Orbital Angular Momentum(OAM)waves are characterized by helical wave fronts and orthogonality between different modes.Therefore,OAM waves have huge potential in improving wireless communications'channel capacity a...Orbital Angular Momentum(OAM)waves are characterized by helical wave fronts and orthogonality between different modes.Therefore,OAM waves have huge potential in improving wireless communications'channel capacity and radar imaging's resolution.Consequently,the generation and application of OAM waves have attracted a lot of attention.And many methods are proposed to generate OAM waves.Although antenna array is the most popular method of generating OAM waves,OAM waves generated by antenna array have redundant modes.However,all advantages of OAM waves are closely related to infinite OAM modes.Thus,to better apply OAM waves to wireless communications and radar,it is very important to reduce unnecessary OAM modes and improve the OAM mode purity.In order to improve the OAM mode purity,two combined antenna arrays composed of X direction antenna and Y direction antenna array are proposed in this paper.The X direction antenna array and the Y direction antenna array are supplied by the excitations with the same amplitude and fixed phase shift.The overall phase shift of the X direction antenna array isπ/2 more or less than that of the Y direction antenna array.The results of formulas and antenna models in CST show that the combined antenna arrays can generate OAM waves with less redundant modes in x component,y component and z component.Besides,the z component carries pure OAM modes.展开更多
Spectrally uncorrelated biphotons are the essential resources for achieving various quantum information processing protocols.We theoretically investigate the generation of spectrally uncorrelated biphotons emitted by ...Spectrally uncorrelated biphotons are the essential resources for achieving various quantum information processing protocols.We theoretically investigate the generation of spectrally uncorrelated biphotons emitted by spontaneous fourwave mixing from a fiber nonlinear interferometer which consists of an N-stage nonlinear gain fiber and an(N-1)-stage dispersion modulation fiber.The output biphoton states of nonlinear interference are the coherent superposition of various biphoton states born in each nonlinear fiber,and thus the interference fringe will reshape the biphoton joint spectra.As a result,resorting to Taylor expansion to first order for phase mismatching,we theoretically verify that the orientation of phase matching contours will rotate in a specific way with only varying the length of dispersion modulation fiber.The rotation in orientation of phase matching contours may result in spectrally uncorrelated biphotons and even arbitrary correlation biphotons.Further,we choose micro/nanofiber as the nonlinear gain fiber and single-mode communication fiber as dispersion modulation fiber to numerically simulate the generation of spectrally uncorrelated biphotons from spontaneous fourwave mixing.Here,due to significant frequency detuning(hundreds of THz),Raman background noise can be considerably suppressed,even at room temperature,and photons with largely tunable wavelengths can be achieved,indicating a practicability in many quantum fields.A photon mode purity of 97.2%will be theoretically attained without weakening the heralding nature of biphoton sources.We think that this fiber nonlinear interference with the flexibly engineered quantum state can be an excellent practical source for quantum information processing.展开更多
Dual-polarization(DP)vortex waves(VWs)are widely applied in optical,electromagnetic,and quantum science owing to their ability to simultaneously convey two distinct and non-interfering orbital angular momentums(OAMs)....Dual-polarization(DP)vortex waves(VWs)are widely applied in optical,electromagnetic,and quantum science owing to their ability to simultaneously convey two distinct and non-interfering orbital angular momentums(OAMs).Here,we propose a lightweight levitated meta-atom to achieve 360°phase control with a difference of no more than 1°while maximizing the reflection efficiency.In combination with convergent phase modulation,a OAM metasurface array that facilitates the generation of DP VWs with high mode purity and low divergence angles was designed.The measured DP VW bearing mode l=1 had only 4°divergence angle and 84%mode purity at 5.8 GHz.Furthermore,DP VWs with integer,fractional(l=1.5)and higher order(l=8)modes are discussed based on an OAM purity spectrum analysis.The experimental results were consistent with the simulation results,demonstrating the practicality of the proposed DP OAM metasurface and its potential applications in the field of multithreaded communication systems.展开更多
基金supported by the National Science Foundation of China(NSFC 62073334).
