We have established the master equation for the micromaser with Kerr medium field density operator, studied the spectrum of the micromaser with Kerr medium and analyzed the influence of Kerr effect and the detuning on...We have established the master equation for the micromaser with Kerr medium field density operator, studied the spectrum of the micromaser with Kerr medium and analyzed the influence of Kerr effect and the detuning on the spectrum. In the thermal-atom regime, we find that Kerr effect broadens linewidth D and increases frequency-shift S, and that the detuning Δ narrows linewidth D and increases frequency-shift S as a whole. Moreover Kerr effect leads to oscillatings more rapidly in the resonance peaks, which means that it causes quantum noise. As a whole, with the increase of cavity-length L, the linewidth D and frequency-shift S gradually increase.展开更多
We have investigated the steady-state cavity-field properties of a single-mode two-photon microreader when the atoms in a cascade three-level configuration are initially prepared in a mixture of the upper and intermed...We have investigated the steady-state cavity-field properties of a single-mode two-photon microreader when the atoms in a cascade three-level configuration are initially prepared in a mixture of the upper and intermediate states. The mean photon number, trapping state and sub-Poissonian effect are discussed with upper （intermediate）-state population changing from 1（0） to 0（1）. These properties are very different from those in a pure two- or one-photon transition process, due to the competition among different transition processes. In particular, the trapping states of nonzero photons are discovered in this system under some conditions, which is contrary to the previous findings.展开更多
Based on step-by-step microscopic calculation, the regular pumping one-atom micromaser is studied when the cavity decay in interaction time is considered. By numerical simulation, the steady-state photon distribution ...Based on step-by-step microscopic calculation, the regular pumping one-atom micromaser is studied when the cavity decay in interaction time is considered. By numerical simulation, the steady-state photon distribution and mean photon number are presented, and influence of cavity loss in the interaction time on the micromaser discussed. It has been found that, for different loss in the interaction time, the discrepancy is large.展开更多
We have established the master equation for the micromaser with Kerr medium field density operator,studied the spectrum of the micromaser with Kerr medium and analyzed the influence of Kerr effect and the detuning ont...We have established the master equation for the micromaser with Kerr medium field density operator,studied the spectrum of the micromaser with Kerr medium and analyzed the influence of Kerr effect and the detuning onthe spectrum. In the thermal-atom regime, we find that Kerr effect broadens linewidth D and increases frequency-shiftS, and that the detuning A narrows linewidth D and increases frequency-shift S as a whole. Moreover Kerr effect leadsto oscillatings more rapidly in the resonance peaks, which means that it causes quantum noise. As a whole, with theincrease of cavity-length L, the linewidth D and frequency-shift S gradually increase.展开更多
The generation of study state hisher-Order squeezing in the sense of Hons andMandel [Phys. Rey. Lett. 54, 323 (1985) ; phys. Rev. A32,974 ( 1985 )] andalso of Hillery [Phys. Rev. A36 , 3796 (1987) ] in a multiphoton m...The generation of study state hisher-Order squeezing in the sense of Hons andMandel [Phys. Rey. Lett. 54, 323 (1985) ; phys. Rev. A32,974 ( 1985 )] andalso of Hillery [Phys. Rev. A36 , 3796 (1987) ] in a multiphoton micromaser isstudied. The results show that the cotangent state which is generated by thecoherent trapping scheme in a niultiphoton microniaser can exhibit not onlysecond-order squeezing but alaso fourth-order and squared field aniplitudesqueezing. The influence of the cavity loss on the squeezings is investigated.展开更多
A high quality-factor （Q） cavity based on a one-dimensional （1D） photonic crystal with gradated elliptical holes was designed using FDTD simulation. Different gradient profiles of the mirror holes were found to co...A high quality-factor （Q） cavity based on a one-dimensional （1D） photonic crystal with gradated elliptical holes was designed using FDTD simulation. Different gradient profiles of the mirror holes were found to correspond to different Q- values of the cavities. A simple strategy is proposed to construct high-Q cavities by using an S-shaped gradient profile for the elliptical holes＇ minor axes, such as a cosine function or Gaussian function. Using such a strategy, a Q value exceeding two million is obtained with only ten mirror holes in a cavity.展开更多
