A technique capable of focusing and bending electromagnetic （EM） waves through plasmonic gratings with equally spaced alternately tapered slits has been introduced. Phase resonances are observed in the optical respo...A technique capable of focusing and bending electromagnetic （EM） waves through plasmonic gratings with equally spaced alternately tapered slits has been introduced. Phase resonances are observed in the optical response of transmission gratings, and the EM wave passes through the tuning slits in the form of surface plasmon polaritons （SPPs） and obtains the required phase retardation to focus at the focal plane. The bending effect is achieved by constructing an asymmetric phase front which results from the tapered slits and gradient refractive index （GRIN） distribution of the dielectric material. Rigorous electromagnetic analysis by using the two-dimensional （2D） finite difference time domain （FDTD） method is employed to verify our proposed designs. When the EM waves are incident at an angle on the optical axis, the beam splitting effect can also be achieved. These index-modulated slits are demonstrated to have unique advantages in beam manipulation compared with the width-modulated ones. In combination with previous studies, it is expected that our results could lead to the realization of ootimum designs for plasmonic nanolenses.展开更多
Metallic gratings with narrow slits can lead to special optical properties such as strongly enhancing the trans- mission and considerably strengthening the polarized effect. A narrow-band filter suitable for applicati...Metallic gratings with narrow slits can lead to special optical properties such as strongly enhancing the trans- mission and considerably strengthening the polarized effect. A narrow-band filter suitable for application in optical communication is designed by sandwiching a metallic grating between two identical dielectric films. The maximum transmission can reach 96% after optimizing the parameters of films and grating at a central wavelength of 1053 nm. It is the first time, to our knowledge, that such high transmission has been reported since the discovery of the extraordinarily high transmission through periodic holes or slits; moreover, the extremely polarized effect is also found in P mode of this symmetric grating.展开更多
We present a silicon slot waveguide with metallic gratings embedded on the silicon surface in the slot region. The dependence of the optical coupling between two silicon wires on the width of the metal gap and the slo...We present a silicon slot waveguide with metallic gratings embedded on the silicon surface in the slot region. The dependence of the optical coupling between two silicon wires on the width of the metal gap and the slot size are studied in detail. The results show that the optical field in the slot region with metallic gratings is significantly enhanced compared with the traditional slot waveguide due to the surface plasmon polaritons coupling on metallic gratings. The extraordinary optical confinement is attributed to the low effective dielectric constant of metallic gratings. The effective dielectric constant decreases with the increasing wavelength, and reaches the minimum when the width of the metal gap is about 0.01 times the wavelength.展开更多
Starting from piezoelectric crystal dynamic equation etc., both the electric potential and surface charge induced by the incident wave are obtained with electrical boundary perturbation technique. The scattered waves ...Starting from piezoelectric crystal dynamic equation etc., both the electric potential and surface charge induced by the incident wave are obtained with electrical boundary perturbation technique. The scattered waves are then derived including both surface and bulk waves through integral transformation with the induced charge as exciting source.The scattered surface waves from the grating on YZ-LiNbO3 are then numerically calculated, and both the reflective and forward scattering coefficients are given vs. the strip width. Furthermore, the surface wave phase velocity change when passing the grating is derived and numerically calculated too. The theoretical prediction agrees well with measured results.展开更多
The exceptional point（EP） is a significant and attractive phenomenon in an open quantum system. The scattering properties of light are similar to those in the open quantum system, which makes it possible to achieve ...The exceptional point（EP） is a significant and attractive phenomenon in an open quantum system. The scattering properties of light are similar to those in the open quantum system, which makes it possible to achieve EP in the optic system. Here we investigate the EP in a Fabry–P′erot（F–P） resonant coupling structure. The coupling between different types of F–P resonances leads to a near zero reflection, which results in a degeneration of eigenstates and thus the appearing of EP. Furthermore, the multi-wavelength EPs and unidirectional invisibility can be achieved which may be used in integrated photonics systems.展开更多
