Er was doped into porous Si by immersing the porous Si sample in a saturated ErCl3,ethanol solution. Sharp and intense 1.54 μm photoluminescence caused by intra-4f-shefl transitions in Er3+ ions was observed up to ro...Er was doped into porous Si by immersing the porous Si sample in a saturated ErCl3,ethanol solution. Sharp and intense 1.54 μm photoluminescence caused by intra-4f-shefl transitions in Er3+ ions was observed up to room temperature. It is shown that the immersing process is valid to dope Er in high concentration in porous Si. Time resolved study of the Er-doped porous Si revealed that the doped Er3+ ions are excited by energy transfer from photo-generated electron-hole pairs in the host. The energy back transfer process from the excited 4f electrons in the Er3+ion to the host is not a dominant factor to quench the Er-related emission in porous Si. Ourresults are well explained by a proposed model in which an intermediate state was introduced.展开更多
Recent years, optically controlled phase-change memory draws intensive attention owing to some advanced applications including integrated all-optical nonvolatile memory, in-memory computing, and neuromorphic computing...Recent years, optically controlled phase-change memory draws intensive attention owing to some advanced applications including integrated all-optical nonvolatile memory, in-memory computing, and neuromorphic computing. The light-induced phase transition is the key for this technology. Traditional understanding on the role of light is the heating effect. Generally, the RESET operation of phase-change memory is believed to be a melt-quenching-amorphization process. However, some recent experimental and theoretical investigations have revealed that ultrafast laser can manipulate the structures of phase-change materials by non-thermal effects and induces unconventional phase transitions including solid-to-solid amorphization and order-to-order phase transitions. Compared with the conventional thermal amorphization,these transitions have potential superiors such as faster speed, better endurance, and low power consumption. This article summarizes some recent progress of experimental observations and theoretical analyses on these unconventional phase transitions. The discussions mainly focus on the physical mechanism at atomic scale to provide guidance to control the phase transitions for optical storage. Outlook on some possible applications of the non-thermal phase transition is also presented to develop new types of devices.展开更多
In this paper,we theoretically investigate the total optical coefficient(TOAC)considering 1S-2P and 2S-2P conduction subband transitions in a single parabolic quantum well(SPQW)with an on-center hydrogen-like impurity...In this paper,we theoretically investigate the total optical coefficient(TOAC)considering 1S-2P and 2S-2P conduction subband transitions in a single parabolic quantum well(SPQW)with an on-center hydrogen-like impurity.Within the framework of the effective-mass approximation,the Schrödinger equation is solved numerically to obtain the eigenvalues and their corresponding eigenvectors using the finite difference method.The calculations are performed for finite confinement potential height,taking into account the dielectric and effective mass mismatches between GaN and InGaN materials under the considered electric field and temperature effects.The temperature dependence of the effective mass,dielectric constant and band gap energy are obtained accordingly.On the one hand,the results show that a significant shift is produced with the variation of both the temperature and the intensity of the electric field.On the other hand,the absorption spectrum is shifted to lower energies with increasing both electric field strength and temperature.Moreover,its amplitude is enhanced with an increase in the intensity of the electric field,and show a slight drop with increasing temperature for the two optical transitions considered.The results show that such parameters can be used to adjust the optical properties of single parabolic Quantum Well for solar cell applications.展开更多
Profile function properties with different variables are discussed, the formulae of stimulated absorption, spontaneous and stimulated emission, absorption and emission coefficients, and cross sections are deduced, and...Profile function properties with different variables are discussed, the formulae of stimulated absorption, spontaneous and stimulated emission, absorption and emission coefficients, and cross sections are deduced, and some confusing issues are clarified.展开更多
