A horizonless ultracompact object can have a stable antiphoton sphere,which causes the photons inside the unstable photon sphere to strongly deflect,thereby leading to the formation of distinctive inner photon rings.I...A horizonless ultracompact object can have a stable antiphoton sphere,which causes the photons inside the unstable photon sphere to strongly deflect,thereby leading to the formation of distinctive inner photon rings.In this study,we present analytical descriptions for the shape,thickness,and interference pattern of higher-order inner photon rings.By taking the static spherically symmetric Schwarzschild star with a photon sphere as an example,we find that its inner photon rings can be more non-circular and thicker than the outer ones and show that the inclusion of the inner photon rings can result in new features in the interferometric pattern.Further,our formulae can be applied to other ultracompact objects,providing a convenient approach for studying the observational properties of their higher-order photon rings.展开更多
We calculate photon sphere r_(ph) and critical curve b_(c) for a quantum corrected Schwarzschild black hole,finding that they violate universal inequalities proved for asymptotically flat black holes that satisfy the ...We calculate photon sphere r_(ph) and critical curve b_(c) for a quantum corrected Schwarzschild black hole,finding that they violate universal inequalities proved for asymptotically flat black holes that satisfy the null energy condition in the framework of Einstein gravity.This violation seems to be a common phenomenon when considering quantum modification of Einstein gravity.Furthermore,we study the shadows,lensing rings,and photon rings in the quantum corrected Schwarzschild black hole.The violation leads to a larger bright lensing ring in the observational appearance of the thin disk emission near the black hole compared with the classical Schwarzschild black hole.Our analysis may provide observational evidence for the quantum effect of general relativity.展开更多
In this paper,we study the optical properties of asymmetric thin-shell wormholes(ATWs)under torsion charge.Utilizing the cut-and-paste method developed by Visser,we construct these wormholes and determine their key ph...In this paper,we study the optical properties of asymmetric thin-shell wormholes(ATWs)under torsion charge.Utilizing the cut-and-paste method developed by Visser,we construct these wormholes and determine their key physical properties,such as the radius of the photon sphere and critical impact parameters,under different torsion charges.Furthermore,we investigate the effective potential and behavior of photon motion within the wormhole spacetime,identifying a relationship between photon trajectories and impact parameters.The study focuses on scenarios where thin accretion disks act as the primary light source.It reveals that the optical features of ATWs under torsion charge significantly differ from those of black holes(BHs).Notably,an increase in torsion charge leads to a reduction in the sizes of both extra photon rings and lensing bands,which serve as important markers for distinguishing and characterizing ATW spacetimes from those of BHs.展开更多
In this paper,dual L defected hexagonal Photonic Crystal Ring Resonator(PCRR)using Channel Drop Filter(CDF)is designed for Coarse Wavelength Division Multiplexing(CWDM)systems.In this structure,the external rods of th...In this paper,dual L defected hexagonal Photonic Crystal Ring Resonator(PCRR)using Channel Drop Filter(CDF)is designed for Coarse Wavelength Division Multiplexing(CWDM)systems.In this structure,the external rods of the ring resonator are arranged in a hexagon and the internal rods are removed in L arrangement for introducing defects.Scatter rods are used to prevent leakage.By using the L defected hexagonal resonator,a multi-channel CDF is designed,which exhibits multiple wavelengths of CWDM(1500 nm–1600 nm)region.In addition,the selection of rod size and the position of rods in the proposed multi-channel CDF are validated by varying the radius of coupling and scattering rods,as well as the position of resonators,respectively.By using plane wave expansion and opti Finite Difference Time Domain(FDTD)method,the electromagnetic wave propagation and the photonic band gap are obtained.展开更多
A novel hybrid air-core photonic band-gap fiber(PBF) ring resonator with twin 90° polarization-axis rotated splices is proposed and demonstrated. Frist, we measure the temperature dependent birefringence coeffici...A novel hybrid air-core photonic band-gap fiber(PBF) ring resonator with twin 90° polarization-axis rotated splices is proposed and demonstrated. Frist, we measure the temperature dependent birefringence coefficient of air-core PBF and Panda fiber. Experimental results show that the relative temperature dependent birefringence coefficient of air-core PBF is 1.42×10^(-8)/℃, which is typically ~16 times less than that of Panda fiber. Then, we extract the geometry profile of air-core PBF from scanning electron microscope(SEM) images. Numerical modal is built to distinguish the fast axis and slow axis in the fiber. By precisely setting the length difference in air-core PBF and Panda fiber between two 90° polarization-axis rotated splicing points, the hybrid air-core PBF ring resonator is constructed, and the finesse of the resonator is 8.4. Environmental birefringence variation induced by temperature change can be well compensated, and experimental results show an 18-fold reduction in thermal sensitivity, compared with resonator with twin 0° polarization-axis rotated splices.展开更多
