The theoretical mechanism for realizing a negative refractive index material in an optical frequency range with an atomic gas system of electromagnetically induced transparency (EIT) is studied. It is shown that under...The theoretical mechanism for realizing a negative refractive index material in an optical frequency range with an atomic gas system of electromagnetically induced transparency (EIT) is studied. It is shown that under certain conditions such a dense gas can exhibit simultaneously negative permittivity and negative permeability, and negligibly small loss.展开更多
Light propagation in nanoparticle-loaded encapsulants is simulated based on the method of Monte Carlo,referring to the multilayer graded-refractive-index structure for LED encapsulants.And the influence of scattering ...Light propagation in nanoparticle-loaded encapsulants is simulated based on the method of Monte Carlo,referring to the multilayer graded-refractive-index structure for LED encapsulants.And the influence of scattering coefficient on the transmittance is analyzed.The results show that the transmittance decreases with scattering coefficient.For a given number of layers,the encapsulants will yield maximum transmittance if the refractive index value of each layer is optimized.The nanoparticle-loaded encapsulant consists of multiple layers with refractive-index values that gradually decrease.The transmittance will be higher than that of traditional non-graded encapsulants,and will improve light extraction efficiency of LED.展开更多
A closed four-level system in atomic vapour is proposed, which is made to possess left handedness by using the technique of quantum coherence. The density matrix method is utilized in view of the rotating-wave approxi...A closed four-level system in atomic vapour is proposed, which is made to possess left handedness by using the technique of quantum coherence. The density matrix method is utilized in view of the rotating-wave approximation and the effect of a local field in dense gas. The numerical simulation result shows that the negative permittivity and the negative permeability of the medium can be achieved simultaneously （i.e. the left handedness） in a wider frequency band under appropriate parameter conditions. Furthermore, when analysing the dispersion property of the left-handed material, we can find that the probe beam propagation can be controlled from superluminal to subluminal, or vice versa via changing the detuning of the probe field.展开更多
An effective method to design structural Left-handed material（LHM） was proposed. A commercial finite element software HFSS and S-parameter retrieval method were used to determine the effective constitutive parameter...An effective method to design structural Left-handed material（LHM） was proposed. A commercial finite element software HFSS and S-parameter retrieval method were used to determine the effective constitutive parameters of the metamaterials, and topology optimization technique was introduced to design the microstructure configurations of the materials with desired electromagnetic characteristics. The material considered was a periodic array of dielectric substrates attached with metal film pieces. By controlling the arrangements of the metal film pieces in the design domain, the potential microstructure with desired electromagnetic characteristics can be obtained finally. Two different LHMs were obtained with maximum bandwidth of negative refraction, and the experimental results show that negative refractive indices appear while the metamaterials have simultaneously negative permittivity and negative permeability. Topology optimization technique is found to be an effective tool for configuration design of LHMs.展开更多
It is shown that the deflection of star light passing by the Sun, which is allegedly explainable only by general relativity, can be understood quantitatively as a quasi-classical effect of light refraction in the vac...It is shown that the deflection of star light passing by the Sun, which is allegedly explainable only by general relativity, can be understood quantitatively as a quasi-classical effect of light refraction in the vacuum polarized by the Sun's gravitational field. The theory of the dielectric polarization of the vacuum proposed pre- viously is further developed for the corresponding effect of the polarization of the vacuum in a gravitational field. The resulting refractive index of the vacuum in the presence of a gravitational field gives for the deflection of light by the Sun an angle |0| = 1.77', which is in good agreement with the experimental observations and the result of general relativity. From the theory Presented, it can also be deduced that the velocity of a horizontal light beam at 1000 km above ground level of the Earth has a velocity deficit - c= 5.73 cm / s in comparison to the light velocity on the ground.展开更多
In this paper we will try to create, propose and analyze structure of a slow light device, based on plasmonic induced transparency in a metal-dielectric-metal based ring resonator. Group index by first design about 37...In this paper we will try to create, propose and analyze structure of a slow light device, based on plasmonic induced transparency in a metal-dielectric-metal based ring resonator. Group index by first design about 37 and second design about 35 earned. The proposed dielectric material is Poly Methyl Meta Acrylate (PMMA) sandwiched by gold metal cladding. Finite Element Method-con- ducted Electromagnetic simulations are employed to evaluate the plasmonic designs for behavior of slow light. The signal and pump wavelength are assumed to be 830 nm and 1550 nm respectively in the systems. The overall length of the plasmonic slow light system is 600 nm. In a wide range of frequency bands, the optical properties of metals can be described with a plasma model. The optical signal can be achieved with the use of surface waves on the boundary between the insulating materials and metals with dimensions smaller than the diffraction limit. The main goal, is estimation of optical characteristics such as bandwidth, the Real and Imaginary parts of refractive index, group velocity and slow down factor in such optical devices. The obtained results and observations, can be useful in basic research and the production of highly integrated plasmonic devices.展开更多
