无衍射贝塞尔光束的实现方法

无衍射光束是一种新兴的光束，它具有很好的应用前景，本文给出了无射贝塞尔光束的理论背景、实现方法及相应实验结果，比较了这些方法的优缺点，提出了无衍射光束的应用范围。     

离轴障碍物Bessel光束的重建

利用Hankel理论,对障碍物离轴时Bessel光束的重建过程进行了分析.实验中,用体视显微镜及CCD系统记录了Bessel光束经离轴障碍物遮挡后的光强变化.针对Bessel光束被障碍物阻碍后的重建现象,对轴上障碍物及离轴障碍物两种情况进行了比较.结果表明,两种情况的遮挡均能使Bessel光束重建,不同的是对相同尺寸的障碍物离轴障碍物完全重建比轴上障碍物完全重建需要更长的距离.     

贝塞尔光束的特性及参量的影响

本文利用数值计算研究了Bessel光束的传播特性及参量对其的影响,发现Bessel光束的最大无 射距离与光矢量横向分量系数kr成 反比,而与光阑半径R成正比。最后,得到了一个计算最大无衍射距离的经验公式。     

A new I-V model for light-emitting devices with a quantum well

This letter reports a new current versus voltage model for light-emitting devices with a quantum well where electrons and holes are injected and recombine. The current is entirely caused by the recombination of electrons and holes. Historically, the equation used for light-emitting diodes (LEDs) and laser diodes (LDs) has been the renowned Sah-Noyce-Shockley (SNS) diode equation. In this equation at typical forward bias condition, most of the current is caused by the diffusion of carriers over the depletion region. It is clear that this condition is different from what actually happen in LEDs and LDs. We thus looked into the fundamental of carrier transport and developed a new model for devices with a quantum well. Based on the new model, calculated I-V curves agree well with measurement results of GaN/sapphire LEDs with GaInN quantum wells. In calculation, junction temperature T_j rather than case temperature T_c is used to achieve better agreement.     

Bessel光束的传输模型

研究了参量对Bessel光束性质的影响并发现了参量Kr与无衍射距离之间的关系，进一步建立了Bessel光束的传输模型并用数值误差计算进行了证明。     

无衍射光束的传输

本文使用稳相法对无衍射光束的传输特性作了详细的理论分析,并与高斯光束作了比较.选用轴棱镜产生近似零阶贝塞尔光来的方案,进行有关零阶见塞尔光束传输特性的实验研究,取得了在误差范围内实验与理论计算一致的结果.     

超细激光束准直器的原理与设计

提出一种用衍射光学器件产生超细准直激光束的方法。该方法具有设计、制造和装配简便等特点。介绍了器件设计的原理，给出了一种实用的设计方案和模拟结果。     

Quantum light sources from semiconductor

Semiconductor provides a physics-rich environment to host various quantum light sources applicable for quantum information processing. These light sources are capable of deterministic generation of non-classical photon streams that demonstrate antibunching photon statistics, strong indistinguishability, and high-fidelity entanglement. Some of them have even successfully transitioned from proof-ofconcept to engineering efforts with steadily improving performance[ 1]. Here, we briefly summarize recent efforts and progress in the race towards ideal quantum light sources based on semiconductor materials. The focus of this report will be on group III–V semiconductor quantum dots, defects in wide band-gap materials, emitters in two-dimensional van der Waals layered hosts, and carbon nanotubes, as these systems are well-positioned to benefit from recent breakthroughs in nanofabrication and materials growth techniques.     

轴棱锥聚焦涡旋光束获得高阶贝塞尔光束

采用轴棱锥聚焦涡旋光束,获得了高阶贝塞尔(Bessel)光束.首先,从理论模拟了涡旋光束经过轴棱锥聚焦后所获得的聚焦光强分布,结果表明,涡旋光束经过轴棱锥聚焦后可获得高阶贝塞尔光束.并且所获得的高阶贝塞尔光束的阶数与涡旋光束的拓扑电荷数相司.进而,从实验获得高阶贝塞尔光束,并且采用不同锥角的轴棱锥对涡旋光束进行聚焦,研...     

贝塞耳光束相干产生局域空心光束的实验研究

利用轴棱锥产生的两束贝塞耳光相干实现局域空心光束.基于"相干贝塞耳光产生具有塔尔博特效应的局域空心光束"的理论,数值模拟了两束贝塞耳光干涉后光场沿传输距离变化的光强分布及一个周期内光强的演变和局域空心光束的形成过程.实验中通过两个不同底角的轴棱锥产生两束具有不同径向波矢的贝塞耳光进行相干形成局域空心光束,实验结果与理论分析及数值模拟相吻合.     

A Comparison of Propagation Between Apertured Bessel and Gaussian beams

A true Bessel beam is a family of diffraction-free beams. Thus the most interesting and attractive characteristic of such beam is non-diffracting propagation. In optics, the comparisons of maximum propagation distance had been done between Bessel and Gaussian beams by Durnin and Sprangle, respectively. However, the results obtained by them are conflict due to the difference between their criteria. Because Bessel beams have many potential applications in millimeter wave bands, therefore, it is necessary and significant that the comparison is carried out at these bands. A new contrast criterion at millimeter wavelengths is proposed in our paper. Under this criterion, the numerical results are presented and a new conclusion is drawn.     