In this paper, we present a simple theoretical approach to calculate the multiple ionization of big atoms and molecules induced by very high-q fast projectiles in a strong coupling regime （q/v 〉 1）. The results obt...In this paper, we present a simple theoretical approach to calculate the multiple ionization of big atoms and molecules induced by very high-q fast projectiles in a strong coupling regime （q/v 〉 1）. The results obtained from this approach are in excellent agreement with the available experimental data. A probable scenario of molecular multiple ionization by fast and very high-q projectiles is discussed. The very small computational time required here and the good agreement with the existing experimental data make it a good candidate for studying the multiple ionization of complex molecules under high linear energy transfers.展开更多
Space–time metasurfaces are promising candidates for breaking Lorentz reciprocity,which constrains light propagation in numerous practical applications.There is a substantial difference between carrier and modulation...Space–time metasurfaces are promising candidates for breaking Lorentz reciprocity,which constrains light propagation in numerous practical applications.There is a substantial difference between carrier and modulation frequencies in space–time photonic metasurfaces that leads to negligible spatial pathway variation of light and weak nonreciprocal response.To surmount this obstacle,herein,the design principle of a high-quality-factor space–time gradient metasurface is demonstrated at the near-infrared regime that increases the lifetime of photons and allows for strong power isolation by lifting the adiabaticity of modulation.The all-dielectric metasurface consists of an array of silicon subwavelength gratings(SWGs)that are separated from distributed Bragg reflectors by a silica buffer.The resonant mode with ultrahigh quality-factor exceeding 10^(4)is excited within the SWG,which is characterized as magnetic octupole and features strong field localization.The SWGs are configured as multijunction p–n layers,whose multigate biasing with time-varying waveforms enables modulation of carriers in space and time.The proposed nonreciprocal metasurface is exploited for free-space optical power isolation by virtue of modulationinduced phase shift.It is shown that under time reversal and by interchanging the directions of incident and observation ports,power isolation of≈35 dB can be maintained between the two ports in free space.展开更多
In a novel microlaser configuration with Ramsey separated-field cavity, we investigate a two-level atomic beam interacting with a single-mode high-Q Ramsey cavity, which is composed by two separated resonators. By usi...In a novel microlaser configuration with Ramsey separated-field cavity, we investigate a two-level atomic beam interacting with a single-mode high-Q Ramsey cavity, which is composed by two separated resonators. By using the well-known Ramsey cavity, one can recover the characters of microlaser even with a high flux atomic beam.展开更多
An adjustable mixer for surface acoustic wave( SAW)-less radio frequency( RF) front-end is presented in this paper. Through changing the bias voltage,the presented mixer with reconfigurable voltage conversion gain( VC...An adjustable mixer for surface acoustic wave( SAW)-less radio frequency( RF) front-end is presented in this paper. Through changing the bias voltage,the presented mixer with reconfigurable voltage conversion gain( VCG) is suitable for multi-mode multi-standard( MMMS) applications. An equivalent local oscillator( LO) frequency-tunable high-Q band-pass filter( BPF) at low noise amplifier( LNA) output is used to reject the out-of-band interference signals. Base-band( BB) capacitor of the mixer is variable to obtain 15 kinds of intermediate frequency( IF) bandwidth( BW). The proposed passive mixer with LNA is implemented in TSMC 0. 18μm RF CMOS process and operates from 0. 5 to 2. 5 GHz with measured maximum out-of-band rejection larger than 40 d B. The measured VCG of the front-end can be changed from 5 to 17 d B; the maximum input intercept point( IIP3) is0 d Bm and the minimum noise figure( NF) is 3. 7 d B. The chip occupies an area of 0. 44 mm^2 including pads.展开更多
In this paper, we extend our previous work of classical over barrier ionization (COBI) model to study the multiple ionization cross section of Ne and CO molecule collided by very high-q fast projectiles(q/v > 1). T...In this paper, we extend our previous work of classical over barrier ionization (COBI) model to study the multiple ionization cross section of Ne and CO molecule collided by very high-q fast projectiles(q/v > 1). The model gives similar results to the independent-electron-approximation calculation and is in good agreement with experimental data. The very small computational time required makes it a good candidate for studying the multiple ionization of complex molecules under high linear energy transfers.展开更多
