Beam-splitting Method Research Articles

Experimentation and Analysis of Intra-Cavity Beam-Splitting Method to Enhance the Uniformity of Light in the Powersphere

The powersphere is a spherical enclosed receiver composed of multiple photovoltaic cells. It serves as a replacement for traditional photovoltaic panels in laser wireless power transmission systems for optoelectronic conversion. The ideal powersphere aims to achieve a uniform distribution of light within the cavity through infinite reflections, reducing energy losses in the circuit. However, due to the high absorption rate of the photovoltaic cells, the direct irradiation area on the inner surface of the powersphere exhibits a significantly higher light intensity than the reflected area, resulting in a suboptimal level of light uniformity and certain circuit losses. To address the aforementioned issues, a method of intra-cavity beam splitting in the powersphere is proposed. This solution aims to increase the area of direct illumination and reduce the intensity difference between direct and reflected lights, thereby improving the light uniformity on the inner surface of the powersphere. Utilizing the transformation matrix of Gaussian beams, the q parameters for each optical path with beam splitting were calculated, and the equality of corresponding q values was demonstrated. Further, based on the q parameter expression for the electric field of Gaussian beams, the intensities for each optical path were calculated, and it was demonstrated that their values are equal. Additionally, an optical software was utilized to establish a model for intra-cavity beam splitting in the powersphere. Based on this model, a beam-splitting system was designed using a semi-transparent and semi-reflective lens as the core component. The light uniformity performance of the proposed system was analyzed through simulations. To further validate the effectiveness of the calculations, design, and simulations, multiple lenses were employed to construct the beam-splitting system. An experimental platform was set up, consisting of a semiconductor laser, monocrystalline silicon photovoltaic cells, beam expander, Fresnel lens, beam-splitting system, and powersphere. An experimental verification was conducted, and the results aligned with the theoretical calculations and simulated outcomes. The above theory, simulations, and experiments demonstrate that the intra-cavity beam-splitting method effectively enhances the optical uniformity within the powersphere.

Single line of sight frame camera based on the RadOptic effect of ultrafast semiconductor detector

A new optical beam splitting method is proposed, based on which the optical frame camera capable of capturing multiple frames in a single exposure is designed and experimentally verified. The operation of the frame camera is based on an ultra-fast response semiconductor detector. It is equipped with an optical beam splitter and an optical imaging module. The ultrafast semiconductor detector receives an optical pulse that produces a transient refractive index change, and ultrafast physical processes are recorded by diffracting the probe laser through the transient phase grating. The interaction of an X-ray pulse with a semiconductor detector to produce a phase grating is simulated, based on the Monte Carlo method. The optical beam splitting mode separates a laser into two optical pulses with a certain time difference in the direction of polarization perpendicular to each other. The imaging module filters the diffracted probe laser in the spectral plane and then images multiple frames. The frame camera was used to record the temporal and spatial distribution characteristics of femtosecond laser pulses with a temporal resolution of 4.1 ps. This frame camera has great potential and value for applying to experimental studies of inertial confinement fusion.

Ultra-high consistency multichannel SERF atomic magnetometer based on diffractive optics

Multichannel spin-exchange relaxation-free (SERF) atomic magnetometers (AMs) have broad application prospects in array biomagnetic measurement systems because of their high spatial resolution. This study proposed an efficient and high-quality beam-splitting method based on a diffractive optical element (DOE), which enables multichannel SERF AM to maintain ultrahigh consistency with a channel interval of 3.27 mm. Based on the relaxation rate model under zero-field resonance, the minor differences in the magnetic linewidth of each channel were analyzed. The experimental results demonstrated ultra-high consistency of the magnetic field measurement signals between multiple channels, with a nonlinear error of less than 0.1%. The optimal sensitivity for a single channel was 11.9 fT/Hz1/2 @31.5 Hz, and 9.3 fT/Hz1/2 @31.5 Hz in the first-order gradiometer mode. The structure also satisfied the requirements of long-term high stability and high sensitivity, which are expected to further obtain more measurement channels. This method plays a critical role in improving the accuracy of magnetocardiography (MCG) and magnetoencephalography (MEG) systems.

Wide range retina-like scanning based on liquid crystal optical phased array

A retina-like scanning method based on liquid crystal optical phased array (LCOPA) is proposed to improve field of view and efficiency. The functions of human retina, lens and fovea gaze control are achieved with optimized designed scanning strategy. Beam splitting method and angular magnification system are used to meet the requirements of the efficient scanning and large FOV. The models are verified by several experiments and the results show that the scanning performance well with the flexible retina-like strategy, especially for eccentric fovea. The scanning FOV is magnified 2.2 times and the average scanning error is less than 5%.

