Analysis of focal length of blue-phase liquid crystal (BPLC) cylindrical lens for the light of the various incident angles and polarisations

Horizontally non-uniform electric field along the vertical direction inside blue-phase liquid crystal (BPLC) layer induces the Gradient index (GRIN) lens effect. Dependence of lens performance on the incident angle and polarisation is investigated by calculating the spatial phase distribution and the direction of wave front for lights passing through the BPLC layer. The calculated trajectories of light rays show that the focal distance for e-wave is less affected by the incidence angle than the focal distance of the o-wave. This can be attributed to the fact that steepness of spatial distribution of the effective refractive index for e-wave decreases for the larger incident angles.     

On the Possibility of Evanescent Wave Excitation Distal from a Solid-Liquid Interface Using Light Quenching

Abstract— Evanescent wave illumination with total internal reflection is often used to provide excitation near a quartz-water interface. We now show that evanescent illumination at one wavelength and incident angle, coupled with light quenching at a second wavelength and incident angle, can be used for selective excitation of fluorophores located up to 5000 Å into the aqueous phase. The displacement of the fluorophore population from the solid-liquid interface depends on the angles of incidence of the excitation and quenching beams and the optical power of the quenching beam. Light quenching with an evanescent wave was demonstrated to be experimentally possible using Pyridinez and a light-quenching wavelength of 736 nm. The use of combined evanescent wave excitation and evanescent wave quenching could provide selective excitation of fluorophores in the cytoplasmic region of cells and may provide improved response times for optical sensors based on evanescent excitation.     

An X-ray refractive lens comprising two sections cut from a gramophone record for a portable total reflection X-ray fluorescence spectrometer

An X-ray refractive lens is assembled from two sections cut from a gramophone record. The refractive lens is placed in a portable total reflection X-ray fluorescence (TXRF) spectrometer, and it is used for collimation of the incident X-ray beams. A TXRF spectrum measured with the refractive lens is compared with that measured with a waveguide. Compared with the refractive lens, the waveguide enhances the intensities of the X-rays illuminating an analyte. Therefore, fluorescent X-ray intensities increase when using the waveguide. On the other hand, the vertical angular divergence of the incident X-ray beams is smaller when using the refractive lens, and the smaller angular divergence results in a reduction of the scattering of the incident X-rays from a sample holder. Therefore, the spectral background is reduced when using the refractive lens, resulting in an increase of the signal to background ratios of the fluorescent X-rays. Detection limits for 3d transition metals obtained with the refractive lens are sub-nanograms to a few nanograms, and the detection limits are similar to those obtained with the waveguide.     

Coaxially bifocal liquid crystal lens with switchable optical aperture

An electrically tunable liquid crystal (LC) lens with dual hole-patterned electrodes is demonstrated. When the LC lens is operated at low voltages, the dual hole-patterned electrodes with different diameters impart the lens with a coaxial bifocal characteristic. At high voltages, the proposed LC lens functions as a conventional lens with a single focal length but with a switchable optical aperture. The demonstrated LC lens is free of disclination lines because of the presence of voltage-assisted high pretilt angles created from the upmost hole-patterned electrode with small diameter.     

Angular-Dependent Metal-Enhanced Fluorescence from Silver Island Films

In this letter we report the observation of angular-dependent Metal Enhanced Fluorescence (MEF) from fluorophores deposited onto silver island films (SiFs). When illuminated with laser light (473 nm) at angles of 45 and 90 degrees from the surface, SiFs scattered light at wide observation angles biased by the direction of the incident light. We observed angular-dependent MEF (10-fold) from FITC-HSA immobilized onto the SiFs, again slightly biased with respect to the direction of the incident light. We also measured the photostability of FITC from the back of the glass substrate at angles of 225 and 340 degrees.     

Liquid crystal Pancharatnam-Berry phase lens with spatially separated focuses

In this paper, we proposed and fabricated a liquid crystal (LC) lens with spatially separated focuses via liquid crystal photoalignment technology. The novel lens is an integration of the polarisation grating and conventional LC lens. The two focuses of that new lens, one of which is real while the other is virtual, can be spatially separated. When combined with normal convex lens and illuminated by a linearly polarised beam, the two emergent light beams become all convergent and the two focuses are separated in three-dimension space. Moreover, the focal lengths of the lens system can be artificially controlled by adjusting the distance between our new lens and the conventional lens. Our results achieve the potential of LC lens’ application in imaging devices such as multifocal cameras, bifocal eyeglasses and so on.     