Avalanche photon diode and avalanche diode array, working in Geiger mode, have single photon detection capability. The structure of guard ring is the key factor to avoid the premature edge breakdown of the avalanche d...Avalanche photon diode and avalanche diode array, working in Geiger mode, have single photon detection capability. The structure of guard ring is the key factor to avoid the premature edge breakdown of the avalanche diode and increase the maximum bias voltage. A new structure of the guard ring is proposed in this letter, in which the floating guard ring is put outside the p-well guard ring. Simulation results indicate that the maximum bias voltage of the proposed guard ring is higher than that of the state-of-the-art methods.展开更多
To study ultrafast processes at the sub-picosecond level, novel methods based on coherent harmonic generation technologies have been proposed to generate ultrashort radiation pulses in existing ring-based light source...To study ultrafast processes at the sub-picosecond level, novel methods based on coherent harmonic generation technologies have been proposed to generate ultrashort radiation pulses in existing ring-based light sources. Using the High Energy Photon Source as an example, we numerically test the feasibility of implementing one coherent harmonic generation technology, i.e.,the echo-enabled harmonic generation(EEHG) scheme, in a diffraction-limited storage ring(DLSR). Two different EEHG element layouts are considered, and the effect of the EEHG process on the electron beam quality is also analyzed. Studies suggest that soft X-ray pulses, with pulse lengths of a few femtoseconds and peak powers of up to1 MW, can be generated by using the EEHG scheme, while causing little perturbation to the regular operation of a DLSR.展开更多
A theoretical analysis of a tuneable optical filter is presented by proposing an optical ring resonator (ORR) using photonic crystal fiber (PCF) as the resonance loop. The influences of the characteristic parameters o...A theoretical analysis of a tuneable optical filter is presented by proposing an optical ring resonator (ORR) using photonic crystal fiber (PCF) as the resonance loop. The influences of the characteristic parameters of the PCF on the filter response have been analyzed under steady-state condition of the ORR. It is shown that the tuneability of the filter is mainly achieved by changing the modulation frequency of the light signal applied to the resonator. The analyses have shown that the sharpness and the depth of the filter response are controlled by parameters such as amplitude modulation index of applied field, the coupling coefficient of the ORR, and hole-spacing and air-filling ratio of the PCF, respectively. When transmission coefficient of the loop approaches the coupling coefficient, the filter response enhances sharply with PCF parameters. The depth and the full-width half-maximum (FWHM) of the response strongly depends on the number of field circulations in the resonator loop. With the proposed tuneability scheme for optical filter, we achieved an FWHM of ~1.55 nm. The obtained results may be utilized in designing optical add/drop filters used in WDM communication systems.展开更多
基金Supported by the National Natural Science Foundation of China(12447143,12273116,62394350,and 62394351)science research grants from the China Manned Space Project(CMS-CSST-2021-A12 and CMS-CSST-2021-B10)+1 种基金Strategic Priority Research Program of the Chinese Academy of Sciences(XDA0350302)Opening Project of National Key Laboratory of Aerospace Flight Dynamics of China(KGJ6142210220201)。
文摘A horizonless ultracompact object can have a stable antiphoton sphere,which causes the photons inside the unstable photon sphere to strongly deflect,thereby leading to the formation of distinctive inner photon rings.In this study,we present analytical descriptions for the shape,thickness,and interference pattern of higher-order inner photon rings.By taking the static spherically symmetric Schwarzschild star with a photon sphere as an example,we find that its inner photon rings can be more non-circular and thicker than the outer ones and show that the inclusion of the inner photon rings can result in new features in the interferometric pattern.Further,our formulae can be applied to other ultracompact objects,providing a convenient approach for studying the observational properties of their higher-order photon rings.
基金J.P.is supported by the China Scholarship Council.M.G.is supported by National Natural Science Foundation of China(NSFC)(11947210)funded by China Postdoctoral Science Foundation(2019M660278)X.H.F.is supported by NSFC(11905157,11935009)。
文摘We calculate photon sphere r_(ph) and critical curve b_(c) for a quantum corrected Schwarzschild black hole,finding that they violate universal inequalities proved for asymptotically flat black holes that satisfy the null energy condition in the framework of Einstein gravity.This violation seems to be a common phenomenon when considering quantum modification of Einstein gravity.Furthermore,we study the shadows,lensing rings,and photon rings in the quantum corrected Schwarzschild black hole.The violation leads to a larger bright lensing ring in the observational appearance of the thin disk emission near the black hole compared with the classical Schwarzschild black hole.Our analysis may provide observational evidence for the quantum effect of general relativity.
