大口径KDP晶体折射率非均匀性检测

KDP晶体的折射率不均匀性将导致光束的空间分布存在不同程度的相位失配,从而使得三倍频系统的转换效率下降。为了得到KDP晶体折射率非均匀性的高精度检测结果,基于正交偏振干涉法,采用ZYGO MST大口径干涉仪,测量得到了大口径KDP晶体折射率非均匀性分布,其测量精度达到10-7,并通过实验研究了晶体面形对测量结果的影响。对晶体e光折射率非均匀性的高精度检测,为大口径晶体材料生长工艺、加工工艺等改进和提高提供了定量的检测依据。     

Nonlinear index of refraction in semiconductors

Summary Experimental work on light refraction in semiconductors suggests that there are two separate mechanisms by which the index of refraction becomes nonlinear: direct saturation, on the one hand, and the Burstein-Moss effect, on the other hand. We show that this picture is incorrect, since it was based on the usage of the Bloch equation. Electron systems are not Boltzmann systems and the appropriate Fermi-Dirac master equation leads to a saturation that differs from the saturation of the Bloch equation. We show, using a simple two-level system, that this result may look like the spin result in one extreme (phonon bottleneck saturation), while it shows the features of the Burnstein-Moss effect in the limit of small degeneracy of the upper level (Fermi saturation).

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Riassunto I lavori sperimentali sulla rifrazione della luce nei semiconduttori suggeriscono la presenza di due meccanismi separati grazie ai quali l'indice di rifrazione diventa non lineare: la saturazione diretta, da un lato, e l'effetto Burstein-Moss, dall'altro. Noi mostriamo che questo quadro non è corretto, in quanto basato sull'equazione di Bloch. I sistemi di elettroni non sono sistemi di Boltzmann e l'appropriata ?master equation? produce una saturazione differente da quella dell'equazione di Bloch. Si mostra, usando un semplice sistema a due livelli, che questo risultato assomiglia a quello di un sistema di ?spin? ad un limite estremo (saturazione fononica a collo di bottiglia), mentre mostra le caratteristiche dell'effetto Burstein-Moss nel limite di piccola degenerazione del livello superiore (saturazione di Fermi).

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Резюме Экспериментальная работа по преломлению света в полупроводниках предполагает, что существуют два различных механизма, благодаря которым преломление становится нелинейным: с одной стороны прямое насыщение, а с дуугой стороны эффект ъурштейна-Мосса. Мы показываем, что эта картина не является корректной, т.к.основана на использовании уравнения ълоха. Электронные системы не являются больцмановскими системами и соответствующее управляющее уравнение Ферми-Дирака приводит к насыщению, котрое отличается от насыщения уравнения Блоха. Мы показываем, используя простую двухуровневую систему, что этот результат похож на результат для спина в случае одного максимума, тогда как этот результат обнаруживает особенности эффекта Бурштейна-Мосса в пределе малой вырожденности верхнего уровня.

     

决定介质折射率因素的经典计算

就介质折射率的物理意义首先从理论上作了说明,然后从经典概念出发对介质折射率的表达式作了推导,指出了决定介质折射率的因素,即组成介质的原子结构、原子种类、每一个原子周围电子分布的情况及辐射的频率。通过理论计算和实验数值的对比表明,所推导出的结论及相关的计算方式是正确的,对介质折射率的研究和在特殊领域对折射率有一定要求的材料的制备具有一定的指导意义。     

Measurement of negative refraction index from simulative results and experimental data by a new metamaterial sample

This work presents simulations and experimental measurements of two negative refraction metamaterial samples at microwave frequencies. The two samples are composed of Four-Triangle Split Resonant Rings and Metal Wires (FTSRRs–MWs) with different cell sizes which are found to play an important role in the location of resonant frequency. The small cell sample is chosen to recover the effective index by utilizing the simulative permittivity and permeability, as well as the angle detection from the experimental data. The experimental data shows good agreement with the simulation result.     

Photon mass and negative index of refraction

A mathematical expression is established for negative refractive index within the context of non-zero photon rest-mass. From this expression, a key inequality involving the mass in question as a function of wavelength is derived. In addition, an approximate parabolic relationship for the refractive index is obtained.     