The method of terahertz(THz)resonance with a high-quality(high-Q)factor offers a vital physical mechanism for metasurface sensors and other high-Q factor applications.However,it is challenging to excite the resonance ...The method of terahertz(THz)resonance with a high-quality(high-Q)factor offers a vital physical mechanism for metasurface sensors and other high-Q factor applications.However,it is challenging to excite the resonance with a high-Q factor in metasurfaces with proper sensitivity as well as figure of merit(FOM)values.Here,an all-dielectric metasurface composed of two asymmetrical rectangular blocks is suggested.Quartz and silicon are the materials applied for the substrate and cuboids respectively.The distinct resonance governed by bound states in the continuum(BIC)is excited by forming an asymmetric cluster by a novel hybrid method of cutting and moving the cuboids.The investigation focuses on analyzing the transmission spectra of the metasurface under different variations in structural parameters and the loss of silicon refractive index.When the proposed defective metasurface serves as a transmittance sensor,it shows a Q factor of 1.08×10^(4)and achieves an FOM up to 4.8×10^(6),which is obtained under the asymmetric parameter equalling 1μm.Simultaneously,the proposed defective metasurface is sensitive to small changes in refractive index.When the thickness of the analyte is 180μm,the sensitivity reaches a maximum value of 578 GHz/RIU.Hence,the proposed defective metasurface exhibits an extensive number of possible applications in the filters,biomedical diagnosis,security screening,and so on.展开更多
With the increasing frequency of wireless mobile communication,dielectric materials with higher Q×f are required to enhance the signal strength of microwave passive devices and thus compensate for the rapid atten...With the increasing frequency of wireless mobile communication,dielectric materials with higher Q×f are required to enhance the signal strength of microwave passive devices and thus compensate for the rapid attenuation of high-frequency signals during propagation.In order to improve the Q×f of the MgNb2O6 system and study the internal mechanism between the structure and microwave dielectric properties,Ta5+ion is introduced to design and fabricate MgNb_(2-x)Ta_(x)O_(6)(0≤x≤0.8)ceramics by the solid-state reaction method.The single columbite phase and dense structure are observed throughout the entire composition range.All elements(Mg,Nb,Ta,and O)can be detected by X-ray photoelectron spectroscopy.Insights from the Raman spectroscopy and group theoretical analysis reveal that the Ag(2)and Ag(3)modes located at∼905 cm−1 dominate the Raman vibration.In addition,theɛr depends on the polarizability reflected by the C–M equation and Raman shift.Theτf closely relates to the bond energy of the Nb/Ta–O bond and restoring force characterized by average octahedral distortion of[Nb/TaO6].Notably,the crucial factors for the huge improvement of Q×f are clarified deeply,in terms of the lower internal strain,the reduced ordering-induced domain size,and the chemical bond valence closer to the ionic valence state,which promotes the stability of crystal structure.Moreover,the introduction of lower electronegative ions enhances the ability of electrons to compensate for oxygen vacancies,thereby reducing the dielectric loss caused by the conductance.Excellent microwave properties(ɛr=19.2,Q×f=170,000 GHz,andτf=−55.6 ppm℃–1)are achieved in MgNb1.4Ta0.6O6 ceramic,specifically a nearly 40%increase in the Q×f.This work has enriched the theory associated with low dielectric loss and provided the MgNb_(1.4)Ta_(0.6)O_(6) ceramic with a pretty high-Q×f for the application in the design of the 5G/6G wireless communication devices.展开更多
文摘We have established the master equation for the micromaser with Kerr medium field density operator, studied the spectrum of the micromaser with Kerr medium and analyzed the influence of Kerr effect and the detuning on the spectrum. In the thermal-atom regime, we find that Kerr effect broadens linewidth D and increases frequency-shift S, and that the detuning Δ narrows linewidth D and increases frequency-shift S as a whole. Moreover Kerr effect leads to oscillatings more rapidly in the resonance peaks, which means that it causes quantum noise. As a whole, with the increase of cavity-length L, the linewidth D and frequency-shift S gradually increase.
基金Project supported by the National Natural Science Foundation of China, the National Key Basic Research Special Foundation of China, the Major Program of the National Natural Science Foundation of China （Grant No 10234040）, and the Shanghai Foundation for Development of Science and Technology （Grant No 02DJ14066）.
文摘We have investigated the steady-state cavity-field properties of a single-mode two-photon microreader when the atoms in a cascade three-level configuration are initially prepared in a mixture of the upper and intermediate states. The mean photon number, trapping state and sub-Poissonian effect are discussed with upper （intermediate）-state population changing from 1（0） to 0（1）. These properties are very different from those in a pure two- or one-photon transition process, due to the competition among different transition processes. In particular, the trapping states of nonzero photons are discovered in this system under some conditions, which is contrary to the previous findings.
