The electrical and optical properties of the indium tin oxide (ITO)/epoxy composite exhibit dramatic variations as functions of the ITO composition and ITO particle size. Sharp increases in the conductivity in the v...The electrical and optical properties of the indium tin oxide (ITO)/epoxy composite exhibit dramatic variations as functions of the ITO composition and ITO particle size. Sharp increases in the conductivity in the vicinity of a critical volume fraction have been found within the framework of percolation theory. A conductive and insulating transition model is extracted by the ITO particle network in the SEM image, and verified by the resistivity dependence on the temperature. The dependence of the optical transmittance on the particle size was studied. Further decreasing the ITO particle size could further improve the percolation threshold and light transparency of the composite film.展开更多
In this paper human face machine identification is experienced using optical correlation techniques in spatial frequency domain. This approach is tested on ORL dataset of faces which includes face images of 40 subject...In this paper human face machine identification is experienced using optical correlation techniques in spatial frequency domain. This approach is tested on ORL dataset of faces which includes face images of 40 subjects, each in 10 different positions. The examined optical setup relies on optical correlation based on developing optical Vanderlugt filters and its basics are described in this article. With the limitation of face database of 40 persons, the recognition is examined successfully with nearly 100% of accuracy in matching the input images with their respective Vanderlugt synthesized filters. Software simulation is implemented by using MATLAB for face identification.展开更多
In this paper, an optical waveguide junction is introduced to reduce crosstalk based on a hexagonal structure of photonic crystals for TE modes. The wavelength is 1330 nm which is an important wavelength for optical f...In this paper, an optical waveguide junction is introduced to reduce crosstalk based on a hexagonal structure of photonic crystals for TE modes. The wavelength is 1330 nm which is an important wavelength for optical fiber data transmission. Simulation results show that the proposed design exhibits a reduction of -50 dB in crosstalk. It translates to a considerable isolation improvement between two crossover waveguides. FDTD method is used to obtain the transmission coefficient.展开更多
In this paper we simulate and analyze a sample of slow light semiconducting device with quantum dot structure based on coherent population oscillation (CPO). The simulation is conducted to enhance the main parameters ...In this paper we simulate and analyze a sample of slow light semiconducting device with quantum dot structure based on coherent population oscillation (CPO). The simulation is conducted to enhance the main parameters of slow light device and a method is presented for setting the output specifications of this kind of devices. In this paper, we deal with changing the size of quantum dot to find the ideal size. The simulation results indicate that as the size of quantum dot changes properly (with reducing more than 50 percent of quantum dots both radius and height), then the slope of diagram of the real part of refractive index increases significantly so that the Slow Down Factor (SDF) predicted to be18 times greater. Analysis and simulations based on cylinderical quantum dots structure slow light devices based on exitonic cpo.展开更多
Symmetry plays a crucial role in explorations of the laws of nature.Parity-time(PT)symmetry phenomena can lead to entirely real spectra in non-Hermitian systems,which attracts considerable attention in the fields of o...Symmetry plays a crucial role in explorations of the laws of nature.Parity-time(PT)symmetry phenomena can lead to entirely real spectra in non-Hermitian systems,which attracts considerable attention in the fields of optics and electronics because these phenomena provide a new tool for the manipulation of oscillation modes and nonreciprocal signal transmission.A potential new field of application is microwave photonics,an interdisciplinary field in which the interaction between microwaves and optical signals is exploited.In this article,we report the experimental use of PT symmetry in an optoelectronic oscillator(OEO),a key microwave photonics system that can generate singlefrequency sinusoidal signals with high spectral purity.PT symmetry is theoretically analyzed and experimentally observed in an OEO with two mutually coupled active oscillation cavities via a precise manipulation of the interplay between gain and loss in the two oscillation cavities.Stable single-frequency microwave oscillation is achieved without using any optical/electrical filters for oscillation mode selection,which is an indispensable requirement in traditional OEOs.This observation opens new avenues for signal generation and processing based on the PT symmetry principle in microwave photonics.展开更多
