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A direct UV grating writing technique based on phase-controlled interferometry is proposed and demonstrated in a silica-on-silicon platform, with a wider wavelength detuning range than any previously reported UV writing technology. Electro-optic phase modulation of one beam in the interferometer is used to manipulate the fringe pattern and thus control the parameters of the Bragg gratings and waveguides. Various grating structures with refractive index apodization, phase shifts and index contrasts of up to 0.8×10-3 have been demonstrated. The method offers significant time/energy efficiency as well as simplified optical layout and fabrication process. We have shown Bragg gratings can be made from 1200 nm to 1900 nm exclusively under software control and the maximum peak grating reflectivity only decreases by 3dB over a 250 nm (~32THz) bandwidth.

Direct UV Grating Writing (DGW) is effective route for fabricating high quality Bragg gratings, similar to fiber Bragg gratings, in a planar geometry. We will present a phase modulation controlled DGW method using an Electro-Optical Modulator for planar Bragg grating fabrication that offers improved performance. This new approach not only provides much greater modulation depths for stronger and shorter Bragg gratings but also offers greater fabrication speed and a higher fidelity of control than previous amplitude modulation methods [1].

Summary form only given. Microbeams integrated with optical components have found applications in telecoms and sensing applications[1][2]. We present fabrication, characterisation and modelling of silica microbeams containing an integration optical waveguide and Bragg reflectors. These optical elements, fabricated using direct UV writing process, have applications in telecoms and sensing[3]. Thermal tuning of the integral Bragg gratings is enhanced and the energy requirements greatly reduced by a factor of 50.The ability to tune a Bragg grating's reflected wavelength provides a route to numerous potential applications such as tunable add/drop multiplexers. While this has already been achieved in fibre optics there are situations where the planar format has advantages in terms of compactness and integration. Of the possible tuning mechanisms, temperature tuning is most common, yielding wide tuning ranges as well as uniform spectral response. Temperature tuning can however suffer from power inefficiency and poor time response due to the large thermal mass of the device. Locating the optical elements in a microbeam is an elegant way to provide localised tuning to a small thermal mass, thereby increasing energy efficiency and reducing crosstalk with other components on the device. Silica microbeams have been fabricated using a series of microfabrication techniques including micro-milling, KOH etching of silicon and evaporative metal deposition. The resultant devices are geometrically uniform and surprisingly robust although only 100μm wide.The devices characterized show that the observed Bragg peak shift is close to linear with the applied electrical power. The data in figure 1 shows a tuning of almost 0.5 nm with 12 mW of heating power. Another potentially useful property of microbeams is elastic buckling[4]. Buckling either occurs following fabrication due to the stresses caused by the silica deposition process or can be induced by other forms of actuation such as thermal stress. Utilizing buckling in thermal tuning could allow tuning between bi-stable states with no requirement for continuous energy supply. We shall present our findings including the fabrication and characterization of microbeam devices and applications of a tunable Bragg grating.

Summary form only given. To achieve low-loss free space coupling for integrated optics, device facets need to be smooth, free of chips and flat. The typical route for accomplishing these requirements is by traditional lapping and polishing. We report that high quality optical quality facets with a S a = 4.9 nm can be machined using a simple dicing technique. In order to directly measure the scatter loss a device with a series of Bragg gratings is used to characterise the average interface loss per facet.Traditional lapping and polishing of planar integrated optics is time consuming due to the multiple tasks required to perform the process, i.e. sample stacking and bonding, plate preparation, which all require constant human attention to ensure good facet quality. Created for the semiconductor industry, precision dicing saws are normally used to separate ICs from wafers but can be used to dice optical grade surfaces into materials such as silica. Dicing has been used to create such photonic structures as silica microcantilevers [1], multimode interference devices in silica flat fibre [2] and waveguides in lithium niobate [3]. Compared to traditional techniques, dicing offers automated wafer scale facet preparation requiring seconds to machine each facet. We optimised dicing machining parameters to obtain optical quality facets in flame hydrolysis deposition silica-on-silicon. We focused on changing the feed rate and blade rotational speed while keeping constant the blade type (i.e. diamond size, diamond concentration and diamond bond type) and depth of cut. The diced silica surface roughness was analysed using a white light interferometer (Zemetrics, ZeScope). The smoothest silica facets produced had a three dimensional (areal), average surface (Sa) of 4.9 nm, as shown in Fig. 1 a). The optimised machining parameters for machining smooth silica facets, was found to be