Magic wavelengths for laser trapping of barium atoms in the optical clock transition at l107nm between the 6s2 1So state optical lattices are calculated with considering the and 6s5d 3D1 state. Theoretical calculation...Magic wavelengths for laser trapping of barium atoms in the optical clock transition at l107nm between the 6s2 1So state optical lattices are calculated with considering the and 6s5d 3D1 state. Theoretical calculation shows that there are several magic wavelengths with the linearly polarized trapping laser. The trap depths of the optical lattice and the slope of light shift difference with different magic wavelengths are also calculated, Some of these magic wavelengths are selected and recommended as potentially suitable magic wavelengths for the optical lattice trapping laser.展开更多
A simple scheme is proposed to generate the W state of N A-type neutral atoms trapped in an optical cavity via Raman transition. Conditional on no photon leakage from the cavity, the N-qubit W state can be prepared pe...A simple scheme is proposed to generate the W state of N A-type neutral atoms trapped in an optical cavity via Raman transition. Conditional on no photon leakage from the cavity, the N-qubit W state can be prepared perfectly by turning on a classical coupling field for an appropriate time. Compared with the previous ones, our scheme requires neither individual laser addressing of the atoms, nor demand for controlling N atoms to go through an optical cavity simultaneously with a constant velocity. We investigate the influence of cavity decay using the quantum jump approach and show that the preparation time decreases and the success probability increases with atom number because of a collective enhancement of the coupling.展开更多
The absolute frequency of 87Rb 5S1/2 （F=2）→5D5/2 （F＂ = 4） two-photon transition at 778nm is measured in an accuracy of 44kHz. A home-made erbium-doped fiber laser frequency comb with frequency stability of 5.0 ...The absolute frequency of 87Rb 5S1/2 （F=2）→5D5/2 （F＂ = 4） two-photon transition at 778nm is measured in an accuracy of 44kHz. A home-made erbium-doped fiber laser frequency comb with frequency stability of 5.0 × 10-13@1 s is employed for the light source. By using a periodically poled lithium niobate, the femtosecond pulse operating in 1556 nm is frequency-doubled to 778 nm to obtain the direct two-photon transition spectroscopy of thermal rubidium vapor. Through sweeping the carrier envelope offset frequency （fceo）, the 5S1/2 （F=2）→5D5/2 （F＂ = 4） two-photon transition line is clearly resolved and its absolute frequency is determined via the peak-finding of the fitting curve. After the frequency correction, the measured result agrees well with the previous experiment on this transition. The entire potential candidate of optical frequency standard for system configuration is compact and robust, providing a telecommunication applications.展开更多
An optical atomic clock with 171yb atoms is devised and tested. By using a two-stage Doppler cooling technique, the 171Yb atoms are cooled down to a temperature of 6 ± 3 μK, which is close to the Doppler limit. ...An optical atomic clock with 171yb atoms is devised and tested. By using a two-stage Doppler cooling technique, the 171Yb atoms are cooled down to a temperature of 6 ± 3 μK, which is close to the Doppler limit. Then, the cold 171Yb atoms are loaded into a one-dimensional optical lattice with a wavelength of 759 nm in the Lamb-Dicke regime. Furthermore, these cold 171yb atoms are excited from the ground-state 1S0 to the excited-state 3P0 by a clock laser with a wavelength of 578 nm. Finally, the 1S0-3P0 clock-transition spectrum of these 171yb atoms is obtained by measuring the dependence of the population of the ground-state 1 S0 upon the clock-laser detuning.展开更多
The first-order-like phase transition (FOLT) in the dispersive optical bistability is investigated when the fluctuation in the incident light field is considered as colored noise. A unified colored-noise approximation...The first-order-like phase transition (FOLT) in the dispersive optical bistability is investigated when the fluctuation in the incident light field is considered as colored noise. A unified colored-noise approximation is applied to obtain the steady state distribution (SSD) when either the intensity or phase fluctuations of the incident field are included in the system. For intensity fluctuations only, the curve of SSD is changed from single extreme to two extremes, and then to three extremes. The colored nature of the noise can reduce the fluctuation in the system. However, for phase fluctuations only, the FOLT is mainly induced by the colored nature of the noise. The curve of SSD is changed from single extreme to three extremes directly. There is no FOLT existing for white noise.展开更多
