The gravimeter inclination is a significant parameter for cold atom gravimeters,and the counter-propagating Raman beams should be exactly parallel to the local vector of gravity.The tiltmeters,essential devices in col...The gravimeter inclination is a significant parameter for cold atom gravimeters,and the counter-propagating Raman beams should be exactly parallel to the local vector of gravity.The tiltmeters,essential devices in cold atom gravimeters,are used to determine the optimum inclination of Raman beams and compensate for the inclination error.However,the conventional tiltmeters may lead to system errors in cold atom gravimeters due to insufficient nonlinearity and drift.In this study,we establish an optical interferometer inside the cold atom gravimeter by placing a hollow beam splitter plate in the path of the Raman beams.This optical interferometer acts as a tiltmeter to measure the inclination change of the Raman beams without influencing the gravity measurement.We prove that our optical tiltmeter(OT)works well with field assembly.Comparisons of our OT and commercial tiltmeters reveal that the nonlinearity of our OT is at least one-tenth of that of the commercial tiltmeters,and that the drift of our OT is at least 23μrad less than that of the commercial tiltmeters over 90 h measurements.This can reduce the typical value of the atom gravimeter system error by 4μGal.Further,a comparison of measured gravity to inclination deviation calibrated our OT and further validated that our OT outperforms commercial tiltmeters.This work enables more precise measurement of Raman beam angle variations and facilitates the calibration of installed tiltmeters,whether in the laboratory or the field.展开更多
In this study,we design and numerically investigate a novel all optical D flip-flop(AODFF)based on linear photonic crystal(LPhC)structure that is composed of optical waveguides using the finite difference time domain(...In this study,we design and numerically investigate a novel all optical D flip-flop(AODFF)based on linear photonic crystal(LPhC)structure that is composed of optical waveguides using the finite difference time domain(FDTD)method.The proposed structure has the hexagonal close packed of 16×20 circular rods that are suspended in the air substrate with a lattice constant of 606 nm.The plane wave expansion(PWE)method is used to obtain the band diagram for AODFF at an operating wavelength of 1550 nm.The proposed optical flip-flop achieves a low delay time of 0.2 ps and a high contrast ratio(CR)of 10.33 dB.The main advantage of this design is that the input power as low as 1 mW/μm^(2) is sufficient for its operation,since no nonlinear rods are included.In addition,the footprint of the proposed AODFF is 100μm^(2),which is smaller compared to the structures reported in the literature,and it has a fast switching frequency of 5 Tbit/s.展开更多
To obtain a good interference fringe contrast and high fidelity,an automated beam iterative alignment is achieved in scanning beam interference lithography(SBIL).To solve the problem of alignment failure caused by a l...To obtain a good interference fringe contrast and high fidelity,an automated beam iterative alignment is achieved in scanning beam interference lithography(SBIL).To solve the problem of alignment failure caused by a large beam angle(or position)overshoot exceeding the detector range while also speeding up the convergence,a weighted iterative algorithm using a weight parameter that is changed linearly piecewise is proposed.The changes in the beam angle and position deviation during the alignment process based on different iterative algorithms are compared by experiment and simulation.The results show that the proposed iterative algorithm can be used to suppress the beam angle(or position)overshoot,avoiding alignment failure caused by over-ranging.In addition,the convergence speed can be effectively increased.The algorithm proposed can optimize the beam alignment process in SBIL.展开更多
基金supported by the National Natural Science Foundation of China(Nos.U2341246,U24A20319,2022010202,and 61875175)the National Key Research and Development Program of China(No.2023YFC2907000)+1 种基金the Research and Application Experiment of Carrying Measurement and Support Technology for Ocean Route(No.DD2021085)the Fundamental Research Funds for Key Laboratory of State Administration for Market Regulation of China(No.AKYKF2302)。
文摘The gravimeter inclination is a significant parameter for cold atom gravimeters,and the counter-propagating Raman beams should be exactly parallel to the local vector of gravity.The tiltmeters,essential devices in cold atom gravimeters,are used to determine the optimum inclination of Raman beams and compensate for the inclination error.However,the conventional tiltmeters may lead to system errors in cold atom gravimeters due to insufficient nonlinearity and drift.In this study,we establish an optical interferometer inside the cold atom gravimeter by placing a hollow beam splitter plate in the path of the Raman beams.This optical interferometer acts as a tiltmeter to measure the inclination change of the Raman beams without influencing the gravity measurement.We prove that our optical tiltmeter(OT)works well with field assembly.Comparisons of our OT and commercial tiltmeters reveal that the nonlinearity of our OT is at least one-tenth of that of the commercial tiltmeters,and that the drift of our OT is at least 23μrad less than that of the commercial tiltmeters over 90 h measurements.This can reduce the typical value of the atom gravimeter system error by 4μGal.Further,a comparison of measured gravity to inclination deviation calibrated our OT and further validated that our OT outperforms commercial tiltmeters.This work enables more precise measurement of Raman beam angle variations and facilitates the calibration of installed tiltmeters,whether in the laboratory or the field.
文摘In this study,we design and numerically investigate a novel all optical D flip-flop(AODFF)based on linear photonic crystal(LPhC)structure that is composed of optical waveguides using the finite difference time domain(FDTD)method.The proposed structure has the hexagonal close packed of 16×20 circular rods that are suspended in the air substrate with a lattice constant of 606 nm.The plane wave expansion(PWE)method is used to obtain the band diagram for AODFF at an operating wavelength of 1550 nm.The proposed optical flip-flop achieves a low delay time of 0.2 ps and a high contrast ratio(CR)of 10.33 dB.The main advantage of this design is that the input power as low as 1 mW/μm^(2) is sufficient for its operation,since no nonlinear rods are included.In addition,the footprint of the proposed AODFF is 100μm^(2),which is smaller compared to the structures reported in the literature,and it has a fast switching frequency of 5 Tbit/s.
基金The research was supported by the National Natural Science Foundation of China(NSFC)(Grant No.61227901)Jilin Province Science&Technology Development Program Project in China(Grant No.20190103157JH).
文摘To obtain a good interference fringe contrast and high fidelity,an automated beam iterative alignment is achieved in scanning beam interference lithography(SBIL).To solve the problem of alignment failure caused by a large beam angle(or position)overshoot exceeding the detector range while also speeding up the convergence,a weighted iterative algorithm using a weight parameter that is changed linearly piecewise is proposed.The changes in the beam angle and position deviation during the alignment process based on different iterative algorithms are compared by experiment and simulation.The results show that the proposed iterative algorithm can be used to suppress the beam angle(or position)overshoot,avoiding alignment failure caused by over-ranging.In addition,the convergence speed can be effectively increased.The algorithm proposed can optimize the beam alignment process in SBIL.