A novel optimal design of sub-wavelength metal rectangular gratings for the polarizing beam splitter （PBS） is proposed. The method is based on effective medium theory and the method of designing single layer antiref...A novel optimal design of sub-wavelength metal rectangular gratings for the polarizing beam splitter （PBS） is proposed. The method is based on effective medium theory and the method of designing single layer antireflection coating. The polarization performance of PBS is discussed by rigorous couple-wave analysis （RCWA） method at a wavelength of 1550 nm. The result shows that sub-wavelength metal rectangular grating is characterized by a high reflectivity, like metal films for TE polarization, and high transmissivity, like dielectric films for TM polarization. The optimal design accords well with the results simulated by RCWA method.展开更多
A surface plasmon interference lithography assisted by a Fabry-Perot （F-P） cavity composed of subwavelength metal gratings and a thin metal fihn is proposed to fabricate high-quality nanopatterns. The calculated res...A surface plasmon interference lithography assisted by a Fabry-Perot （F-P） cavity composed of subwavelength metal gratings and a thin metal fihn is proposed to fabricate high-quality nanopatterns. The calculated results indicate that uniform straight interference fringes with high contrast and high electric-field intensity are formed in the resist under the F-P cavity. The analyses of spatial frequency spectra illuminate the physical mechanism of the formation for the interference fringes. The influence of the F-P cavity spacing is discussed in detail. Moreover, the error analyses reveal that all parameters except the metal grating period in this scheme can bear large tolerances for the device fabrication.展开更多
The authors numerically investigated the characteristics of surface plasmons excited on a thin metal grating placed in planer or conical mounting. After formulating the problem, the solution method, Yasuura＇s method ...The authors numerically investigated the characteristics of surface plasmons excited on a thin metal grating placed in planer or conical mounting. After formulating the problem, the solution method, Yasuura＇s method （a modal expansion approach with least-squares boundary matching） was described. Although the grating is periodic in one direction, coupling between TE and TM waves Occurs because arbitrary incidence is assumed. This requires the employment of both TE and TM vector modal functions in the analysis. Numerical computations showed： （l） the excitation of surface plasmons with total or partial absorption of incident light; （2） the resonance character of the coefficient of an evanescent order that couples the plasmon surface wave; （3） the field profile and Poynting＇s vector. The plasmons excited on the surfaces of a thin metal grating are classified into three types： SISP, SRSP, and LRSP, different from each other in the feature of field profile and energy flow. In addition, the eigenvalue of a plasmon mode was obtained by solving a sequence of diffraction problems with complex-valued angles of incidence and using the quasi-Newton algorithm to predict the real angle of incidence at which the absorption occurs.展开更多
We investigate the transmission properties of a normally incident TM plane wave through metal films with periodic parabolic-shaped grooves on single and double surfaces using the finite-difference-time-domain method. ...We investigate the transmission properties of a normally incident TM plane wave through metal films with periodic parabolic-shaped grooves on single and double surfaces using the finite-difference-time-domain method. Nearly zero transmission efficiency is found at wavelengths corresponding to surface plasmon excitation on a fiat surface in the case where the single surface is grooved. Meanwhile, resonant excitation of surface plasmon polariton （SPP） Bloch modes leads to a strong transmission peak at slightly larger wavelengths. When the grating is grooved on double surfaces, the transmission enhancement can be dramatically improved due to the resonant tunnelling between SPP Bloch modes.展开更多
To obtain the influence rules of the coating parameters of a long-period fiber grating(LPFG)with respect to temperature,strain and refractive index sensing properties,based on the mode coupling theory,a strict four-la...To obtain the influence rules of the coating parameters of a long-period fiber grating(LPFG)with respect to temperature,strain and refractive index sensing properties,based on the mode coupling theory,a strict four-layer theorietical model of a metal film coated LPFG is established,and these parameters that affect the spectral characteristics of the metal film coated LPFG are studied.The simulation results show that there is an optimal metal film thickness on the surface of the LPFG that will induce the surface-plasmon resonance(SP R)effect,which results in higher sensitivity to the environmental temperature and refractive index but has little influence on the strain There is theoretical evidence that when the silver thickness is between0.8and1.2nm,the refractive index sensitivity will reach the peak point of42.4026,at which the refractive index sensor sensitivity is increased by4.S%.The theoretical results of coating a long-period fiber grating provide a good theoretical basis and guidance for LPFG design and parameters optimization展开更多
