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Electrically polarizable micro- and nanoparticles and droplets can be trapped using the gradient electric field of electrodes. But the spatial profile of the resultant dielectrophoretic force is fixed once the electrode structure is defined. To change the force profile, entire complex lab-on-a-chip systems must be re-fabricated with modified electrode structures. To overcome this problem, we propose an approach for the dynamic control of the spatial profile of the dielectrophoretic force by interfacing the trap electrodes with a resistor and an inductor to form a resonant resistor–inductor–capacitor (RLC) circuit. Using a dielectrophoretically trapped water droplet suspended in silicone oil, we show that the resonator amplitude, detuning, and linewidth can be continuously varied by changing the supply voltage, supply frequency, and the circuit resistance to obtain the desired trap depth, range, and stiffness. We show that by proper tuning of the resonator, the trap range can be extended without increasing the supply voltage, thus preventing sensitive samples from exposure to high electric fields at the stable trapping position. Such unprecedented dynamic control of dielectrophoretic forces opens avenues for the tunable active manipulation of sensitive biological and biochemical specimen in droplet microfluidic devices used for single-cell and biochemical reaction analysis.

Trapping and manipulation of micro and nanoparticles are essential functional elements of lab-on-a-chip and micro total analysis systems with applications ranging from single cell analysis, diagnostics, drug discovery, and chemical synthesis. Reliable optical trapping of subwavelength particles is difficult due to the diffraction limited gradient of the optical intensity. Near-field traps have emerged as excellent systems to overcome this bottleneck. Using a periodic arrangement of C-shaped apertures we demonstrate the on-chip manipulation of single sub-wavelength polystyrene beads. The wavelength and polarization sensitivity of these resonant nanostructures is exploited to expose the trapped bead to a time varying near-field force using wavelength and polarization multiplexing schemes. While optical trapping has the advantage of being contactless, dielectrophoresis provides higher forces due to the flexibility of applying larger voltages and field gradients. The RF/Microwave frequency regime where dielectrophoresis operates allows increased polarizability of certain samples due to contribution from orientational, molecular and atomic polarizations as well as particle’s electrical conductivity. Combining the above advantages of both the techniques we discuss photoinduced dielectrophoretic trapping and manipulation of nanoparticles. Using dielectrophoretic trapping we discuss the simultaneous manipulation of beads and droplets as a route for on chip chemical synthesis.

We present a device that can achieve controlled transport of colloidal microparticles using an array of micro-electrodes. By exciting the micro-electrodes in regular sequence with an AC voltage, a time-varying moving dielectrophoretic force-field is created. This force propels colloidal microparticles along the electrode array. Using this method, we demonstrate bidirectional transport of polystyrene micro-spheres. Electromagnetic simulation of the device is performed, and the dielectrophoretic force profile around the electrode array is mapped. We develop a Brownian dynamics model of the trajectory of a particle under the influence of the time-varying force-field. Numerical and experimental results showing controlled particle transport are presented. The numerical model is found to be in good agreement with experimental data. The developed numerical framework can be useful in designing and modeling lab-on-a-chip devices that employ external non-contact forces for micro-/nanoparticle manipulation.

Typical x-ray detectors have a fundamental trade-off between resolution and quantum efficiency (QE). High quantum efficiency x-ray detection requires a thick conversion medium, but decreases the resolution due to limited pixel aspect ratios for both direct and indirect x-ray detection. We present a method for x-ray detection, holographic x-ray detection, which uses photorefractive materials to create a high resolution and high efficiency detector. The x-ray image is recorded in the volume of the photorefractive material, bypassing the aspect ratio issue of typical x-ray detectors. Holographic x-ray detection operates in three stages: recording an x-ray hologram in a photorefractive crystal, reading the hologram with visible light, and then erasing the hologram using ultraviolet light. We have experimentally demonstrated holographic x-ray detection with a resolution of 208 lp/mm (80% QE at 40 keV), an order of magnitude resolution improvement over commercially available x-ray detectors while maintaining > 80% QE.