The TDDFT method is first applied in a series of tetra-nuclear transition metal clusters studies for nonlinear optical properties. The results indicate that the charge transfer inside the metal core [MCu3X4] (M=W, Mo...The TDDFT method is first applied in a series of tetra-nuclear transition metal clusters studies for nonlinear optical properties. The results indicate that the charge transfer inside the metal core [MCu3X4] (M=W, Mo; X=S, O, Cl, Se, Br) makes contribution to the optical nonlinearity. It is possible to enhance the hyperpolarizability by substituting the ligands of the clusters.展开更多
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
文摘Er was doped into porous Si by immersing the porous Si sample in a saturated ErCl3,ethanol solution. Sharp and intense 1.54 μm photoluminescence caused by intra-4f-shefl transitions in Er3+ ions was observed up to room temperature. It is shown that the immersing process is valid to dope Er in high concentration in porous Si. Time resolved study of the Er-doped porous Si revealed that the doped Er3+ ions are excited by energy transfer from photo-generated electron-hole pairs in the host. The energy back transfer process from the excited 4f electrons in the Er3+ion to the host is not a dominant factor to quench the Er-related emission in porous Si. Ourresults are well explained by a proposed model in which an intermediate state was introduced.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61922035 and 11904118)
文摘Recent years, optically controlled phase-change memory draws intensive attention owing to some advanced applications including integrated all-optical nonvolatile memory, in-memory computing, and neuromorphic computing. The light-induced phase transition is the key for this technology. Traditional understanding on the role of light is the heating effect. Generally, the RESET operation of phase-change memory is believed to be a melt-quenching-amorphization process. However, some recent experimental and theoretical investigations have revealed that ultrafast laser can manipulate the structures of phase-change materials by non-thermal effects and induces unconventional phase transitions including solid-to-solid amorphization and order-to-order phase transitions. Compared with the conventional thermal amorphization,these transitions have potential superiors such as faster speed, better endurance, and low power consumption. This article summarizes some recent progress of experimental observations and theoretical analyses on these unconventional phase transitions. The discussions mainly focus on the physical mechanism at atomic scale to provide guidance to control the phase transitions for optical storage. Outlook on some possible applications of the non-thermal phase transition is also presented to develop new types of devices.
基金This research received no specific grant from any funding agency in the public,commercial,or not-for-profit sectors.
文摘In this paper,we theoretically investigate the total optical coefficient(TOAC)considering 1S-2P and 2S-2P conduction subband transitions in a single parabolic quantum well(SPQW)with an on-center hydrogen-like impurity.Within the framework of the effective-mass approximation,the Schrödinger equation is solved numerically to obtain the eigenvalues and their corresponding eigenvectors using the finite difference method.The calculations are performed for finite confinement potential height,taking into account the dielectric and effective mass mismatches between GaN and InGaN materials under the considered electric field and temperature effects.The temperature dependence of the effective mass,dielectric constant and band gap energy are obtained accordingly.On the one hand,the results show that a significant shift is produced with the variation of both the temperature and the intensity of the electric field.On the other hand,the absorption spectrum is shifted to lower energies with increasing both electric field strength and temperature.Moreover,its amplitude is enhanced with an increase in the intensity of the electric field,and show a slight drop with increasing temperature for the two optical transitions considered.The results show that such parameters can be used to adjust the optical properties of single parabolic Quantum Well for solar cell applications.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51172236,51272254,51102239,61205173,and 61405206)
文摘Profile function properties with different variables are discussed, the formulae of stimulated absorption, spontaneous and stimulated emission, absorption and emission coefficients, and cross sections are deduced, and some confusing issues are clarified.