Tilted Bragg grating refractometers have been subject to continuous interest in recent years [1]. They operate by diffracting a well-confined core mode into a discrete set of cladding [2] or plasmonic modes [3], whose properties are dependent upon an external refractive index. Traditionally these components have been fabricated in an optical fibre platform. However, recent work from the authors has demonstrated this concept in an optical planar platform [2-5]. The key advantages of these tilted planar Bragg gratings (TPBGs) include compact multiparameter sensing, signal multiplexing and the potential to seamlessly integrate operation with microfluidics. In addition, there is an increased level of design flexibility that continues to be explored; including waveguide-to-waveguide assisted coupling [5], controllability of cladding thickness, multi-waveguide arrangements and asymmetric waveguide positioning.

Summary form only given. Grating stabilized diode lasers exist in many different configurations, typically using bulk and fiber Bragg gratings. In the last couple of years grating stabilized lasers based on a semiconductor gain chips coupled to integrated or planar lightwave circuits containing Bragg gratings have been demonstrated and developed. These devices not only exhibit excellent optical properties such as ultra-low RIN and phase noise, but also compact size and greater opportunities for mass production. We shall present our latest developments of silica planar Bragg grating stabilized diode lasers, and in particular the generation of tunable narrow linewidth sources for gas sensing.

We have demonstrated two monolithically integrated Bragg grating based accelerometers, both with the optical path and mechanical structure being made from the same substrate. The unique fabrication techniques, Direct UV Writing and precision dicing, used to create the glass microcantilevers are discussed. We show experimental results from two different Bragg grating based interrogation systems, one utilizing a single Gaussian apodized Bragg grating and the other utilizes two spectrally matched Bragg gratings forming a Fabry-Perot interferometer. Sinusoidal accelerations were applied to both devices and their sensitivities were found to be 0.67±0.035 mV/g and 14.0±0.44 mV/g for the single Bragg grating and Fabry-Perot interferometer respectively.

Tilted Bragg gratings (TBGs) have been shown to have a number of practical uses in planar geometries, demonstrating polarization capabilities and allowing excitation of surface plasmons. Fabrication and characterization of TBGs has been carried out in silica-on-silicon waveguides to highlight potential planar applications. An initial investigation into the coupling behaviour of TBGs has been undertaken, with greater than -20 dB coupling achieved for even small angle gratings (5 °). Experimental analysis of these TBG systems provides insight into future applications of the planarized devices.

Direct UV Grating Writing (DGW) is an attractive technique for simultaneously fabricating integrated Bragg grating devices in a silica-on-silicon platform, yielding losses as low as 0.03dB/cm. Previously, an Acousto-Optical Modulator has been used for writing planar Bragg gratings; in this new work we demonstrate a new phase modulation fabrication technique that offers improved performance. We report a novel phase control DGW method using an Electro-Optical Modulator for planar Bragg grating fabrication. We phase modulate one laser beam in a focusing interferometer as a photosensitive silica-on-silicon sample is translated under the spot to give a moving fringe pattern that allows high quality Bragg gratings and waveguides to be fabricated in a single step. This new approach has allowed us to achieve a 1mm long uniform Bragg grating with ~70% reflectivity and a 1.4nm 3dB bandwidth; while a 3mm long grating has 100% top flat reflectivity and a 1.22nm 3dB reflection bandwidth - refractive index changes of up to 0.001 can be achieved. Since there is neither laser power reduction nor writing speed variation, the method offers significantly faster writing speeds. The simplified optical layout offers greater laser power on sample and furthermore the design coding is simplified. By applying Gaussian apodisation to the grating design we can achieve sidelobe suppression of >15dB. Using grating detuning and this new phase control method we have shown that Bragg gratings can be written from 1200nm to 1900nm on a single chip under software control and with less than 3dB variation across a 250nm bandwidth high chemical stability, which makes these materials very interesting for active photonics applications. In particular, Yb3+-doped RTP exhibits a broad fluorescence spectrum that has been exploited to demonstrate ultrafast operation, with pulses as short as 155 fs being generated [1]. Recently, planar waveguiding has been demonstrated in an (Yb3+, Nb5+):RTP film grown by liquid phase epitaxy [2], opening the possibility of planar integrated devices based on this highly functional material.

