Induced Smectic X Phase Through Intermolecular Hydrogen-Bonded Liquid Crystals Formed Between Citric Acid and <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">n</Emphasis>-(Octyloxy)Benzoic Acid

Hydrogen-bonded liquid crystal (HBLC) is synthesized from citric acid (CA) and 4-(octyloxy)benzoic acid (8OBA) with different mole ratios. Fourier transform infrared spectroscopy (FT-IR) confirms the presence of hydrogen bond between CA and 8OBA. Nuclear magnetic resonance (NMR) spectroscopic studies validate the intermolecular complementary, cyclic type of hydrogen bond, and molecular environment in the designed HBLC complex. Powder X-ray diffraction analysis reveals the monoclinic nature of liquid crystal complex in solid phase. Liquid crystal parameters such as phase transition temperature and enthalpy values for the corresponding mesogenic phases are investigated using a polarizing optical microscope (POM) and differential scanning calorimetry (DSC). It is observed that the change in chain length and steric hindrance while increasing the mole ratio in HBLC complex induces a new smectic X (Sm X) along with higher-order smectic G (Sm G) phases by quenching of smectic C (Sm C). From the experimental observations, induced Sm X phase has been identified as a finger print texture. Also, Sm G is a multi-colored mosaic texture in 1:1, 1:2, and 1:3 mol ratios. The optical tilt angle, thermal stability factor, and enhanced thermal span width of CA + 8OBA complex are discussed.     

CCl4喇曼光谱退偏度在超声空化作用下的变化研究

本文测量了在超声空化作用下CCl4喇曼光谱退偏度的变化，通过假设超声空化拉长了样品的分子轴，解释了超声空化使所测样品的退偏度减小这一实验现象，并指出不同振动谱线的退偏度变化不同。     

Testing discrete quantum mechanics using neutron interferometry and the superposition principle—Agedanken experiment

Using a neutron interferometer and the phase difference calculated from spatial discrete quantum mechanics, a test for discrete quantum theory may implemented by measuring the X spin polarization and its variation with position.     

Equilibrium superradiance in a Bose gas

A model of free₄He atoms interacting with radiation exhibits an equilibrium phase transition in which the atomic ground-state Bose condensation is coupled to condensations of virtual photons and virtually excited atoms of the same macroscopic wavelength. The condensed phase has a twofold polarization degeneracy. It is suggested that this might furnish a mechanism for a discrete symmetry-related phase degeneracy of superfluid liquid⁴He required to explain the transition according to Tisza's generalized Gibbsian thermodynamics. A more realistic model would require inclusion of repulsive interactions.Supported in part by the National Science Foundation, Grant DMR76-17467.     

Electromagnetically induced transparency in degenerate two-level systems

The evolution of an electromagnetic wave with slowly varying polarization, which interacts resonantly with the medium formed by degenerate two-level atoms, is studied using the wave function approach under the conditions of electromagnetically induced transparency. It is shown that the amplitude of the wave field propagates at the velocity of light in such a medium. The equation obtained for the polarization parameter has a solution in the form of a simple wave. The breaking length is determined. It is shown that the velocity of propagation of polarization waves may be much smaller than the velocity of light. The proposed approach is common for two-level systems with an arbitrary degeneracy. The case of a system with Zeeman degeneracy is analyzed in detail. The dependence of the velocity of propagation of the polarization structure on the amplitude and polarization is determined for an arbitrary level degeneracy. The evolution of the polarization structure in such a medium is discussed.     

Structural and Magnetic Properties of Sm Implanted GaN

The structural and magnetic properties of Sm ion-implanted GaN with different Sm concentrations are investigated. XRD results do not show any peaks associated with second phase formation. Magnetic investigations performed by superconducting quantum interference device reveal ferromagnetic behavior with an ordering tem- perature above room temperature in all the implanted samples, while the effective magnetic moment per Sin obtained from saturation magnetization gives a much higher value than the atomic moment of Sm. These results could be explained by the phenomenological model proposed by Dhar et al. [Phys. Rev. Lett. 94（2005）037205, Phys. Rev. B 72（2005）245203] in terms of a long-range spin polarization of the GaN matrix by the Sm atoms.     

