Lateral groove geometry for planar UV written evanescent devices - new flexibility new devices

Conventional evanescent optical devices have made use of etched windows to allow access of an optical field to a material of interest. Such devices are a route to accurate refractive index sensors and to realising modulators, however, the geometry of etching the cladding to give the fluid access to a pre-defined core waveguide mode is limiting. In this work, we present an alternative approach in which a groove is cut using a polishing saw blade to give a vertical, high optical quality trench. Optical waveguides are then UV written to allow evanescent lateral access of the mode to a fluid placed in the trench. This seemingly subtle change in geometry provides greatly increased flexibility to tailor the interaction between the optical mode and the surrounding material, by, for example, changing the mode size and the allowing couplers or tapers to be used

Direct optical observation of walls and disclination effects in active photonic devices

Liquid crystal tunable Bragg Gratings defined in planar substrates via a laser patterning technique exhibit complex wavelength tuning. This tuning displays threshold points and hysteresis. These tuning features are shown to be a manifestation of physical processes occurring in the confined geometry of our tunable devices. Such physical processes include the formation and removal of line disclinations and an associated wall. We discuss the effect of walls in the liquid crystal with regards to voltage tuning characteristics and whether they may allow faster wavelength tuning

Surface plasmon in slab waveguide: a verification test-bed

Since its first use in a real-time analysis of a biological system in 1990s, surface plasmon resonance (SPR) has become an important optical biosensing technology for its real-time, label-free, and noninvasive nature. In this paper we review electromagnetic theory of surface plasmons in dielectric-metal-dielectric planar waveguides and verify capabilities of an emerging computational package, COMSOL, that uses finite element methods (FEM) for analysis of plasmonic phenomena. Results of analytical and numerical methods are compared and accuracy of FEM solver is discussed

Confocal luminescence investigations of two-beam direct-UV-written silica-on-silicon waveguides

Two-beam direct-UV-written silica-on-silicon waveguides have been investigated by confocal micro-luminescence experiments. The spatial and spectral analysis of the visible luminescence observed after 488 nm excitation has revealed the presence of various UV-induced defects due to the different compositions of core and under/over clad layers. The shape and waveguide's dimensions have been estimated from the spatial distribution of defect luminescence generated at the photosensitive core layer. The persistence of the defect luminescence induced in the core layer with increasing temperatures has been used to examine the thermal stability of two-beam UV-written waveguides as well as to determine the recombination energy of the corresponding luminescent defects

Liquid crystal based tunable WDM planar Bragg grating devices based on precision sawn groove substrates

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

UV written planar Bragg grating sensors: geometries and applications

Bragg gratings in optical fibres are a well developed technology that finds many applications in photonics, including wavelength stabilization, dispersion compensation, and use as temperature and strain sensors. In recent years we have developed planar Bragg grating devices as integrated counterparts to fibre based devices[1]. The implementation of Bragg gratings in planar opens many new degrees of freedom because it is possible to make more intricate circuits incorporating splitters, interferometers, couplers, etc

Line defects and temperature effects in liquid crystal tunable planar Bragg gratings

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

Design and demonstration of direct UV-written small angle X couplers in silica-on-silicon for broadband operation

Experimental demonstration of small angle (0.8°-5°) direct UV-written X couplers in silica-on-silicon is presented. Maximum and minimum coupling ratios of 95% (±0.8%) and 1.9% (±1%), respectively, were recorded. The structures also display very low polarization and wavelength dependence. A typical excess loss of 1.0 dB (±0.5 dB) was recorded. Device modeling using the beam propagation method and an analytical model showed good agreement with experimental results over a broad crossing angle and wavelength range

Sense and fibrelity: next generation optical biosensors

Biosensors now play a vital and essential role in medicine, industry and the environment, providing routine analysis, crucial monitoring, and early detection of problems and crisis points. Biosensors are increasingly finding applications in homeland security, as well as in bio/pharmaceutical research. The market for biosensors is forecast to swell to £5.7 billion in 2007, with an annual growth rate of around 10 per cent [1], as new techniques address the issues of accuracy, response time, ease of use and cost, which currently determine specific implementation in different sectors