This PDF file contains the front matter associated with SPIE Proceedings Volume 6801, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

Near-field imaging through plasmonic 'superlensing' layers can offer advantages of improved working distance (i.e. introducing the equivalent of a focal length) and control over image intensity compared to simple near-field imaging. In a photolithographic environment at ultra-violet (UV) wavelengths the imaging performance of single- and multi-layer silver plasmonic superlenses has been studied both experimentally and via computer simulations. Super-resolution imaging has been demonstrated experimentally, with the sub-100 nm resolution currently being limited by issues of roughness in the silver layers and the ability to deposit high-quality silver-dielectric multilayers. The simulation studies have shown that super-resolved imaging should be possible using surprisingly thick silver layers (>100 nm), with the cost of much reduced image intensity, which is something that is yet to be shown experimentally. The use of multilayer plasmonic superlenses also introduces richness to the imaging behaviour, with very high transmission possible for certain spatial frequency components in the image. This has been widely touted as a means for improving image resolution, but the complexity of the spatial-frequency transfer functions for these systems does not make this a universal fact for all classes of objects. Examples of imaging situations are given where multi-layer superlenses are actually detrimental to the image quality, such as the case of closely-separated dark-line objects on an otherwise bright background.

I review our recent work in the area of high power 2 μm silica fibre laser development particularly in the area of highly efficient Tm³⁺-doped silica and Ho³⁺-doped silica fibre lasers that are excited with diode lasers operating at 1150 nm.

We present experimental and theoretical study of refractive index modification induced by femtosecond laser pulses in photorefractive crystals. The single pulses with central wavelength of 800 nm, pulse duration of 150 fs, and energy in the range of 6-130 nJ, tightly focused into the bulk of Fe-doped LiNbO₃ and stoichiometric LiTaO₃ crystals induce refractive index change of up to about 10^-3 within the volume of about (2.0 x 2.0 x 8.0) μm³. The photomodification is independent of the polarization orientation with respect to the crystalline c-axis. The recorded region can be erased optically by a defocused low-intensity single pulse of the same laser. Recording and erasure can be repeated at the same position many times without loss of quality. These findings demonstrate the basic functionality of the ultrafast three-dimensional all-optical rewritable memory. Theoretically they are interpreted by taking into account electron photogeneration and recombination as well as formation of a space-charge field. The presented analysis indicates dominant role of photovoltaic effect for our experimental conditions, and suggests methods for controlling various parameters of the photomodified regions.

Polymer waveguides have long been of interest for low cost integrated optical devices. Inorganic Polymer glasses are a class of materials based around polysiloxanes which have many attractive features for low cost integrated optics and meet the stringent reliability requirements for deployment in carrier networks. The inorganic polymer glasses available for this work are normally patterned as negative photoresists but this leads to a resolution limit on the achievable feature size due to free radical diffusion. Therefore we demonstrate here high quality dry etching of these materials using standard photoresist masking and the fabrication of small high index contrast waveguides with losses marginally higher than the intrinsic materials losses.

We study soliton compression in bulk quadratic nonlinear materials at 800 nm, where group-velocity mismatch dominates. We develop a nonlocal theory showing that efficient compression depends strongly on characteristic nonlocal time scales related to pulse dispersion.

We demonstrate a method of local spectral enhancement of an ultrafast soliton pulse. We use an in-line acoustic long-period grating (LPG), a periodic structure modifying both the phase and the loss of the propagating light, and which is readily tuned by simple adjustment of an applied electrical signal. The soliton perturbed by this narrow-band filter evolves with nonlinear propagation into an intense localised spectral peak. Our setup consists of creation of a red-shifted optical soliton by propagation of pulses from a fibre laser in standard single-mode optical fibre, followed by imposition of a spectrally narrow LPG near to the soliton peak, and then continuing propagation. The wavelength and the peak value of the resulting local enhancement can be tuned by adjustment of the applied acoustic frequency and amplitude. The physics of the observed local spectral enhancement will be discussed in detail here.

