Single-beam optical bottle for cold atoms using a conical lens

We report a new method to generate an optical dipole potential with a null intensity region surrounded in all directions by light walls. This is achieved with a simple scheme based on a conical lens. Applications to optical trapping of neutral atoms are discussed. Received 4 September 2000 and Received in final form 21 January 2001     

Enhancement of single-molecule fluorescence using a gold nanoparticle as an optical nanoantenna

We investigate the coupling of a single molecule to a single spherical gold nanoparticle acting as a nanoantenna. Using scanning probe technology, we position the particle in front of the molecule with nanometer accuracy and measure a strong enhancement of more than 20 times in the fluorescence intensity simultaneous to a 20-fold shortening of the excited state lifetime. Comparisons with three-dimensional calculations guide us to decipher the contributions of the excitation enhancement, spontaneous emission modification, and quenching. Furthermore, we provide direct evidence for the role of the particle plasmon resonance in the molecular excitation and emission processes.     

Multimode optical fiber demultiplexer-star coupler using a single gradient-index-rod lens and a multi-facet grating

An optical fiber multi-function device consisting of a single gradient-index-rod lens and a multi-facet blazed reflection grating is proposed to simultaneously realize functions of wavelength demultiplexing and optical signal distribution in a multimode optical fiber transmission system. We analyzed the demultiplexing characteristics and the tolerance of optical components using the ray trace method. This device can realize not only low loss optical signal distribution but also offers improved demultiplexing characteristics in comparison with the previously proposed demultiplexer-multiposition switch. The following characteristics are expected from the design using commercially available optical components: a working band of 0.64–0.88 μm, channel separation of 34–36 nm, 3 dB bandwidth of 27–28 nm, channel cross-talk of less than - 40 dB and minimum excess insertion loss of 0.9–2.1 dB.     

Third-order nonlinear optical response in transparent solids using ultrashort laser pulses

The third-order optical nonlinearity, χ ⁽³⁾, is measured in transparent glasses (BK7 and fused silica) and crystals (BaF₂ and quartz) using 36-fs, 800-nm laser pulses and the optical Kerr gate (OKE) technique; values are found to lie in the range 1.3–1.7×10^-14 esu, in accordance with theoretical estimates. We probe the purely electronic response to the incident ultrashort laser pulse in fused silica and BK7 glass. In BaF₂ and quartz, apart from the electronic response we also observe contribution from the nuclear response to the incident ultrashort pulses. We observe oscillatory modulations that persist for ～400 fs. The response of the media (glasses and crystals) to ultrashort pulses is also measured using two-beam self-diffraction; the diffraction efficiency in the first-order grating is measured to be in the range of 0.06–0.13 %. Third harmonic generation due to self-phase matching in the transient grating geometry is measured as a function of temporal delay between the two incident ultrashort pulses, yielding the autocorrelation signal.     

Enhancement of sensitivity in optical waveguide sensors using left-handed materials

We show analytically that the sensitivity of an optical waveguide sensor can be dramatically enhanced by using a metamaterial with negative permittivity and permeability. The variation of the sensitivity of the proposed waveguide sensor with different parameters of the waveguide is studied. It is found that the sensitivity of the sensor increases with the increasing thickness of the metamaterial due to the surface polariton generation.     

固体浸没透镜光存储的信号探测技术

信号探测是固体浸没透镜成为实用存储技术的一个必需的组成部分。对在该项研究中获得的理论和实验成果进行了介绍。总结了针对固体浸没透镜机理的三维矢量理论 ,对影响信号探测的因素 ,例如头盘间距、盘片结构和光的偏振态等进行了讨论。介绍了基于固体浸没透镜光存储中信号探测的新技术和重要的实验结果。     

Measuring the topological charge of an optical vortex by using a tilted convex lens

We demonstrate, analytically and experimentally, a simple, but effective method to determine the topological charge of an optical vortex by using a spherical bi-convex lens, a ubiquitous optical element found in any optics laboratory. Just by tilting the lens and recording the intensity distribution of a propagating vortex at a predicted position past the lens, we have been able to measure both the sign and the magnitude of the topological charge m   up to m=±14$m=\pm 14$. Our experimental results are in excellent agreement with analytical predictions.     

