1,721,122 research outputs found
Integrated photonics in CMOS-compatible dielectric platforms
No full textPlanar processing technology enables great complexity at low cost for electronic systems and now has the potential to provide a revolution in mass-manufacture for all-optical systems. For this to be realised, new materials and fabrication processes suitable for advanced photonic applications must be devised. Silica is ideal for many photonics applications but its small nonlinearity, low refractive index, poor rare-earth solubility and limited IR transmission precludes its application to high-density all-optical circuits or new wavelength windows. Silicon has exhibited remarkable performance for compact linear and nonlinear optical devices and while waveguiding in silicon is attractive at wavelengths beyond 1.1µm, the recent use of Si3N4 for optical parametric oscillators [J.S. Levy et al., Nat. Photon., 4, 37-40 (2010)] has emphasised that silicon does not meet every need. Tantalum pentoxide (Ta2O5) is an alternative CMOS-compatible waveguide material and in recent years several important properties and functions for high-density photonic circuits have been demonstrated. These include suitability as a host for rare-earth ions with amplification and lasing at 1.5µm [A.Z. Subramanian et al., IEEE Photon. Technol. Lett., 22, 1571-1573 (2010)] and third-order nonlinearity 30 times that of silica at 1.5µm [C.-Y. Tai et al., Opt. Exp. 12, 5110-5116 (2004)]. Ta2O5 has a large bandgap (4-2 – 5.2 eV) so that, at a conservative estimate, two-photon absorption (TPA) is not evident for wavelengths beyond 700nm, while in the case of Si, TPA is significant at wavelengths below 2.25µm; Ta2O5 also exhibits good transmission at wavelengths between 350nm and 8µm. For many short-pulse interactions, precise control of group velocity dispersion is needed, and waveguide engineering in high index materials such as Si3N4 and Ta2O5 allows this. The CMOS compatibility of these materials allows combination in a multilayer configuration with silicon photonics to offer additional functionality to silicon photonic circuits
Planar lightwave platforms for bio- and chemical sensing
No full textSimple planar waveguides are well established components for the optical interrogation of chemical processes at surfaces, with total internal reflection fluorescence (TIRF) elements having a long pedigree and surface plasmon resonance (SPR) sensors finding widespread use in biomolecular research, for example. Key attributes of these devices are that the optical fields are confined to a submicrometer region above the solid surface of the transducer and that the light is delivered to the surface in a well-controlled way without passing through the bulk of the sample
Integrated optical chemical sensing
No full textIntegrated optical techniques offer the potential for miniature, low-cost, reliable microsystems for chemical analysis which may be exploited in monitoring environmental pollution, food contamination, state of health, and threats to security. Some approaches towards providing flexible multisensor platforms for a wide variety of chemical and biochemical species will be presented
BIOPTICAS: optical biosensing techniques for monitoring organic pollutants in the aquatic environment
No full textThe BIOPTICAS project aims to develop optically-based analytical techniques for the detection and measurement of low concentrations of organic pollutants in the aquatic environment. Two basic types of measurement systems are being developed. Low cost, fast, and highly sensitive immunoassay-based assay kits for use by water monitoring authorities for pesticide-level monitoring and, thin film and integrated optical-based technologies that provide opportunities to develop semi- or fully automated sensing systems for pollution monitoring. Although these systems are directed primarily towards pesticide detection, it is foreseen that far wider applications for diagnostics and monitoring can be addressed by the technologies developed by this project
Advanced materials for fibre and waveguide amplifiers
No full textRecent research into optical fibre and waveguide amplifiers has been characterised by steady but unrevolutionary progress. Advances in the 1.5µm telecommunications window include erbium doped materials with flatter gain spectra, and planar amplifiers in a broad range of materials. At 1.3µm, substantial improvements in praseodymium doped fluoride fibre amplifiers have been witnessed and chalcogenide glasses have shown promise for enhanced gain efficiency
Waveguide surface plasmon resonance sensors
No full textGuided-wave optical biosensors have great potential for use in the field of environmental monitoring. In particular, planar waveguide technologies offer the possibility of producing compact, monolithic, multisensor devices which may be connected to instrumentation using optical fibres, allowing remote operation. Optical evanescent field sensing techniques presently under investigation include grating couplers, waveguide interferometers and surface plasmon resonance (SPR) sensors. In the latter case, the surface plasmon is generally excited using a "bulk" optical component such as a prism, and equipment using this technique is now commercially available. One potential advantage of the SPR technique is that the metal film which supports the surface plasmon may also be used as an electrode for electrochemical control of sensing reactions. However, recent reports have indicated that the "bulk" SPR devices may not ultimately be as sensitive as fully guided-wave approaches such as the Mach-Zehnder interferometer. An alternative to the "bulk" SPR devices which has recently emerged is the use of distributed coupling between a dielectric waveguide and the surface plasmon mode in a metal-coated waveguide. This has the advantage of combining greater design flexibility and the potential for monolithic integration with the well-established technique of SPR. However, at present no adequate model for the performance of these devices exists. ..
