Spherical Micro-lens Array of PMMA Produced by Micro-molding

Micro-lens （ML） and Micro-lens array （MLA） are important optical components widely used in many fields; Soft-lithography, a vital little process technology, has its unique performance to produce ML and MLA; The cylinder and spherical MLA of polymethyl methacrylate （PMMA） were successfully obtained by micromolding inSoft-lithography. Some suitable experimental parameters in the process were discussed, and the imaging property of the MLA was also studied simply.

Wideband acoustic source localization using multiple spherical arrays : anangular-spectrum smoothing approach

A novel algorithm using multiple spherical arrays based on spherical harmonic analysis is proposed to localize wideband acoustic sources. In the novel spherical harmonic algorithm, the re- ceived microphone signals are firstly used to do the spherical Fourier transformation. Then, the mul- tiple signal classification （MUSIC） algorithm is applied to the spherical components to obtain the an- gular-spectrum. Finally, the angular-spectrum smoothing technique is proposed to obtain the accu- rate localization of wideband sources. In contrast to the traditional single spherical array, the multi- pie spherical arrays used in this paper consist of several randomly distributed spheres in a given plane. The microphones are uniformly placed on each sphere, the same as the usual single spherical array. Simulation comparison of wideband sources localization between a single spherical array and multiple spherical arrays based on the novel algorithm is carried out to validate our proposed meth- od.

Magnetic field of mathematical modeling and simulation of 3D magnetic pole array spherical actuator

In this paper a new spherical actuator is designed and its advantages are compared to an existing spherical actuator, which function is limited by several design bottlenecks. First the output torque is too small. Second, the attitude is difficult to be accurately detected. The new three-dimen- sional magnetic pole array can solve these major problems. The new actuator features an outer rotor with multiple permanent magnet （PM） poles. Using an analytical solution and the finite element so- lution simulation, the feasibility of the approach is verified. A prototype was developed, tested, and experiments were conducted to obtain the practical value of the magnetic flux density.

Modular Extremely Large-Scale Array Communication:Near-Field Modelling and Performance Analysis

This paper investigates the wireless communication with a novel architecture of antenna arrays,termed modular extremely large-scale array(XLarray),where array elements of an extremely large number/size are regularly mounted on a shared platform with both horizontally and vertically interlaced modules.Each module consists of a moderate/flexible number of array elements with the inter-element distance typically in the order of the signal wavelength,while different modules are separated by the relatively large inter-module distance for convenience of practical deployment.By accurately modelling the signal amplitudes and phases,as well as projected apertures across all modular elements,we analyse the near-field signal-to-noise ratio(SNR)performance for modular XL-array communications.Based on the non-uniform spherical wave(NUSW)modelling,the closed-form SNR expression is derived in terms of key system parameters,such as the overall modular array size,distances of adjacent modules along all dimensions,and the user's three-dimensional(3D)location.In addition,with the number of modules in different dimensions increasing infinitely,the asymptotic SNR scaling laws are revealed.Furthermore,we show that our proposed near-field modelling and performance analysis include the results for existing array architectures/modelling as special cases,e.g.,the collocated XL-array architecture,the uniform plane wave(UPW)based far-field modelling,and the modular extremely large-scale uniform linear array(XL-ULA)of onedimension.Extensive simulation results are presented to validate our findings.

A non-two-dimensional van der Waals In Se semispherical array grown by vapor-liquid-solid method for hydrogen evolution

Two-dimensional(2D)layered materials with layer-number dependent properties are promising candidates for next-generation noble-metal-free electrocatalytic reaction.However,the main group metal chalcogenides(MMCs)used for this purpose are rarely explored.Herein,we report the controlled growth of indium selenide(In Se)with a novel morphology(semispherical array)on a silicon substrate and its application in hydrogen evolution reaction(HER).The formation of the spherical InSe is explained with a vapor-liquid-solid growth mechanism,in which the distribution and size of the spheres could be facilely tuned by the reaction parameters.The InSe semispherical array was demonstrated as more efficient catalyst for HER than the flake-like 2D InSe counterparts,originating from the fully exposed InSe spherical surface with abundant adsorbing sites and the high crystalline quality for electron transport.This work provides a controlled synthesis way of the layered In Se with a distinct spherical morphology used for the electrocatalysis applications and could be extended to other main group metal chalcogenides.

High-speed, large-area and high-precision fabrication of aspheric micro-lens array based on 12-bit direct laser writing lithography

Aspheric micro-lens array(AMLA),featured with low dispersion and diffraction-limited imaging quality,plays an important role in advanced optical imaging.Ideally,the fabrication of commercially applicable AMLAs should feature low cost,high precision,large area and high speed.However,these criteria have been achieved only partially with conventional fabrication process.Herein,we demonstrate the fabrication and characterization of AMLAs based on 12-bit direct laser writing lithography,which exhibits a high fabrication speed,large area,perfect lens shape control via a three-dimensional optical proximity correction and average surface roughness lower than 6 nm.In particular,the AMLAs can be flexibly designed with customized filling factor and arbitrary off-axis operation for each single micro-lens,and the proposed pattern transfer approach with polydimethylsiloxane(PDMS)suggests a low-cost way for mass manufacturing.An auto-stereoscopic-display flexible thin film with excellent display effect has been prepared by using above technology,which exhibits a new way to provide flexible auto-stereoscopic-display at low cost.In brief,the demonstrated fabrication of AMLAs based on direct laser writing lithography reduce the complexity of AMLA fabrication while significantly increasing their performance,suggesting a new route for high-quality three-dimentional optical manufacturing towards simplified fabrication process,high precision and large scale.