Removal of surface plasmon polariton eigenmodes degeneracy

The effect of the tilt angle of a metal film on the transmissivity of subwavelength holes in optically thick metal film is investigated. We found that the transmission efficiency can be highly dependent on the tilt angle. It is also found that when the input photons are not polarized along the eigenmode directions of surface plasmon polariton, a birefringent phenomenon is observed when a periodic array of subwavelength holes is tilted. Linear polarization states can be changed to elliptical polarization states, and a phase can be added between two eigenmodes. The phase is changed with the tilt angle. A model based on surface plasmon polariton eigenmodes degeneracy is presented to explain these experimental results. PACS 81.07.-b; 71.36.+c; 78.66.Bz     

Robust generation,properties and potential applications of quadratic spatial solitons generated by optical parametric amplification

Quadratic spatial solitary waves are predicted and observed experimentally near degeneracy for Type II optical parametric amplification in bulk KTP, by seeding an intense pump optical field with a control signal at half the pump wave frequency. The self-trapping of light at the two wavelengths has been shown to be insensitive to phase, polarization and magnitude of the control input, and can be exploited in novel schemes for robust all-optical processing.     

饮用水激光拉曼光谱的比较与分析

为了对我国目前饮用水的质量进行有效检测,对市面上几种常用品牌的饮用水以及实验室提供的蒸馏水等样品做了测量和计算。运用激光拉曼光谱的分析方法,测量了它们的激光拉曼光谱。同时,通过测量计算了样品在对称伸缩振动处拉曼谱的退偏度。结果表明,在水样品的对称伸缩振动处,其拉曼谱的相对强度大小和退偏度的大小有着相同的规律。对结果进行比较和分析后得出了如下结论：可以从拉曼光谱特征峰相对强度的大小和同一特征峰下退偏度的大小两方面来判断饮用水中矿物质含量的相对多少。为鉴定饮用水的质量提供了新的有效途径。     

Cones of optical axes in gyrotropic crystals with scalar permittivity

A theory is constructed for the degeneracy of electromagnetic waves in gyrotropic crystals near their isotropy points (in temperature and other parameters), in which permittivity ? becomes scalar due to dispersion and optical anisotropy is entirely determined by gyrotropy. It is shown that closed lines of intersection of sheets of the refraction surface, which correspond to the cones and, in particular, planes of the optical axes, are formed for isotropic ?. The polarization characteristics of wave fields experience a jump upon a transition through such lines. The conditions for the existence and geometry of the degeneracy cones under investigation are analyzed for crystals of all symmetry classes permitting optical activity. It is shown that the degeneracy lines disappear for a small deviation of ? from isotropy, while polarization anomalies persist. Isolated (one or two) degeneracy points may retain in place of the lines in the case when the optical axes of a perturbed crystal with “switched-off” gyrotropy belong to the initial cone.     

Level-degeneracy effects in resonant nonlinear phenomena: Three-level atomic model

The role of level degeneracy in resonant nonlinear phenomena is examined by considering theJ=1 →J=0 atomic transition. The atomic medium is modelled as a homogeneously broadened three-level system and a closed-form expression for the medium susceptibility is obtained. It is used to discuss several nonlinear phenomena such as saturated absorption, optical bistability, and phase conjugation. The two-photon-induced coupling of the ground-state Zeeman sublevels leads to interesting polarization effects.     

Dispersion effects in a highly birefringent fiber laser sensor with fiber Bragg grating reflectors

The effects of dispersion in the highly birefringent fiber Bragg grating reflectors of a polarimetric elliptical-core fiber laser sensor are experimentally and theoretically investigated. The laser sensor is designed to measure fluid pressure. It is experimentally and theoretically shown that the wavelength-dependent phase shifts in the gratings can be employed to remove the near degeneracy of the polarization mode beat frequencies of a given order, which substantially improves the resolution of the sensor. A resolution of a few parts in 10(6) of the free spectral range of the laser is demonstrated.     

Mode characteristics of hollow core Bragg fiber

Analytical expression to calculate propagation constant and mode field of the hollow core Bragg fiber is derived. Numerical results are presented. It is shown that the fundamental mode of the hollow core Bragg fiber is circularly symmetric TE01 mode with no polarization degeneracy, while the higher order mode may be HE11, TM01, or TE02 etc.. This property is different from conventional optical fiber that its fundamental mode is the linearly polarized HE11 mode and is polarization degeneracy.     

Raman sideband cooling of rubidium atoms in optical lattice

We develop a simple and practical scheme to apply sideband cooling to a cloud of rubidium atoms. A sample containing 4 × 10~(70) ~(87)Rb is trapped in a far red detuned optical lattice. Through optimizing the relevant parameters, i.e., laser detuning, magnetic field, polarization, and duration time, a temperature around 1.5 μK and phase space density close to 1/500 are achieved. Compared with polarization gradient cooling, the temperature decreases by around one order of magnitude. This technique could be used in high precision measurement such as atomic clocks and atom interferometer. It could also serve as a precooling means before evaporation cooling in a dipole trap, and may be a promising method of achieving quantum degeneracy with purely optical means.     