A polarization control device was developed using a plasmonic metasurface with the aim of achieving the desired polarization state. In this study, the Ag metal grating structure was fabricated as a plasmonic metasurfa...A polarization control device was developed using a plasmonic metasurface with the aim of achieving the desired polarization state. In this study, the Ag metal grating structure was fabricated as a plasmonic metasurface by electron beam lithography and a lift-off process. The phase difference of the fabricated sample was 21.0°. This value is almost consistent with the simulation (24.0°). Then, the transmission and phase difference is dependent on the structural parameter. Because of the propagation of surface plasmon polariton at the interface between Ag and SiO<sub>2</sub> or Ag and air, it is believed that the transmittance and the phase difference for TM polarized light can be controlled by the structural parameters. By plotting on the Poincaré sphere after calculating the S-parameter by simulation, it is clear that the arbitrary polarization status can be controlled by the structural parameter.展开更多
We investigate a modified surface wave splitter with a double-layer structure, which consists of symmetrical metallic grating and an asymmetrical dielectric, using the finite-difference time-domain （FDTD） simulation...We investigate a modified surface wave splitter with a double-layer structure, which consists of symmetrical metallic grating and an asymmetrical dielectric, using the finite-difference time-domain （FDTD） simulation method. The metal/dielectric interface structure at this two-side aperture can support bound waves of different wavelengths, thus guiding waves in opposite directions. The covered dielectric films play an important role in the enhancement and confinement of the diffraction wave by the waveguide modes. The simulation result shows that the optical intensities of the guided surface wave at wavelengths of 760-nm and 1000-nm are about 100 times and 4-5 times those of the weaker side, respectively, which means that the surface wave is split by the proposed device.展开更多
The transmitting light in GaN-based LED with 30 nm thickness metal film grating is investigated. We proposed a basic grating structure model to enhance light intensity in GaN material, which was simpler and cheaper. W...The transmitting light in GaN-based LED with 30 nm thickness metal film grating is investigated. We proposed a basic grating structure model to enhance light intensity in GaN material, which was simpler and cheaper. We calculated and analyzed the structure with different parameters, and studied the numerical simulation results of Ag-films/Al-films/Au-films. With a simple A1 or Ag basic grating structure, the 7.4-7.6 times intensity of 550 nm light can be obtained easily, and the enhancement efficiency is better than others.展开更多
The excitation of a surface-plasmon-polariton(SPP) wave guided by a columnar thin film(CTF) deposited on a one-dimensional metallic surface-relief grating was investigated for sensing the refractive index of a fluid i...The excitation of a surface-plasmon-polariton(SPP) wave guided by a columnar thin film(CTF) deposited on a one-dimensional metallic surface-relief grating was investigated for sensing the refractive index of a fluid infiltrating that CTF. The Bruggemann homogenization formalism was used to determine the relative permittivity scalars of the CTF infiltrated by the fluid. The change in the refractive index of the fluid was sensed by determining the change in the incidence angle for which an SPP wave was excited on illumination by a p-polarized plane wave, when the plane of incidence was taken to coincide with the grating plane but not with the morphologically significant plane of the CTF. Multiple excitations of the same SPP wave were found to be possible, depending on the refractive index of the fluid, which can help increase the reliability of results by sensing the same fluid with more than one excitation of the SPP wave.展开更多
A theoretical method is presented,which analyzes properties of surface acoustic waves propagating on metallic gratings with finite thickness by combining finite element method with variational principle on surface aco...A theoretical method is presented,which analyzes properties of surface acoustic waves propagating on metallic gratings with finite thickness by combining finite element method with variational principle on surface acoustic waves propagating on periodic metal gratings. Based on D.P.Chen and Haus theory,a finite element method is used to investigate the effects of metallic gratings upon the propagation of surface acoustic waves.The coupling-of-modes parameters contributed by mechanical loading are expressed by the matrix derived from the finite element method.Consequently D.P.Chen and Haus theory can also be applied to analyze the properties of surface acoustic waves propagating on metallic gratings with finite thickness and arbitrary shape.Finally,the characteristics of surface acoustic waves propagating under gold and aluminum or silver gratings on a few piezoelectric crystals are studied.Numerical results of the coupling-of-modes parameters of the surface acoustic waves are obtained.展开更多