Lithium-ion batteries (LIBs) have profoundly advanced the development of electric vehicles (EVs). However, one of the remaining bottlenecks in their widespread deployment is the long charging time required for commercial LIBs. Today, there is a global push towards extreme fast charging (XFC) to reduce charging times to 10-15 minutes.1 But existing LIBs cannot achieve this goal without significantly reducing battery performance, mainly due to the loss of active Li. The lost Li either becomes “dead” from being electronically disconnected after plating on the anode or “inactive” because of the irreversible reaction of Li with the electrolyte to form a solid electrolyte interphase. Since lithium plating is identified as one of the major degradation mechanisms from XFC in LIBs,2 understanding its origin and characteristics is essential to developing designs to enable fast-charged batteries. Several studies have characterized Li plating using techniques such as cryo-electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray micro-computed tomography (CT) among others.3 While valuable, these characterization techniques have limitations4 in terms of their sample preparation, spatial resolution, and imaging contrast required to distinguish between materials of similar atomic number (Z). In addition, due to the complex electrochemical reaction mechanisms of Li metal plating, multiple methods for detecting Li metal and understanding the mechanistic details of Li plating are needed. Here, we are using simultaneous neutron and X-ray-based dual-mode micro-computed tomography, a non-destructive imaging modality, to investigate the characteristics of Li plating during XFC in LIBs. Since X-rays and neutrons are sensitive to the electron and nuclear density of the material, respectively, dual-mode X-ray and neutron CT allows the easy separation of the different anode components in a LIB such as Li, graphite, and pores. Higher energy X-rays are needed to get through the metallic components in batteries such as copper and aluminum. However, they do not have sufficient contrast to separate lithium from graphite. Thus, neutrons are used due to their high sensitivity to lighter elements such as lithium, especially 6Li, and carbon. We have performed multi-modal imaging experiments at the Neutron and X-ray Tomography (NeXT)5 system located on the BT-2 beamline at the National Institute of Standards and Technology Center for Neutron Research. We characterized pristine and cycled graphite anode strips containing plated lithium at different regions. For cycled anode strips, we disassembled the battery pouch cells and imaged the graphite anodes cycled under XFC conditions for 450 cycles at fully discharged condition. These strips were used to get sample sizes small enough to achieve the highest possible spatial resolution. The spatial resolution achieved by this technique was ~10-15 μm, thus providing sufficient resolution to pinpoint the location of Li plating within the thickness of the anode. For image processing, we employed bivariate histogram segmentation that uses information from both X-rays and neutrons to segment different anode components. With these dual-imaging datasets, we are now investigating whether a link exists between the spatial heterogeneity of Li metal plating and the local microstructure of the battery anode including porosity, tortuosity, and thickness. We want to investigate why and where Li plating occurs on the battery anode. Addressing these fundamental questions will inform improved battery designs, graphite anode architectures, and charging protocols that will reduce Li plating during XFC in LIBs. Ultimately, these improvements based on our research findings will help make charging an EV similar to filling up at a gas station. References: Liu, Y., Zhu, Y., & Cui, Y. (2019). Challenges and opportunities towards fast-charging battery materials. Nature Energy, 1. Tomaszewska, A., Chu, Z., Feng, X., O'Kane, S., Liu, X., Chen, J., ... & Li, Y. (2019). Lithium-ion battery fast charging: A review. eTransportation, 1, 100011. Liu, Qianqian, et al. "Understanding undesirable anode lithium plating issues in lithium-ion batteries." RSC advances91 (2016): 88683-88700. Li, Y., Li, Y., & Cui, Y. (2018). Catalyst: how cryo-EM shapes the development of next-generation batteries. Chem, 4(10), 2250-2252. LaManna, J. M., Hussey, D. S., Baltic, E., & Jacobson, D. L. (2017). Neutron and X-ray Tomography (NeXT) system for simultaneous, dual modality tomography. Review of Scientific Instruments, 88(11), 113702. Figure 1

We propose a method for peristaltic transport of nanoparticles using the optical force field over a nanostructured surface. Nanostructures may be designed to produce strong near-field hot spots when illuminated. The hot spots function as optical traps, separately addressable by their resonant wavelengths and polarizations. By activating closely packed traps sequentially, nanoparticles may be handed off between adjacent traps in a peristaltic fashion. A linear repeating structure of three separately addressable traps forms a "nano-optical conveyor belt"; a unit cell with four separately addressable traps permits controlled peristaltic transport in the plane. Using specifically designed activation sequences allows particle sorting.