We demonstrate external control of metamaterials operating at terahertz frequencies. Through photodoping of semiconducting substrates, used to support metamaterial arrays, we show ultrafast switching times. New metamaterial "grids" are presented, which may be formed by the union of electric metamaterials arrays. Metamaterial grids are then utilized to form a Schottky contact are used to demonstrate voltage switching of the metamaterials resonance. Both devices presented may be utilized to form novel devices at terahertz frequencies and also scaled to other energy regimes of interest.

Resonant nanostructured metallic devices have attracted considerable recent attention through phenomena such as extraordinary transmission and their potential application as sensing elements, metamaterials and for enhancing nonlinear optical effects. Here we report on the investigation of the geometry and material properties on the performance of periodic and random arrays of coaxial apertures in thin metallic films. Such apertures in perfect conductors have been shown to resonate at a wavelength governed by the geometry of the apertures leading to enhanced transmission. This resonant wavelength is dictated by the cutoff wavelength of the fundamental mode propagating in the corresponding coaxial waveguide and, as a consequence, is largely independent of whether the apertures are isolated or in random or periodic arrangements. In the case of periodic samples, however, these resonances can coherently couple to surface waves to produce an analogue of the enhanced optical transmission seen in arrays of circular and other apertures. We have previously shown that as the width of the rings decreases, there are substantial red-shifts in the resonant wavelength from that predicted for perfect conductivity when the optical properties of the metal are considered. Here we report on recent developments in fabrication, design and modelling of metallic resonant structures and their near- and far-field optical characterisation. In particular, we consider the relationship between random and regular arrangements of apertures.

Diamond has a range of extraordinary properties and the recent ability to produce high quality synthetic diamond has paved the way for the fabrication of practical diamond devices. This paper details the recent progress in the fabrication of waveguide structures in diamond which are desirable as the basis for quantum key distribution (QKD), quantum computing and high-power, high speed microwave chips. The diamond ridge waveguide structures are produced by photolithography and reactive ion etching (RIE) with some additional processing with a focused ion beam (FIB). The processes currently used are discussed along with experimental results. Future fabrication goals and potential methods for achieving these goals are also presented.

Traditional Fibre Bragg Grating (FBG) sensing systems acquire data about the measurand via the spectral response of the FBG. Edge filter methods are also used in the acquisition of data from FBGs. In edge filter systems, the spectral shift in the FBG due to the measurand is converted into an optical power change. This optical power change can then be easily measured using conventional optoelectronic devices. We demonstrate the use of a Transmit Reflect Detection System (TRDS) for Fibre Bragg Grating (FBG) sensors. The TRDS is in essence a dual edge filter detection method. In conventional edge filter detection schemes, the reflected portion of the incident spectrum is monitored to determine the change in the measurand. In the TRDS, both the transmitted and reflected portions of the input spectrum, from a narrow band light source, are utilised. The optical power of the transmitted and reflected signals are measured via two separate photoreceivers, where each generates a single edge filter signal. As the spectral response of the FBG shifts due to the measurand, the transmitted power will increase, and the reflected power will decrease, or vice versa. By differentially amplifying the transmitted and reflected components, the overall signal is increased. This results in improved sensitivity and efficiency of the photonic sensor. In this work, the FBG sensor and TRDS are used in the measuring and monitoring of temperature, force and strain. As such, results are presented for the FBG TRDS for all of the measurands.

We report on the development of a compact, all fibre laser source operating at 1 μm with a linearly polarized (extinction ratio > 20 dB) and very narrow linewidth (12 pm) output. The unique cavity design included a fibre Bragg grating high reflector and output coupler, inscribed via the point-by-point method directly into the active core. A single splice within the cavity between the fibre incorporating the high reflector and the output coupler permitted re-orientation of the stressors at an angle of 90 degrees to each other, which produced a single lasing polarisation. This simple technique removed the need for a more complicated and expensive polarization controller.