This paper reviews the demonstrations of photonic Hilbert transformers (PHTs), describing their progress and recent developments. The physical operating principles of PHTs including fractional Hilbert transformers are discussed, together with device applications in all-optical signal processing. Versatile approaches to realize PHTs are discussed, e.g., discrete free space optics, fiber-based schemes and integrated planar geometry. The numerical designs and experimental performances of these PHTs are analyzed in terms of spectral quality, operating bandwidth, system integration, and mechanical and thermal stability. Recent developments of the monolithically integrated photonic Hilbert transform (HT) devices include directional couplers and planar Bragg gratings which allow all-optical single-sideband (SSB) suppression and sideband switching.Erratum: The author of Ref. [1] Frederick W K should be King F W.

The first monolithically integrated all-optical single-sideband filter based on photonic Hilbert transform and planar Bragg gratings is proposed and experimentally demonstrated. Single-sideband suppression of 12 dB at 6 GHz and sideband switching are achieved via thermal tuning. An X-coupler, photonic Hilbert transformer, flat top reflector and a micro heater are incorporated in a single silicon-on-silica substrate. The device can be thermally tuned by the micro heater on top of the channel waveguide. The device is fabricated using a combination of direct UV grating writing technology and photolithography.

We recently proposed that an array of optical cavities containing quantum emitters could be interconnected by an optical bus made of Fabry Perot resonators lying side by side, for applications in quantum information processing and quantum simulation. Here, we demonstrate the feasibility of this geometry. We show that the resonators can be conveniently coupled, and that the coupling rate between adjacent waveguides can be widely tuned using the thermo-optic effect. The device is linearly scalable and can be combined with other integrated devices, making it more generally applicable as an adjustable optical delay line or optical interconnect.

Integrated quantum optics provides great promise for enabling photonic experiments to reach new regimes of complexity. Chip-based fabrication enables sophisticated networks involving multiple interfering pathways in a compact and stable physical architecture. In a recent work [1] we demonstrated an advance in the complexity of these integrated devices by showing the first quantum interference of three separate input photons. Such complexity allows the demonstration of three qubit protocols never before realised on-chip. Here, we report the first results showing quantum teleportation on an integrated photonic circuit. Quantum teleportation provides the mechanism for quantum relay schemes and is an important constituent in linear optical quantum computing. Whilst demonstrations to date have relied upon complex and fragile bulk optical systems, being able to teleport quantum states on a compact and stable integrated architecture will be a critical step towards scalable realisations of these schemes. © 2013 IEEE.

Summary form only given. The recent trend towards integration of quantum optics experiments has produced a demand for on-chip single photon detectors with high quantum efficiencies. In previous work we demonstrated integrated photon number resolving detectors for use at telecommunications wavelengths [1], here we outline developments of this design which have enabled improvements in the quantum efficiency, permitting an on-chip detection efficiency of 92% to be obtained in the device of Fig. 1.

Planar Bragg grating based photonic Hilbert transformers (PHTs) with THz bandwidths are proposed and practically demonstrated. An X-coupler, PHT, and a flat-top reflector are incorporated, demonstrating 2THz all-optical single-sideband filters. Devices are fabricated via a direct UV grating writing technique on a silica-on-silicon platform.

The presentation will give an overview of the fabrication process of direct UV written planar Bragg grating sensors and the various geometries and applications investigated over the last several years.