Height Measurement With Meter Wave MIMO Radar Based on Precise Signal Model Under Complex Terrain

Meter wave radar height measurement is one of the most difficult problems in meter wave radar system. At present, the most popular height measurement methods of meter wave radar include beam splitting method, MUSIC algorithm and maximum likelihood estimation method, which can achieve good performance under flat ground. However, the real ground is not ideal condition, and the situation of undulating ground is also very complicated. Under this condition, the performance of the above algorithm dropped sharply. Many researchers solve this problem by improving the robustness of the algorithm. However, the authors think that the key to solve the problem is to establish a refined height measurement signal model. In this paper, the accurate model of reflection coefficient, reflection height and reflection point under the condition of undulating ground are established to provide accurate signal model for meter wave radar height measurement. Then we deduce the application of generalized MUSIC algorithm and maximum likelihood estimation algorithm for MIMO radar in the accurate terrain signal model. In fact, the method proposed in this paper is a terrain matching MIMO radar target height measurement, and the traditional algorithm can be regarded as terrain mismatch. The simulation results show that the accuracy of terrain matching estimation of the precise signal model established in this paper is much better than that of the traditional simplified signal model.

An improved beam splitting method for intensity modulated proton therapy

The pencil beam algorithm (PBA) has become the predominant dose calculation method in proton therapy, due to its high level of efficiency. However, density heterogeneity decreases the accuracy of PBA. To improve PBA’s accuracy, a beam splitting method is used to divide the original scanning beam into multiple thinner beamlets. Beam splitting should ensure that the beamlets’ summed fluence is as close to the original beam fluence as possible, while keeping the spatial variance of beamlets small, and minimizing the number of beamlets. In this work, the generalized differential evolution (GDE) algorithm is utilized for the optimal scheme. Under reasonable constraints for the radius and weight of beamlets, several schemes are optimized via the GDE algorithm. In order to achieve a trade-off between accuracy and calculation speed, three hexagon-based schemes, which split the original beam into 7, 13, and 19 beamlets, respectively, are proposed and compared with the scheme of Raystation 4.5. The fluence distribution calculated by the schemes with 13 beamlets and 19 beamlets are demonstrated to be more accurate than the Raystation scheme, which has 19 beamlets, with a maximum absolute difference between the summed beamlets fluence and the original beam fluence of 2.12%, and 0.93%, respectively. Furthermore, beam splitting schemes are implemented into a proton dose calculation algorithm based on the KylinRay-IMPT TPS. These schemes, based on the dose algorithm, are compared with the Monte Carlo program TOPAS 3.2 in slab geometry with lateral heterogeneity. The dose, calculated by the dose algorithm using a scheme of 13 beamlets, shows a good agreement with the dose from TOPAS. In addition, an abdominal geometry is used for further verification. Gamma analysis passing rates greater than 99.7% are observed, with a 2%/2 mm criterion. Thus, the accuracy and effectiveness of the improved beam splitting method are preliminarily verified.

Neutron Zeeman beam-splitting for the investigation of magnetic nanostructures

Zeeman spatial splitting of a neutron beam takes place during a neutron spin-flip in magnetically non-collinear systems at grazing incidence geometry. We apply the neutron beam-splitting method for the investigation of magnetically non-collinear clusters of submicron size in a thin film. The experimental results are compared with ones obtained by other methods.

一种混合迭代算法在大离焦距离TIE相位恢复中的应用

The method of Raman-Nath symmetric beam splitting based on magnetically insensitive states and the scheme of internal state interference are proposed.The interference based on magnetically insensitive states is insensitive to the magnetic fluctuation,which is beneficial to the contrast enhancement of interference fringes.If such a Raman-Nath symmetric beam splitting method is applied in the path-conjugate atom gyroscope,the system noise is obviously reduced.By means of optimizing the symmetric-beam-splitting parameters of double pulses,it is possible to obtain a high diffraction efficiency.The scheme of internal state interference is successfully used to solve the problem of momentum state interference being susceptible to the environment.

Single-exposure polarization phase-shifting interferometer using an azo-polymer orientation array

We propose a single-exposure polarization phase-shifting interferometer based on a beam-splitting method using an azo-polymer orientation array, which is prepared from an ordinary azo-polymer film with photo-induced optical anisotropy. The azo-polymer orientation array gives a four-step phase shift on the interferogram, from which phase differences between the orthogonal polarized reference and object beam can be calculated. Experimental results are provided to verify the feasibility of the proposed interferometer. The azo-polymer orientation array is easy to fabricate, making this method convenient and low-cost.

Time-delayed beam splitting with energy separation of x-ray channels

We introduce a time-delayed beam splitting method based on the energy separation of x-ray photon beams. It is implemented and theoretically substantiated on an example of an x-ray optical scheme similar to that of the classical Michelson interferometer. The splitter/mixer uses Bragg-case diffraction from a thin diamond crystal. Another two diamond crystals are used as back-reflectors. Because of energy separation and a minimal number (three) of optical elements, the split-delay line has high efficiency and is simple to operate. Due to the high transparency of diamond crystal, the split-delay line can be used in a beam sharing mode at x-ray free-electron laser facilities.