The growing three-dimensional nanostructures colloidal crystal on the end face of optical fiber by isothermal heating evaporation induced self-assembly method is presented. The wet chemical etching technique is used to etch single mode fiber to obtain a shallow circular cavity between the coating and cladding. The optical fiber with the etched cavity was immersed upside into solution containing polymethylmethacrylate (PMMA). The PMMA spheres used here had an average diameter of 690nm; it takes one week for the sphere particles to completely settle. The nanostructure morphology of the colloidal crystal is examined by using the SEM. The colloidal crystal has a face-centered-cubic (FCC) structure. The optical characterization of the colloidal crystal is also analyzed. The simulation and experiment result show that the colloidal crystal formed by PMMA spheres has an obvious photonic band gap in the wavelength 1543nm that is typical wavelength of optical communication. The spectra feature of the optical fiber colloidal crystal is measured by using optical sensing analyzer. The experimental results show the band gap at the 1543nm, consistent with the simulation results.

This paper describes the realization of high quality factor (Q-factor) single row photonic crystal extended cavity structures embedded in 500 nm wide photonic wire waveguides. Cavities spacer lengths of between 2 µm and 9 µm have been inserted between two periodic mirrors with aperiodic tapering of the hole diameter and the spacing between holes. A Q-factor value of approximately 74,000 has been measured for a 5 µm long cavity at a selected resonance frequency. We have also demonstrated experimentally a tuning capability for the resonance frequency by means of small variations of the cavity length. A shift of approximately 10 nm in resonance frequency has been obtained for a 250 nm variation of the cavity length, both in simulation and in measured results. In addition, a free spectral range (FSR) in resonance frequency of between 20 nm and 30 nm has also been demonstrated for a small variation in the mirror hole diameter of approximately 20 nm. Tapering within and outside the cavity has produced a substantial increase in both the Q-factor and the optical transmission at resonance. Both 2D and 3D finite-difference time-domain (FDTD) computations have been used to simulate the device structures. Comparisons between the simulation and measured results show reasonably good agreement.

This paper is focused on the design, fabrication and characterization of the conventional and tunable photonic devices based on grooved silicon, serving as one-dimensional (1D) photonic crystal. The advantages of these photonic structures are as follows: the large refractive index contrast, in-plane moulding of the light flow, the possibility to fabricate a composite photonic structures by filling the grooves with a different compounds and compatibility with current semiconductor processing techniques. The optical properties of grooved Si structures were simulated using a transfer matrix method and gap map method and have been verified experimentally using FTIR microscopy. The air spaces in the basic silicon-air matrices were infiltrated with nematic liquid crystal E7. It is shown that the optical properties of the obtained composite 1D photonic crystals can be tuned by means of electro- and thermo-optical effects. Such a structures suit well for the various elements of the integrated optics and can serve as a building blocks for optical interconnects.

Progress towards semiconductor laser frequency stabilization using optical feedback from microtoroidal resonators is presented. A simple model of the feedback mechanism is provided, and equations of motion describing the system fields are given. Reactive ion etcher based fabrication of microtoroidal resonators with intrinsic quality factors as high as 1.6 x 10⁵ is demonstrated. This fabrication technique enables improved silicon surface quality and greater control of the physical structure of the microresonators.

This paper examines the fundamental resolution limit of particle positioning with optical tweezers due to the combined effects of Brownian motion and optical shotnoise. It is found that Brownian motion dominates at low signal frequencies, whilst shotnoise dominates at high frequencies, with the exact crossover frequency varying by many orders of magnitude depending on experimental parameters such as particle size and trapping beam power. These results are significant both for analysis of the bandwidth limits of particle monitoring with optical tweezers and for enhancements of optical tweezer systems based on non-classical states of light.