Optical tweezers have been widely used to manipulate biological and colloidal material, but the diffraction limit of far-field optics makes focused beams unsuitable for manipulating nanoscale objects with dimensions much smaller than the wavelength of light. While plasmonic structures have recently been successful in trapping nanoscale objects with high positioning accuracy, using such structures for manipulation over longer range has remained a significant challenge. In this work, we introduce a conveyor belt design based on a novel plasmonic structure, the resonant C-shaped engraving (CSE). We show how long-range manipulation is made possible by means of handoff between neighboring CSEs, and we present a simple technique for controlling handoff by rotating the polarization of laser illumination. We experimentally demonstrate handoff between a pair of CSEs for polystyrene spheres 200, 390, and 500 nm in diameter. We then extend this technique and demonstrate controlled particle transport down a 4.5 μm long "nano-optical conveyor belt."

Nanoparticles trapped on resonant near-field structures engraved on a metallic substrate experience forces due to the engravings, as well as the image-like interaction with the substrate. In the case of normally incident optical excitation, the force due to the substrate is solely perpendicular to its surface. Numerical simulations are presented to demonstrate that under the combined influence of the aforementioned forces, a plasmonic nanoparticle can be repelled from the engraving along the substrate, while attracting it towards the substrate along its normal. This behavior can be achieved over a range of excitation wavelengths of the short wavelength mode of the coupled particle-substrate-trap system. To the best of our knowledge, this is the first illustration of an in-plane near-field optical barrier on a chip. The barrier is stable against resistive heating of the nanoparticle, as well as the induced non-isothermal flow. The wavelength-dependent switch between the proposed in-plane potential barrier and the stable potential well can pave the way for the gated transport of single nanoparticles, while holding them bound to the chip.

We have carried out boundary-layer-resolved, unstructured fully-compressible Navier--Stokes simulations of an ultrasonic standing-wave thermoacoustic engine (TAE) model. The model is constructed as a quarter-wavelength engine, approximately 4 mm by 4 mm in size and operating at 25 kHz, and comprises a thermoacoustic stack and a coin-shaped cavity, a design inspired by Flitcroft and Symko (2013). Thermal and viscous boundary layers (order of 10 $\mathrm{\mu}$m) are resolved. Vibrational and rotational molecular relaxation are modeled with an effective bulk viscosity coefficient modifying the viscous stress tensor. The effective bulk viscosity coefficient is estimated from the difference between theoretical and semi-empirical attenuation curves. Contributions to the effective bulk viscosity coefficient can be identified as from vibrational and rotational molecular relaxation. The inclusion of the coefficient captures acoustic absorption from infrasonic ($\sim$10 Hz) to ultrasonic ($\sim$100 kHz) frequencies. The value of bulk viscosity depends on pressure, temperature, and frequency, as well as the relative humidity of the working fluid. Simulations of the TAE are carried out to the limit cycle, with growth rates and limit-cycle amplitudes varying non-monotonically with the magnitude of bulk viscosity, reaching a maximum for a relative humidity level of 5%. A corresponding linear model with minor losses was developed; the linear model overpredicts transient growth rate but gives an accurate estimate of limit cycle behavior. An improved understanding of thermoacoustic energy conversion in the ultrasonic regime based on a high-fidelity computational framework will help to further improve the power density advantages of small-scale thermoacoustic engines., Comment: 55th AIAA Aerospace Sciences Meeting, AIAA SciTech, 2017