In recent years, semiconductor quantum dots （QDs） have been widely used as photon sources in quantum optics due to their special properties, such as high quantum effi- ciency, narrow and tunable emission spectrum, e...In recent years, semiconductor quantum dots （QDs） have been widely used as photon sources in quantum optics due to their special properties, such as high quantum effi- ciency, narrow and tunable emission spectrum, easy manipulation, and so on. The spontaneous emission of QDs also depends on the surrounding environment.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61203211 and 20907021)the Foundation for Outstanding Young Teachers of Nanjing University of Information Science&Technology,China(Grant No.20110423)
文摘A technique capable of focusing and bending electromagnetic （EM） waves through plasmonic gratings with equally spaced alternately tapered slits has been introduced. Phase resonances are observed in the optical response of transmission gratings, and the EM wave passes through the tuning slits in the form of surface plasmon polaritons （SPPs） and obtains the required phase retardation to focus at the focal plane. The bending effect is achieved by constructing an asymmetric phase front which results from the tapered slits and gradient refractive index （GRIN） distribution of the dielectric material. Rigorous electromagnetic analysis by using the two-dimensional （2D） finite difference time domain （FDTD） method is employed to verify our proposed designs. When the EM waves are incident at an angle on the optical axis, the beam splitting effect can also be achieved. These index-modulated slits are demonstrated to have unique advantages in beam manipulation compared with the width-modulated ones. In combination with previous studies, it is expected that our results could lead to the realization of ootimum designs for plasmonic nanolenses.
基金supported by the National Natural Science Foundation of China (Grant No 10704079)
文摘Metallic gratings with narrow slits can lead to special optical properties such as strongly enhancing the trans- mission and considerably strengthening the polarized effect. A narrow-band filter suitable for application in optical communication is designed by sandwiching a metallic grating between two identical dielectric films. The maximum transmission can reach 96% after optimizing the parameters of films and grating at a central wavelength of 1053 nm. It is the first time, to our knowledge, that such high transmission has been reported since the discovery of the extraordinarily high transmission through periodic holes or slits; moreover, the extremely polarized effect is also found in P mode of this symmetric grating.
基金Supported by the Key Grant Project of the Ministry of Education of China under Grant No 313007
文摘We present a silicon slot waveguide with metallic gratings embedded on the silicon surface in the slot region. The dependence of the optical coupling between two silicon wires on the width of the metal gap and the slot size are studied in detail. The results show that the optical field in the slot region with metallic gratings is significantly enhanced compared with the traditional slot waveguide due to the surface plasmon polaritons coupling on metallic gratings. The extraordinary optical confinement is attributed to the low effective dielectric constant of metallic gratings. The effective dielectric constant decreases with the increasing wavelength, and reaches the minimum when the width of the metal gap is about 0.01 times the wavelength.
文摘Starting from piezoelectric crystal dynamic equation etc., both the electric potential and surface charge induced by the incident wave are obtained with electrical boundary perturbation technique. The scattered waves are then derived including both surface and bulk waves through integral transformation with the induced charge as exciting source.The scattered surface waves from the grating on YZ-LiNbO3 are then numerically calculated, and both the reflective and forward scattering coefficients are given vs. the strip width. Furthermore, the surface wave phase velocity change when passing the grating is derived and numerically calculated too. The theoretical prediction agrees well with measured results.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61377054 and 61675140)
文摘The exceptional point（EP） is a significant and attractive phenomenon in an open quantum system. The scattering properties of light are similar to those in the open quantum system, which makes it possible to achieve EP in the optic system. Here we investigate the EP in a Fabry–P′erot（F–P） resonant coupling structure. The coupling between different types of F–P resonances leads to a near zero reflection, which results in a degeneration of eigenstates and thus the appearing of EP. Furthermore, the multi-wavelength EPs and unidirectional invisibility can be achieved which may be used in integrated photonics systems.