文摘Based on step-by-step microscopic calculation, the regular pumping one-atom micromaser is studied when the cavity decay in interaction time is considered. By numerical simulation, the steady-state photon distribution and mean photon number are presented, and influence of cavity loss in the interaction time on the micromaser discussed. It has been found that, for different loss in the interaction time, the discrepancy is large.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 90108026, 10125419, and 60078023
文摘We have established the master equation for the micromaser with Kerr medium field density operator,studied the spectrum of the micromaser with Kerr medium and analyzed the influence of Kerr effect and the detuning onthe spectrum. In the thermal-atom regime, we find that Kerr effect broadens linewidth D and increases frequency-shiftS, and that the detuning A narrows linewidth D and increases frequency-shift S as a whole. Moreover Kerr effect leadsto oscillatings more rapidly in the resonance peaks, which means that it causes quantum noise. As a whole, with theincrease of cavity-length L, the linewidth D and frequency-shift S gradually increase.
文摘The generation of study state hisher-Order squeezing in the sense of Hons andMandel [Phys. Rey. Lett. 54, 323 (1985) ; phys. Rev. A32,974 ( 1985 )] andalso of Hillery [Phys. Rev. A36 , 3796 (1987) ] in a multiphoton micromaser isstudied. The results show that the cotangent state which is generated by thecoherent trapping scheme in a niultiphoton microniaser can exhibit not onlysecond-order squeezing but alaso fourth-order and squared field aniplitudesqueezing. The influence of the cavity loss on the squeezings is investigated.
基金supported by the National Natural Science Foundation of China(Grant Nos.61275045,91121019,and 61021003)the National Basic Research Program of China(Grant No.2013CB632105)
文摘A high quality-factor （Q） cavity based on a one-dimensional （1D） photonic crystal with gradated elliptical holes was designed using FDTD simulation. Different gradient profiles of the mirror holes were found to correspond to different Q- values of the cavities. A simple strategy is proposed to construct high-Q cavities by using an S-shaped gradient profile for the elliptical holes＇ minor axes, such as a cosine function or Gaussian function. Using such a strategy, a Q value exceeding two million is obtained with only ten mirror holes in a cavity.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11174116 and 11175075)
文摘In this paper, we present a simple theoretical approach to calculate the multiple ionization of big atoms and molecules induced by very high-q fast projectiles in a strong coupling regime （q/v 〉 1）. The results obtained from this approach are in excellent agreement with the available experimental data. A probable scenario of molecular multiple ionization by fast and very high-q projectiles is discussed. The very small computational time required here and the good agreement with the existing experimental data make it a good candidate for studying the multiple ionization of complex molecules under high linear energy transfers.
基金supported in part by Air Force Office of Scientific Research(Grant No.FA9550-18-1-0354).
文摘Space–time metasurfaces are promising candidates for breaking Lorentz reciprocity,which constrains light propagation in numerous practical applications.There is a substantial difference between carrier and modulation frequencies in space–time photonic metasurfaces that leads to negligible spatial pathway variation of light and weak nonreciprocal response.To surmount this obstacle,herein,the design principle of a high-quality-factor space–time gradient metasurface is demonstrated at the near-infrared regime that increases the lifetime of photons and allows for strong power isolation by lifting the adiabaticity of modulation.The all-dielectric metasurface consists of an array of silicon subwavelength gratings(SWGs)that are separated from distributed Bragg reflectors by a silica buffer.The resonant mode with ultrahigh quality-factor exceeding 10^(4)is excited within the SWG,which is characterized as magnetic octupole and features strong field localization.The SWGs are configured as multijunction p–n layers,whose multigate biasing with time-varying waveforms enables modulation of carriers in space and time.The proposed nonreciprocal metasurface is exploited for free-space optical power isolation by virtue of modulationinduced phase shift.It is shown that under time reversal and by interchanging the directions of incident and observation ports,power isolation of≈35 dB can be maintained between the two ports in free space.
文摘In a novel microlaser configuration with Ramsey separated-field cavity, we investigate a two-level atomic beam interacting with a single-mode high-Q Ramsey cavity, which is composed by two separated resonators. By using the well-known Ramsey cavity, one can recover the characters of microlaser even with a high flux atomic beam.