Three-dimensional optical data storage using a solid immersion lens to focus a femtosecond laser pulse

A solid immersion lens (SIL) has been applied to the writing and reading of three-dimensional optical datastorage in transparent materials. Using a SIL with n=1.516 to focus a 150-fs, 800-nm Ti:sapphire laser,the 5-layer reading and writing of data are achieved in fused silica and polyethylene methacrylate at adensity of 1.1× 1012b/cm3. Some advantages of the employment of SIL have been discussed.     

Radiation-detected optical pumping in solids

Radiation-detected optical pumping in solids has been developed to investigate the structure of unstable nuclei. Appreciable nuclear polarization of implanted or doped unstable-nuclei in a host crystal is achieved with the optical pumping in solids. The nuclear polarization achieved is enhanced/reduced by applying a radio-frequency magnetic field together with the optical pumping, radiation-detected magnetic resonance being thus observed to get information on electromagnetic properties of unstable nuclei. Two schemes have been successfully developed for the optical pumping of unstable nuclei in solids. One is to directly pump the atoms by the excitation from the ground state to a broad absorption band in visible and UV regions which shows a large magnetic circular dichroism. This scheme is applicable to many rare-earth atoms in alkaline-earth fluoride host. The other scheme is to pump the electrons in the conduction band of direct-type semiconductor and thus indirectly polarize the nuclei in the host material via a hyperfine interaction between the nuclei and the polarized conduction electrons. This scheme can be especially applied to the III to VI families of atoms in direct-type semiconductors. Principle of the methods, on-line experimental system, and a few examples of the results obtained so far are presented and discussed.     

Improving the resolution of a solid immersion lens optical system using a multiphase Fresnel zone plate

We propose a method to improve the resolution of near-field optical system with a solid immersion lens by using a multiphase level Fresnel zone plate. The analyses are based on scalar angular spectrum theory. The results show that the multiphase Fresnel zone plate can not only decrease the spot size but also decrease the sidelobe intensity and enhance greatly the diffractive efficiency compared with annular amplitude filter or binary 2-, 3-, 4-zone phase filter.     

Measuring optical properties of an eye lens using magnetic resonance imaging

We compare the focal lengths of porcine lenses measured optically and by using a novel MRI technique. The geometric properties of the lenses were also measured and compared. The MRI technique exploits the dependence of both the lens refractive index and relaxation rates on the local protein concentration. By measuring the refractive index and corresponding values of R2 (=1/T2) for samples of lens homogenates with different protein concentrations, the dependence of refractive index on R2 was determined empirically. R2 maps, constructed from monoexponential fits to multiecho images of a slice through the lens containing the optical axis, were converted to refractive index maps using this relationship. A simulated ray trace through the refractive index map provided an estimate of lens focal length that was compared to a direct optical measurement of focal length using a laser ray-tracing method. It was found that the mean focal lengths estimated from the two techniques agreed within experimental uncertainty. The refractive index profile along the optical axis was found to be well described by a simple function of the form n=n0 + n1 x ra where r is the (normalized) lens radius.     

Simple and high efficient optical trapping using a cylindrical lens and a single plane wave of incidence

We suggest a simple and high efficient method for trapping particles in the evanescent field. In this method, a single plane wave is normally incident on the cylindrical surface of a cylindrical lens and then incident on the plane surface of the lens at an angle larger than the critical angle. Multiple reflections of light within the cylindrical lens create two evanescent waves with different directions in the transmitted field. Interference of two evanescent waves comes into being a standing wave which can stably trap particles close to the top of the cylindrical lens. Based on the Rayleigh approximation, we obtain analytical expressions of optical force acting on a Rayleigh particle placed in the vicinity of the lens. We find that the trap stiffness and trap depth is dependent on the radius of the cylindrical lens, wavelength and polarization of light, and incident angle at the lens–liquid interface.     