High-intensity focused ultrasound with large scale spherical phased array for the ablation of deep tumors

Under some circumstances surgical resection is feasible in a low percentage for the treatment of deep tumors. Nevertheless, high-intensity focused ultrasound （HIFU） is beginning to offer a potential noninvasive alternative to conventional therapies for the treatment of deep tumors. In our previous study, a large scale spherical HIFU-phased array was developed to ablate deep tumors. In the current study, taking into account the required focal depth and maximum acoustic power output, 90 identical circular PZT-8 elements （diameter=1.4 cm and frequency=l MHz） were mounted on a spherical shell with a radius of curvature of 18 cm and a diameter of 21 cm. With the developed array, computer simulations and ex vivo experiments were carried out. The simulation results theoretically demonstrate the ability of the array to focus and steer in the specified volume （a 2 cm×2 cm×3 cm volume） at the focal depth of 15 to 18 cm. Ex vivo experiment results also verify the capability of the developed array to ablate deep target tissue by either moving single focal point or generating multiple foci simultaneously.

Crosstalk-free integral imaging display based on double plano-convex micro-lens array

A crosstalk-free integral imaging display consisting of a display panel and double piano-convex micro-lens array is proposed. The double piano-convex micro-lens array includes two micro-lens arrays, A and B. Micro-lens array A is used to eliminate crosstalk by completely reflecting crosstalk lights. Micro-lens array B, located near microqens array A, is used to display three-dimensional images. Computer simulations based on ray-tracing are conducted. Crosstalk-free reconstruction images may be clearly observed from the simulation results.

Direct generation of a stable multi-beam pulsed 355 nm UV laser based on a micro-lens array

Multi-beam laser processing is a very popular method to improve processing efficiency. For this purpose, a compact and stable multi-beam pulsed 355 nm ultraviolet(UV) laser based on a micro-lens array(MLA) is presented in this Letter. It is worth noting that the MLA is employed to act as the spatial splitter as well as the coupling lens. With assistance of the MLA,the 1064 nm laser and 532 nm laser are divided into four sub-beams and focused at different areas of the third-harmonic generation(THG) crystal. As a result, the multi-beam pulsed 355 nm UV laser is successfully generated inside the THG crystal. The measured pulse widths of four sub-beams are shorter than 9 ns. Especially, the generated four sub-beams have good long-term power stability benefitting from the employed MLA. We believe that the generated stable multi-beam355 nm UV laser can meet the requirement of high-efficiency laser processing, and the presented method can also pave the way to generate stable and long-lived multi-beam UV lasers.

A Novel Artificial Superposition Compound Eye

A new artificial superposition compound eye model is presented based on micro-lens array. In all compound eyes,it has the advantages of small volume,light weight,wide FOV,high sensitivity and much higher energy utilization ratio. Nevertheless,its structure is relatively complicated,especially the GRIN medium in the crystalline cone. Therefore,the modeling,analysis and fabrication for it are burdensome. In the established model,the GRIN is replaced by a curved micro-lens array. Thus,the modeling,analysis and optimization process are simple,and the components of artificial superposition compound eye are easy to be fabricated. The system is modeled by ZEMAX software. With the help of raytracing,its principle is analyzed,and the sensitivity comparison between the superposition compound eye and the apposition compound eye is done. The model's validity is proven.

Self-organized voids revisited:Experimental verification of the formation mechanism

We conduct several experiments to further clarify the formation mechanism of a self-organized void array induced by a single laser beam, including energy-related experiments, refractive-index-contrast-related experiments, depth-related ex- periments, and effective-numerical-aperture experiment. These experiments indicate that the interface spherical aberration is indeed responsible for the formation of void arrays.

Measurement.Based Spatial-Consistent Channel Modeling Involving Clusters of Scatterers

In this paper,the conventional method of establishing spatial channel models(SCMs)based on measurements is extended by including clusters-of-scatterers(CoSs)that exist along propagation paths.The channel models resulted utilizing this new method are applicable for generating channel realizations of reasonable spatial consistency,which is required for designing techniques and systems of the fifth generation wireless communications.The scatterers’locations are estimated from channel measurement data obtained using large-scale antenna arrays through the Space-Alternating Generalized Expectation-Maximization(SAGE)algorithm derived under a spherical wavefront assumption.The stochastic properties of CoSs extracted from real measurement data in an indoor environment are presented.

Multi-element Ultrasound Phased Array Applicator for the Ablation of Deep-seated Tissue

High-intensity focused ultrasound (HIFU) has attracted increasing interests as a promising noninvasive modality for the treatment of deep tumors in the thoracic and abdominal cavity.A 90-element HIFU spherical phased array applicator operated at 1 MHz has been developed for deep tissue ablation.The spherical array with a 5 cm wide central hole has a 21 cm diameter and an 18 cm radius of curvature.Annular element distribution with unequal element spacing is used to reduce the number of elements.The array is constructed with piezoelectric lead zirconate titanate (PZT-8) circular elements that are 1.4 cm in diameter and have a wall with thickness of 0.2 cm.The array offers an effective ablating depth of at least 8 cm in the tissue for both simulations and ex vivo experiments.The simulations demonstrate that the developed array can steer the focus with good quality of intensity distributions up to 6 mm off center over ranges from 17 to 21 cm when the water depth is set at 11 cm.We also present the beam focusing capability in deep tissue through a series of ex vivo experiments by measuring discoloration areas after sonications.These results indicate that the developed array is ideal for the ablation of deep-seated tissue.