Spectral technique for measuring hyperfine structure of atoms

A new spectral technique for measuring the hyperfine structure of atoms is reported. A divergent atomic beam and a divergent laser beam are crossed. Because of the Doppler effect, the hyperfine structure of atomic levels will be directly displayed in the interaction region in the form of spatially resolved fluorescence arc bands. By measuring the spatial-fluorescence intensity distribution, it is possible to obtain the hyperfine splittings of atomic levels. Basic principles and experimental results are given.

Nonlinear spectroscopy of cold atoms in diffuse laser light

The nonlinear spectroscopy of cold atoms in the diffuse laser cooling system is studied in this paper. We present the theoretical models of the recoil-induced resonances (RIR) and the electromagnetically-induced absorption (EIA) of cold atoms in diffuse laser light, and show their signals in an experiment of cooling Rb-87 atomic vapor in an integrating sphere. The theoretical results are in good agreement with the experimental ones when the light intensity distribution in the integrating sphere is considered. The differences between nonlinear spectra of cold atoms in the diffuse laser light and in the optical molasses are also discussed. (c) 2009 Optical Society of America

体全息光栅透镜的设计和应用

设计了一种新型的体全息光栅透镜，在一块光学平板(体全息记录材料)内可以将输入光束产生横向传输并聚焦，或对输入光点产生横传的准直．它由一束平面波和一束球面波正交入射到光学平板上干涉形成的．研究了该体全息透镜的光栅间距变化情况，为设计和制备体全息光栅透镜及相关器件提供了理论依据．基于两光束耦合波理论，得到了该光栅透镜的耦合波方程，近似计算了该透镜的衍射效率及其达到高衍射效率时透镜的最佳尺寸．最后，讨论了该透镜在集成光学等领域中的应用．

Three-dimensional superresolution by three-zone complex pupil filters

Complex pupil filters are introduced to improve the three-dimensional resolving power of an optical imaging system. Through the design of the essential parameters of such filters, the transmittance and radius of the first zone, three-dimensional superresolution is realized. The Strehl ratio and the transverse and axial gains of such filters are analyzed in detail. A series of simulation examples of such filters are also presented that prove that three-dimensional superresolution can be realized. The advantage of such filters is that it is easy to realize three-dimensional superresolution, and the disadvantage is that the sidelobes of the axial intensity distribution are too high. But this can be overcome by the application of a confocal system. (C) 2005 Optical Society of America.

提高能量密度的超衍射极限激光光束相位补偿技术

定义了激光光束衍射远场光斑压缩前后的能量比以及能量密度比来衡量超衍射极限激光光束的质量。通过利用反向传递算法设计了合适的补偿相位板，不但对准直放大的单一横模激光光束进行小于光学衍射极限的发散度的压缩，同时又保证光束能量集中于压缩后的远场衍射主瓣中，使压缩后的远场衍射光斑的能量密度增加。给出了相应的实例。这一结论不但解决了光学超分辨中光束压缩与能量损失不可避免这一矛盾，而且为发散度小且能量密度高的超衍射极限激光光束的实验工作以及该类光束的实际应用提供了理论基础。

Superresolution, extended focal depth or focal shift with electrically controllable radial birefringent filter

In this paper an electrically controllable radial birefringent pupil filter is proposed. It consists of two polarizers and an improved electrically controllable optical azimuth rotator which has two lambda/4 retarders, one electro-optical crystal and one radial birefringent crystal. The evolution and distribution of polarization states of this pupil filter are discussed. The most interesting and useful advantage of such a structure is that the characteristic of transverse superresolution and axial extended focal depth or focal shift can be obtained merely by controlling the applied voltage on the electro-optical crystal. The radial birefringent crystal azimuth angle cooperating with different electrical inductive phase differences will determine the transverse and axial intensity distribution. It is shown that for particular ranges of electrical inductive phase difference it is possible to obtain transverse superresolution along with extended focal depth or with a focal shift.

Tunable transverse superresolution with phase-only pupil filters

A new set of pure phase filters for realizing transverse superresolution is presented in this paper. The filters, whose significant features are their ability to tune and their simplicity, consist of one half-wave plate between two quarter-wave plates; the half-wave plate is made of two zones that can rotate with respect to each other. By rotating any zone of the half-wave plate, the central lobe width of the irradiance point spread function (PSF) in the transverse direction can be tunably reduced. At the same time, the axial intensity distribution is analysed in detail.