Sm(Co,Cu,Fe,Zr)z反磁化过程的微磁学分析

通过微磁学有限元方法研究了微结构对各向异性的Sm(Co,Cu,Fe,Zr)z磁性能的影响， 并 对不同温度下的退磁曲线进行了计算.计算结果表明，矫顽力随着2∶17相晶粒尺寸的增大 而增大，随1∶5晶界相厚度的增大而减小；通过减小晶界相厚度或增大晶粒尺寸可以有效提 高 磁能积.反磁化的物理机制主要为形核机制，主要表现为首先在晶界相形成反磁化核，随 着 磁场的增大反磁化核不断长大，最后导致整个磁体的磁化反转；而当温度升高时，晶界相逐 渐变成非磁性相，使得反磁化核难以形成，因此出现了反常的矫顽力温度依赖关系. 关键词： 微磁学 有限元 微结构 磁性能     

Polarization modulation of light in an optical waveguide under lateral compression

It is shown that a lateral pressure applied to a circular single-mode optical waveguide changes the phase difference between two orthogonally polarized modes and thereby modulates the polarization state of light (elastooptic effect). The efficiency of polarization modulation is characterized by a strain-to-phase difference conversion factor as applied to polarization modes of the fiber. An expression relating the phase difference between the modes and the displacement of squeezing plates is obtained and checked in real experiments and numerically. The efficiency of conversion of lateral pressure to phase difference between the polarization modes is shown to be fairly high, on the order of 10⁴ rad/(μm m).     

Spin polarization in quantum dots by radiation field with circular polarization

For circular quantum dot (QD), taking into account the Razhba spin-orbit interaction (SOI), an exact energy spectrum is obtained. For a small SOI constant, the eigenfunctions of the QD are found. It is shown that the application of a radiation field with circular polarization removes the Kramers degeneracy of the QD eigenstates. Effective spin polarization of electrons transmitted through the QD owing to a radiation field with circular polarization is demonstrated.     

Polarization instabilities in a two-photon laser

We describe the operating characteristics of a new type of quantum oscillator that is based on a two-photon stimulated emission process. This two-photon laser consists of spin-polarized and laser-driven 39K atoms placed in a high-finesse transverse-mode-degenerate optical resonator and produces a beam with a power of approximately 0.2 microW at a wavelength of 770 nm. We observe complex dynamical instabilities of the state of polarization of the two-photon laser, which are made possible by the atomic Zeeman degeneracy. We conjecture that the laser could emit polarization-entangled twin beams if this degeneracy is lifted.     

光学腔内两正交偏振模振幅和相位的补偿

本文开展了光学腔内两正交偏振模振幅和相位补偿的实验研究。通过采用特殊腔型和两个λ/2波片,补偿腔内反射镜对水平偏振模和垂直偏振模的反射率差异,使两个偏振模的输出振幅相等。利用一组λ/4-λ/2-λ/4波片补偿光学腔内水平偏振模和垂直偏振模的相位差,使两个模的输出重合。通过上述的振幅和相位补偿方法,可实现任意偏振光经过环形腔后偏振不变,为任意偏振比特在腔内冷原子系综中的高效率高保真度存储提供了实验基础。     

Conical refraction of elastic waves in absorbing crystals

The absorption-induced acoustic-axis splitting in a viscoelastic crystal with an arbitrary anisotropy is considered. It is shown that after “switching on” absorption, the linear vector polarization field in the vicinity of the initial degeneracy point having an orientation singularity with the Poincaré index n = ±1/2, transforms to a planar distribution of ellipses with two singularities n = ±1/4 corresponding to new axes. The local geometry of the slowness surface of elastic waves is studied in the vicinity of new degeneracy points and a self-intersection line connecting them. The absorption-induced transformation of the classical picture of conical refraction is studied. The ellipticity of waves at the edge of the self-intersection wedge in a narrow interval of propagation directions drastically changes from circular at the wedge ends to linear in the middle of the wedge. For the wave normal directed to an arbitrary point of this wedge, during movement of the displacement vector over the corresponding polarization ellipse, the wave ray velocity s runs over the same cone describing refraction in a crystal without absorption. In this case, the end of the vector moves along a universal ellipse whose plane is orthogonal to the acoustic axis for zero absorption. The areal velocity of this movement differs from the angular velocity of the displacement vector on the polarization ellipse only by a constant factor, being delayed by π/2 in phase. When the wave normal is localized at the edge of the wedge in its central region, the movement of vector s along the universal ellipse becomes drastically nonuniform and the refraction transforms from conical to wedge-like.