基金Supported by the Scientific Research Program Funded by Shaanxi Provincial Education Department under Grant No 14JK1402
文摘Magic wavelengths for laser trapping of barium atoms in the optical clock transition at l107nm between the 6s2 1So state optical lattices are calculated with considering the and 6s5d 3D1 state. Theoretical calculation shows that there are several magic wavelengths with the linearly polarized trapping laser. The trap depths of the optical lattice and the slope of light shift difference with different magic wavelengths are also calculated, Some of these magic wavelengths are selected and recommended as potentially suitable magic wavelengths for the optical lattice trapping laser.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10504042)the Key Laboratory of Low Dimensional Quantum Structures and Quantum Control (Hunan Normal University)Ministry of Education of China (Grant No.QSQC0902)
文摘A simple scheme is proposed to generate the W state of N A-type neutral atoms trapped in an optical cavity via Raman transition. Conditional on no photon leakage from the cavity, the N-qubit W state can be prepared perfectly by turning on a classical coupling field for an appropriate time. Compared with the previous ones, our scheme requires neither individual laser addressing of the atoms, nor demand for controlling N atoms to go through an optical cavity simultaneously with a constant velocity. We investigate the influence of cavity decay using the quantum jump approach and show that the preparation time decreases and the success probability increases with atom number because of a collective enhancement of the coupling.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61405002,91336103,10934010,61535001 and 61078026
文摘The absolute frequency of 87Rb 5S1/2 （F=2）→5D5/2 （F＂ = 4） two-photon transition at 778nm is measured in an accuracy of 44kHz. A home-made erbium-doped fiber laser frequency comb with frequency stability of 5.0 × 10-13@1 s is employed for the light source. By using a periodically poled lithium niobate, the femtosecond pulse operating in 1556 nm is frequency-doubled to 778 nm to obtain the direct two-photon transition spectroscopy of thermal rubidium vapor. Through sweeping the carrier envelope offset frequency （fceo）, the 5S1/2 （F=2）→5D5/2 （F＂ = 4） two-photon transition line is clearly resolved and its absolute frequency is determined via the peak-finding of the fitting curve. After the frequency correction, the measured result agrees well with the previous experiment on this transition. The entire potential candidate of optical frequency standard for system configuration is compact and robust, providing a telecommunication applications.
基金supported by the National Basic Research Program of China (Grant Nos. 2012CB821302 and 2010CB922903)the National Natural Science Foundation of China (Grant Nos. 11134003 and 10774044)the Shanghai Excellent Academic Leaders Program of China (Grant No. 12XD1402400)
文摘An optical atomic clock with 171yb atoms is devised and tested. By using a two-stage Doppler cooling technique, the 171Yb atoms are cooled down to a temperature of 6 ± 3 μK, which is close to the Doppler limit. Then, the cold 171Yb atoms are loaded into a one-dimensional optical lattice with a wavelength of 759 nm in the Lamb-Dicke regime. Furthermore, these cold 171yb atoms are excited from the ground-state 1S0 to the excited-state 3P0 by a clock laser with a wavelength of 578 nm. Finally, the 1S0-3P0 clock-transition spectrum of these 171yb atoms is obtained by measuring the dependence of the population of the ground-state 1 S0 upon the clock-laser detuning.
文摘The first-order-like phase transition (FOLT) in the dispersive optical bistability is investigated when the fluctuation in the incident light field is considered as colored noise. A unified colored-noise approximation is applied to obtain the steady state distribution (SSD) when either the intensity or phase fluctuations of the incident field are included in the system. For intensity fluctuations only, the curve of SSD is changed from single extreme to two extremes, and then to three extremes. The colored nature of the noise can reduce the fluctuation in the system. However, for phase fluctuations only, the FOLT is mainly induced by the colored nature of the noise. The curve of SSD is changed from single extreme to three extremes directly. There is no FOLT existing for white noise.
基金supported by the National Natural Sci-ence Foundation of China(No.21972083,No.22102129)the Fundamental Research Funds for the Central Universities(GK202102008)+1 种基金the Support Program for top-notch young talents in Shaanxi Province(1511000066)the China Postdoctoral Science Foundation(2021M692615,2022T150528)。
基金supported in part by the National Natural Science Foundation of China under Grant Nos.10575040.90503010.10634060,and 10747133the National Basic Research Program of China under Grant No.2005CB724508
文摘The TDDFT method is first applied in a series of tetra-nuclear transition metal clusters studies for nonlinear optical properties. The results indicate that the charge transfer inside the metal core [MCu3X4] (M=W, Mo; X=S, O, Cl, Se, Br) makes contribution to the optical nonlinearity. It is possible to enhance the hyperpolarizability by substituting the ligands of the clusters.
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.