Laser beam shaping system with a radial birefringent filter

Reshaping of a Gaussian laser beam into a uniform or other intensity distribution is required for various applications. The laser beam shaping system with a radial birefringent filter is presented in this paper. With such a system the Gaussian beams can be transformed into uniform or annular beams. The theory and simulation of the proposed systems are described in detail. The primary advantage of such a system is that the out beam pro. le can be tunable with the rotation of the radial birefringent element.

Series representation of the Gaussian beam far-field diffracted by annular aperture

Accurate, analytical series expressions for the far-field diffraction of it Gaussian beam normally incident on a circular and central obscured aperture are derived with the help of the integration of parts method. With this expression, the far-field intensity distribution pattern can be obtained and the divergence angle is deduced too. Using the first five items of the series, the accuracy can satisfy most laser application fields. Compared with the conventional numerical integral method, the series representation is very convenient for understanding the physical meanings. (C) 2007 Elsevier GmbH. All rights reserved.

Fields of apertured polychromatic laser beams with Gaussian and Hermite-Gaussian transverse modes

Starting from the Huygens-Fresnel diffraction integral, the field expressions of apertured polychromatic laser beams with Gaussian and Hermite-Gaussian transverse modes are derived. Influence of the bandwidth on the intensity distributions of the laser beams is analyzed. It is found that when the bandwidth increases, the amplitudes and numbers of the intensity spikes decrease and beam uniformity is improved in the near field and the width of transverse intensity distribution of the apertured beams decreases in the far field. Thus, the smoothing and narrowing effects can be achieved by increasing the bandwidth. Also, these effects are found in the laser beams with Hermite-Gaussian transverse modes as the bandwidth increases.(c) 2006 Elsevier Ltd. All rights reserved.

利用石英晶体平凸透镜实现激光束的空间整形

基于石英晶体的旋光特性，我们提出利用石英晶体平凸透镜和偏振片来实现线偏振光的空间强度整形，通过控制入射光的偏振方向可以方便地改变输出激光的空间强度分布。

High focal depth with a pure-phase apodizer

High-density optical data storage requires high-numerical-aperture (NA) lenses and short wavelengths, But, with increasing NA and decreasing wavelength, the depth of focus (DOF) decreases rapidly. We propose to use pure-phase superresolution apodizers to optimize the axial intensity distribution and extend the DOF of an optical pickup. With this kind of apodizer, the expected DOF can be 2-4.88 times greater than that of the original system, and the spot size will be smaller than that of the original system. (C) 2001 Optical Society of America.

Phase-shifting apodizers for increasing focal depth

We propose the use of a phase-shifting apodizers to increase focal depth, and we study the axial and radial behavior of this kind of apodizer under the condition that the axial intensity distribution is optimized for high focal depth. (C) 2002 Optical Society of America.

Phase-shifting apodizer for next-generation digital versatile disk

The next generation digital versatile disk (DVD) using blue lasers will have a capacity of 13 to 15 Gbytes. Compared with current DVD, the wavelength will be shorter and the numerical aperture (NA) will be higher. But with the increase of NA and decrease of wave length, the depth of focus (DOF) decrease rapidly, which makes it hard for the servo-system to track. We propose an optimized three-portion phase-shifting apodizer to increase the depth of focus and at the same time minimize the spot size, which makes the DOF of next generation DVD comparable to current DVD. The simulation result shows that an optical system with this apodizer also has a good defocus characteristic. (C) 2001 Society of Photo-Optical Instrumentation Engineers.

Tunable focal depth of an apodized focusing optical system

The axial intensity distribution and focal depth of an apoclized focusing optical system are theoretically investigated with two kinds of incident light fields: a uniform-intensity-distribution beam and a Gaussian beam. Both a low-numerical-aperture and a high-numerical-aperture optical system are considered. Numerical results show that the depth of focus can be adjusted by changing the geometrical parameters and transmissivity of the apodizer in the focusing optical system. When a Gaussian beam is employed as the incident beam, the waist width also affects the depth of focus. The tunable range of the focal depth is very considerable. (c) 2005 Society of Photo-Optical Instrumentation Engineers.