This PDF file contains the front matter associated with SPIE Proceedings Volume 6905, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

On the propagation of radiation with a suitably resonant optical frequency through a dense chromophoric system - a doped solid for example - photon capture is commonly followed by one or more near-field transfers of the resulting optical excitation, usually to closely neighboring chromophores. Since the process results in a change to the local electronic environment, it can be expected to also shift the electromagnetic interactions between the participant optical units, producing modified inter-particle forces. Significantly, it emerges that energy transfer, when it occurs between chromophores or particles with electronically dissimilar properties (such as differing polarizabilities), engenders hitherto unreported changes in the local potential energy landscape. This paper reports the results of quantum electrodynamical calculations which cast a new light on the physical link between these features. The theory also elucidates a significant relationship with Casimir-Polder forces; it transpires that there are clear and fundamental links between dispersion forces and resonance energy transfer. Based on the results, we highlight specific effects that can be anticipated when laser light propagates through an interface between two absorbing media. Both steady-state and pulsed excitation conditions are modeled and the consequences for interface forces are subjected to detailed analysis.

We use an algebraic method to derive explicit expressions for the structure of paraxial modes in a cavity consisting of astigmatic mirrors. The algebra is based upon the use of ladder operators that raise or lower the mode indices, when acting on a mode function. We show that the method is also applicable when the mirrors perform a uniform rotation about their axes. We also find expressions for the orbital angular momentum in these modes.

This work started the dynamic singular optics, or real-time topological dynamics of developing singular light fields. We have used the system "laser beam → photorefractive crystal LiNbO₃: Fe" which generates slowly developing scalar or vector random scattered singular light field (speckle patterns). It was investigated by elaborated technique of phase reconstruction for a scalar field or real-time Stokes-polarimetry for reconstruction of a vector field ellipticity and azimuth. It was shown the "life-story" of pair singularities from pre-nucleation up to after-annihilation states is realized as 'local topological transition' with fully reversible scenarios. Applications of dynamic singular optics are discussed.

Instead of the well-known line type of phase singularities in optical and coherence fields, we introduce a new concept of what we call Vortex Sheet into singular optics. This vortex sheet has a surface topological structure, on which the phase of the scalar optical or the coherence fields becomes undefined with zero amplitude. Some properties related to these surface topological deformations, such as optical and coherence surface flow, are investigated both theoretically and experimentally for the first time.

We report holographic generation of higher-order Laguerre-Gaussian (LG) beams using a liquid crystal on silicon spatial light modulator (LCOS-SLM) device. In our experimental set-up, a flat-top light beam was projected on the LCOS-SLM to generate LG beams of various mode indices without changes of the optical system. Additionally, the size of the holographic phase pattern was optimized for each beam to maximize the mode purity of the obtained beam. Holographic generation of LG beams is easily influenced by a distortion of the optical system and deviation of the phase setting from an ideal one. Nevertheless, we obtained high-quality LG beams with an additional phase pattern on the LCOS-SLM for canceling the distortion of the optical system and with calibration of the phase control voltage for precise expression of the phase patterns. Numerical analyses are also performed for two-dimensional beam profiles to verify the quality of the obtained beams. Through fitting the obtained profiles to theoretical ones, we calculate the correlation coefficients R between the observed and fitted profiles to find that R > 0.95 for all beams and that the correlation coefficients behave similarly to the theoretically estimated mode purities, facts indicating that the quality of the obtained LG beams is close to the theoretical limit in our experiments.

We present a method that enables the generation of arbitrary positioned dual-beam traps without additional hardware in a single-beam holographic optical tweezers setup. By this approach stable trapping at low numerical aperture and long working distance is realized with an inverse standard research microscope. Simulations and first experimental results are presented. Additionally we present first steps towards using the method to realize a holographic 4π-microscope. We will also give a detailed analysis of the phase-modulating properties and especially the spatial-frequency dependent diffraction efficiency of holograms reconstructed with the phase-only LCOS spatial light modulator used in our system. Finally, accelerated hologram optimization based on the iterative Fourier transform algorithm is done using the graphics processing unit of a consumer graphics board.

The Pancharatnam-Berry phase is a geometric phase associated with the polarization of light. We present novel optical phase elements based on the space-domain Pancharatnam-Berry phase. Such elements can be realized using inhomogeneous anisotropic micro and nanostructures, where the geometric phase is induced by spin-to orbital angular momentum transfer. The elements are polarization dependent, thereby enabling multipurpose optical elements. Vectorial vortices, and vectorial vortex mode transformation for a hollow waveguide are demonstrated. Manipulating of thermal radiation by use of anisotropic micro and nanostructures is also investigated. We demonstrate an extraordinary coherent thermal radiation from coupled resonant cavities; each of them supports standing wave surface polaritons.

We outline the specifications of a portable Bio-photonics Workstation we have developed that utilizes just a single spatial light modulator to generate an array of up to 100 reconfigurable laser-traps with adjustable power ratios making 3D real-time optical manipulation possible with the click of a laptop mouse. We employ a simple patented optical mapping approach from a fast spatial light modulator to obtain reconfigurable intensity patterns corresponding to two independently addressable regions relayed to the sample volume where the optical manipulation of a plurality of nano-featured micro-objects takes place. The stand-alone Biophotonics Workstation is currently being tested by external partners with micro-biologic and chemistry expertise.