We study the second-harmonic generation via transversely-matched interaction of two counter-propagating ultra-short pulses in χ⁽²⁾ photonic structures with either random ferroelectric domains or annular periodic poling. The profile of the transverse second-harmonic signal is given by the cross-correlation of the pulses and can be used to characterise the temporal structure of the pulses.

We generate conical second-harmonic waves through the parametric frequency conversion in a two-dimensional annular, periodically poled nonlinear photonic structure under the transverse excitation with a fundamental Gaussian beam. We explain the effects observed experimentally by applying the concept of nonlinear Bragg diffraction to the case of the conical frequency generation. We study the polarization properties of the conical emission at the second-harmonic frequency and demonstrate that each of the parametrically generated waves represents a superposition of the Bessel beams.

This study analyzes phase mismatching values of guided-modes in a multimode waveguide with a weak-guiding configuration. In addition, a previously undefined self-imaging phenomenon, referred to herein as the extraneous self-imaging (Ex_SI) phenomenon, was found to result from the modal phase mismatching effect. The evolution principle of the Ex_SI phenomenon is theoretically verified, while the results from the numerical method are compared with graphical and analytical forms of the newly suggested method. Moreover, under a specific condition, the numerical results and the analytical results are compared to analyze the evolution of the Ex_SI phenomenon.

By identifying appropriate quasi-phase-matching (QPM) conditions in z-cut congruent lithium niobate, we demonstrate simultaneous QPM of type-I (ooe) and higher order type-0 (eee) second-harmonic-generation, which share a common second harmonic wave. We demonstrate this experimentally at 1064nm, and show that cascading between these processes occurs. The cascading can result in energy exchange between the cross-polarized fundamentals, indicative of an equivalent 3rd order process. The nonlinear phase shifts and transfer functions resulting from this cascading are explored numerically.

We experimentally demonstrate novel hybrid photonic crystal fibres incorporating a single ring of high-index inclusions surrounded by several rings of holes. These fibres are designed to exhibit large bandwidths of guidance combined with periodic group velocity dispersion zeros. While the multimode character of these fibres limits their use, they are an ideal platform to experimentally demonstrate the emergence of photonic bandgaps.

We have performed measurements using a purpose-built Near-field Scanning Optical Microscope and shown that waveguides written with a fs laser in the kHz regime have an asymmetry associated with the unidirectional nature of the writing beam. Further, the asymmetry becomes more pronounced with increasing pulse energy. At very high pulse energies (5-10 J) the presence of multiple guided regions was also observed, indicating that the refractive index profile of the waveguide possesses several maxima, a result which is consistent with current studies on the filamentation process that high-powered laser pulses experience in a dielectric medium. In this paper we will present these observations, their subsequent analysis and implications for photonic device fabrication using this method.

We present a parametric study of self-assembled photonic crystal growth as a function of radius of curvature. To do this, we used a combination of microscope slides, glass capillaries and optical fibres as substrates to grow the self-assembled films on. Microscope and SEM images, as well as broadband transmission spectra were used to characterise the crystal, and the effect the changing surface curvature had on the crystal quality. Limitations for fabricating the crystals on highly curved surfaces will be presented.

An application of surface plasmon resonance (SPR) angular sensor in the surface defect measurement is proposed. The method based on geometrical optics, SPR effects and heterodyne interferometry technique could transform a phase shift into a surface height. As a beam normally is incident into a plate that is with a very small apex angle, the angle is a function of the flatness or defect directly. Thus, to scan the specimen, the surface defect or its flatness is detected. It has some merits, such as, simple, sensitive, and real-time measurements.

One of the great diffculties of carrying out Terahertz experiments is the alignment of the laser beam that is used to generate the Terahertz radiation. High precision and stability of the beam direction is required over long time periods. Manual adjustments must be made regularly due to the undesired fluctuations of the laser beam direction. A dynamic laser beam alignment system actively reduces misalignment from vibration sources, thermal gradients and mechanical creep. Commercial automatic systems for laser beam stabilization exist but are expensive especially when they must be employed in multiples. We have designed a system that is straightforward and inexpensive using a simple mirror actuation device based on the concept of thermal expansion. Nichrome wire coils surrounding four aluminium rods are used in the mirror actuator. By varying the current through these coils the amount of expansion caused by the dissipated heat in the rods can be controlled. Our circuit consists of a number of stages including a novel feedback design that prevents the rod from ever reaching its maximum length. Our hardware implementation is able to automatically compensate laser beam pointing in real-time and over extended periods of time.