Long range dipole-dipole correlations in nitrobenzene-benzene solutions

Hyper-Rayleigh scattering (HRS) from liquid nitrobenzene-benzene solutions with nitrobenzene mole fraction in the range 0.001 < x(NB) < 1 was measured for several combinations of linear polarized incident and scattered light, for scattering angles near 90°. Polar collective modes are identified by their distinctive HRS polarization dependence. At all concentrations the nitrobenzene HRS intensity is dominated by the transverse polar collective mode contribution and the longitudinal collective mode contribution is near zero. The transverse polar mode HRS is due to long range dipole-dipole orientation correlations between the nitrobenzene molecules, such that the molecular dipoles are oriented transverse to the wave vector for each spatial Fourier component of the orientation distribution.     

应用于助航系统的赋形曲面光学系统研究

非对称式光度系统技术可以实现光能量的收集与再分配，已经广泛应用于照明领域。基于非成像光学理论的自由曲面照明光学设计具有体积小、设计自由度高、出光光形准确可控等优点。通过采用自由曲面对LED进行合理的二次配光，可以实现绿色环保的照明，给未来照明行业的发展指明了新的方向。本文通过对关于LED自由曲面的光学设计进行研究，提出了一种满足侧边发光照明方式的自由曲面透镜设计方法。将得到的自由曲面透镜实体模型作为立式滑行道边灯透镜设计的基本结构。仿真与实验结果表明，仅用一颗LED光源即可实现联邦航空局（FAA）对立式滑行道边灯的光强分布要求。     

Angle dependent total cross sections and the optical theorem

Cross sections are either represented by generalized asymptotical partial wave expansions or obtained as a spherical average of an appropriate differential cross section. In these cases it is usually assumed that the total scattering cross section, as a property of a scattering object, does not depend on the incident angles. This viewpoint is supported by common knowledge in connection with low energy scattering. However this unconscious belief is not always correct. In the present paper we will show that a non-spherical scatterer may exhibit strong dependence on the incident direction. To do this we will represent the scattering data of the most general potential, separable in ellipsoidal coordinates, in perturbed ellipsoidal (Lamé) wave functions. These functions arise when variables in the Schr?dinger equation are separated in an ellipsoidal coordinate system. The Lamé wave functions are analogous to spherical- and Bessel functions in the case of spherical symmetry. We will expand the total scattering cross section and derive the optical theorem explicitly demonstrating the incident angle dependence for such a class of potentials. As an illustration we will present and display some calculations of the total cross section versus incident direction. Unexpected behavior will be discussed and explained. We also use results from classical acoustic scattering by a triaxial ellipsoid. The general character of the ellipsoidal coordinate system is emphasized.     

Optics of light scattering caused by liquid-crystal-director fluctuations

We have applied the light-scattering equation caused by liquid-crystal (LC)-director fluctuations as derived by De Gennes [1] to the case where the polarization direction of the incident light is at an arbitrary angle with respect to the LC directors within the cell. Based on the De Gennes’s equation, we have used an out-of-plane (OPR) cell-rotation method to measure the pretilt angles of a tilted-homogeneously aligned LC cell. Our measured pretilt angles are in good agreement with that obtained by the published OPR-rotation method [2] based on a different mechanism. Our method is simple in setup and requires no complicated data-fitting calculations when the pretilt angles are below about 30°. In addition, there is no need to know cell parameters except the ordinary and extraordinary refractive indices of the LC medium at the wavelength of incident light.     