While universal quantum computers ideally solve problems such as factoring integers exponentially more efficiently than classical machines, the formidable challenges in building such devices motivate the demonstration of simpler, problem-specific algorithms that still promise a quantum speedup. We construct a quantum boson sampling machine (QBSM) to sample the output distribution resulting from the nonclassical interference of photons in an integrated photonic circuit, a problem thought to be exponentially hard to solve classically. Unlike universal quantum computation, boson sampling merely requires indistinguishable photons, linear state evolution, and detectors. We benchmark our QBSM with three and four photons and analyze sources of sampling inaccuracy. Our studies pave the way to larger devices that could offer the first definitive quantum-enhanced computation., Main text: 5 pages, 4 figures. Supp Info: 6 pages

A planar Bragg grating device has been developed that is capable of detecting changes in the refractive index of a wide range of fluids including solvents, acids and bases. The integration of this high precision refractive index sensor within a chemically resistant microfluidic flow system has enabled the investigation of diverse fluid interactions. By cycling between different solvents, both miscible and immiscible, within the microfluidic system it is shown that the previous solvent determines the nature of the refractive index profile across the transition in composition. This solvent dispersion effect is investigated with particular attention to the methanol–water transition, where transients in refractive index are observed that are an order of magnitude larger in amplitude than the difference between the bulk fluids. The potential complications of such phenomenon are discussed together with an example of a device that exploits this effect for the unambiguous composition measurement of a binary solvent system.

We present direct UV-written waveguides and Bragg gratings operating at 780 nm. By combining two gratings into a Fabry-Perot cavity we have devised and implemented a novel and practical method of measuring the group delay of Bragg gratings., 10 pages, 8 figures

All-optical signal processing offers the prospect of realizing high sampling bandwidth and overcoming many of the limitations of electronics. This work introduces the use of planar Bragg gratings in all-optical signal processing. The key fabrication technique is direct grating writing (DGW). One significant advantage of the DGW system is the small spot size of the focused laser beam used to inscribe the waveguide and grating. Rather than using the wide area exposure such as that from a phase mask, DGW uses a direct UV laser spot such that the dimensions of the UV induced structure are determined by the focal spot size. For complex grating engineering this feature is superior to the conventional phase mask techniques, allowing accurate control of the chirp, phase shifts, apodisation and other parameters to produce intricate optical response.

Tilted Bragg grating refractometers are ideal devices for sensing applications. They work by diffracting light from a confined core mode into a series of well-defined cladding modes that are sensitive to the refractive index of an adjacent fluid. Using the Cauchy integral method, we find the modes of a ridge waveguide refractometer. To gain good agreement with the experiment, the method requires us to take into account the dispersion and the 2-D geometry of the waveguide. The resulting modes are then used to predict the coupling dips in the reflection spectrum. Comparison with experimental measurements verifies the ability of this method to accurately determine the mode structure in the waveguide and, with minimal calibration, the refractive index of the adjacent fluid with error less than 2 ×10-4.

We present a planar-integrated optical surface plasmon refractometer. The fabricated device operates by grating-matched coupling between a core waveguide mode and a set of hybrid plasmon-dielectric modes of a much wider integrated structure. The constructed device incorporates a 50-nm-thin gold layer that separates a tilted planar-waveguide Bragg grating and a liquid analyte. It is demonstrated that polarization-dependent plasmon anomalies occur in the transmission spectra of the device, which are understood using a numerical Cauchy integral mode solving approach. Sensitivities in this planar-integrated device are comparable with existing fiber-based plasmonic sensors but with the advantages of planar integration and microfluidic adaptation.

Integration is currently the only feasible route toward scalable photonic quantum processing devices that are sufficiently complex to be genuinely useful in computing, metrology, and simulation. Embedded on-chip detection will be critical to such devices. We demonstrate an integrated photon-number-resolving detector, operating in the telecom band at 1550 nm, employing an evanescently coupled design that allows it to be placed at arbitrary locations within a planar circuit. Up to five photons are resolved in the guided optical mode via absorption from the evanescent field into a tungsten transition-edge sensor. The detection efficiency is 7.2 +/- 0.5%. The polarization sensitivity of the detector is also demonstrated. Detailed modeling of device designs shows a clear and feasible route to reaching high detection efficiencies.

Oxygen sensing is required for the understanding of many chemical processes across a diverse set of fields including medicine, environmental science and chemical synthesis. Oxygen sensing can be achieved through the use of electronic sensors. However, there are limitations associated with electronic sensors including susceptibility to electromagnetic interference and presenting a spark risk in flammable environments. Optical fiber and integrated optical chemical sensors overcome these limitations of electrical based sensing methods.