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological and physical sciences over the past few decades. The progress made in this field invites further study of even smaller systems and at a larger scale, with tools that could be distributed more easily and made more widely available. Unfortunately, the fundamental laws of diffraction limit the minimum size of the focal spot of a laser beam, which makes particles smaller than a half-wavelength in diameter hard to trap and generally prevents an operator from discriminating between particles which are closer together than one half-wavelength. This precludes the optical manipulation of many closely-spaced nanoparticles and limits the resolution of optical-mechanical systems. Furthermore, manipulation using focused beams requires beam-forming or steering optics, which can be very bulky and expensive. To address these limitations in the system scalability of conventional optical trapping our lab has devised an alternative technique which utilizes near-field optics to move particles across a chip. Instead of focusing laser beams in the far-field, the optical near field of plasmonic resonators produces the necessary local optical intensity enhancement to overcome the restrictions of diffraction and manipulate particles at higher resolution. Closely-spaced resonators produce strong optical traps which can be addressed to mediate the hand-off of particles from one to the next in a conveyor-belt-like fashion. Here, we describe how to design and produce a conveyor belt using a gold surface patterned with plasmonic C-shaped resonators and how to operate it with polarized laser light to achieve super-resolution nanoparticle manipulation and transport. The nano-optical conveyor belt chip can be produced using lithography techniques and easily packaged and distributed.

We performed a parametric study to suppress secondary phases in lithium niobate thin films by using pulsed laser deposition (PLD). By reducing the growth rate and changing the ambient gas pressure respectively, we found that the main parameter suppressing secondary phases is controlling the plume strength. For investigating the relation between film phases and the plume strength, extensive parametric studies were performed by changing the oxygen ambient pressure, the target to substrate distance, and also the Li content in the target. The surface morphologies of single phase films obtained with different deposition parameters are compared and deposition parameters to achieve lower loss single-phase films are discussed.

In this paper, we report the effects of direct-write e-beam parameters on achieving sub-micron periodic domain structures in homoepitaxial liquid phase epitaxy (LPE) LiNbO 3 thin films. We have studied the effects of the e-beam acceleration voltage, the areal dose, and the scanning speed on the domain structure regularity, and we have obtained optimal conditions for achieving improved structures. The most regular structures appear at acceleration voltages higher than 20 kV and areal dose ranges of 350–450 μC/cm 2 with lower scanning speeds. Under these optimal conditions we have fabricated approximately 500 μm-long gratings with 1.1 μm periods consisting of ∼180 nm domains. By simulating the optical reflectance based on a transfer matrix analysis, we have shown that the grating has a reflectance close to that of a perfect grating, in spite of the existence of stitching errors. The results indicate that using this fabrication approach, a switchable Bragg filter for optical communications may be fabricated by direct-write e-beam sub-micron domain engineering in LPE LiNbO 3 .

We demonstrate the controlled transport of simultaneous nano-scale particles across a gold film patterned with nanopillars and C-shaped engravings. Nanopillars load particles onto nearby plasmonic conveyor belts formed from sequences of C-shaped engravings.

We transport nano-scale objects across a distance of many microns using a repeated sequence of rotated C-shaped plasmonic resonators. Rotating the polarization angle of the overhead laser illumination drives the particles' motion.

Nanoparticles trapped on resonant near-field apertures/engravings carved in plasmonic films experience optical forces due to the steep intensity gradient field of the aperture/engraving as well as the image like interaction with the substrate. For non-resonant nanoparticles the contribution of the substrate interaction to the trapping force in the vicinity of the trap (aperture/engraving) mode is negligible. But, in the case of plasmonic nanoparticles, the contribution of the substrate interaction to the low frequency stable trapping mode of the coupled particle-trap system increases as their resonance is tuned to the trap resonance. The strength of the substrate interaction depends on the height of the nanoparticle above the substrate. As a result, a difference in back action mechanism arises for nanoparticle displacements perpendicular to the substrate and along it. For nanoparticle displacements perpendicular to the substrate, the self induced back action component of the trap force arises due to changing interaction with the substrate as well as the trap. On the other hand, for displacements along the substrate, it arises solely due to the changing interaction with the trap. This additional contribution of the substrate leads to more pronounced back action. Numerical simulation results are presented to illustrate these effects using a bowtie engraving as the near-field trap and a nanorod as the trapped plasmonic nanoparticle. The substrate's role may be important in manipulation of plasmonic nanoparticles between successive traps of on-chip optical conveyor belts, because they have to traverse over regions of bare substrate while being handed off between these traps.