Analysis of polyhexamethylene biguanide in multipurpose contact lens solutions

The objective of this study was to establish a reasonably simple and reliable method to measure very low concentrations of polyhexamethylene biguanide (PHMB) in multipurpose contact lens solutions (MPSs). By using a weak cation exchange solid phase extraction cartridge to extract the PHMB from MPS, followed by HPLC analysis using an evaporative light scattering detector, low levels (0.1 ppm) of PHMB were detected. Application of this method to a series of off-the-shelf MPS with PHMB as the active ingredient demonstrated these solutions contain 1 ppm. The contact lens solution with hydrogen peroxide as the active ingredient gave no peak where the PHMB peak eluted. The Polyquad^® contact lens solution generated a peak close to the retention time of PHMB. Recovery of PHMB from fortified hydrogen peroxide contact lens solution was good at 0.25 ppm and above; 105% with a RSD of 17% or less. The repeatability of the HPLC system ranged from 4 to 11% RSD; the reproducibility of the entire method was less than 17.5% RSD. Storage and stability studies indicated that storage of MPS with PHMB for chemical analysis are not temperature dependent, but are affected by the composition of the container in which the contact lens solution is stored.     

溶剂散逸自组装法制备具有电致收缩性能的聚苯胺/聚氨酯凹透镜阵列

以水珠为模板,采用溶剂散逸自组装法制备了表面具有特殊形貌的有序多孔膜. 以此多孔膜为模板制备了聚苯胺/聚氨酯（PANI/PU）的凹透镜阵列. 采用红外光谱（FTIR）和扫描电子显微镜（SEM）对界面聚合得到的PANI/PU纳米复合物的结构和凹透镜阵列的形貌进行了表征,研究了不同合成条件对纳米复合物导电性能的影响,并对PANI/PU凹透镜阵列的电学和光学性能进行了研究. 结果表明,PANI/PU凹透镜阵列同时具有导电性、电致收缩性和光衍射性质;其收缩率与外加电压成反比,而透光率与收缩率成正比.     

Temperature-dependent optical band structure and defect mode in a one-dimensional photonic liquid crystal

We analysed the propagation of an electromagnetic wave in a one-dimensional periodic system composed of a finite set of E7 liquid crystal mixture slabs in a twisted configuration alternated by homogeneous and isotropic dielectric layers. For different incident angles of the circularly polarised wave, we studied the optical band structure for reflectance and transmittance considering that the dielectric matrix of the device depends on temperature and wavelength. We demonstrated that the position of the band can be moved from visible to short-infrared spectrum region by increasing the thickness of the layers. We found that for a fixed incident angle, the band spectrum shifts towards the short-wavelength region as the temperature gets increasing, whereas, for a constant temperature, such a spectrum moves towards larger frequencies as the incident angle increases. We show that when one of the homogeneous and isotropic slabs has a different size compared with the remaining ones, a defect mode is induced in the band structure whose frequency can be thermally tuned.     

Multi-wavelength thermal lens spectrophotometer

A novel four-wavelength pump-probe configuration thermal lens spectrophotometer that is capable of simultaneously measuring thermal lens signals at four different wavelengths has been developed. The four excitation beams were derived from the same argon ion laser, which operated in a multi-line mode. The sample was sequentially excited by these four and the corresponding thermal lens signals were monitored by a He-Ne laser. Compared with other existing thermal lens apparatus, this four-color spectrophotometer has advantages that include its ability to provide identification of the analyte (as the ratios of the signals at four different excitation wavelengths) and to analyze simultaneously four-component samples without the need for any prior sample preparation. With this apparatus and with the use of 6-mW excitation beams modulated at 1.02 Hz, the detection limit for four-component samples is estimated to be about 10^?9 M, which is similar to the detection limit obtained for a one-component sample using a single-wavelength system.     

Polymer network liquid crystal grating/Fresnel lens fabricated by holography

In this article, polymer network liquid crystal (PNLC) grating/Fresnel lens is fabricated by holography. The exposure light pattern for the grating is obtained by interfering two planar wave fronts, while the Fresnel pattern is achieved by interfering a planar wave front and a spherical wave front. Owing to the alignment effect and anchoring power of polymer network, the holographic PNLC grating achieves improved diffraction efficiency, and remarkably reduced operation voltage (reduced by 80%) compared with holographic polymer-dispersed-liquid-crystal and holographic polymer-stabilised blue-phase liquid-crystal gratings, while maintaining submillisecond response. Moreover, it achieves high spatial frequency with a 2-μm grating period, thanks to the holographic fabrication. The holographic PNLC Fresnel lens also exhibits attractive electro-optical properties.     