Measuring the dispersion characteristics of a planar waveguide is typically difficult due to the short lengths of waveguides involved. Traditional dispersion measurement techniques were developed in fibre [1] and bulk glass [2], and thus do not take into account the intricacies of the short planar waveguide. The fibre techniques typically require far more material than is available in a short planar waveguide, resulting in an imprecise measurement. The bulk measurement techniques do not take into account the specific structure and dimensions of the waveguide under test, so again do not provide a realistic interpretation of the dispersion characteristics of a specific waveguide.

Turning or corner mirrors can be used to redirected light on an integrated chip, providing a route to higher density of optical components. Mirrors have been demonstrated in silicon-on-insulator with losses of 0.9dB [1] and in hollow waveguides with losses of 0.8dB [2]. We demonstrate an alternative method of fabricating mirrors on a silica-on-silicon substrate. The method employs the complimentary techniques of physical micromachining and direct UV writing, both provide rapid prototyping outside the cleanroom environment.

Microcantilevers are the workhorse for ultra sensitive force sensors and are used in applications such as atomic force microscopy, sensing forces as small as 10pN [1]. In previous work [2] we have demonstrated the first integrated optical glass microcantilever, and we now show for the first time Bragg gratings forming a Fabry-Perot interferometer acting to increase the force-sensitivity of the device. The fabrication of the glass microcantilever is based on a novel physical micromachining and etching approach, combined with UV written Bragg gratings. The advantages of the in-situ Fabry-Perot interferometer will also be discussed.

Tilted Bragg gratings (TBG) offer discrimination between different environmental perturbations, such as localised strain (including thermal expansion) and external refractive index [1]. Discrimination can usually be made in this way as the external refractive index is not in direct contact with the core mode. Such technology has been primarily exploited in optical fibre [1-3], with some recent progress demonstrating multiplexed multi-point sensing networks [2], and the employment of enhancement layers to increase external refractive index resolution [3]. Despite significant developments made in fibre, relatively few reports have been made for such components in a planar geometry, which have the added advantage of compact integration and offers ready integration with microfluidics. A recent patent application for a refractometer device [4], has proposed the use of planar tilted Bragg gratings (PTBG) but it only describes geometries in which the measurand is in direct contact with the core of the waveguide. This work details a novel PTBG structure whose core mode is not in contact with the external refractive index.

The use of weakly tilted Bragg gratings to couple light from core waveguide modes to plasmon resonances within thin gold layers has gained increased interest over recent years [1–3]. Chemical sensing using such techniques has a multitude of advantages, including access to developed gold based chemistry for surface functionalisation and an enhancement of chemical sensitivity, particularly for the biochemically ubiquitous solvent, water (1.33). Despite the obvious benefits of such devices, fabrication has principally been limited to optical fibre platforms, with little fabrication development being made in the planar regime [4]. This work reports the use of a thin (50 nm) sputtered gold layer to enhance the chemical sensitivity of a weakly tilted planar Bragg grating (TPBG), illustrated in Figure 1 (a). Therefore, allowing access to the benefits of planar integration for this newly emerging technology.

With low thresholds and high gain, channel and rib waveguide lasers are of interest both as stand-alone devices and as components in integrated optical circuits. A number of approaches may be taken to fabricate such structures, including direct bonding, ion implantation or diffusion and post-processing of deposited films. However, many of these techniques can be prohibitively slow and costly, particularly for rapid prototyping.

High demand on structural health monitoring has encouraged the development of smart structure geometries to be more effective and competitive [1]. One of the technologies that has been integrated into these structures is the fiber Bragg grating (FBG) [2]. The FBG is a mature technology that has seen many applications, particularly the field of sensing where it has many advantages such as immunity to electromagnetic field, long lifetime, high sensitivity, lightweight and low loss. There are several types of optically based physical sensors. Most of which are fabricated in a standard dimension silica optical fiber which due to its cylindrical structure are unable to independently measure twist. Here we demonstrate a bending and twist sensor fabricated in a flat-fiber substrate. A Y-splitter and a series of Bragg gratings along the 50 mm length provides a differential signal providing distinction between bend and twist within the sample.