The refractive index ofas-evaporatedamorphous semiconductor As2S8 film upon an annealing and saturation irradiation and annealing cycle is reversible. Upon successive treatment with annealing and non-saturation irradi...The refractive index ofas-evaporatedamorphous semiconductor As2S8 film upon an annealing and saturation irradiation and annealing cycle is reversible. Upon successive treatment with annealing and non-saturation irradiation and further annealing, the refractive index of the as-evaporated amorphous semiconductor As2S8 film reaches a maximum value and then its reversibility occurs upon annealing. The annealing of the amorphous semiconductor AS2S8 films results in the stabilization of the structure through changes of the S-S bonds in the nearest environment, accompanied by a decrease of film thickness. The As2S8 planar waveguide after annealing （130 ℃） and saturation irradiation and annealing （130 ℃） shows a good propagation characteristic with ca, 0.27 dB/cm low propagation loss of the 632.8 nm guided mode.展开更多
In this Letter, a refractive index measurement of a dielectric sample using highly focused radially polarized light is reported. Through imaging analysis of the optical field at the pupil plane of a high numerical ape...In this Letter, a refractive index measurement of a dielectric sample using highly focused radially polarized light is reported. Through imaging analysis of the optical field at the pupil plane of a high numerical aperture （NA） objective lens reflected by the sample under study, the Brewster angle is found. Employing a high NA objective lens allows the measurement of multiple angles of incidence from 0° to 64° in a single shot. The refractive index of the sample is estimated using the measured Brewster angle. The experimental results are compared with the theoretical images computed with the Fresnel theory, and a good agreement is obtained.展开更多
Cuticles of some Chrysina scarabs are characterized by flat, graded, and twisted structures of nanosized chitin fibrils. As inferred from SEM images, each species has its own spatial period or pitch P which is depende...Cuticles of some Chrysina scarabs are characterized by flat, graded, and twisted structures of nanosized chitin fibrils. As inferred from SEM images, each species has its own spatial period or pitch P which is dependent on the depth z through the cuticle. From Berreman’s formalism, taking into account the corresponding P(z) dependence, we evaluate reflection spectra of C. aurigans and C. chrysargyrea scarabs. The spectra display the main spectral features observed in the measured ones when small sections of the cuticles are illuminated with non-polarized light, for wavelengths between 300 and 1100 nm. By considering these twisted structures as 1D photonic crystals, an approach is developed to show how the broad band characterizing the reflection spectra arises from a narrow intrinsic photonic band width, whose spectral position moves through visible and near infrared wavelengths. The role of the epicuticle that covers the twisted structures is analyzed in terms of a waxy layer acting as an anti-reflecting coating that also shows low levels of light scattering.展开更多
基金Project supported by the National Natural Science Foundation(NSF) of China (Nos. 90101024 and 60378037) and the NationalBasic Research Program (973) of China (No. 2004CB719805)
文摘The theoretical mechanism for realizing a negative refractive index material in an optical frequency range with an atomic gas system of electromagnetically induced transparency (EIT) is studied. It is shown that under certain conditions such a dense gas can exhibit simultaneously negative permittivity and negative permeability, and negligibly small loss.
基金National High-tech R&D Programof China "863" Program(2006AA03A130)
文摘Light propagation in nanoparticle-loaded encapsulants is simulated based on the method of Monte Carlo,referring to the multilayer graded-refractive-index structure for LED encapsulants.And the influence of scattering coefficient on the transmittance is analyzed.The results show that the transmittance decreases with scattering coefficient.For a given number of layers,the encapsulants will yield maximum transmittance if the refractive index value of each layer is optimized.The nanoparticle-loaded encapsulant consists of multiple layers with refractive-index values that gradually decrease.The transmittance will be higher than that of traditional non-graded encapsulants,and will improve light extraction efficiency of LED.
基金supported by the National Natural Science Foundation of China (Grant Nos. 60768001 and 10464002)
文摘A closed four-level system in atomic vapour is proposed, which is made to possess left handedness by using the technique of quantum coherence. The density matrix method is utilized in view of the rotating-wave approximation and the effect of a local field in dense gas. The numerical simulation result shows that the negative permittivity and the negative permeability of the medium can be achieved simultaneously （i.e. the left handedness） in a wider frequency band under appropriate parameter conditions. Furthermore, when analysing the dispersion property of the left-handed material, we can find that the probe beam propagation can be controlled from superluminal to subluminal, or vice versa via changing the detuning of the probe field.