Codoped lithium niobate of congruent and stoichiometric compositions had been successfully grown specifically for holographic data storage applications. The dopants we have selected are Mn and Ce and their role in the recording process is described. Growth methods, sample preparation, doping level measurements, holographic recording data as well as the results of optical characterization and photorefractive properties of the two-photon sensitivity are discussed. Compared to the previously grown crystals, the codoped LiNbO 3 shows a higher sensitivity and dynamic range for recording in red ( λ=632 nm ).

Lead barium niobate (Pb1−xBaxNb2O6) is a very promising material for photorefractive applications in that it has a high ferroelectric-to-paraelectric transition temperature (300–500 °C depending on composition) and simultaneously can have large electro-optic coefficients, because of the nearly vertical morphotropic phase boundary (MPB) near 1−x=0.63. Pb1−xBaxNb2O6 crystals have been grown by the vertical Bridgman method for near-MPB compositions (0.5

Lead barium niobate crystals (Pb1−xBaxNb2O6) are attractive photorefractive materials for holographic data storage. The electro-optic coefficients r33 and r13 are determined using a Mach–Zehnder interferometer setup, and are measured to be 160±20 and 32±4 pm/V, respectively. The angular dependence of the photorefractive two-beam coupling gain is also investigated, and the products of the electro-optic coefficients and the electron-hole competition factor rζ are determined and compared with the electro-optic coefficients obtained using the interferometric method. It is found that the electron-hole competition factor is at least 0.7, indicating that the photorefractive process is mostly due to electrons. The effective trap densities at several wavelengths are also determined from the gain dispersion measurements, and are found to be 1.3–2.2×1016 cm−3.

We develop a near-field based optical trapping and conveyor belt system based on a novel plasmonic structure: C-shaped engraving. Using polarization rotation and wavelength switching, we demonstrate controlled transport of nanoparticles along different paths.

New multicomponent InF 3 -based bulk glasses have been investigated. The molar composition of the base glass is 28% InF 3 –20% ZnF 2 –16.5% BaF 2 –12% GaF 3 –9% PbF 2 –6% NaCl–5% SrF 2 –3% CaF 2 –0.5% PrF 3 . A number of variations of the base glass were prepared and their refractive indices and densities measured. Resistance to crystallization allowed the preparation of large pieces of the base glass. The infrared and Raman spectra show that the base composition has a longer wavelength multiphonon edge at 10 μm and a phonon energy of 509 cm −1 , in comparison with 8 μm and 574 cm −1 for ZBLAN, which reveals that the present glasses have a lower phonon energy and a greater transparency in the infrared than ZBLAN. Reduction of PbF 2 concentration in the base composition provided glasses with smaller refractive indices than the base glass.

In order to study these inhomogeneities, Ce-doped and undoped strontium-barium niobate (SBN) fibers were grown by a laser-heated pedestal growth (LHPG) technique in various Ce:Sr x Ba 1− x Nb 2 O 6 compositions along both c [001] and a [100] crystallographic axes. Specific optical inhomogeneities distributed in a radial manner (core effects) are observed in such crystals. Two-dimensional scanning electron microprobe analysis (SEPMA) indicated Ba enrichment and Sr decrease in the cores. An approximate control segregation coefficient (' k oA ) was introduced to characterize the segregation in the fibers. For different cations ' k oSr = 0.98, ' k oBa = 1.04 and ' k oNb = 0.99 were obtained which both determine and demonstrate the complexity of the inhomogeneities in the core in the radial direction.

A three-color, solid-state, volumetric display based on two-step, two-frequency upconversion in rare earth-doped heavy metal fluoride glass is described. The device uses infrared laser beams that intersect inside a transparent volume of active optical material to address red, green, and blue voxels by sequential two-step resonant absorption. Three-dimensional wire-frame images, surface areas, and solids are drawn by scanning the point of intersection of the lasers around inside of the material. The prototype device is driven with laser diodes, uses conventional focusing optics and mechanical scanners, and is bright enough to be seen in ambient room lighting conditions. QuickTime movie of the three-dimensional display.