Multi-mode photonic lightwave circuits (PLCs) provide new avenues for extending the performance of single mode systems. As an example, they can potentially provide increased bandwidth by multiplexing information into different waveguide modes[1]. For practical applications of multi-mode PLCs to be developed, a measurement technique is required to investigate detailed mode profiles and propagation constants in complex circuits. Photon scanning tunnelling microscopy (PSTM) provides a means of experimentally tracking the femtosecond inter-modal delays observed in PLCs with the ability to discriminate modes by their spatial profiles inside the waveguide.

We report on an integrated optical trapping platform operated by simple fiber coupling. The system consists of a dielectric channel optical waveguide decorated with an array of gold micro-pads. Through a suitable engineering of the waveguide mode, we achieve light coupling to the surface plasmon resonance of the gold pads that act as individual plasmonic traps. We demonstrate parallel trapping of both micrometer size polystyrene beads and yeast cells at predetermined locations on the chip with only 20 mW total incident laser power.

Photonic Hilbert transformers (PHT) offer potential for a wide range of applications in telecommunication, information processing and signal analysis [1]. They provide operational bandwidths and speeds far beyond current electronic technologies. PHTs have been realized in discrete free space components and recently in fiber using multi-tapped sampled fiber Bragg gratings (FBGs), and single phase-shifted FBGs with appropriate apodisation profile [2]. Recently we have presented preliminary spectra from a fabricated PHT device in a planar waveguide [3]. This device employs a single pi phase shift and an apodised grating profile. In this work we use the freedom of the planar format to fabricate a single-side-band suppression (SSBS) module combining regular and phase shifted gratings on a single chip.

A photoactive material has been synthesised in which azobenzene units are attached to a methyl methacrylate/2-hydroxyethyl methacrylate co-polymer and shows repeated photoresponsive switching upon irradiation at 365 nm and 254 nm with long term thermal stability. In combination with a direct UV-written silica-on-silicon Bragg grating, this has been used to fabricate a prototype optical device which undergoes reversible refractive index changes at telecom wavelengths. The 63 GHz tuning response demonstrated by this device has potential applicability for reconfigurable dispersion compensation for use in optical networks.

In this work the theoretical design and experimental realisation of a photonic Hilbert transformer is investigated. Planar Bragg gratings are proposed as a route to realise photonic Hilbert transformers in terms of a finite bandwidth and temporal impulse response. With proper grating apodisation and π-phase shift, the Bragg grating will display the spectral features expected from a Hilbert transformer. The unique features of Direct UV grating writing technology are used to fabricate the proposed device in silica-on-silicon

Nonlinear conversion of diode based sources using MgO doped PPLN provides a viable route to watt level power visible laser wavelength systems with high electrical efficiency and offer a low cost solution for applications in laser projection and bio-optics. Recent developments of superior nonlinear materials together with brighter and more powerful diode sources provide an excellent opportunity for optical technology over the coming decade.

Multiplexed direct UV written planar Bragg gratings are integrated into a compact silica-on-silicon chip, with the ability to locally monitor temperature, chemical species, pressure and flow.

A novel flat-fiber platform is presented for fabricating integrated optical multimode interference (MMI) devices. Fabrication is achieved by modifying a standard optical fiber drawing process and applying a micromachining technique. The fabricated structure consists of an MMI region within the flat-fiber that is defined by micromachined trenches, illustrated in Figure 1(a). A 1×3 splitter has been demonstrated, with a spatial output mode that be tuned by placing refractive index oils within the micromachined trenches. MMI devices have been demonstrated in different planar platforms such as silicon-on-insulator and silica-on-silicon. However, many of these materials are potentially expensive, high loss or have a complex fabrication process. The desire to have a fiber-like platform, capable of supporting multiple waveguides in a planar format, led us to develop a novel silica optical flat-fiber technology. This allows us to overcome the limitations of existing planar technologies by offering a low cost, low loss substrate with fiber-like flexibility, long lengths and the ability to make integrated devices. The flat-fiber substrate is fabricated using standard silica fiber fabrication but differs by collapsing the preform during the fiber drawing stage by using a vacuum. The trenches of the device were diced using an ultra-precision micromachining technique.

Strong transitional mixing effects were observed by a planar Bragg grating sensor within a microfluidic system. This property was used to develop an integrated optofluidic sensor for detection of the composition of mixed solvent systems.