The demand for green energy is growing these days as a result of the world energy crisis,as well as global warm-ing.Solar cells are in great interest due to the fact that solar energy can be easily converted to electr...The demand for green energy is growing these days as a result of the world energy crisis,as well as global warm-ing.Solar cells are in great interest due to the fact that solar energy can be easily converted to electricity,if the photovoltaic cell’s cost can be lowered.One of the methods to make low-cost energy is using Luminescent solar concentrators.They have the advantage of directly integrating solar cells to dense urban areas as well as skyscrapers.Different materials and waveguide sizes have been investigated for use in luminescent solar concen-trators.However,the optimized waveguide geometry and quantum dots concentrators have not been thoroughly studied.In this paper,we have simulated graphene quantum dots using density function theory.A Monte-Carlo ray-tracing simulation was developed to model our device.We have optimized the luminescent solar concentrator geometry by Monte-Carlo simulation.The optimization results show a 99%enhancement in the energy flux gain of the final device.Besides,we have calculated and analyzed the fate of all photons.展开更多
We propose and demonstrate a reconfigurable and single-shot incoherent optical signal processing system for chirped microwave signal compression, using a programmable optical filter and a multiwavelength laser(MWL). T...We propose and demonstrate a reconfigurable and single-shot incoherent optical signal processing system for chirped microwave signal compression, using a programmable optical filter and a multiwavelength laser(MWL). The system is implemented by temporally modulating a specially shaped MWL followed by a suitable linear dispersive medium. A microwave dispersion value up to 1.33 ns/GHz over several GHz bandwidth is achieved based on this approach. Here we demonstrate a singleshot compression for different linearly chirped microwave signals over several GHz bandwidth. In addition, the robustness of the proposed system when input RF signals are largely distorted is also discussed.展开更多
An optoelectronic oscillator(OEO)is a microwave photonic system that produces microwave signals with ultralow phase noise using a high-quality-factor optical energy storage element.This type of oscillator is desired i...An optoelectronic oscillator(OEO)is a microwave photonic system that produces microwave signals with ultralow phase noise using a high-quality-factor optical energy storage element.This type of oscillator is desired in various practical applications,such as communication links,signal processing,radar,metrology,radio astronomy,and reference clock distribution.Recently,new mode control and selection methods based on Fourier domain mode-locking and parity-time symmetry have been proposed and experimentally demonstrated in OEOs,which overcomes the long-existing mode building time and mode selection problems in a traditional OEO.Due to these mode control and selection methods,continuously chirped microwave waveforms can be generated directly from the OEO cavity and single-mode operation can be achieved without the need of ultranarrowband filters,which are not possible in a traditional OEO.Integrated OEOs with a compact size and low power consumption have also been demonstrated,which are key steps toward a new generation of compact and versatile OEOs for demanding applications.We review recent progress in the field of OEOs,with particular attention to new mode control and selection methods,as well as chip-scale integration of OEOs.展开更多
The optoelectronic oscillator(OEO)is a hybrid electrical/photonic device that leverages on the use of a high Q-factor energy storage element,such as a long and low loss fiber delay line to generate single frequency mi...The optoelectronic oscillator(OEO)is a hybrid electrical/photonic device that leverages on the use of a high Q-factor energy storage element,such as a long and low loss fiber delay line to generate single frequency microwave signals with ultra-low phase noise[1–8].However,a long fiber delay line results in a long mode building time associated with the cavity round trip,which makes impossible to generate a展开更多
A novel ultrahigh-speed all-optical demultiplexer (DMUX) with polarization-shift-keying (PolSK) modula- tion input signals is proposed. This design is based on four-wave mixing (FWM) in a semiconductor optical a...A novel ultrahigh-speed all-optical demultiplexer (DMUX) with polarization-shift-keying (PolSK) modula- tion input signals is proposed. This design is based on four-wave mixing (FWM) in a semiconductor optical amplifier (SOA). For analyzing each amplifier, we use finite-difference method (FDM) based on solution of the traveling wave coupled equations. Using numerical simulation, the all-optical DMUX is theoretically realized at 40 Gb/s. We also study the relation between optical confinement factor and thickness of active layer of the SOA section successfully, and investigate the increasing effect of confinement factor on the DMUX optical output power. With this work, the confinement factor is increased from 0.3 to 0.48, and as a result, the output power approximately twice of its initial value is achieved. Moreover, the effects of polarization dependence of SOA on the output performance of all-optical DMUX for PolSK signal are theoretically investigated in detail.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.61222501 and 61335004)
文摘The electrical and optical properties of the indium tin oxide (ITO)/epoxy composite exhibit dramatic variations as functions of the ITO composition and ITO particle size. Sharp increases in the conductivity in the vicinity of a critical volume fraction have been found within the framework of percolation theory. A conductive and insulating transition model is extracted by the ITO particle network in the SEM image, and verified by the resistivity dependence on the temperature. The dependence of the optical transmittance on the particle size was studied. Further decreasing the ITO particle size could further improve the percolation threshold and light transparency of the composite film.
