三维光存储中折射率失配引起的球差补偿

为实现三维光存储中折射率失配引起的球差补偿,建立了光学存储系统模型,获得了折射率失配引起的波前偏差函数与存储深度的表达式.采用泽尔尼克循环多项式对波前偏差函数进行补偿展开.在双光子荧光和单光子共焦荧光读出方式下,均可获得读出荧光强度与存储深度的关系:在折射率失配引起的球差未得到补偿矫正的情况下,存储深度在200 μm左右读出荧光强度基本上下降为零;当折射率失配引起的初级球差被补偿矫正后,读出荧光强度随存储深度的下降得到较好改善;当折射率失配引起的二级球差被补偿矫正后,存储深度在1 mm内存储点强度随深度基本上没有明显地变化.并且对像差补偿方法进行了具体地分析.     

Effects of low order atmosphere-turbulence aberrations on the vortex carrying Gaussian beam

The normalized intensity distributions at the focal plane of a vortex carrying Gaussian beam propagating in weak/middle turbulent atmosphere channel with z-tilt aberration, defocus aberration, astigmatism aberration or total turbulent aberration are discussed by numerical calculation. Our results show that the effect of z-tilt aberration on the intensity distribution of optical vortex beam is main effect of total turbulent aberration. In weak turbulent region, the effects of defocus and astigmatism aberration on the intensity distribution of a vortex carrying Gaussian beam can be ignored. In middle turbulent region, the effect of z-tilt aberration is still the most significant, but the effects of defocus and astigmatism aberrations, specially the effect of astigmatism on the center dark core of the intensity distribution at focal plane, can no longer be disregarded. Our results also show that for three low order aberrations, the beam with values of the topological charge, the beam have larger beam-radius and undergo smaller effects of z-tilt turbulent aberration on the doughnut distribution. For defocus aberration, the radius of the center dull of beam intensity increases with the values of topological charges increasing. And for astigmatism aberration, the beam with odd number topological charges, the center dull speck of beam intensity becomes to the bright speck. But for even number topological charges, the center dull speck of beam intensity maintains the dull one.     

Effect of tilt and astigmatism aberration of turbulent atmosphere on the intensity distributions of a LG11 beam

The effects of turbulent aberration such as z-tilt aberration, and astigmatism on the intensity distribution of double ring shaped LG₁₁ beam have been investigated using the Fresnel–Kirchhoff diffraction integral and the quadratic approximation. The effect of turbulent aberration on the intensity distributions at the focal plane with different turbulent strength, and propagation distance is analyzed numerically. It is observed that the effect of tilt aberration gives major effect on the intensity distribution of the LG_(1,1) beam in the turbulent atmosphere.     

球差对圆偏涡旋贝塞耳-高斯光束聚焦场的影响

利用理查德-沃耳夫矢量衍射积分,分析了初级球差对圆偏振涡旋贝塞耳-高斯光束聚焦光场的影响,获得不同球差系数下的光强分布.结果表明,当初级球差系数增加,会聚光点偏离系统焦平面,纵向光场发生改变;焦点光强逐渐减小,焦平面光场发生变化;光轴上光强峰值逐渐减小,峰值两侧的旁瓣变化趋势相反,光强由对称分布变成非对称分布;初级球差对贝塞耳-高斯光束聚焦光场的影响不依赖其偏振态;离焦无法完全补偿初级球差对聚焦光场的影响.     

The effect of tilt aberration and astigmatism of turbulent atmosphere on the intensity distribution of a vortex carrying Gaussian beam

The effect of tilt and astigmatism aberration of the turbulent atmosphere on the intensity distribution of a focused vortex carrying Gaussian beam was investigated based on the extended Fresnel-Kirchhoff diffraction integral and the quadratic approximation of phase structure function. Our results have shown that the intensity distribution on the focal plane in the effect of tilt aberration changes with the turbulent strength, the propagation distance and the topological charge of the initial beam. The propagation distance is larger, the focal spot size will be larger, and the central dip will be less deep. It is also noticed that the intensity distribution of a beam with single topological charge is affected more by tilt aberration in comparison to the beam with double topological charge. The effect of astigmatism on the intensity distribution is quite less than that of tilt aberration. For focused beam propagation in atmosphere, the effect of the tilt aberration on the intensity distribution of optical vortex beam is the main effect of total turbulent aberration.     

The intensity distribution of hollow Gaussian beams focused by a lens with spherical aberration

We developed an expression that describes the hollow Gaussian beams (HGBs) passing through a spherically aberrated lens by using the Collins formula. The radial intensity distribution in both spherical aberration SA free lens, lens that exhibits relatively large in both positive spherical aberration PSA, and negative spherical aberration NSA is calculated. Numerical calculations are made and the results show that the PSA and NSA have a strong influence on the intensity distribution especially at the focus. The study showed remarkable results for which there is no hollow Gaussian beam at a large NSA along the optical axis at the focus. In addition, we found that the DSS, and w_r of focused hollow Gaussian beams in the focal region depend not only on the beam radius, and beam order; but also on the spherical aberration.     