基金Supported by the National Basic Research Program of China(No.2010CB327404)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘An adjustable mixer for surface acoustic wave( SAW)-less radio frequency( RF) front-end is presented in this paper. Through changing the bias voltage,the presented mixer with reconfigurable voltage conversion gain( VCG) is suitable for multi-mode multi-standard( MMMS) applications. An equivalent local oscillator( LO) frequency-tunable high-Q band-pass filter( BPF) at low noise amplifier( LNA) output is used to reject the out-of-band interference signals. Base-band( BB) capacitor of the mixer is variable to obtain 15 kinds of intermediate frequency( IF) bandwidth( BW). The proposed passive mixer with LNA is implemented in TSMC 0. 18μm RF CMOS process and operates from 0. 5 to 2. 5 GHz with measured maximum out-of-band rejection larger than 40 d B. The measured VCG of the front-end can be changed from 5 to 17 d B; the maximum input intercept point( IIP3) is0 d Bm and the minimum noise figure( NF) is 3. 7 d B. The chip occupies an area of 0. 44 mm^2 including pads.
文摘In this paper, we extend our previous work of classical over barrier ionization (COBI) model to study the multiple ionization cross section of Ne and CO molecule collided by very high-q fast projectiles(q/v > 1). The model gives similar results to the independent-electron-approximation calculation and is in good agreement with experimental data. The very small computational time required makes it a good candidate for studying the multiple ionization of complex molecules under high linear energy transfers.
基金the Key Research and Development Program of Ningxia Province,China(2021BEB04068)。
文摘The method of terahertz(THz)resonance with a high-quality(high-Q)factor offers a vital physical mechanism for metasurface sensors and other high-Q factor applications.However,it is challenging to excite the resonance with a high-Q factor in metasurfaces with proper sensitivity as well as figure of merit(FOM)values.Here,an all-dielectric metasurface composed of two asymmetrical rectangular blocks is suggested.Quartz and silicon are the materials applied for the substrate and cuboids respectively.The distinct resonance governed by bound states in the continuum(BIC)is excited by forming an asymmetric cluster by a novel hybrid method of cutting and moving the cuboids.The investigation focuses on analyzing the transmission spectra of the metasurface under different variations in structural parameters and the loss of silicon refractive index.When the proposed defective metasurface serves as a transmittance sensor,it shows a Q factor of 1.08×10^(4)and achieves an FOM up to 4.8×10^(6),which is obtained under the asymmetric parameter equalling 1μm.Simultaneously,the proposed defective metasurface is sensitive to small changes in refractive index.When the thickness of the analyte is 180μm,the sensitivity reaches a maximum value of 578 GHz/RIU.Hence,the proposed defective metasurface exhibits an extensive number of possible applications in the filters,biomedical diagnosis,security screening,and so on.
基金supported by the National Natural Science Foundation of China(No.52172122).
文摘With the increasing frequency of wireless mobile communication,dielectric materials with higher Q×f are required to enhance the signal strength of microwave passive devices and thus compensate for the rapid attenuation of high-frequency signals during propagation.In order to improve the Q×f of the MgNb2O6 system and study the internal mechanism between the structure and microwave dielectric properties,Ta5+ion is introduced to design and fabricate MgNb_(2-x)Ta_(x)O_(6)(0≤x≤0.8)ceramics by the solid-state reaction method.The single columbite phase and dense structure are observed throughout the entire composition range.All elements(Mg,Nb,Ta,and O)can be detected by X-ray photoelectron spectroscopy.Insights from the Raman spectroscopy and group theoretical analysis reveal that the Ag(2)and Ag(3)modes located at∼905 cm−1 dominate the Raman vibration.In addition,theɛr depends on the polarizability reflected by the C–M equation and Raman shift.Theτf closely relates to the bond energy of the Nb/Ta–O bond and restoring force characterized by average octahedral distortion of[Nb/TaO6].Notably,the crucial factors for the huge improvement of Q×f are clarified deeply,in terms of the lower internal strain,the reduced ordering-induced domain size,and the chemical bond valence closer to the ionic valence state,which promotes the stability of crystal structure.Moreover,the introduction of lower electronegative ions enhances the ability of electrons to compensate for oxygen vacancies,thereby reducing the dielectric loss caused by the conductance.Excellent microwave properties(ɛr=19.2,Q×f=170,000 GHz,andτf=−55.6 ppm℃–1)are achieved in MgNb1.4Ta0.6O6 ceramic,specifically a nearly 40%increase in the Q×f.This work has enriched the theory associated with low dielectric loss and provided the MgNb_(1.4)Ta_(0.6)O_(6) ceramic with a pretty high-Q×f for the application in the design of the 5G/6G wireless communication devices.