文摘In this paper human face machine identification is experienced using optical correlation techniques in spatial frequency domain. This approach is tested on ORL dataset of faces which includes face images of 40 subjects, each in 10 different positions. The examined optical setup relies on optical correlation based on developing optical Vanderlugt filters and its basics are described in this article. With the limitation of face database of 40 persons, the recognition is examined successfully with nearly 100% of accuracy in matching the input images with their respective Vanderlugt synthesized filters. Software simulation is implemented by using MATLAB for face identification.
文摘In this paper, an optical waveguide junction is introduced to reduce crosstalk based on a hexagonal structure of photonic crystals for TE modes. The wavelength is 1330 nm which is an important wavelength for optical fiber data transmission. Simulation results show that the proposed design exhibits a reduction of -50 dB in crosstalk. It translates to a considerable isolation improvement between two crossover waveguides. FDTD method is used to obtain the transmission coefficient.
文摘In this paper we simulate and analyze a sample of slow light semiconducting device with quantum dot structure based on coherent population oscillation (CPO). The simulation is conducted to enhance the main parameters of slow light device and a method is presented for setting the output specifications of this kind of devices. In this paper, we deal with changing the size of quantum dot to find the ideal size. The simulation results indicate that as the size of quantum dot changes properly (with reducing more than 50 percent of quantum dots both radius and height), then the slope of diagram of the real part of refractive index increases significantly so that the Slow Down Factor (SDF) predicted to be18 times greater. Analysis and simulations based on cylinderical quantum dots structure slow light devices based on exitonic cpo.
基金supported by the National Natural Science Foundation of China under 61535012 and 61522509supported by the National High-Tech Research and Development Program of China under 2015AA017102supported in part by the Thousand Young Talents Program.
文摘Symmetry plays a crucial role in explorations of the laws of nature.Parity-time(PT)symmetry phenomena can lead to entirely real spectra in non-Hermitian systems,which attracts considerable attention in the fields of optics and electronics because these phenomena provide a new tool for the manipulation of oscillation modes and nonreciprocal signal transmission.A potential new field of application is microwave photonics,an interdisciplinary field in which the interaction between microwaves and optical signals is exploited.In this article,we report the experimental use of PT symmetry in an optoelectronic oscillator(OEO),a key microwave photonics system that can generate singlefrequency sinusoidal signals with high spectral purity.PT symmetry is theoretically analyzed and experimentally observed in an OEO with two mutually coupled active oscillation cavities via a precise manipulation of the interplay between gain and loss in the two oscillation cavities.Stable single-frequency microwave oscillation is achieved without using any optical/electrical filters for oscillation mode selection,which is an indispensable requirement in traditional OEOs.This observation opens new avenues for signal generation and processing based on the PT symmetry principle in microwave photonics.
