Third-order dispersion in a pair of prisms

The general equation for third-order group velocity dispersion is derived in this paper, which contains all the terms of equation (11) in Arissian and Diels [1], as well as one extra term, which we have verified is not negligible. To verify our equation we have modeled the sum of Gaussian modulated frequencies. We show the electric field of bandwidth limited incident ultrashort pulses with a time duration of: 5 fs, 10 fs, 15 fs, 20 fs, 30 fs and 50 fs after propagating through a pair of identical isosceles prisms for a central frequency of 0.8 µm and 0.620 µm. The model is applied by using (a) the finite phase, (b) the phase approximated up to the second-order dispersion and (c) up to the third-order dispersion for each frequency component of the pulse. Graphs are presented for prisms made with fused silica and SF14.     

Squeezing of light field in a dissipative Jaynes–Cummings model

Based on the time-convolutionless master-equation approach, we investigate squeezing of light field in a dissipative Jaynes–Cummings model. The results show that squeezing light can be generated when the atom transits to a ground state from an excited state, and then a collapse-revival phenomenon will occur in the squeezing of light field due to atom-cavity coupling. Enhancing the atom-cavity coupling can increase the frequency of the collapse-revival of squeezing. The stronger the non-Markovian effect is, the more obvious the collapse-revival phenomenon is. The oscillatory frequency of the squeezing is dependent on the resonant frequency of the atom-cavity.     

Spin operator for quantum light in integrated photonic waveguides

In this work a quantum mechanical derivation of the Spin operator in integrated isotropic and anisotropic photonic waveguides is obtained from both first principles of the electromagnetic theory and conservation laws, and moreover, within a phenomenological quantization approach. The Spin operator will be derived by starting from the spin conservation law to obtain the spin flux density and by means of a quantization based on the vector structure and orthonormality property of guided modes; likewise, since anisotropic guides produce polarization changes, and consequently changes of the expected values of spin, we will also present the Momentum operator for anisotropic guides. The expression for the Spin angular momentum operator shows that both the presence of modal longitudinal components and the modal mismatching reduces the spin values, but it comes into the standard expression when it is used in homogeneous media and in particular with uniform and infinite plane modes. Likewise these results have a direct influence on the Stokes's operators which allow one to analyze quantum polarization in integrated photonics.     

Binary spatial amplitude modulation of continuous transverse modal electric field using a single lens for mode selectivity in multimode fiber

The demand for portable real-time optical applications such as medical optical sensors and optical transceivers instigate the need for compact optical designs. The aim of this paper is to demonstrate a new, compact design for binary spatial amplitude modulation in a mode-selective transmitter in a multimode fiber, adapted from microscopy. Results show that it is possible to retrieve the original continuous-amplitude transverse modal electric field from the binary amplitude-modulated image using a single lens. The retrieved image is in good agreement with the original image.     

Compression and localization of an atomic cloud in a time dependent optical lattice

We analyze a method of compressing a cloud of cold atoms by dynamic control of a far off-resonance optical lattice. We show that by reducing the lattice spacing either continuously or in discrete steps while cooling the atoms with optical molasses large compression factors can be achieved. Particle motion in the time-dependent lattice is studied numerically using a three-dimensional semiclassical model. Two experimentally realistic models are analyzed. In the first we continuously vary the lattice beam angles to compress atoms initially in a Gaussian distributed cloud with standard deviation of 250 µm into a single site of a two-dimensional lattice of area A ～ 35 × 35λ², with λ the wavelength of the lattice beams. This results in an optical depth for an on-resonant probe beam >80 which is an increase by a factor of about 1800 compared to the uncompressed cloud. In the second approach we use a discrete set of lattice beam angles to decrease the spatial scale of the cloud by a factor of 500, and localize a few atoms to a single lattice site with an area A ? λ².     

Tight focusing induces pulse delay and pulse compression of double-ring-shaped radially polarized ultrashort light pulses

The focusing of double-ring-shaped radially polarized ultrashort light pulses by a high-numerical aperture objective is investigated using vectorial Debye theory. After focusing, the double-ring-shaped radially polarized ultrashort light pulses slow down near the focus, and this pulse delay induces pulse compression in the propagation direction. That is, without changing the pulse duration, the spatial pulse length of the ultrashort light pulse is decreased near the focus. The velocity of the longitudinal component of the light pulse near the focus is lower than that of the radial component. The simulation results demonstrate that control of the ratio of the pupil radius to the beam radius affects not only the longitudinal component of the light pulse, but also the velocity and spatial pulse length of the light pulse because of the destructive interference between the longitudinal components of the inner and outer rings of the light pulse.     

一种新型楔形膜在真空中的制作方法及测试结果

提出了一种新型楔形膜在真空中的制作方法,可以替代白光干涉位移传感器中的关键元件.该方法采用两层复制技术,用有机材料SU8胶作为楔形膜中间的材料.同时,搭建了白光干涉位移传感器系统,对制作的楔形膜进行了测量.实验结果表明,该解调系统具有较好的稳定性及较高的测量精度.     

Bi2O2CO3/TiO2复合粉体的制备及其光催化性能研究

采用水热法制备了Bi2O2CO3,并将其与TiO2进行了复合。XRD数据表明此复合光催化剂中Bi2O2CO3结晶性良好,紫外-可见漫反射光谱说明Bi2O2CO3的加入使其吸收带边有一定的红移。研究了紫外-可见光照射下Bi2O2CO3/TiO2复合光催化剂对亚甲基蓝溶液的降解性能,结果表明当Bi2O2CO3与TiO2的质量比为0.032时,得到性能最优的复合光催化剂,其光催化活性优于TiO2。     

La、Fe共掺杂TiO2/膨润土的制备及其光催化性能

采用超声辅助溶胶-凝胶法制备了La、Fe共掺杂TiO2/膨润土复合光催化材料。采用X射线衍射(XRD)、傅里叶变换红外(FT-IR)光谱和紫外-可见漫反射吸收光谱(DRS)等测试技术对其进行了表征分析。在紫外光照射下,通过对TNT废水的光催化降解,考察其光催化活性。结果表明,La、Fe的共掺杂抑制了TiO2的晶型转变和晶粒生长,增强了复合材料的吸光性能;适量的La、Fe共掺杂能提高复合材料的光催化性能,当La与Fe的掺杂量分别为0.5%和0.05%(摩尔分数),煅烧温度为400℃时,其光催化活性达到最佳效果。