基金Project supported by Science Foundation of the Chongqing Committee of Education,China (Grant No KJ071205)
文摘A novel optimal design of sub-wavelength metal rectangular gratings for the polarizing beam splitter （PBS） is proposed. The method is based on effective medium theory and the method of designing single layer antireflection coating. The polarization performance of PBS is discussed by rigorous couple-wave analysis （RCWA） method at a wavelength of 1550 nm. The result shows that sub-wavelength metal rectangular grating is characterized by a high reflectivity, like metal films for TE polarization, and high transmissivity, like dielectric films for TM polarization. The optimal design accords well with the results simulated by RCWA method.
基金Supported by the Natural Science Foundation of Hebei Province under Grant Nos A2013402069 and A2013402081
文摘A surface plasmon interference lithography assisted by a Fabry-Perot （F-P） cavity composed of subwavelength metal gratings and a thin metal fihn is proposed to fabricate high-quality nanopatterns. The calculated results indicate that uniform straight interference fringes with high contrast and high electric-field intensity are formed in the resist under the F-P cavity. The analyses of spatial frequency spectra illuminate the physical mechanism of the formation for the interference fringes. The influence of the F-P cavity spacing is discussed in detail. Moreover, the error analyses reveal that all parameters except the metal grating period in this scheme can bear large tolerances for the device fabrication.
基金Project supported by Grants-in-Aid for Scientific Research fromJapan Society for the Promotion of Science (No. 17560313), and theNational Basic Research Program (973) of China (No. 2004CB719801)
文摘The authors numerically investigated the characteristics of surface plasmons excited on a thin metal grating placed in planer or conical mounting. After formulating the problem, the solution method, Yasuura＇s method （a modal expansion approach with least-squares boundary matching） was described. Although the grating is periodic in one direction, coupling between TE and TM waves Occurs because arbitrary incidence is assumed. This requires the employment of both TE and TM vector modal functions in the analysis. Numerical computations showed： （l） the excitation of surface plasmons with total or partial absorption of incident light; （2） the resonance character of the coefficient of an evanescent order that couples the plasmon surface wave; （3） the field profile and Poynting＇s vector. The plasmons excited on the surfaces of a thin metal grating are classified into three types： SISP, SRSP, and LRSP, different from each other in the feature of field profile and energy flow. In addition, the eigenvalue of a plasmon mode was obtained by solving a sequence of diffraction problems with complex-valued angles of incidence and using the quasi-Newton algorithm to predict the real angle of incidence at which the absorption occurs.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60708008)the Project of Academic Leaders in Shanghai (Grant No. 07XD14030)the Knowledge Innovation Program of the Chinese Academy of Sciences
文摘We investigate the transmission properties of a normally incident TM plane wave through metal films with periodic parabolic-shaped grooves on single and double surfaces using the finite-difference-time-domain method. Nearly zero transmission efficiency is found at wavelengths corresponding to surface plasmon excitation on a fiat surface in the case where the single surface is grooved. Meanwhile, resonant excitation of surface plasmon polariton （SPP） Bloch modes leads to a strong transmission peak at slightly larger wavelengths. When the grating is grooved on double surfaces, the transmission enhancement can be dramatically improved due to the resonant tunnelling between SPP Bloch modes.
基金National Natural Science Foundation of China(No.51309001)Scientific Research Key Project of Anhui Province(No.KJ2017A041)
文摘To obtain the influence rules of the coating parameters of a long-period fiber grating(LPFG)with respect to temperature,strain and refractive index sensing properties,based on the mode coupling theory,a strict four-layer theorietical model of a metal film coated LPFG is established,and these parameters that affect the spectral characteristics of the metal film coated LPFG are studied.The simulation results show that there is an optimal metal film thickness on the surface of the LPFG that will induce the surface-plasmon resonance(SP R)effect,which results in higher sensitivity to the environmental temperature and refractive index but has little influence on the strain There is theoretical evidence that when the silver thickness is between0.8and1.2nm,the refractive index sensitivity will reach the peak point of42.4026,at which the refractive index sensor sensitivity is increased by4.S%.The theoretical results of coating a long-period fiber grating provide a good theoretical basis and guidance for LPFG design and parameters optimization
文摘A polarization control device was developed using a plasmonic metasurface with the aim of achieving the desired polarization state. In this study, the Ag metal grating structure was fabricated as a plasmonic metasurface by electron beam lithography and a lift-off process. The phase difference of the fabricated sample was 21.0°. This value is almost consistent with the simulation (24.0°). Then, the transmission and phase difference is dependent on the structural parameter. Because of the propagation of surface plasmon polariton at the interface between Ag and SiO<sub>2</sub> or Ag and air, it is believed that the transmittance and the phase difference for TM polarized light can be controlled by the structural parameters. By plotting on the Poincaré sphere after calculating the S-parameter by simulation, it is clear that the arbitrary polarization status can be controlled by the structural parameter.