文摘The demand for green energy is growing these days as a result of the world energy crisis,as well as global warm-ing.Solar cells are in great interest due to the fact that solar energy can be easily converted to electricity,if the photovoltaic cell’s cost can be lowered.One of the methods to make low-cost energy is using Luminescent solar concentrators.They have the advantage of directly integrating solar cells to dense urban areas as well as skyscrapers.Different materials and waveguide sizes have been investigated for use in luminescent solar concen-trators.However,the optimized waveguide geometry and quantum dots concentrators have not been thoroughly studied.In this paper,we have simulated graphene quantum dots using density function theory.A Monte-Carlo ray-tracing simulation was developed to model our device.We have optimized the luminescent solar concentrator geometry by Monte-Carlo simulation.The optimization results show a 99%enhancement in the energy flux gain of the final device.Besides,we have calculated and analyzed the fate of all photons.
基金supported by research grants from NSERC(Canada)agenciesalso partly supported by the National Natural Science Foundation of China(61522509,61377002 and 61090391)+2 种基金Beijing Natural Science Foundation(4152052)the National High-Tech Research and Development Program of China(2015AA017102)M.L.was supported partly by the Thousand Young Talent Program
文摘We propose and demonstrate a reconfigurable and single-shot incoherent optical signal processing system for chirped microwave signal compression, using a programmable optical filter and a multiwavelength laser(MWL). The system is implemented by temporally modulating a specially shaped MWL followed by a suitable linear dispersive medium. A microwave dispersion value up to 1.33 ns/GHz over several GHz bandwidth is achieved based on this approach. Here we demonstrate a singleshot compression for different linearly chirped microwave signals over several GHz bandwidth. In addition, the robustness of the proposed system when input RF signals are largely distorted is also discussed.
基金supported by the National Key Research and Development Program of China(2018YFB2201902,2018YFB2201901,2018YFB2201903)the National Natural Science Foundation of China(61925505,61535012,61705217)
文摘An optoelectronic oscillator(OEO)is a microwave photonic system that produces microwave signals with ultralow phase noise using a high-quality-factor optical energy storage element.This type of oscillator is desired in various practical applications,such as communication links,signal processing,radar,metrology,radio astronomy,and reference clock distribution.Recently,new mode control and selection methods based on Fourier domain mode-locking and parity-time symmetry have been proposed and experimentally demonstrated in OEOs,which overcomes the long-existing mode building time and mode selection problems in a traditional OEO.Due to these mode control and selection methods,continuously chirped microwave waveforms can be generated directly from the OEO cavity and single-mode operation can be achieved without the need of ultranarrowband filters,which are not possible in a traditional OEO.Integrated OEOs with a compact size and low power consumption have also been demonstrated,which are key steps toward a new generation of compact and versatile OEOs for demanding applications.We review recent progress in the field of OEOs,with particular attention to new mode control and selection methods,as well as chip-scale integration of OEOs.
文摘The optoelectronic oscillator(OEO)is a hybrid electrical/photonic device that leverages on the use of a high Q-factor energy storage element,such as a long and low loss fiber delay line to generate single frequency microwave signals with ultra-low phase noise[1–8].However,a long fiber delay line results in a long mode building time associated with the cavity round trip,which makes impossible to generate a
文摘A novel ultrahigh-speed all-optical demultiplexer (DMUX) with polarization-shift-keying (PolSK) modula- tion input signals is proposed. This design is based on four-wave mixing (FWM) in a semiconductor optical amplifier (SOA). For analyzing each amplifier, we use finite-difference method (FDM) based on solution of the traveling wave coupled equations. Using numerical simulation, the all-optical DMUX is theoretically realized at 40 Gb/s. We also study the relation between optical confinement factor and thickness of active layer of the SOA section successfully, and investigate the increasing effect of confinement factor on the DMUX optical output power. With this work, the confinement factor is increased from 0.3 to 0.48, and as a result, the output power approximately twice of its initial value is achieved. Moreover, the effects of polarization dependence of SOA on the output performance of all-optical DMUX for PolSK signal are theoretically investigated in detail.