基金Funded by the National Natural Science Foundation of China (Nos.90605002, 90816025 and 10721062)the National Basic Research Programof China (No. 2006CB601205)
文摘An effective method to design structural Left-handed material（LHM） was proposed. A commercial finite element software HFSS and S-parameter retrieval method were used to determine the effective constitutive parameters of the metamaterials, and topology optimization technique was introduced to design the microstructure configurations of the materials with desired electromagnetic characteristics. The material considered was a periodic array of dielectric substrates attached with metal film pieces. By controlling the arrangements of the metal film pieces in the design domain, the potential microstructure with desired electromagnetic characteristics can be obtained finally. Two different LHMs were obtained with maximum bandwidth of negative refraction, and the experimental results show that negative refractive indices appear while the metamaterials have simultaneously negative permittivity and negative permeability. Topology optimization technique is found to be an effective tool for configuration design of LHMs.
文摘It is shown that the deflection of star light passing by the Sun, which is allegedly explainable only by general relativity, can be understood quantitatively as a quasi-classical effect of light refraction in the vacuum polarized by the Sun's gravitational field. The theory of the dielectric polarization of the vacuum proposed pre- viously is further developed for the corresponding effect of the polarization of the vacuum in a gravitational field. The resulting refractive index of the vacuum in the presence of a gravitational field gives for the deflection of light by the Sun an angle |0| = 1.77', which is in good agreement with the experimental observations and the result of general relativity. From the theory Presented, it can also be deduced that the velocity of a horizontal light beam at 1000 km above ground level of the Earth has a velocity deficit - c= 5.73 cm / s in comparison to the light velocity on the ground.
文摘In this paper we will try to create, propose and analyze structure of a slow light device, based on plasmonic induced transparency in a metal-dielectric-metal based ring resonator. Group index by first design about 37 and second design about 35 earned. The proposed dielectric material is Poly Methyl Meta Acrylate (PMMA) sandwiched by gold metal cladding. Finite Element Method-con- ducted Electromagnetic simulations are employed to evaluate the plasmonic designs for behavior of slow light. The signal and pump wavelength are assumed to be 830 nm and 1550 nm respectively in the systems. The overall length of the plasmonic slow light system is 600 nm. In a wide range of frequency bands, the optical properties of metals can be described with a plasma model. The optical signal can be achieved with the use of surface waves on the boundary between the insulating materials and metals with dimensions smaller than the diffraction limit. The main goal, is estimation of optical characteristics such as bandwidth, the Real and Imaginary parts of refractive index, group velocity and slow down factor in such optical devices. The obtained results and observations, can be useful in basic research and the production of highly integrated plasmonic devices.
基金supported by the National Natural Science Foundation of China(Nos.60967003,61077042)the Scientific Research Program Foundation of Jiangxi Provincial Education Department,China(No.GJJ11303)
文摘The refractive index ofas-evaporatedamorphous semiconductor As2S8 film upon an annealing and saturation irradiation and annealing cycle is reversible. Upon successive treatment with annealing and non-saturation irradiation and further annealing, the refractive index of the as-evaporated amorphous semiconductor As2S8 film reaches a maximum value and then its reversibility occurs upon annealing. The annealing of the amorphous semiconductor AS2S8 films results in the stabilization of the structure through changes of the S-S bonds in the nearest environment, accompanied by a decrease of film thickness. The As2S8 planar waveguide after annealing （130 ℃） and saturation irradiation and annealing （130 ℃） shows a good propagation characteristic with ca, 0.27 dB/cm low propagation loss of the 632.8 nm guided mode.
基金GLM and VMRB acknowledge CONACYT-M6xico for the scholarship 353317 and 394565, respectively, which were given to them to do their graduate studies.
文摘In this Letter, a refractive index measurement of a dielectric sample using highly focused radially polarized light is reported. Through imaging analysis of the optical field at the pupil plane of a high numerical aperture （NA） objective lens reflected by the sample under study, the Brewster angle is found. Employing a high NA objective lens allows the measurement of multiple angles of incidence from 0° to 64° in a single shot. The refractive index of the sample is estimated using the measured Brewster angle. The experimental results are compared with the theoretical images computed with the Fresnel theory, and a good agreement is obtained.
文摘Cuticles of some Chrysina scarabs are characterized by flat, graded, and twisted structures of nanosized chitin fibrils. As inferred from SEM images, each species has its own spatial period or pitch P which is dependent on the depth z through the cuticle. From Berreman’s formalism, taking into account the corresponding P(z) dependence, we evaluate reflection spectra of C. aurigans and C. chrysargyrea scarabs. The spectra display the main spectral features observed in the measured ones when small sections of the cuticles are illuminated with non-polarized light, for wavelengths between 300 and 1100 nm. By considering these twisted structures as 1D photonic crystals, an approach is developed to show how the broad band characterizing the reflection spectra arises from a narrow intrinsic photonic band width, whose spectral position moves through visible and near infrared wavelengths. The role of the epicuticle that covers the twisted structures is analyzed in terms of a waxy layer acting as an anti-reflecting coating that also shows low levels of light scattering.
