Paraxial designing of planar waveguide variable-index focusing elements: Part 1—lenses of circular symmetry

A paraxial ray equation is used to evaluate refractive index profiles for a family of radially symmetric planar waveguide lenses. Two cases are considered: the (theoretically) full-aperture solution, and the solution with smooth index variation (non-full-aperature case). In deriving the latter case a new method has been applied that consists of the proper choice of a continuous deflection function. Both types of index profiles are described by exceptionally simple formulas.     

Microwave Photonic Phase Shifter Based on an Integrated Dual-polarization Dual-parallel Mach-Zehnder Modulator without Optical Filter

ABSTRACT

A frequency-doubled microwave photonic phase shifter (MPPS) without optical filter is proposed. The MPPS is based on an integrated dual-polarization dual-parallel Mach-Zehnder modulator (DP-DPMZM) and a polarization modulator (PolM). The DP-DPMZM with a 90° polarization rotator in one arm is used to generate an optical carrier suppressed double sideband (OCS-DSB) signal with orthogonal polarization, and the PolM with two modes opposite phase modulation is used to introduce the optical phase shift between the two orthogonally polarized tones. Simulations show that the MPPS can realize a continuously tunable phase shift of 360° with only one DC bias voltage, and is not sensitive to the optical carrier wavelength and microwave signal frequency since no optical filter is used.     

Inertial spin Hall effect in non-commutative space

In the present Letter the study of inertial spin current (that appears in an accelerated frame of reference) is extended to Non-Commutative (NC) space. In the Hamiltonian framework, the Dirac Hamiltonian in an accelerating frame is computed in the low energy regime by exploiting the Foldy–Wouthuysen scheme. The NC θ-effect appears from the replacement of normal products and commutators by Moyal ?-products and ?-commutators. In particular, the commutator between the external magnetic vector potential and the potential induced by acceleration becomes non-trivial. Expressions for θ-corrected inertial spin current and conductivity are derived explicitly. We have provided yet another way of experimentally measuring θ. The θ bound is obtained from the out of plane spin polarization, which is experimentally observable.     

Modified Spectral Neugebauer Model for Printer Characterization

Spectral Neugebauer model is widely used for spectral reflectance prediction during printer characterization. However, several factors reduce the predication precision. Thus, an improved cellular Yule-Nielson spectral Neugebauer (CYNSN) model is proposed, which modifies the traditional spectral Neugebauer model in three main aspects: (1) First, in order to adjust the nonlinearities between the predicated and measured spectral reflectance, an iteratively calculated Yule-Nielson exponent is added to the reflectance values within the Neugebauer equations. (2) Second, the quantity of Neugebauer primaries is increased by dividing the CMY colorant space into 4³ uniform cellular subdomains. (3) Third, the mapping functions are developed to map the area coverages' theoretical values to their effective values within the subdomains, and the mapped values highly improve the matching degree of the predicated and measured reflectance values. In the experiment, four related spectral Neugebauer models are employed during printer characterization, which are the traditional spectral Neugebauer model, Yule-Nielson spectral Neugebauer (YNSN) model, traditional CYNSN model, and the modified CYNSN model, respectively. And the experimental results show the modified CYNSN model yields a significant improvement over the other spectral Neugebauer models, by comparing the characterization errors in the form of colorimetry and spectroscopy.     

Spectral Characterization of Nitrogen in Farmland Soil by Laser-Induced Breakdown Spectroscopy

Nitrogen is one of the most important elements in farmland soil, and nitrogen content is one of the evaluation indicators of fertilizers. It is difficult to measure the nitrogen content in farmland soil because the chemical and physical properties of farmland soil are complex. Through the adoption of buffer gases to remove the influence of the nitrogen in air, this paper studied the laser-induced breakdown spectroscopy (LIBS) characteristics of nitrogen in soil to establish a foundation for in situ measurement of nitrogen in farmland soil. Three characteristic spectral lines have been found. Based on the precise controlling of laser power and triggering of delay time between laser generation and spectra collection, we have studied the effects of laser energy on LIBS spectral characteristics and the time evolution characteristics to supply the basis of parameter optimization for the measurement. In addition, we have studied the relationship between nitrogen concentration and LIBS spectral intensity. The results demonstrated that LIBS was an effective measurement method of nitrogen content in farmland soil with simple hardware structure, fast detection, and high precision.     

宽光谱棱镜型太阳光谱仪设计

为实现大气层外太阳光谱辐照度(SSI)变化的长期例行监测,设计了一种星载宽光谱太阳光谱仪结构。全系统仅使用单片折反式曲面棱镜实现太阳光谱250～2500 nm的分光,并通过棱镜转动实现谱平面上多探测器的同步扫描探测;同时基于Huygens子波点扩展函数（PSF）仿真了光谱仪的光谱响应函数（SRF）和光谱分辨率。分光棱镜在±2.5°扫描转角内的全谱段子午像差小于8μm;光谱分辨率在紫外谱段(250～400 nm)为0.7～3.5 nm,可见/近红外谱段(400～1000 nm)为3.5～35.0 nm,短波红外谱段(1000～2500 nm)内为28.5～41.2 nm。整个系统结构简单紧凑,性能稳定可靠,分光和像差校正能力满足大气层外太阳光谱辐照度长期监测需求。     

铈掺杂高钆镥氧化物玻璃制备和光谱性能

实验中采用高温熔融法制备了一系列高钆镥硼硅酸盐新型玻璃体系样品,研究了这种新型玻璃体系的玻璃形成区,测量了样品的玻璃稳定性和密度。结果表明,玻璃体系的玻璃形成区较广,玻璃稳定性良好（析晶温度与转变温度的差为262 ℃）,且玻璃样品的密度达到5 g/cm3。以此种玻璃体系作为基质掺入Ce3+离子,测量其透过光谱、激发光谱、发射光谱、X射线激发发射光谱以及Gd3+离子的衰减时间。结果表明,玻璃的透过性能适合Ce3+离子的掺杂,并且Gd2O3和Lu2O3对闪烁体发光都具有积极的影响,同时研究了Gd3+离子和Ce3+离子的能量传递机理及最佳能量传递掺杂摩尔比。从玻璃的物理性能和光谱性能考虑,这种闪烁玻璃系统具有广泛应用于高能物理材料中的一定潜力。     

A note on the spectral distribution of toeplitz matrices

An elementary and direct proof of the Szegö formula is given, for both eigen and singular values. This proof, which is based on tools from linear algebra and does not rely on the theory of Fourier series, simultaneously embraces multilevel Toeplitz matrices, block Toeplitz matrices and combinations of them. The assumptions on the generating

function f are as weak as possible; indeedf is a matrix-valued function of p variables, and it is only supposed to be integrable. In the case of singular values f(x), and hence the block p-level Toeplitz matrices it generates, are not even supposed to be square matrices. Moreover, in the asymptotic formulas for eigen and singular values the test functions involved are not required to have compact support.