Negative index of refraction in optical metamaterials

A double-periodic array of pairs of parallel gold nanorods is shown to have a negative refractive index in the optical range. Such behavior results from the plasmon resonance in the pairs of nanorods for both the electric and the magnetic components of light. The refractive index is retrieved from direct phase and amplitude measurements for transmission and reflection, which are all in excellent agreement with simulations. Both experiments and simulations demonstrate that a negative refractive index n' approximately -0.3 is achieved at the optical communication wavelength of 1.5 microm using the array of nanorods. The retrieved refractive index critically depends on the phase of the transmitted wave, which emphasizes the importance of phase measurements in finding n'.     

用光束位移法测定透明玻璃板的折射率

采用光束位移法测量了透明玻璃板的折射率 ,分析了折射率的公式和实验误差处理公式 .结果显示 :实验的准确性主要取决于折射角 θ,并且 θ在 2 0°～ 35°范围内 ,实验的效果较好 .     

Glory oscillations in the index of refraction for matter waves

We have measured the index of refraction for sodium de Broglie waves in gases of Ar, Kr, Xe, and N2 over a wide range of sodium velocities. We observe glory oscillations--a velocity-dependent oscillation in the forward scattering amplitude. An atom interferometer was used to observe glory oscillations in the phase shift caused by the collision, which are larger than glory oscillations observed in the cross section. The glory oscillations depend sensitively on the shape of the interatomic potential, allowing us to discriminate among various predictions for these potentials, none of which completely agrees with our measurements.     

Determination of the index of refraction and the polydispersion of hydrosols

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 52, No. 4, pp. 654–659, April, 1990.     

共振光的大折射率

揭示了在多能级原子介质中的一种新现象:利用原子相干可使共振光获得明显大于1的折射率.     

Nonperturbative quantum calculation of the index of refraction of multilevel systems

We calculate the index of refraction (n) nonperturbatively for a multilevel ladder of states, and show that the dependence of n on the strength of an applied laser field departs qualitatively from that expected for a two-level system and employed in previous phenomenological models of self-focusing.     

Effect of exciton condensation on the optical refraction index of CdS

Detailed measurements of the transmission spectrum of CdS under high pumping excitation were performed. A variation of the refractive index with increasing excitation power is observed. This we attribute to the increase in the number of photoinjected carriers. A saturation of the effect is observed for intensities above a certain level. A simple model is used to evaluate the concentration of photoinjected carriers the saturated regime which turns out to be approximately 1.4 x 10¹⁸ cm^-3. It is shown that the results are compatible with the assumption of formation of an electron- hole liquid (EHL) in CdS.     

Calculation of the intensity-dependent changes of the index of refraction in GaAS

In order to explain the recently observed optical bistability in GaAs we calculate the intensity-dependent changes of the index of refraction on the basis of the previously developed many-body theory of the gain and absorption spectra of highly excited direct-gap semiconductors.     

用二次成像法测量透明玻璃板的折射率

介绍了用二次成像法测定透明玻璃板折射率的原理和方法.由于采用线阵光电耦合器件(CCD)测量,提高了测量精度.     

Plasmas with an index of refraction greater than 1

Over the past decade, x-ray lasers in the wavelength range 14-47 nm have been used for interferometry of plasmas. As in optical interferometry of plasmas, the experimental analysis assumed that the index of refraction is due only to free electrons. This makes the index of refraction less than 1. Recent experiments in A1 plasmas have shown fringe lines bending the wrong way as though the electron density were negative. We show how the bound electrons can dominate the index of refraction in many plasmas and make the index greater than 1 or enhance the index such that one would greatly overestimate the density of the plasma using interferometry.     

All angle negative refraction with the effective phase index of-1

We theoretically studied a left-hand structure based on a two-dimensional (2D) photonic crystal (PC)with a negative refractive index. The propagation of electromagnetic waves in the proposed PC structure is investigated through dispersion characteristic analysis and numerical simulation of field pattern. The designed PC structure can exhibit all angle negative refraction, and the corresponding effective refractive indices along all directions are almost same and close to the ideal value of -1. A flat lens formed from such a PC has been designed and its imaging properties have been investigated systematically.