We designed, fabricated, and characterized single C-shaped apertures in an Au film, resonant in the visible regime. Our C-shaped apertures showed transmission enhancement of 13–22 times over a square aperture of the same area and suggest as high as 106 enhancement over square apertures that are designed to produce the same near-field spot size. Spectra from individual apertures demonstrate the ability to tune this resonance over 70nm by scaling the dimensions of the apertures. This shows the C aperture to be a versatile tool for gaining high-resolution, enhanced transmission through single subwavelength apertures at optical wavelengths.

We report abnormally large positive and negative lateral optical beam shifts at a metal–air interface when the surface plasmon resonance of the metal is excited. The optimal thickness for minimal resonant reflection is identified as the critical thickness above which a negative beam displacement is observed. Experimental results show good agreement with theoretical predictions and the large observed bidirectional beam displacements also indicate the existence of forward and backward surface propagating waves at the surface plasmon resonance of the metal.

Plasmonic Near-Field Transducers (NFTs) find use in Energy-Assisted Magnetic Recording (EAMR) schemes, where a high-anisotropy recording medium is locally heated to the Curie temperature, allowing conventional magnetic recording heads to overcome the high coercivity of the medium. However, coupling efficiency is low, and the conditions for excitation and resonance are poorly understood. In this work, we explore the behavior of a canonical EAMR setup including rectangular dielectric waveguide, elliptic cylinder gold NFT, and conductive planar recording medium. We systematically examine the effects of polarization and angle; spacing between NFT, waveguide, and recording medium; and variations in NFT size and incident wavelength.

We report a new optical near-field transducer comprised of a metallic nano-antenna extending from the ridge of a C-shaped metallic nano-aperture. Finite-difference time domain simulations predict that the C-aperture nano-tip (CAN-Tip) provides high intensity (650x), high optical resolution (~λ/60), and background-free near-field illumination at a wavelength of 980 nm. The CAN-Tip has an aperture resonance and tip antenna resonance which may be tuned independently, so the structure can be made resonant at ultraviolet wavelengths without being unduly small. This near-field optical resolution of 16.1 nm has been experimentally confirmed by employing the CAN-Tip as an NSOM probe.

A novel optical system architecture employing local holographic recording with a pico-second pulsed fiber laser and a small page size SLM has the potential towards realizing compact, high capacity and high data transfer rate optical storage.

We present a numerical technique for design and optimization of nanometallic structures for near-field optical applications such as heat-assisted magnetic recording (HAMR). The sensitivity of the optical behavior of a nanostructure with respect to its size and shape may be efficiently obtained with a pair of “forward” and “backward” FDTD simulations. Devices may be optimized by iteratively adjusting their dimensions along direction of highest sensitivity for improvement.

We propose a nano-scale C-aperture nano-tip photo-electron source with a CsBr photo-cathode. We fabricated the structure and estimated the optical spot available in the CsBr thin film with photoresist exposure.

We present a practical real-time optical pre-processor intended to enhance small defects in a smooth surface. The heart of the system is a photorefractive BSO phase conjugate mirror which reflects only the low intensity features of the object’s optical Fourier Transform. By adjusting the beam ratios so that only the low intensity, high spatial frequency image components are phase conjugated and inverse transformed, an image consisting of just the defects is produced. To our knowledge, this is the first use of this technique on opaque and non-periodic objects. We present experimental data showing enhancement of defects smaller than 0.2 μm.

The geometrical design characteristics of multiple-image holograms are evaluated. A figure of merit expressing these characteristics as a function of the hologram diameter and the distance between the hologram and the image plane is developed. This value is then used to compare two designs which are capable of forming several hundred interconnections. The results indicate that these connections can be formed between points on the substrate separated by 2-3 cm provided that the holograms are separated from the substrate plane by 0.5-1 cm. Each hologram design is experimentally demonstrated in bleached photographic emulsions.

We present a defect-enhancement system capable of detecting submicrometer defects on opaque periodic structures using real-time holography in photorefractive crystals. We detect 0.5-microm defects with ~90% success rate and 0.3-microm defects with85% success rate while inspecting an area greater than 1 mm(2) in real time. To our knowledge, these defects have an area 100 times smaller than those previously detected with any real-time holographic technique.

