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1

Design and analysis of multi-angle diffraction efficiency distribution for all-dielectric transmissive grating

Zhu Jiaze, Feng Huizhen, Huang Wenkang, Xu Jianfeng, Tian Ying, Jia Mian, Gu Manna

Optica Applicata

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2025

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Vol. 55, nr 2

225--239

EN

This paper presents the design of a C-shaped all-dielectric metasurface. The C-shaped dielectric structure and its substrate materials are Si and SiO2, respectively. This unit structure enables independent control of the amplitude and phase of cross-polarized transmitted terahertz electromagnetic waves. Byusing parameter scanning method, four different unit structures were optimized at 0.1 and 1 THz, achieving unit phase distributions with a 45° interval within the range of 0° to 180°. Additionally, a 180° phase jump occurs when the unit structure rotates by 90°, achieving full phase control over the 360° range. By adjusting the orientation of the unit structure, arbitrary amplitude control can also be achieved. The highest transmission coefficients for the unit structures at 0.1 and 1 THz are 0.62 and 0.56, respectively. To verify the control capability of the designed unit structure on transmitted electromagnetic waves, metasurface gratings were designed based on these unit structures, enabling arbitrary control of diffraction angles and orders. At both frequencies, two different metasurface gratings were designed with diffraction orders of (m = +1) and (m = +1, +3). Near-field and far-field simulations of the super-grating structures were conducted using the finite integral method. The designed metasurface grating demonstrates effective control of cross-polarized transmitted waves, and its deflection angles conform to diffraction laws.

2

Broadband convolutional scattering characteristics of all dielectric transmission Pancharatnam–Berry geometric phase metasurfaces

Li Yiyun, Jin Yongxing, Jing Xufeng, Shi Lijiang, Li Chenxia, Hong Zhi

Optica Applicata

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2022

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Vol. 52, nr 2

297--323

EN

In order to obtain the broadband scattering characteristics, we propose a superperiodic cell structure with all-dielectric material to construct Pancharatnam–Berry geometric phase encoding metasurfaces. Because we cannot design or prepare infinitesimal coding unit particles, according to the generalized Snell’s law, we can only obtain discrete scattering angle regulation for the basic coding metasurface sequence. In order to obtain multi-angle scattering characteristics, we introduce the Fourier convolution principle in digital signal processing on the Pancharatnam–Berry geometric phase encoding metasurfaces. By using the addition and subtraction operations on two encoding metasurface sequences, a new encoding metasurface sequence can be obtained with different deflection angle. Fourier convolution operations on the encoding metasurfaces can provide an efficient method in optimizing encoding patterns to achieve continuous scattering beams. The addition and subtraction methods are also applicable to the checkerboard coding mode. The combination of Fourier convolution principle and Pancharatnam–Berry phase coded metasurface in digital signal processing can realize more powerful electromagnetic wave manipulation capability.

3

Emission-intensity-enhanced GaN-based LED based on multilayer grating structures

Li Xin, Sun Dejie, Han Kun, Cao Lijun, Guo Shiliang, Li Zhiquan

Optica Applicata

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2021

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Vol. 51, nr 4

529--540

EN

A novel surface-plasmon-enhanced GaN-LED is proposed to improve the emission efficiency of the traditional LED. The SiO2 film, Ag triangular structure and ITO film were coated on the rectangularly-patterned p-GaN layer sequentially, which can form the quasi-symmetrical waveguide structure to enhance the internal quantum efficiency and the light extraction efficiency. The COMSOL software is used to simulate the LED structure. The radiated powers, absorbed powers and distribution of electric field are obtained and analyzed. The results reveal that emission efficiency of the proposed GaN-LED can be greatly improved.

4

An improved cordic for digital subdivision of Moiré signal

Zhu Weibin, Ye Shengjin, Huang Yao, Xue Zi

Metrology and Measurement Systems

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2020

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Vol. 27, nr 1

51--64

EN

The contradiction between the restriction of grating manufacturing technology and high-resolution measurement requirements has been the focus of attention. The precision requirement of angle calculation during the digital subdivision processing of a Moiré signal is focused on, the causes of errors in the solution of arcsine function are analysed, and an improved coordinate rotation digital computer (CORDIC) with double-rotation iteration is proposed by discussing the principle of the conventional CORDIC in detail herein. Because the iterative number and data width of the improved CORDIC are limited by the finite digital circuit resources and thus determine the calculation accuracy directly, subsequently the overall quantization error (OQE) of the improved CORDIC is analysed. The approximate error and rounding error of the algorithm are deduced, and the error models of iterative number and data width are established. The validity and application value of the improved CORDIC are proved through simulations and experiments involving a subdividing circuit. The corresponding relation between the approximate error, rounding error and iteration number, as well as the bit width are proved by quantization. The error of subdivision with the improved CORDIC, obtained through a calibration experiment, is within ±0.5′′ and the mean variance is 0.2′′. The results of the research can be applied directly to a digital subdivision system to guide the parameter setting in the iterative process, which is of crucial importance in the quantitative analysis of error separation and error synthesis.