Near-perfect sorting of orbital angular momentum and angular position states of light

We present a novel method for efficient sorting of photons prepared in states of orbital angular momentum (OAM) and angular position (ANG). A log-polar optical transform is used in combination with a holographic beam-splitting method to achieve better mode discrimination and reduced cross-talk than reported previously. Simulating this method for 7 modes, we have calculated an improved mutual information of 2.43 bits/photon and 2.29 bits/photon for OAM and ANG modes respectively. In addition, we present preliminary results from an experimental implementation of this technique. This method is expected to have important applications for high-dimensional quantum key distribution systems.

SU-FF-T-626: Dynamic Splitting of Gaussian Pencil Beams in Heterogeneity-Correction Algorithms for Radiotherapy with Heavy Charged Particles

Purpose: To develop an algorithm to resolve intrinsic problems with dose calculations using pencil beams when particles involved in each beam are overreaching a lateral density interface or when they are detouring in a laterally heterogeneous medium. Method and Materials: A finding on a Gaussian distribution, such that it can be approximately decomposed into multiple narrower, shifted, and scaled ones, was applied to dynamic splitting of pencil beams implemented in a dose calculation algorithm for proton and ion beams. The method was tested in an experiment with a range-compensated carbon-ion beam. Its effectiveness and efficiency were evaluated for carbon-ion and proton beams in a heterogeneous phantom model. Results: The splitting dose calculation reproduced the detour effect observed in the experiment, which amounted to about 10% at a maximum or as large as the lateral particle-disequilibrium effect. The proton-beam dose generally showed large scattering effects including the overreach and detour effects. The overall computational times were 9 s and 45 s for non-splitting and splitting carbon-ion beams and 15 s and 66 s for non-splitting and splitting proton beams. Conclusions: The beam-splitting method was developed and verified to resolve the intrinsic size limitation of the Gaussian pencil-beam model in dose calculation algorithms. The computational speed slowed down by factor of 5, which would be tolerable for dose accuracy improvement at a maximum of 10%, in our test case.

A Video Method to Study Drosophila Sleep

To use video to determine the accuracy of the infrared beam-splitting method for measuring sleep in Drosophila and to determine the effect of time of day, sex, genotype, and age on sleep measurements. A digital image analysis method based on frame subtraction principle was developed to distinguish a quiescent from a moving fly. Data obtained using this method were compared with data obtained using the Drosophila Activity Monitoring System (DAMS). The location of the fly was identified based on its centroid location in the subtracted images. The error associated with the identification of total sleep using DAMS ranged from 7% to 95% and depended on genotype, sex, age, and time of day. The degree of the total sleep error was dependent on genotype during the daytime (P < 0.001) and was dependent on age during both the daytime and the nighttime (P < 0.001 for both). The DAMS method overestimated sleep bout duration during both the day and night, and the degree of these errors was genotype dependent (P < 0.001). Brief movements that occur during sleep bouts can be accurately identified using video. Both video and DAMS detected a homeostatic response to sleep deprivation. Video digital analysis is more accurate than DAMS in fly sleep measurements. In particular, conclusions drawn from DAMS measurements regarding daytime sleep and sleep architecture should be made with caution. Video analysis also permits the assessment of fly position and brief movements during sleep.

Polarization structure of lidar signals reflected from ice crystal clouds

Polarization characteristics of signals of a monostatic lidar intended for sensing of homogeneous ice crystal clouds are calculated by the Monte Carlo method. Clouds are modeled as monodisperse ensembles of randomly oriented hexagonal ice crystals. The polarization state of multiply scattered lidar signal components is analyzed for different scattering orders depending on the crystal shapes and sizes as well as on the optical and geometrical conditions of observation. Light-scattering phase matrices (SPMs), calculated by the beam splitting method (BSM), are used as input data for solving the vector radiative transfer equation. The principles of the BSM method are briefly described, and the SPM components are given for hexagonal ice plates and columns of different sizes and linearly polarized incident radiation with the wavelength lambda = 0.55 microm.

Reflection and refraction of spin-flip neutrons in a Fe-Gd structure

Neutron reflection and refraction in the glass/Fe(1000 Å)/Gd(50 Å) structure were investigated in the regime of generating a neutron standing wave. The polarized neutron beam-splitting method has been used. An external magnetic field, changing within the range 18 Oe to 4.4 kOe at room temperature, was applied in the plane of the film. Three sequentially occurring neutron spin transitions were discovered. Two of them were accompanied with a momentum transfer in the plane of the film, and the third was accompanied with a momentum transfer in the direction perpendicular to the plane. This can be explained by the existence of a domain structure where the magnetization vector is directed out of the film plane.

Calculations on modulation transfer function of a read-only optical disk system with super resolution

Simulations have been performed for signal reproduction from a read-only super resolution optical disk using a beam splitting method, in which a collimated laser beam generated by a laser diode is split into two beams with orthogonal polarizations and then recombined using polarizing beamsplitters. The beam with a higher power is used to raise the temperature of the mask layer, while the one with a lower power is employed to reproduce the recorded data. Tilting one of the laser beams against the other results in two laser spots partially overlapped at the focal plane, and the distance between the center of the two spots can be controlled by a galvanomirror. This allows signal readout with maximum resolution independent of the disk rotation speed.