating with two defects and state in a grating with a single defect.

On the Maxwell-Duffing Approach to Model Photonic Deflection Sensor

This paper deals with the conceptualization of Maxwell-Duffing theory to model photonic deflection sensor along with functionality, which is based on the phenomena of optical bi- and multistabilities. The sensing system is considered to be consisting of Kerr nonlinear material along with suitably positioned mirrors. The efficacy of the approach is emphasized through a series of numerical simulations, and the reliability of the system is discussed. Effects due to system memory and periodicity in the optical bistability threshold have been demonstrated. It has been found that the approach provides a powerful tool to study optical bistability in resonating structures, particularly for materials with large third-nonlinearity and for operating frequencies near the natural resonance of the material.

Metal–insulator–metal waveguide-based band-pass filter with circular ring resonator containing Kerr nonlinear medium

Tunable band-pass filter based on metal–insulator–metal (MIM) plasmonic circular ring resonators filled with Kerr nonlinear material is designed and numerically investigated by finite-difference time-domain (FDTD) simulations. Indium tin oxide (ITO) thin film with χ(3)=2×10−10esu is chosen to fill in the circular ring resonator. The designed filter has one stopband within the spectra range of 800nm to 1100nm and the bandwidth of a resonance is 32nm. It is found that the transmitted-peak can be tuned by changing the intensity of incident light. Due to the Kerr nonlinear effect, the resonant wavelength of the cavity exhibits a red-shift with the increasing of the incident intensity. Narrow band filtering function at desired wavelength can be realized through tuning of peak resonance wavelength by changing the intensities of incident light. The designed plasmonic filter can find important potential applications in highly integrated optical circuits.

All-Optical EXOR for Cryptographic Application Based on Spatial Solitons

The purpose of this paper is to present an all-optical EXOR for cryptographic application based on spatial soliton beams. The device is based on the propagation and interactions properties of spatial soliton in a Kerr nonlinear material. The interaction force between parallel soliton beam is analyzed from the analytical point of view and an exact solution is presented.

Optical bistability based on an analog of electromagnetically induced transparencyin plasmonic waveguide-coupled resonators

We have investigated numerically an optical bistability effect based on an analog of electromagnetically induced transparency (EIT) in a nanoscale plasmonic waveguide-coupled resonator system. The system consists of a metal-insulator-metal waveguide side-coupled with a slot cavity and a nanodisk cavity containing Kerr nonlinear material. By finite-difference time-domain simulations, the EIT-like spectral peak has a redshift with an increase of the dielectric constant of the nanodisk cavity. More importantly, we have achieved an optical bistability with threshold intensity about three times lower than that of recent literature [Appl. Opt.50, 5287 (2011)]. The results show that our plasmonic structure can find more excellent application in highly integrated optical circuits, especially all-optical switching.

Active Focusing of Light in Plasmonic Lens via Kerr Effect

We numerically demonstrate the performance of a plasmonic lens composed of an array of nanoslits perforated on thin metallic film with slanted cuts on the output surface. Embedding Kerr nonlinear material in nanoslits is employed to modulate the output beam. A two dimensional nonlinear-dispersive finite-difference time-domain (2D N-D-FDTD) method is utilized. The performance parameters of the proposed lens such as focal length, full-width half-maximum, depth of focus and the efficiency of focusing are investigated. The structure is illuminated by a TM-polarized plane wave and a Gaussian beam. The effect of the beam waist of the Gaussian beam and the incident light intensity on the focusing effect is explored. An exact formula is proposed to derive electric field E from electric flux density D in a Kerr-Dispersive medium. Surface plasmon (SPs) modes and Fabry-Perot (F-P) resonances are used to explain the physical origin of the light focusing phenomenon. Focused ion beam milling can be implemented to fabricate the proposed lens. It can find valuable potential applications in integrated optics and for tuning purposes.

All-optical switching in MIM waveguide resonator with an outer portion smooth bend structure containing nonlinear optical materials

All-optical switching based on metal-insulator-metal (MIM) waveguide resonator with an outer portion smooth bend structure containing Kerr nonlinear materials has been proposed and numerically investigated. In our structure, we let pump light locate at mixed-modes (the dips overlap), and then keep strong resonance in the resonator which is helpful for the enhancement of nonlinear effect. Signal light locates at split modes, which makes the full width at half-maximum (FWHM) of dips significantly decrease, and increase the difference of signal light transmittance consequently when pump light is on or off. With the finite-difference time-domain (FDTD) simulations, it is demonstrated that a tiny optical bistability (owing to small detuning parameter which is only 1.143) of the signal light appears by varying the control-light intensity, and the switching time is at approximately the picosecond level.

Nonlinear spoof surface plasmon polariton phenomena based on conductor metamaterials

We present nonlinear phenomena produced from spoof surface plasmon polariton (SSPP) modes. Below the THz spectrum, artificially textured conducting metastructures on a subwavelength scale generate surface-bound modes and are called SSPP modes, similar to surface plasmon polariton (SPP) modes in the visible spectrum. Even though nonlinear effects in the THz domain are negligible, subwavelength metallic gap structures are ideal candidates to realize nonlinear behavior in the THz domain because of slow light propagation, strong electromagnetic confinement, and a high quality factor Q. In particular, when SSPP structures are combined with Kerr nonlinear materials, nonlinear-bistable curves can be observed below the THz spectrum.

Beam focusing from double subwavelength metallic slits filled with nonlinear material surrounded by dielectric surface gratings

Based on the radiation properties of surface plasmon polaritons (SPPs) can be controlled by adjusting the refractive indexes of dielectric materials in the metallic slits, a novel plasmonic focusing structure formed by two subwavelength metal apertures filled with Kerr nonlinear material surrounded by surface dielectric gratings is proposed and demonstrated numerically. Directions of radiation fields are determined by the phase difference of the surface waves at the exit interface and resonance property of each surface grating. Numerical simulations using two-dimensional (2D) Finite-Difference Time-Domain (FDTD) method verify that the deflection angle and focal length can be controlled easily by changing the intensity of incident light, dynamically tunable on-axis and off-axis focusing effects can be achieved.

Ultrafast all-optical switching in nanoplasmonic waveguide with Kerr nonlinear resonator

A novel ultrafast all-optical switching based on metal-insulator-metal nanoplasmonic waveguide with a Kerr nonlinear resonator is proposed and investigated numerically. With the finite-difference time-domain simulations, it is demonstrated that an obvious optical bistability of the signal light appears by varying the control-light intensity, and an excellent switching effect is achieved. This bistability originates from the intensity-dependent change induced in the dielectric constant of Kerr nonlinear material filled in the nanodisk resonator. It is found that the proposed all-optical switching exhibits femtosecond-scale feedback time.