文摘Orbital Angular Momentum(OAM)waves are characterized by helical wave fronts and orthogonality between different modes.Therefore,OAM waves have huge potential in improving wireless communications'channel capacity and radar imaging's resolution.Consequently,the generation and application of OAM waves have attracted a lot of attention.And many methods are proposed to generate OAM waves.Although antenna array is the most popular method of generating OAM waves,OAM waves generated by antenna array have redundant modes.However,all advantages of OAM waves are closely related to infinite OAM modes.Thus,to better apply OAM waves to wireless communications and radar,it is very important to reduce unnecessary OAM modes and improve the OAM mode purity.In order to improve the OAM mode purity,two combined antenna arrays composed of X direction antenna and Y direction antenna array are proposed in this paper.The X direction antenna array and the Y direction antenna array are supplied by the excitations with the same amplitude and fixed phase shift.The overall phase shift of the X direction antenna array isπ/2 more or less than that of the Y direction antenna array.The results of formulas and antenna models in CST show that the combined antenna arrays can generate OAM waves with less redundant modes in x component,y component and z component.Besides,the z component carries pure OAM modes.
基金Project supported by the Science and Technology Key Project of Henan Province,China(Grant No.182102210577)the National Natural Science Foundation of China(Grant No.61605249)。
文摘Spectrally uncorrelated biphotons are the essential resources for achieving various quantum information processing protocols.We theoretically investigate the generation of spectrally uncorrelated biphotons emitted by spontaneous fourwave mixing from a fiber nonlinear interferometer which consists of an N-stage nonlinear gain fiber and an(N-1)-stage dispersion modulation fiber.The output biphoton states of nonlinear interference are the coherent superposition of various biphoton states born in each nonlinear fiber,and thus the interference fringe will reshape the biphoton joint spectra.As a result,resorting to Taylor expansion to first order for phase mismatching,we theoretically verify that the orientation of phase matching contours will rotate in a specific way with only varying the length of dispersion modulation fiber.The rotation in orientation of phase matching contours may result in spectrally uncorrelated biphotons and even arbitrary correlation biphotons.Further,we choose micro/nanofiber as the nonlinear gain fiber and single-mode communication fiber as dispersion modulation fiber to numerically simulate the generation of spectrally uncorrelated biphotons from spontaneous fourwave mixing.Here,due to significant frequency detuning(hundreds of THz),Raman background noise can be considerably suppressed,even at room temperature,and photons with largely tunable wavelengths can be achieved,indicating a practicability in many quantum fields.A photon mode purity of 97.2%will be theoretically attained without weakening the heralding nature of biphoton sources.We think that this fiber nonlinear interference with the flexibly engineered quantum state can be an excellent practical source for quantum information processing.
基金supported by the Key Research and Development Program of Shaanxi Province(No.2022GDTSLD-64).
文摘Dual-polarization(DP)vortex waves(VWs)are widely applied in optical,electromagnetic,and quantum science owing to their ability to simultaneously convey two distinct and non-interfering orbital angular momentums(OAMs).Here,we propose a lightweight levitated meta-atom to achieve 360°phase control with a difference of no more than 1°while maximizing the reflection efficiency.In combination with convergent phase modulation,a OAM metasurface array that facilitates the generation of DP VWs with high mode purity and low divergence angles was designed.The measured DP VW bearing mode l=1 had only 4°divergence angle and 84%mode purity at 5.8 GHz.Furthermore,DP VWs with integer,fractional(l=1.5)and higher order(l=8)modes are discussed based on an OAM purity spectrum analysis.The experimental results were consistent with the simulation results,demonstrating the practicality of the proposed DP OAM metasurface and its potential applications in the field of multithreaded communication systems.