5

Improvement of accuracy of simple methods for design and analysis of a blazed phase grating microstructure

Wang W., Jing X., Zhao J., Li Y., Tian Y.

Optica Applicata

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2017

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Vol. 47, nr 2

183--198

EN

In order to precisely analyze and design the transmittance characteristics of a blazed grating, the validity of both the scalar diffraction theory and the effective medium theory is quantitatively demonstrated. By making a comparison of diffraction efficiencies calculated by the two simplified methods and Fourier modal method, the accuracy can be obtained. It is found that when the normalized period is more than three wavelengths of the incident light, the scalar diffraction theory is useful to calculate the transmittance of the blazed grating within the error of less than 3%. The validity of the scalar diffraction theory increases when the normalized period increases. Importantly, by considering the Fresnel reflection effect, the validity of scalar diffraction theory can be significantly enhanced. Furthermore, when no higher-order diffraction waves appear and only zeroth order diffraction wave propagates, the effective medium theory is accurate to compute the diffraction efficiency within the difference of less than 1% between the zeroth order effective medium theory and Fourier modal method. The polarization characteristics of the validity of effective medium theory are also quantitatively demonstrated. The validity of the two simplified theories is dependent on not only the normalized period of surface microstructure but also the normalized groove depth.

6

The Optimum-efficiency Beam Multiplier for an Arbitrary Number of Output Beams and Power Distribution

Frezza F., Marciniak M., Pajewski L.

Journal of Telecommunications and Information Technology

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2017

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nr 3

94--98

EN

This paper deals with phase gratings working in the paraxial domain. The profile of the optimum-efficiency beam multiplier with an arbitrary number of output diffraction orders is derived in an analytic form by exploiting methods from the calculus of variation. The output beams may be equi-intense or with arbitrary distribution of power. Numerical examples are given for different values of the number of output beams.

7

Speckle reduction by angle diversity using a translucent spatial light modulator

Tong Z., Chen X.

Optica Applicata

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2012

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Vol. 42, nr 3

651-658

EN

A translucent spatial light modulator (SLM) and a condenser lens are introduced to suppress the laser speckle effect. The SLM is programmed as a sinusoidal grating with rotating orientation and/or adjustable period. The incident laser beam is diffracted into various diffraction orders after the SLM modulation, and the diffraction light beams with temporally changing incident angles are focused onto a transmission diffuser by a condenser lens. A CCD camera is used to record the speckle patterns in free space, and the speckle effect is reduced after integrating all the speckle patterns together. The speckle reduction principles are discussed, and about 0.3 speckle contrast ratio (CR) is obtained, where the grating rotating orientation span is 5°, and two grating periods have been chosen.

8

Optimal period for diffraction gratings recorded in polymer dispersed liquid crystals

Aslanyan A., Galstyan A.

Opto-Electronics Review

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2007

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Vol. 15, No. 1

66-70

EN

New diffusion model of recording diffraction gratings in the media of PDLC is described in which besides diffusion of monomer molecules also diffusion of polymer molecules and non-locality of diffusion coefficient are taken into account. It lets us to explain why diffraction efficiency is low for low and high values of intensities of grating recording beam. With the considered model, we have theoretically got optimal period for grating recording.

9

Diffraction analysis by periodic structures using a method of coupled waves

Fitio V. M., Bobitski Y. M.

Opto-Electronics Review

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2005

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Vol. 13, No. 4

331-339

EN

The coupled-wave method (CWM) has been used to analyse diffraction on some periodic structures, i.e., on relief gratings including metallized ones having sinusoidal relief as well as on one-dimensional and two-dimensional photonic crystals. Exact boundary conditions were taken into account in numerical calculations. Grating polarizers have been analysed, properties of dielectric gratings wherein coupled-mode resonance occurs have been studied, diffraction efficiency has been calculated for sinusoidal relief metallized gratings. Calculations were carried out for TE and TM polarizations. Band structure of a two-dimensional photonic crystal has been calculated using CWM.