Optical interconnects for highly parallel computer architecture require high density optical switch arrays with dimensions of 100 × 100 or larger. Previously reported integrated switch array designs have been limited to 8 × 8 waveguides.1 While achieving high switching speeds and relatively low insertion losses, these switches are limited by long interaction lengths which lead to array dimensions of as long as 60 mm. Our switch design consists of two sets of parallel waveguides which intersect at right angles. The intersections are doped with a material to locally sensitize the region to the photorefractive effect. We have fabricated arrays based on standard Ti:LiNbO3 technology, using iron as a photorefractive sensitizer. Interfering beams are used to write an index grating at the waveguide intersections. This grating can then be used to diffract a portion of a data beam into the crossing waveguide. The diffraction efficiency depends on the length of the interaction region. Thus, insertion loss is traded off against switch density. We have constructed arrays of 15 × 15 up to 50 × 50 waveguides in an active area of only 5 mm square.

We describe what are to our knowledge the first photorefractive holographic recordings in a fiber. A plane-wave reference and an image-carrying object beam are incident upon the fiber in a reflection geometry. We report results on the angular sensitivity of the recordings, the image quality, and readout efficiency as a function of the reference-wave input angle when the object wave propagates along the bore of the fiber. These experiments are carried out for two relatively short, 4- and 8-mm, multimode 1-mm-diameter fibers. The results suggest that an array of fibers might favorably replace bulk materials for certain computer and signal-processing applications.

A photorefractive crystal (Bi(12)GeO(20)) is used to record double-exposure speckle patterns produced by Q-switched laser pulses in real-time speckle metrology and velocimetry applications. The speckle pattern displacements are immediately measured with an optical processor of the type used for measuring speckle displacements recorded on photographic film. Operation of the optical processor is described and compared with the case of film recording. Observed spatial and temporal recording properties of the crystal in this imaging configuration are discussed and compared with published results for single-frequency grating recording in photorefractives. The system is applied to measuring velocities of a moving solid object.

We report on the use of a sodium-seeded flame as an amplifying phase conjugator. The environment is unique in that a number density of 10(16) cm(-3) is maintained despite a lateral dimension of 1 mm. We combine two of these optically pumped flames to form a phase-conjugate resonator. Finally, we observe oscillation that is due to the action of a single flame and two pump beams.

The first observation to our knowledge of degenerate four-wave mixing in a sodium-seeded flame is reported. In addition, the theoretical dependence of the phase-conjugate output on the sodium concentration is verified experimentally, demonstrating the potential of this procedure for use as a diagnostic tool to measure species concentration in combusting or noncombusting media.

We report high-intensity nano-aperture Vertical-Cavity Surface- Emitting Lasers (VCSELs) with sub-100nm near-field spots using ridge apertures. Power transmission efficiency through different ridge apertures, including bowtie, C, H and I-shaped apertures on VCSELs were studied. Significantly higher transmission efficiencies were obtained from the ridge apertures than those from conventional square apertures. Mechanisms for high transmission through the ridge apertures are explained through simulation and waveguide theory. A new quadruple-ridge aperture is proposed and designed via simulation. With the high-intensity and small spot size, VCSELs using these ridge nano-apertures are very promising means to realize applications such as ultrahigh-density near-field optical data storage and ultrahigh-resolution near-field imaging etc.

Single-crystal Sr0.61Ba0.39Nb2O6 (SBN:61) is a very attractive candidate for a number of optical and acoustical applications. Boules grown by the Czochralski (CZ) method can provide crystals of the required size and quality. The main difficulty in applying the CZ growth technique to SBN stems from an instability of the crystal diameter that is primarily attributed to faceted radial growth. The instability is a principal limiting factor in obtaining large, constant diameter boules. However, this problem can be overcome by weighing the crystal in real time and using a computer to provide temperature-based automatic diameter control (ADC). In this paper a number of important issues concerning unstable growth and its control are addressed. First, the radial growth process is analyzed for the purpose of modeling the corresponding weight signal. In doing so, the standard equations governing the meniscus dynamics (neglecting heat balance) have been modified to accommodate a situation of rapidly-varying diameter. Next, a digital ADC algorithm is presented along with a discussion of noise sources and filtering techniques. Finally, typical results for growth of SBN are given.

