Optical vortex is a kind of unique structure light with a helical phase distribution and contains orbital angular momentum. It has been found a myriad of important applications of optical vortex, such as micromanipulation, remote sensing and communication. In recent years, there are many researches on the particle manipulation based on the orbital angular momentum of optical vortex. Especially, there is a new kind of optical vortex which is so-called “perfect” vortex whose ring radius is independent of its topological charge has an outstanding performance on the micromanipulation. However, the exist experiments can only realize manipulation of particle and the rotation speed is difficult to obtain. In this paper, we proposed a new scheme which can manipulate the particle and simultaneously detect its rotation speed. We employ the superposition perfect vortex as the probe beam. It is worth to note that the topological charge of the perfect vortex we used has an opposite sign and different magnitude. Therefore, the probe beam possesses remaining orbital angular momentum and can generate the rotational Doppler effect. The rotational Doppler effect is the basics of rotation speed detection. A corresponding experiment has been conducted to verify our method. The results have confirmed the existence of orbital angular momentum of superposition optical vortex with different topological charge. Our scheme can realize manipulation and detection the rotation speed of the particle simultaneously. It is an important supplement on the micromanipulation and maybe useful in the optical gyroscope technique.
In order to study the method of optical vortex generation by cascaded spiral phase plates, theoretical analysis, simulations and experimental demonstration of this method are presented. Firstly, theory of optical vortex generation by cascaded spiral phase plates is analyzed. Secondly, an optical vortex generation setup is built, then two experimental groups of optical vortex generation is proposed and generation with single spiral phase plate is set as a control group. On this basis, correlation model is set up, then relative intensity and beam radius with propagation distance are simulated. Simulated graphs of relative intensity and optical radius with propagation distance are plotted and the related rate of change is calculated, initially proving the advantages of cascaded spiral phase plates. Finally, law of relative intensity and optical radius changing of optical vortex with topological charges 5 is studied based on experimental groups and control group, verifying the advantages of optical vortex generation, i.e., law of relative intensity and optical radius changing by cascaded spiral phase plates. By contrast of experimental results, the best configuration of cascaded spiral phase plates is settled.
The vortex light containing orbital angular momentum (OAM) has important application prospects in precision measurement, micro particle manipulation and basic physics. Because the Poynting vector of the vortex wave is not in line with the direction of the optical axis, more information is contained in the echo than the ordinary electromagnetic wave, so it has a unique advantage in the detection of unknown object. The wave propagation characteristics of the vortex beam are modeled and analyzed. Based on the Michelson interference principle, a new type of vortex light interference scheme is designed. The measurement scheme of the wavelength of the vortex light is proposed and the experimental verification is carried out. On this basis, a new method for detecting non-cooperative targets in space is proposed and analyzed theoretically. It provides a new way for measuring angular velocity of objects by vortex optics, and lays a good foundation for remote sensing of non-cooperative targets in actual demand in the future.
In the traditional systematic calibration of inertial devices, the calibration path is designed by the reclosing of the IMU sensitive axis and the turntable rotation axis. The rotation axis is 1 times per rotation, and only 2 sensitive axis positions are changed. In order to effectively motivate the error items of inertial devices, an IMU off-axis installation structure is designed. The rotation axis of the turntable is 1 times per rotation, and 3 sensitive axis positions can be changed at the same time. On this basis, a systematic calibration scheme for inertial devices based on IMU off-axis transposition is designed. A 30 dimensional system errors model including 24 error terms, such as gyro and accelerometer constant errors, installation errors and scale factor errors, is set up. The observability of each state in each calibration path is analyzed by piece-wise constant system (PWCS) and singular value decomposition (SVD) method. Compared with the traditional classical systematic calibration scheme, the proposed scheme can not only realize the full dimensional observation of the state, but also the observability of each state is higher on the whole than that of the traditional scheme. In the process of using filter to calibrate inertial devices, the calibration time is shorter and the precision is higher, and the number of turntable axes required for the proposed scheme is changed from three axis to double axis, which reduces the requirements for hardware conditions.
The motion of soliton centroid in two-dimensional (2D) Bose-Einstein condensate (BEC) is investigated by using the time-dependent variational method in this paper. Similar to the classical 2D harmonic oscillator’s motion equation, the Gaussian trial function with wavepacket centroid coordinates is chosen to get the motion equation of centroid. The Lissajous figures of trajectory are discovered for the first time by solving the motion equations of different initial conditions. This not only proves that the matter wave soliton possesses the motion characteristics of classical particles and shows macroscopic quantum properties, but also provides a new tool for the study of BEC.