高斯光束经过负球差透镜的聚焦

本文讨论高斯光束经过负球差透镜的聚焦，得到了聚焦光场轴上点的光强分布的表示式，并对其进行数值计算。数值计算结果表明，在负球差的情况下，得到光强的最大点位置（最佳聚焦点）相对于无球差情况，往透镜方向移动，并且，最佳聚焦点的光强较无球差时大，当Ｎｗ＝１，Ｎａ＝５，ｋＳ１＝－０．２时，得到的最佳聚焦点的光强是无球差时的１．３４倍。本文还讨论了透镜的菲涅尔数对聚焦光场分布的影响。结果表明，当透镜的菲涅尔数小于１时，球差对高斯光束的聚焦的影响可以忽略。     

Influence of the comatic aberration of an apertured lens on the focused polychromatic Gaussian beams

The focusing of polychromatic Gaussian beams by an apertured lens with comatic aberration is investigated in this paper. We study the influence of the comatic aberration and truncation parameter on the intensity distribution at the focal plane, and singularities and spectral behavior near the focal plane in detail. The simulation results show that the maximum intensity at the focal plane will shift and split with the gradual increment of comatic aberration. We also find that the decrease of truncation parameter will counteract the influence of comatic aberration, which leads to the intensity variation. Furthermore, the singularity transformation and spectral anomalies are discussed. It is found that with the increment of comatic aberration, some singularities are split into several new singularities, and by combining some of these new singularities with other singularities near the focal plane, they vanish or form new singularities with the continuing increase of comatic aberration. The decreasing value of truncation parameter will cause similar phenomena.     

Diffraction patterns of off-axis gaussian beams in the presence of third-order spherical aberration in the optical system

The intensity distribution of diffraction patterns for off-axis gaussian beams at the image plane of an optical system with third-order spherical aberration is calculated by using the concept of the beam aberration function previously introduced by the present authors. The results show how the peak intensity of the diffraction patterns diminishes and how the transversel focal shift occurs as a function of the incident position of the beams at the pupil plane and their beam size.     

Analysis of beam quality for the laser beams after spectral beam combining

The beam quality of the laser beams after spectral beam combining (SBC) has been analyzed in this paper. Based on the propagation model of the spectral beam combining system, the expression for the output field of an individual beam passing through the spectral beam combining system with lens aberration has been given and the intensity distribution of the combined beam has been studied by the principle of incoherent superposition. Consequently, according to the intensity second-order moments method, the M²-factor of the combined beam has been calculated and the effect of lens aberration on the characteristics of the combined beam has been analyzed quantitatively. It can be shown that the SBC system can improve the beam quality of laser array significantly, and the M²-factor of the combined beam passing through the ideal spectral beam combining system is almost the same as that of an individual beam. For the spectral beam combining system with lens aberration, the spherical aberration has greater effect on the off-axis beam than on the on-axis beam, and the beam quality of combined beam degrades with increase in lens aberration.     

球差透镜聚焦部分相干光束获得局域空心光束

基于Collins公式,研究了空间相干度为零阶贝塞耳函数的部分相干光通过球差透镜后在几何焦平面附近的光强分布情况.研究表明,通过改变部分相干光的光谱相干度,球差系数可以得到平顶光束和局域空心光束.球差系数决定了最佳聚焦点的位置.当球差系数为正时,最佳聚焦点随着球差系数的增大向远离透镜的方向运动,甚至超过几何焦点;当球差系数为负时,最佳聚焦点随着球差系数绝对值的增大向靠近透镜方向移动.另外,在正负球差绝对值相等时,光强分布以几何焦点相对称.     

Tight focusing of linearly and circularly polarized vortex beams; effect of third-order spherical aberration

Tight focusing of linearly and circularly polarized vortex beams is studied in the presence of third-order spherical aberration, using vectorial Debye–Wolf integral. Results for total intensity distribution are presented for both polarizations. In addition, results for x-, y-, and z-polarization components are presented for the circularly polarized beam. Generation of longitudinal optical vortex in the tightly focused left circularly polarized beam has also been demonstrated by plotting its phase distribution. Compensation for the effect of spherical aberration has been studied in the presence of defocusing. Effect of aberration on the dark core of a tightly focused azimuthally polarized beam is also investigated.     

Focusing for laser hole drilling

The power intensity distribution of a laser beam across the focal plane is important for producing good hole geometry. To examine the power intensity distribution in the region of the image plane of a practical lens, a diffraction integral method is employed. Lens aberration is accounted for by the intensity of the appropriate phase changes. In the analysis, a free-running pulsed multimode solid-state laser is considered and the lens is assumed to have aberrations. Since an on-axis object is examined, only spherical aberration is taken into account.     