文摘We investigate a modified surface wave splitter with a double-layer structure, which consists of symmetrical metallic grating and an asymmetrical dielectric, using the finite-difference time-domain （FDTD） simulation method. The metal/dielectric interface structure at this two-side aperture can support bound waves of different wavelengths, thus guiding waves in opposite directions. The covered dielectric films play an important role in the enhancement and confinement of the diffraction wave by the waveguide modes. The simulation result shows that the optical intensities of the guided surface wave at wavelengths of 760-nm and 1000-nm are about 100 times and 4-5 times those of the weaker side, respectively, which means that the surface wave is split by the proposed device.
基金supported by the National Natural Science Foundation of China(No.60976070)
文摘The transmitting light in GaN-based LED with 30 nm thickness metal film grating is investigated. We proposed a basic grating structure model to enhance light intensity in GaN material, which was simpler and cheaper. We calculated and analyzed the structure with different parameters, and studied the numerical simulation results of Ag-films/Al-films/Au-films. With a simple A1 or Ag basic grating structure, the 7.4-7.6 times intensity of 550 nm light can be obtained easily, and the enhancement efficiency is better than others.
基金partial support from HEC,Pakistan,via grant 2016-5905the Charles Godfrey Binder Endowment at Penn State for ongoing support of his research activities。
文摘The excitation of a surface-plasmon-polariton(SPP) wave guided by a columnar thin film(CTF) deposited on a one-dimensional metallic surface-relief grating was investigated for sensing the refractive index of a fluid infiltrating that CTF. The Bruggemann homogenization formalism was used to determine the relative permittivity scalars of the CTF infiltrated by the fluid. The change in the refractive index of the fluid was sensed by determining the change in the incidence angle for which an SPP wave was excited on illumination by a p-polarized plane wave, when the plane of incidence was taken to coincide with the grating plane but not with the morphologically significant plane of the CTF. Multiple excitations of the same SPP wave were found to be possible, depending on the refractive index of the fluid, which can help increase the reliability of results by sensing the same fluid with more than one excitation of the SPP wave.
基金supported by the National Nature Science Foundation of China(10974171)Zhejiang Province Nature Science Foundation(LY12A04003)
文摘A theoretical method is presented,which analyzes properties of surface acoustic waves propagating on metallic gratings with finite thickness by combining finite element method with variational principle on surface acoustic waves propagating on periodic metal gratings. Based on D.P.Chen and Haus theory,a finite element method is used to investigate the effects of metallic gratings upon the propagation of surface acoustic waves.The coupling-of-modes parameters contributed by mechanical loading are expressed by the matrix derived from the finite element method.Consequently D.P.Chen and Haus theory can also be applied to analyze the properties of surface acoustic waves propagating on metallic gratings with finite thickness and arbitrary shape.Finally,the characteristics of surface acoustic waves propagating under gold and aluminum or silver gratings on a few piezoelectric crystals are studied.Numerical results of the coupling-of-modes parameters of the surface acoustic waves are obtained.
基金supported by the National Natural Science Foundation of China(Nos.11374289 and 61590932)the National Key R&D Program(No.2016YFA0301700)+2 种基金the Innovation Funds from the Chinese Academy of Sciences(No.60921091)the Fundamental Research Funds for the Central Universitiesthe Open Fund of the State Key Laboratory on Integrated Optoelectronics(No.IOSKL2015KF12)
文摘In recent years, semiconductor quantum dots （QDs） have been widely used as photon sources in quantum optics due to their special properties, such as high quantum effi- ciency, narrow and tunable emission spectrum, easy manipulation, and so on. The spontaneous emission of QDs also depends on the surrounding environment.