文摘In this paper,we study the optical properties of asymmetric thin-shell wormholes(ATWs)under torsion charge.Utilizing the cut-and-paste method developed by Visser,we construct these wormholes and determine their key physical properties,such as the radius of the photon sphere and critical impact parameters,under different torsion charges.Furthermore,we investigate the effective potential and behavior of photon motion within the wormhole spacetime,identifying a relationship between photon trajectories and impact parameters.The study focuses on scenarios where thin accretion disks act as the primary light source.It reveals that the optical features of ATWs under torsion charge significantly differ from those of black holes(BHs).Notably,an increase in torsion charge leads to a reduction in the sizes of both extra photon rings and lensing bands,which serve as important markers for distinguishing and characterizing ATW spacetimes from those of BHs.
文摘In this paper,dual L defected hexagonal Photonic Crystal Ring Resonator(PCRR)using Channel Drop Filter(CDF)is designed for Coarse Wavelength Division Multiplexing(CWDM)systems.In this structure,the external rods of the ring resonator are arranged in a hexagon and the internal rods are removed in L arrangement for introducing defects.Scatter rods are used to prevent leakage.By using the L defected hexagonal resonator,a multi-channel CDF is designed,which exhibits multiple wavelengths of CWDM(1500 nm–1600 nm)region.In addition,the selection of rod size and the position of rods in the proposed multi-channel CDF are validated by varying the radius of coupling and scattering rods,as well as the position of resonators,respectively.By using plane wave expansion and opti Finite Difference Time Domain(FDTD)method,the electromagnetic wave propagation and the photonic band gap are obtained.
基金supported by the National Natural Science Foundation of China(No.61473022)
文摘A novel hybrid air-core photonic band-gap fiber(PBF) ring resonator with twin 90° polarization-axis rotated splices is proposed and demonstrated. Frist, we measure the temperature dependent birefringence coefficient of air-core PBF and Panda fiber. Experimental results show that the relative temperature dependent birefringence coefficient of air-core PBF is 1.42×10^(-8)/℃, which is typically ~16 times less than that of Panda fiber. Then, we extract the geometry profile of air-core PBF from scanning electron microscope(SEM) images. Numerical modal is built to distinguish the fast axis and slow axis in the fiber. By precisely setting the length difference in air-core PBF and Panda fiber between two 90° polarization-axis rotated splicing points, the hybrid air-core PBF ring resonator is constructed, and the finesse of the resonator is 8.4. Environmental birefringence variation induced by temperature change can be well compensated, and experimental results show an 18-fold reduction in thermal sensitivity, compared with resonator with twin 0° polarization-axis rotated splices.
文摘Avalanche photon diode and avalanche diode array, working in Geiger mode, have single photon detection capability. The structure of guard ring is the key factor to avoid the premature edge breakdown of the avalanche diode and increase the maximum bias voltage. A new structure of the guard ring is proposed in this letter, in which the floating guard ring is put outside the p-well guard ring. Simulation results indicate that the maximum bias voltage of the proposed guard ring is higher than that of the state-of-the-art methods.
基金supported by National Natural Science Foundation of China(No.11475202,11405187)the Youth Innovation Association of Chinese Academy of SciencesKey Research Program of Frontier Sciences,CAS(No.QYZDJ-SSW-SLH001)
文摘To study ultrafast processes at the sub-picosecond level, novel methods based on coherent harmonic generation technologies have been proposed to generate ultrashort radiation pulses in existing ring-based light sources. Using the High Energy Photon Source as an example, we numerically test the feasibility of implementing one coherent harmonic generation technology, i.e.,the echo-enabled harmonic generation(EEHG) scheme, in a diffraction-limited storage ring(DLSR). Two different EEHG element layouts are considered, and the effect of the EEHG process on the electron beam quality is also analyzed. Studies suggest that soft X-ray pulses, with pulse lengths of a few femtoseconds and peak powers of up to1 MW, can be generated by using the EEHG scheme, while causing little perturbation to the regular operation of a DLSR.
文摘A theoretical analysis of a tuneable optical filter is presented by proposing an optical ring resonator (ORR) using photonic crystal fiber (PCF) as the resonance loop. The influences of the characteristic parameters of the PCF on the filter response have been analyzed under steady-state condition of the ORR. It is shown that the tuneability of the filter is mainly achieved by changing the modulation frequency of the light signal applied to the resonator. The analyses have shown that the sharpness and the depth of the filter response are controlled by parameters such as amplitude modulation index of applied field, the coupling coefficient of the ORR, and hole-spacing and air-filling ratio of the PCF, respectively. When transmission coefficient of the loop approaches the coupling coefficient, the filter response enhances sharply with PCF parameters. The depth and the full-width half-maximum (FWHM) of the response strongly depends on the number of field circulations in the resonator loop. With the proposed tuneability scheme for optical filter, we achieved an FWHM of ~1.55 nm. The obtained results may be utilized in designing optical add/drop filters used in WDM communication systems.