A phase transition sensor is demonstrated using direct UV written Bragg gratings intrinsically defined within a mechanically resonating silica micro-cantilever. Fabrication is uniquely achieved through a combination of micro-machining and direct UV writing.

UV written planar Bragg grating sensors have been shown to form effective refractometers. Here we show that by using the birefringence of an integrated waveguide a temperature insensitive Bragg grating refractometer can be realised.

Liquid crystal tunable planar Bragg Gratings produced by Direct UV Writing are capable of wavelength tuning of over 100GHz. However, such devices exhibit non-linear tuning curves with threshold points and hysteresis. We show that these effects are due to the formation of disclination structures in the liquid crystal and discuss the role of electrode defects and sample temperature on wavelength tuning.

Integrated planar lightwave circuits (PLCs) provide a promising route to small-scale quantum optical networks [1]. Recent work on quantum logic gates using silica-based PLCs has highlighted the opportunities afforded by the ability to coherently manipulate degrees of freedom at the level of single photons [2]. Increasingly complex waveguide networks are required for linear optics quantum computing (LOQC), a route towards small scale quantum information processing [3]. This approach uses quantum interference between photons and measurements with feedforward to implement the nonlinear interactions between photons that are required for information processing. A major issue in developing such circuits is the internal loss and the coupling efficiency of input photon from optical fibers.

Current optical telecommunication systems employ dense Wavelength Division Multiplexing (WDM) techniques to increase the data carrying capacity of fiber networks. Dynamic add/drop and filtering processes are crucial for the precise control of individual channels on these networks. Reconfigurable integrated optical devices, such as planar Bragg gratings, can tune the reflection wavelength over several standard channel spacings, providing the possibility for all-optical dynamic networks. Planar devices have the potential to address and tune several channels simultaneously, and have greater potential for integration than fiber equivalents.

The demand for photonic pressure sensors is on the increase, driven by the needs of the oil and gas industry, as well as homeland security [1]. The main advantage of such optical devices is that they can operate in strong magnetic fields and environments that require electromagnetic immunity.

Planar waveguides can be written with a UV-laser into photosensitized silica to produce a wide range of optical devices. Careful modulation of two interfering beams allows Bragg gratings to be directly written into the channel (Figure 1.a). These Bragg gratings are inherently sensitive to temperature and strain. However etching away the surface exposes the mode within the grating to its surroundings. The corresponding observed shift in Bragg wavelength can be used to detect changes in this environment [1]. Figure 1.b shows a large wavelength shift due to two analytes of markedly different refractive index. This demonstrates the apodised spectral response that in practice allows resolution of sub-picometer shifts in wavelength.

Nonlinear interactions such as second harmonic generation (SHG) [1] and sum and difference frequency generation are routinely used for the generation of laser wavelengths. With high power lasers it is necessary to use bulk crystals and tight beam focusing to achieve the maximum conversion efficiency. The use of Quasi-phase-matched (QPM) materials such as PPLN and PPKTP are now routinely reported; however, as we will show in this paper, a simple linear QPM crystal does not fully optimize the conversion response. We will report theoretical and experimental results showing that by careful control of the crystal design it is possible to fully compensate for the phase errors associated with the focusing induced Gouy shift.

An exposed Bragg grating incorporated into a planar waveguide was used to form a refractive index sensor. The high sensitivity to subtle changes allowed the study of surface functionalisation and binding within a microfluidic system.

The cost of health and safety failures to UK industry is currently estimated at £6.5 billion per annum. Better health and safety education (particularly re-training) across all skill levels is seen as an integral part of any solution. Traditional lecture-based courses often fail to re-create the dynamic realities of managing health and safety on-site or in-the-lab, and therefore do not sufficiently engage the students in deeper learning (which results in remembering and using what was learned). Current training regimes also have to adapt to increasing numbers of overseas students/employees who often display different attitudes towards health and safety and the perception of risk. The use of video as a training aid is common place, but passively observing a video is not cognitively engaging and therefore learning is not as effective as it could be. This paper will describe the development and testing of an interactive and adaptive video designed to help students understand the risks involved with the set-up and operation of lasers in a laboratory setting. The software allows students to interact and engage with the subject matter by requiring them to identify and describe risks through the technique of video 'hot-spotting' coupled to multiple choice question sets.