Tunneling current and electroluminescence in InGaN: Zn,Si/AlGaN/GaN blue light emitting diodes

We investigate electrical and optical characteristics of Nichia NLPB-500 double-heterostructure blue light-emitting diodes (LEDs), measured over a wide temperature range from 10 to 300K. Current-voltage characteristics have complex character and suggest involvement of at least two different tunneling mechanisms. The peak energy of the optical emission follows the applied bias for voltages between 2.3–2.6 V and can be tuned in large spectral range from 2.3 up to 2.8 eV (yellow to blue). This behavior can be understood invoking the photon-assisted tunneling model which was previously successfully applied to highly doped GaAs LEDs. Even at the lowest temperatures, light emission still continues while the increase in the series resistance does not exceed a few tens of kΩ, which indicates absence of complete carrier freeze-out. On leave from P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow, Russia On leave from High Pressure Research Center, Warsaw, Poland     

贝塞耳光束的特性和无衍射光束相关概念的分析

基于我们的工作，本文分析了无衍射光束的物理意义，贝塞耳光束的传输变换和聚焦特性。然后，对与无衍射光束有关的一些易于混淆的概念提出了我们的看法。最后，对主要结果加以总结。     

Quantification of thermoreflectance temperature measurements in high-power semiconductor devices—lasers and laser bars

In this paper we present results of the analysis of the thermoreflectance (TR) measurements performed on the high-power laser diodes and laser bar emitting at 808 nm. TR is a modulation technique relying on periodic facet temperature modulation induced by pulsed current supply of the laser. The periodic temperature change of the laser induces variation of the refractive index and consequently modulates probe beam reflectivity. Spatially resolved TR spectroscopy is applied to measure line-scans and maps of temperature distribution at the laser mirrors and emitter facets in laser bar. However, to get the absolute values of temperatures, TR needs calibration. Different calibration methods, such as μ-Raman spectroscopy and in situ determination of TR coefficient (C_TR), will be discussed. The knowledge of temperature distribution at laser facets gives insight into thermal processes occurring at devices’ facets and consequently leads to the increased reliability and substantially longer lifetimes of such structures.     

On the physics of semiconductor quantum dots for applications in lasers and quantum optics

The progression of carrier confinement from quantum wells to quantum dots has received considerable interests because of the potential to improve the semiconductor laser performance at the underlying physics level and to explore quantum optical phenomena in semiconductors. Associated with the transition from quantum wells to quantum dots is a switch from a solid-state-like quasi-continuous density of states to an atom-like system with discrete states. As discussed in this paper, the transition changes the role of the carrier interaction processes that directly influence optical properties. Our goals in this review are two-fold. One is to identify and describe the physics that allows new applications and determines intrinsic limitations for applications in light emitters. We will analyze the use of quantum dots in conventional laser devices and in microcavity emitters, where cavity quantum electrodynamics can alter spontaneous emission and generate nonclassical light for applications in quantum information technologies. A second goal is to promote a new connection between physics and technology. This paper demonstrates how a first-principles theory may be applied to guide important technological decisions by predicting the performances of various active materials under a broad set of experimental conditions.     

高阶Bessel-Gauss光束的产生方法

高阶贝塞尔-高斯(Bessel-Gauss)光束在一定条件下呈现"无衍射"特性,是一种具有广阔应用前景的空心光束。本文首先对高阶Bessel-Gauss光束的产生方法进行了分析和归类,将其产生方式分为主动式和被动式两大类。其次对获得高阶Bessel-Gauss光束的谐振腔法、几何光学法、光学全息法、计算全息法、非线性光学法等实验方法进行了阐述。最后总结了各种方法产生高阶Bessel-Gauss光束的优缺点。     

Investigation of light output performance for gallium nitride-based light-emitting diodes grown on different shapes of patterned sapphire substrate

GaN-based blue light-emitting diodes (LEDs) on various patterned sapphire substrates (PSSs) are investigated in detail. Hemispherical and triangular pyramidal PSSs have been applied to improve the performance of LEDs compared with conventional LEDs grown on planar sapphire substrate. The structural, electrical, and optical properties of these LEDs are investigated. The leakage current is related to the crystalline quality of epitaxial GaN films, and it is improved by using the PSS technique. The light output power and emission efficiency of the LED grown on triangular pyramidal PSS with optimized fill factor show the best performance in all the samples, which indicates that the pattern structure and fill factor of the PSS are related to the capability of light extraction.     

Efficient gas lasers pumped by double-discharge circuits with semiconductor opening switch

A review of applications of double-discharge circuits based on generators with inductive energy storage (IES) and semiconductor opening switches (SOS) for efficient excitation of different gas lasers is presented. Using a pre-pulse-sustainer circuit technique based on inductive energy storage and semiconductor opening switch generators allows the formation of a pre-pulse with high amplitude and short rise-time and provides a sharp increase of discharge current which significantly improves discharge stability and life-time of the volume discharge in gas mixtures containing halogens. A pre-pulse with high pumping power forms a high-density discharge plasma and an inversion population in gas mixtures under study within ∼10 ns and provides both early onset of lasing and conditions for efficient excitation of an active medium from the storage capacitor. As a result, pulse duration, output energy and efficiency of the lasers under study were improved.     

一阶贝塞耳光束的存在和演示

一阶贝塞耳光束是标量波动方程的一个特解，本文用瑞利一索末菲衍射理论证明了它的存在并作了实验演示。     

用轴棱锥设计贝塞尔-高斯谐振腔

本文从较直观的角度出发,把贝塞尔光理解为一对趋向于传播轴线和离开轴线的锥形波的叠加,将腔两端的镜面理解为用于改变光场位相的器件,讨沦用轴棱锥设计谐振腔以产生贝塞尔光,我们发现在所设计的腔中振荡的光是受钟形函数调制的锥形波,其模式与贝塞尔一高斯光相似.并且我们所得到的结论与福克斯一厉数值迭代法验证的结果是一致的.