An optical multilayer interference filter is made from two or more different dielectric materials layered in such a way that it promotes constructive or destructive wave interference for a selected frequency in the direction normal to the layers. Usually, each layer has the thickness of a quarter of wavelength at which the stop-band is required. In this paper, a quarter-wavelength multilayer interference filter is realised for T-ray applications. The dielectric materials used are high-resistivity silicon and free space, both of which have high transparency to T-rays and flat all-pass responses over the frequencies of interest. The designed thickness of both materials is in the order of a hundred microns, and thus allows the novelty of a retrofittable assembled structure. An analysis of the affect of the number of layers on the spectral response is given for the first time. The THz-TDS measurement of the fabricated structure is demonstrated to be in agreement with theory.

Conventional time domain Optical Coherence Tomography (OCT) relies on the detection of an interference pattern generated by the interference of backscattered light from the sample and a reference Optical Delay Line (ODL). By referencing the sample interference with the scan depth of the ODL, constructive interference indicates depth in the sample of a reflecting structure. Conventional ODLs used in time domain OCT require some physical movement of a mirror to scan a given depth range. This movement results in instrument degradation. Also in some situations it is necessary to have no moving parts. Stationary ODLs (SODLs) include dual Reflective Spatial Light Modulator (SLM) systems (Type I) and single Transmissive SLM with match-arrayed-waveguide systems (Type II). In this paper, the method of fabrication and characterisation of a number of Stepped Mirrored Structures (SMS) is presented. These structures are intended for later use in proof-of-principle experiments that demonstrate Type II SODL: a six step, 2 mm step depth macro-SMS, an eight step 150 um deep micro-SMS with glue between steps, and a six step 150 um deep micro-SMS with no glue between steps. These SMS are characterized in terms of their fabrication, step alignment and step height increment precision. The degree of alignment of each step was verified using half of a bulk Michelson interferometer. Step height was gauged using a pair of vernier callipers measuring each individual step. A change in notch frequency using an in-fibre Mach-Zhender interferometer was used to gauge the average step height and the result compared to the vernier calliper results. The best aligned SMS was the micro-SMS prepared by method B with no glue between steps. It demonstrated a 95% confidence interval variation of 1% in reflected intensity, with the least variation in intensity within steps. This SMS also had the least absolute variation in step height increment: less than 8 um. Though less variation would be ideal, for producing micro-SMS for proof of principle experiments for Type II stationary ODL, of the method compared, method B, with no glue between steps, produced more reproducible step height increments and step alignment.

Infiltrated photonic crystal fibres (PCFs) offer a new way of studying nonlinearity in periodic systems. A wide range of available structures and the ease of infiltration opens up a large range of new experimental opportunities in bio-physics, nonlinear optics, and the study of long range interactions in nonlinear media. Devices relying on these effects have many applications, from bio-sensors, to all optical switches. To further understand these nonlinear interactions and realise their potential applications, the effects of nonlinearity need to be studied on the short time scale. In this work we study the temporal dynamics of thermally induced spatial nonlinearity in liquid-filled photonic crystal fibres. Light is injected into a single hole of an infiltrated PCF cladding, and the subsequent response is measured at a few milliseconds time scale. We experimentally demonstrate the short time scale behavior of such systems, and characterise the effects of this thermal nonlinearity.