The effect of the incident collision energy on the porosity of vapor-deposited amorphous solid water films

Molecular beam techniques are used to grow water films on Pt(111) with various incident angles and collision energies from 5 to 205 kJ/mol. The effect of the incident angle and collision energy on the porosity and surface area of the vapor-deposited water films was studied using nitrogen physisorption and infrared spectroscopy. At low incident energy (5 kJ/mol), the infrared spectra, which provide a direct measure of the surface area, show that the surface area increases with incident angle and levels off at angles > 65 degrees . This is in contrast to the nitrogen uptake data, which display a maximum near 65 degrees because of the decrease in nitrogen condensation in the larger pores that develop at high incident angles. Both techniques show that the morphology of vapor-deposited water films depends strongly on the incident kinetic energy. These observations are consistent with a ballistic deposition shadowing model used to describe the growth of highly porous materials at glancing angle. The dependence of film morphology on incident energy may have important implications for the growth of porous materials via glancing angle deposition and for the structure of interstellar ices.     

分光光度法与激光热透镜光谱分析法测定高散射物质光吸收的比较

通过理论和实验比较了分光光度法与激光热透镜光谱分析法在高散射背景下测量物质光吸收的差异。研究了在不同含量纳米TiO2的散射背景下，散射对分光光度法和热透镜光谱分析法测定耐尔蓝溶液含量的影响。结果表明，分光光度法对具有光散射性质试样的测定存在较大误差，而激光热透镜光谱分析法能较好的避免散射影响，测定结果准确。实验结果与理论分析相一致。     

Rat lens glycolysis after in vivo exposure to narrow band UV or blue light radiation

UV radiation and short wavelength visible light are known to damage various tissues in the eye. This paper investigates the effect on rat lens glycolysis after in vivo exposure with 90 kJ m⁻² narrow band UV radiation (UVB, 300 nm) and 90 kJ m⁻² blue light (435 nm) radiation. After exposure, all lenses were incubated in Medium 199. Samples of culture medium were withdrawn after 2, 4, 6 h and 5, 10, 20 h in two UVB studies and after 5, 10 and 20 h in a blue light study. Lactate is the major end product of lens glycolysis. Lactate was determined with a modified enzymatic-photometric method. Intralenticular lactate was determined in one UVB experiment. In the UVB experiments we found a lower lactate production in the exposed lenses 2–6 h after exposure. There was an accumulation of lactate inside UVB-exposed lenses after 6 h incubation compared with their contralateral lenses. No significant effect on lactate production was observed in the blue light experiment. Conclusions. UVB induced a reversible inhibition of glycolysis. UVB also induced an accumulation of lactate inside the lens. Blue light tended to increase glycolysis.     

“Cell adhesion resistant,UV curable,polymer zinc oxide nanocomposite materials for intraocular lens application”

Foldable acrylic lenses are used for surgical replacement of diseased intraocular lens in treatment of cataract. One of the main postsurgical complications of this treatment method is postcapsular opacification caused by proliferating epithelial cells. The most common approach taken by research community to address this issue has been modification of lens surface with hydrophobic or hydrophilic moieties to manipulate surface cell interaction. In the present study, inherently cell repellent photopolymer resins are presented. Taking advantage of zinc oxide antiproliferative properties, its nanocomposite resins were made and investigated. Hydrophobically modified zinc oxide nanoparticles and poly(phenylethylacrylate‐co‐phenylethyl methacrylate) were made, and their nanocomposite films were prepared by UV polymerization. Films made with 5 wt% ZnO nanoparticles in them resisted fibroblast attachment substantially. In addition, these films filtered harmful UV light and showed other necessary properties like visible light transparency, glass transition temperatures, mechanical strength, and biocompatibility necessary for making intraocular lenses.     

Studies of surfactant/water systems near the critical micellar concentration using thermal lens spectroscopy

A novel application of photothermal spectroscopy to the study of surfactant-water systems near the critical micellar concentration is reported. The thermal lens signal was induced by a slightly soluble dye and was measured with a dual-beam thermal lens spectrometer.For the two surfactants considered: nonyl phenol and Triton X-100, sharp variations of the thermal lens signal were observed at the critical micellar concentration (CMC), namely an increase for nonyl phenol and a decrease for triton X-100. These effects are arguably related to micelle formation.Our work serves as an initial assessment of the potential of the technique for the study of disperse systems of a higher complexity or dark systems where conventional techniques are impossible to apply.