Effect of refractive index mismatch aberration in arsenic trisulfide

We demonstrate compensation for the spherical aberration due to the refractive index mismatch that occurs when a laser beam is focused into a thick arsenic trisulfide (As $_2$ S $_3$ ) film with a high numerical aperture objective. The effects of the aberration at different focal depths on the point spread function have been calculated numerically and the axial response method shown to be a useful measure for compensating the spherical aberration. We show that with the addition of adaptive optics based on a spatial light modulator, the aberration can be significantly reduced, resulting in an increase in peak intensity by a factor of 2.4 and a decrease in axial elongation by a factor of 2.2.     

Determination of Aberration Coefficient of Microoptic Arrays from Axial Confocal Response by Neural Method

We propose a high-speed and parallel method to determine lens aberrations from its confocal axial response. This method analyzes the intensity confocal response including the aberration information of the objective lens by means of neural network algorithm. This method is designed to work parallely for many microlenses, and simultaneously determines aberrations of each element of a microlens array. A prototype system can determine spherical aberration coefficients of a microlens in the range from −0.7λ to 0.3λ with less than 1% RMS error.     

慧差对线偏振贝塞耳-高斯光束聚焦场的影响

利用Richards-Wolf矢量衍射积分公式,获得线偏振贝塞耳-高斯光束经具有初级慧差的高数值孔径系统聚焦后的三维光场复振幅函数,根据复振幅函数模拟了不同慧差系数下线偏振贝塞耳-高斯光束各分量及总光场在焦平面上的光强分布模式。研究结果表明,初级慧差使线偏振贝塞耳-高斯光束聚焦光场在焦平面的分布由双轴对称变成单轴对称,光强模式发生改变;各分量及总光场的光强模式中的光斑位置随初级慧差系数的增大偏离光轴;大的初级慧差使焦平面出现干涉条纹。     

Chromatic aberration in petawatt-class lasers

In order to avoid optical damage and non-linear effects, high-power, high-energy lasers of the petawatt class like PHELIX (petawatt high-energy laser for heavy-ion experiments) use large-aperture optics. Usually, chromatic aberration associated with these optical elements is neglected. By means of numerical simulations, we show how the chromatic aberration affects the focal intensity pattern. In particular, we make quantitative predictions of how chromatic aberration decreases the focused peak intensity. Furthermore, we prove the feasibility of a new interferometer that measures the temporal pulse front distortions which arise from expansion telescopes. We also propose a scheme that pre-compensates these distortions. PACS 42.65.Re; 42.60.Jf     

Intensity distribution for the broadband aberrated partially coherent flat-topped beam propagating through turbulent atmosphere

In this paper, taking the partially coherent flat-topped (PCFT) beam as an example, we investigate the intensity distribution of broadband beams with astigmatic aberration propagating through a turbulent atmosphere. The analytic expressions for the intensity of the beams propagating through the turbulent atmosphere are derived. It is shown that the intensity distribution of the broadband aberrated PCFT beams in the turbulent atmosphere are closely related with the astigmatism aberration, the strength of atmospheric turbulence, the order of flatness, the correlation of source and the bandwidth of PCFT beams. It is important to note that the position of the focal plane of the broadband aberrated (or not) PCFT beams can be modulated by changing the aberration, the order of flatness, the correlation and the bandwidth of PCFT beams.     

Non-linear aberration of a self-focussing electromagnetic wave beam

In this paper the aberrations of a centered axially symmetric electromagnetic wave beam in a nonlinear medium are examined. A formula is obtained, which describes the intensity distribution of the beam near the aberration point. The procedure for investigating high-order aberrations is demonstrated. The influence of the initial distribution of the intensity and the phase on the picture of the aberration is examined.     

Experimental investigation of a flowing fluid layer on metal surface roughness measurement and aberration correction using adaptive optics

The induced optical aberration of laser beam passing through a transparent flowing fluid layer on a metal specimen is experimentally and empirical formula studied. The proposed study presents an experimental investigation of metal surface roughness measurement by combining an optical probe of laser-scattering phenomena and adaptive optics (AO) for aberration correction. In the absence of the AO correction scheme, induced flow velocity of 0.278 m/s can severely degrade the residual wavefront root mean square (RMS) error to 0.58 μm and decrease the scattered laser intensity. Real-time AO correction in closed-loop at a sampling rate of 8Hz can reduce the wavefront RMS error to 0.19 μm and improve the attenuation of scattered laser intensity. The maximum relative error of the estimated roughness (R _a) is less than 7.8% compared with the stylus method. The experimental results show satisfactory correction in the presence of a flowing fluid layer using the AO system.