We present a technique for characterising metal-clad optical waveguides. Unperturbed Waveguides have been analysed and the results compare well with the theoretical results from finite difference approximation of the scalar wave equation. Waveguides containing periodic perturbations have also been analysed. These perturbed waveguide structures have been characterised using a prism coupler and it has been found that there are images of the guided modes which line up well with theoretical predictions. These images are due to diffractions from the periodic perturbations within the waveguide structure.

A practical optical link system was prepared with a transmitter (Tx) and receiver (Rx). The optical TRx module consisted of a metal optical bench, a module printed circuit board (PCB), a driver/receiver IC, a VCSEL/PD array, and an optical link block composed of plastic optical fiber (POF). For the optical interconnection between the light-sources and detectors, an optical wiring method has been proposed to enable easy assembly. This paper provides a method for optical interconnection between an optical Tx and an optical Rx, comprising the following steps: (a) forming a light source device, an optical detection device, and an optical transmission unit on a substrate (metal optical bench (MOB)); (b) preparing a flexible optical transmission-connection medium (optical wiring link) to optically connect the light source device formed on the substrate with the optical detection device; and (c) directly connecting one end of the surface-finished optical transmission connection medium with the light source device and the other end with the optical detection device. A chip-to-chip optical link system constructed with TRx modules was fabricated and the optical characteristics were measured. The results clearly demonstrate that the use of an optical wiring method can provide robust and cost-effective assembly for vertical-cavity surface-emitting lasers (VCSELs) and photodiodes (PDs). We successfully achieved a 5 Gb/s data transmission rate with this optical link.

There is much interest in nonlinear absorbing chromophores for applications in photonics, nanophotonics and biophotonics. We have performed studies of dispersion of the nonlinear absorption cross sections and the refractive nonlinearities of organic and organometallic nonlinear chromophores using the technique of Z-scan, with a tunable amplified femtosecond laser system. Z-scan is less sensitive than the popular technique of two-photon induced fluorescence but has advantages of being suitable for non-fluorescent substances and providing information on both absorptive and refractive nonlinearities. We have analysed the experimental results in terms of simple models and using the Kramers-Kronig transformation as shown in this paper for Coumarine 307 and an organometallic dendrimer. The dispersion curves are often dominated by two-photon resonances but inclusion of other nonlinear mechanisms seems to be necessary for better understanding of their features.

Optical devices, where light controls light, are of interest to the computing and communications industries due to their potential to vastly improve information capacity and processing speed. One such device is an optical logic gate, based on the interactions of low divergence fields in photorefractive media. Presently, bright solitons in self-focusing photorefractive media offer one attractive possibility. A wide variety of other low divergence fields have also been outlined in recent literature, however, no theoretical model of a single bright soliton propagating in unbiased selfdefocusing photorefractive media is currently available. Evidence is presented of self-defocusing photorefractive media as an intensity dependent Gradient-Index (GRIN) lens with a negative power. Using this model, we outline conditions for the change in the complex beam parameter, and consequently the area and wavefront curvature, of the Gaussian beam to be minimised as it propagates through the selfdefocusing media. This is the first instance where self-defocusing photorefractive media has been modelled as an intensity dependent GRIN lens, and where a low divergence field propagating through unbiased self-defocusing media with a constant complex Gaussian beam parameter has been described.

Using Terahertz (THz) beams with fairly large beam diameters (~20 mm) and short focal length lenses (25 mm) to obtain a high spatial resolution makes it essential to use aspherical lenses. As High Density Polyethylene (HDPE) lenses can be machined to any arbitrary shape with high surface quality, there are several free parameters that can be varied when designing a lens that has no spherical aberrations. We present several different lens designs and evaluate their performances in terms of losses and focal spot sizes. Geometrical optics is used to design the lenses but the Kirchhoff Scalar Diffraction theory is employed to evaluate the beam sizes in the focal planes. The performances of the lenses were also analyzed experimentally, where their focal spot sizes were measured and compared with our models. Results show that spatial resolutions of less than the THz wavelengths (0.3 mm for 1 THz) are achievable with our imaging system.