Achromatic optical vortex lens

A vortex lens is a useful optical device having applications ranging from astronomy to microscopy. Current vortex masks operate across a narrow bandwidth. Two design schemes are proposed for creating a vortex across a bandwidth exceeding 100 nm in the visible region of the spectrum.     

Nonlinear optical interactions in dye-doped solids

We present a brief review of non-linear optical investigations on dye-doped solids using low-power CW lasers. After a brief introduction to the photophysics of the dye molecules, we discuss specific nonlinear processes such as self-diffraction, optical phase conjugation, two-beam coupling and polarization gratings in these systems. The application potential of dye-doped solid devices is discussed.     

光盘镜头的发展

本文概述了光盘镜头的发展历程，着重介绍了光盘用单片非球面物镜的开发和最新进展。     

Laser-modified luminescence for optical data storage

The yearly growing quantities of dataflow create a desired requirement for advanced data storage methods. Luminescent materials, which possess adjustable parameters such as intensity, emission center, lifetime, polarization, etc., can be used to enable multi-dimensional optical data storage (ODS) with higher capacity, longer lifetime and lower energy consumption. Multiplexed storage based on luminescent materials can be easily manipulated by lasers, and has been considered as a feasible option to break through the limits of ODS density. Substantial progresses in laser-modified luminescence based ODS have been made during the past decade. In this review, we recapitulated recent advancements in laser-modified luminescence based ODS, focusing on the defect-related regulation, nucleation, dissociation, photoreduction, ablation, etc. We conclude by discussing the current challenges in laser-modified luminescence based ODS and proposing the perspectives for future development.     

Nonlocal potential and optical properties of solids

Summary The theory of the RPA optical response of a solid has been generalized in order to take into account also the possible presence of spatially nonlocal potentials in the Hamiltonian. Explicit expressions for first- and second-order susceptibilities are given in the new framework. The expressions obtained depend on the matrix elements of operators of the form of a commutator of a component of the position operatorr and an operator that commutes with the lattice translations. The problem of the evaluation of these matrix elements is solved in a simple manner by introducing an auxiliary, periodic position operator,XXXr. In such a way a general formulation is obtained that preserves the gauge invariance. As an application of the new theory, the second harmonic generation (SHG) from a semiconductor in a simple two-band model has been studied. The differences between our correct gauge-invariant results and those obtained in the usual local approximation is an indication of a slow convergence of the expressions obtained in the local approximation.     

Storage of intense optical pulses in solids

Possibility to store optical information in media with fast relaxations is studied in case of arbitrary intensities of probe and control pulses. Analytical solution of the self-consistent system of equations for propagation and density matrix is obtained with allowance for the first non-stationary corrections. A new scheme of storage is proposed which allows an essential reduction of the optical length needed for storage.     

Enhancement of single-walled nanotubes luminescence intensity upon dithiothreitol doping

In the present work the influence of reducing agent dithiothreitol doping on photoluminescence spectra of nanotubes with adsorbed biopolymers (single-stranded DNA and polyC) in aqueous suspensions and films was studied. It is revealed that greater intensity enhancement at 10^?3 mol/L dithiothreitol concentration is observed for (7,5) and (6,5) nanotubes in suspension with single-stranded DNA (by more than 150% of initial intensity) comparing to polyC suspension (less than 60%) while for (6,4) and (9,1) nanotubes enhancement is less than 50% for both suspensions. Photoluminescence intensity increasing for nanotube film with DNA is less than 50% without noticeable dependence on nanotube chirality. It is assumed, that different influence of biopolymers on nanotube luminescence intensity enhancement is due to their different coverage of nanotube surface.