The generalized phase contrast method (GPC) can produce a rich variety of optical landscapes from an incident flattop beam. Here we show that the GPC can generate various intensity distributions directly from an incident Gaussian illumination. This is illustrated by using GPC-based implementation of phase-only apertures that efficiently redirect the available photons from an initial bell-shaped intensity distribution into desired configurations. GPC can reshape a Gaussian beam into patterns having sharp intensity transitions and a flat phase profile in the bright regions with superior energy efficiency over amplitude masks. Eliminating the initial Gaussian-to-flattop beamshaping requirement can be beneficial for various applications employing GPC-based patterns.

Propagating three-dimensional speckle fields are threaded by random networks of nodal lines (optical vortices). We review our recent numerical superpositions of simulations of random plane waves modelling speckle (O'Holleran et al. Phys. Rev. Lett. in press), in which the nodal lines and loops were found to have the fractal structure of brownian random walks. We discuss this result, and its comparison with the discrete vortices of the Z₃ lattice model for cosmic strings. We argue that the scaling depends on the geometry of small vortex loops and avoided crossings. The analytic statistics of these events, along with related singularities are discussed, and the densities of vorticity-vanishing points and anisotropy C lines are found explicitly.

We present a study of composite vortices in light beams using component beams with no integral topological charge. We observed the same general features that are seen in when the component beams have an integral topological charge [E.J. Galvez, N. Smiley, and N. Fernandes, "Composite optical vortices formed by collinear Laguerre-Gauss beams," Proc. SPIE 6131, pp. 19-26, 2006.]. These are: (1) that new vortices appear at distances from the beam that depend on the ratio of the intensity of the component beams, and (2) that the angular location of the vortices depends on the phase difference between them. We also observed that some of the vortices associated with fractional charge that did not follow the same dynamics.

We propose a quantum theory of rotating light beams and study some of its properties. Such beams are polychromatic and have either a slowly rotating polarization or a slowly rotating transverse mode pattern. We show there are, for both cases, three different natural types of modes that qualify as rotating, one of which is a new type not previously considered. We discuss differences between these three types of rotating modes on the one hand and non-rotating modes as viewed from a rotating frame of reference on the other, thus resolving some paradoxes mentioned recently.

We investigate optical properties of semiconductor atoms by absorption and emission spectroscopies. Each of ³P_J' - ³P°_J transitions except for J'=0 (the total angular momentum of the ground state) is confirmed in broad emission spectra in a hollow-cathode discharge in which negative electrodes incorporate semiconductor atoms that are evaporated in the discharge. For finer spectroscopies, the ³P₁ - ³P°₀ cyclic transition for laser cooling of silicon atoms at 252 nm is investigated in absorption spectra with a single-frequency tunable deep-UV coherent light source, which has a high potential for controlling their nuclear spins.

Optical binding can be understood as a laser perturbation of intermolecular forces. Applying state-of-the-art QED theory, it is shown how light can move, twist and create ordered arrays from molecules and nanoparticles. The dependence on laser intensity, geometry and polarization are explored, and intricate potential energy landscapes are exhibited. A detailed exploration of the available degrees of geometric freedom reveals unexpected patterns of local force and torque. Numerous positions of local potential minimum and maximum can be located, and mapped on contour diagrams. Islands of stability and other structures are then identified.

Semiconductor nanowires are drawing more and more interest due to their numerous potential applications in nanoelectronics devices [1,2], including interconnects, transistor channels, nanoelectrodes, or in the emerging application areas of photonics [3], chemistry [4] and photovoltaics [5]. In this context, optical tweezers appear like a pertinent tool for the manipulation and assembly of nanowires into complex structures. It was previously shown that the near-field existing at the surface of a waveguide allows the micromanipulation of nanoparticles and biological objects [6,7]. In this article, we investigate for the first time to our knowledge the motion of silicon nanowires above silicon nitride waveguides. The nanowires in aqueous solution are attracted toward the waveguide by optical gradient forces. The nanowires align themselves according to the axis of the waveguide and get propelled along the waveguide due to radiation pressure. Velocities are up to 40 μm/s. For a better understanding of the experimental results, the distribution of the electromagnetic field in the nanowire is calculated using the finite element method. Then, the resulting optical forces exerted on the nanowires are calculated, thanks to the Maxwell stress tensor formalism.

Previous work has shown that single-beam gradient traps are unable to trap high index particles in fluids where the index contrast is large. However, by changing the refractive index of the surrounding medium to more closely match the index of refraction of the particle, trapping of high index particles is possible. We report preliminary efforts to trap high index glass particles having indices of about 1.9. The experimental trap stiffness data of polystyrene beads with radius 1.8 and 10 µm suspended in water is presented. The next step is to trap high index particles as well as determine the trap stiffness for those particles having diameters in the 3-10 μm range suspended in fluids having refractive indices in the range of 1.4 to 1.6.