Generation of bubbles in glass by a femtosecond laser

Permanent microscale bubbles with varied size and number density are induced in borosilicate glasses by adjusting the focusing depth (FD) of a tightly focused femtosecond laser. With continuously increasing of the focusing depth, the average size of generated bubbles experiences an increase-decrease process. However, the number density of generated bubbles experiences an opposite changing process compared to the change of the size. The possible mechanism for the bubble generation and changing with the focusing depth has been discussed.     

Orbital angular momentum crosstalk of single photons propagation in a slant non-Kolmogorov turbulence channel

We analyze the orbital angular momentum (OAM) crosstalk of single photons propagation through low-order atmospheric turbulence. The probability models of the orbital angular momentum crosstalk for single photons propagation in the channel with the non-Kolmogorov turbulence tilt, coma, and astigmatism and defocus aberration have been established. It is found, for α = 11/3, that the turbulent tilt is the dominant aberration which causes the orbital angular momentum crosstalk, the coma is second and the astigmatism is third, but the defocus aberration has no impact on OAM. The results also indicate that the regularities of orbital angular momentum crosstalk caused by the tilt, the coma and the astigmatism are almost the same, respectively. The crosstalk probability of the orbital angular momentum increases as the azimuth mode index p of Laguerre-Gaussian (LG) beam increases, the turbulent strength C_n² enhances, the orbital angular momentum quantum number rises, the diameter of circular sampling aperture D and the channel zenith angle θ increase.     

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 fluctuating phase error analysis in the digital grating phase-shifting profilometry

The nonlinear response of the experimental system and the saturation of fringe patterns can induce the fluctuating phase error in the projection grating phase-shifting profilometry. Two major factors of the fluctuating phase error are discussed by simulation. The fluctuating phase error caused by the nonlinear response of the system is four times the frequency of the fringe pattern when the conventional four-frame phase extracting algorithm is used. However, such error can be decreased by five-frame algorithm. On the other hand, the fluctuating phase error caused by the fringe saturation is five times the frequency of the fringe pattern by using conventional five-frame phase extracting algorithm. A novel phase recovering algorithm is used to decrease the phase error caused by the saturation. Furthermore, the applicability range of the proposed phase recovering algorithm is analyzed by simulation and experiments with different saturation degree of the fringe pattern and nonlinearity of the measurement system.     

模式偏置波前传感器理论模拟及实验验证

将模式偏置法与全息多重存储法波前传感器原理联系起来,通过研究模式偏置波前传感器的输出响应特性,间接得到全息模式波前传感器的运行规律.对模式偏置波前传感器进行理论分析与总结,并建立简化模型,针对若干阶Zernike像差,通过数值模拟对理论结果进行验证.模拟结果显示:传感器输出信号与各种类型待测像差系数有不同的变化关系,这...     

能量约束自适应迭代算法与光学像差复原

提出了一种新的适用于移变降质图像复原的算法——能量约束自适应迭代复原.算法采用能量约束复原的空域迭代形式,使其能够用于处理光学像差引起的移变降质复原问题;以局部能量约束取代总体能量约束,使算法具有空间自适应特性;并采用双通道处理方法,消除能量约束带来的图像亮度衰减,同时抑制图像边界截断引起的振荡波纹.场曲复原仿真实验结...     

超广角大工作面f-theta镜头的光学设计

 目前国内用于激光标刻机的f-theta镜头的视场角一般小于60°。采用望远镜结构,利用视觉放大率增大视场角,得到了超广角90°镜头。该方法具有简洁、可靠、易实现等特点。通过初级像差分析,确定系统的初级结构参数,利用ZEMAX软件优化得到了大工作面为285 mm的f-theta镜头,镜头线性畸变误差值不超过1 %,在半径为698 μm的圆内,能量集中度为80%,聚焦性能接近衍射极限。     

Recursive computational formulas of the least squares criterion functions for scalar system identification

The paper discusses recursive computation problems of the criterion functions of several least squares type parameter estimation methods for linear regression models, including the well-known recursive least squares (RLS) algorithm, the weighted RLS algorithm, the forgetting factor RLS algorithm and the finite-data-window RLS algorithm without or with a forgetting factor. The recursive computation formulas of the criterion functions are derived by using the recursive parameter estimation equations. The proposed recursive computation formulas can be extended to the estimation algorithms of the pseudo-linear regression models for equation error systems and output error systems. Finally, the simulation example is provided.     

Dilations for systems of imprimitivity acting on Banach spaces

Motivated by a general dilation theory for operator-valued measures, framings and bounded linear maps on operator algebras, we consider the dilation theory of the above objects with special structures. We show that every operator-valued system of imprimitivity has a dilation to a probability spectral system of imprimitivity acting on a Banach space. This completely generalizes a well-known result which states that every frame representation of a countable group on a Hilbert space is unitarily equivalent to a subrepresentation of the left regular representation of the group. We also prove that isometric group representation induced framings on a Banach space can be dilated to unconditional bases with the same structure for a larger Banach space. This extends several known results on the dilations of frames induced by unitary group representations on Hilbert spaces.     

On a New Class of Systems of Generalized Quasi-Variational Inequalities

We introduce new types of systems of generalized quasi-variational inequalities and we prove the existence of the solutions by using results of pair equilibrium existence for free abstract economies. We consider the fuzzy models and we also introduce the random free abstract economy and the random equilibrium pair. The existence of the solutions for the systems of quasi-variational inequalities comes as consequences of the existence of equilibrium pairs for the considered free abstract economies.