Hologram recording in photorefractive media is classically performed in the blue-green spectral range and suffers from optical erasure under continuous readout, unless a thermal fixing technique is applied. Gated optical holographic recording allows us to obtain high-diffraction efficiencies in the near InfraRed (IR) jointly with long-term storage. In particular, the roles of stoichiometry and dopant reduction state in LiNbO3 in the optimization of sensitivity is analyzed, in order to perform digital information storage in such materials via the two-photon technique.

We report a high-intensity nano-aperture vertical-cavity surface-emitting laser (VCSEL) utilizing a bowtie-shaped aperture. A maximum power of 188 microW is achieved from a 180 nm bowtie aperture at a wavelength of 970 nm. The near-field full width at half-maximum intensity spot size 20 nm away from the bowtie aperture is 64 nm x 66 nm from simulation, and the peak near-field intensity is estimated to be as high as 47 mW/microm(2). This intensity is high enough to realize near-field optical recording, and the small spot size corresponds to storage densities up to 150 Gbits/in(2). The bowtie-aperture VCSEL also enables other applications, such as compact high-intensity probes for ultrahigh-resolution near-field imaging and single molecule fluorescence and spectroscopy.

We present a design for a subwavelength C-shaped optical waveguide with a 90 degrees junction that efficiently transports light while maintaining tight confinement with an exit spot size of lambda/7. Finite-difference time-domain simulations of perfect electric conductors and Au C-aperture waveguides are performed for optical frequencies. A design resonant near 780 nm is presented, with a spot size of 107 nm x 107 nm and an energy density enhancement factor of 10 for a bent waveguide of total length 1.4 microm.

PIE-FRET offers significant advantages over conventional single molecule FRET techniques, but it still requires the dilution of samples to biologically low concentrations. Here, we present FRET measurements inside nm-sized apertures at -1000 times higher concentration.

We demonstrated a record-high-intensity bowtie nano-aperture vertical-cavity surfaceemitting laser (VCSEL) with near-field spot size of 65 nm. The bowtie aperture VCSEL is very promising to realize near-field applications such as ultradense optical data storage.

A novel method of phase-detection in the infrared is proposed to enhance the sensitivity and dynamic range of a single-wavelength surface plasmon resonance biosensor. A structure is also proposed to prevent the sensitivity degradation.

A unique C-aperture metallic waveguide with a 90° bend and tapered region having applications to HAMR is presented. The structure has a small footprint and yet shows high throughput and a small spot size.

We present a design of a linear optical waveguide that utilizes a C-shaped metallic nano-aperture that efficiently transports light while maintaining a spot size of lambda/10. The performance of a C-aperture waveguide is superior to both a regular ridge waveguide and other surface plasmon based metal nano-optical waveguides. The energy transport mechanisms are explained by the coupling of an aperture surface resonance and the thickness resonances inside the guide channel. Finite-difference time-domain simulations of gold C-aperture waveguides are performed for a 1.5 microm wavelength incident plane wave. The 1/e decay length in power transmission is predicted to be approximately 2.5 microm. The total power throughput is 1.66 for the 2.55 microm long guide, with an intensity 6 times that of the incident wave at a distance 120 nm from the exit plane, having a spot size of 150 nm.

The resonance enhanced Goos-Hanchen shifts at attenuated total internal reflection enables the possibility for highly sensitive surface plasmon resonance sensor. The observed giant displacements result from the singular phase retardation at the resonance where the phase is continuous but changes dramatically. The phenomenon is proposed for chemical sensing and the superior sensitivity is demonstrated.

For 45nm lithography and beyond, polarization and other electromagnetic effects such as surface plasmons may begin to affect the transmission through a photomask. Such phenomena are highly polarization sensitive, and may amplify the effects of line-edge roughness (LER) and variations in mask composition. A reduction in the mask material conductivity can mitigate the impact of these effects, but more accurate simulation is required to predict these effects well.