Integrated Photonics for Biomedical Spectroscopy
No full textIntegrated photonics is well advanced in applications from long-haul fibre telecommunications to data centres and from novel optical sources to chemical sensing. Silicon photonics [1] in particular has seen enormous growth in recent decades, but there is an increasing need for integrated photonic devices operating at longer wavelengths. Optical techniques are ubiquitous in providing chemical and biochemical information in a laboratory environment, but the demand for fast, low-cost, automated chemical analysis in applications from food safety and water quality to preventative medicine and rapid point-of-care diagnostics requires low-cost, compact devices and instruments with minimal user intervention for local and low-resource settings. The scale of integration, low cost and robustness of the microfabrication approaches which underpin consumer electronics is set to enable widespread deployment of miniaturised chemical and bioanalytical microsystems. However, biosensor and lab-on-chip research and commercialisation have been hampered by the lack of integrated photonic platforms which can operate over full the mid-infrared (MIR) fingerprint region from about 2μm to 18μm [2]. In particular the biomolecular “fingerprint” region from 5μm to 11μm would enable new opportunities for sensitive, selective, label-free biochemical analysis. Progress on new materials and approaches for high-sensitivity waveguide evanescent spectroscopies in the MIR will be described [3], and related to applications from therapeutic drug monitoring to cancer diagnostics [4]. Requirements for MIR components such as sources and detectors will also be considered briefly, to emphasise optical power budget and signal-to-noise requirements, which drive potential lower limits of detection
Integrated lenses for microfluidic systems
No full textGreater integration of optical devices is required in microfluidic systems for on-chip functionality, with lenses being key components. In this paper several candidate lens types are compared and simulations are presented which show that the paraxial kinoform lens offers optimum performance for efficiency and compactness in weak guiding system
Optofluidic integration for microanalysis
No full textThis review describes recent research in the application of optical techniques to microfluidic systems for chemical and biochemical analysis. The "lab-on-a-chip" presents great benefits in terms of reagent and sample consumption, speed, precision, and automation of analysis, and thus cost and ease of use, resulting in rapidly escalating adoption of microfluidic approaches. The use of light for detection of particles and chemical species within these systems is widespread because of the sensitivity and specificity which can be achieved, and optical trapping, manipulation and sorting of particles show significant benefits in terms of discrimination and reconfigurability. Nonetheless, the full integration of optical functions within microfluidic chips is in its infancy, and this review aims to highlight approaches which may contribute to further miniaturisation and integration
Kinoform microlenses for focusing into microfluidic channels
No full textOptical detection in microflow cytometry requires a tightly focused light beam within a microfluidic channel for effective microparticle analysis. Integrated planar lenses have demonstrated this function, but their design is usually derived from the conventional spherical lens. Compact, efficient, integrated planar kinoform microlenses are proposed for use in microflow cytometry. A detailed design procedure is given and several designs are simulated. A paraxial kinoform lens integrated with a microfluidic channel was then fabricated in a silicate glass material system and characterized for focal position and spotsize, in comparison with light emerging directly from a channel waveguide. Focal spotsizes of 5.6 µm for kinoform lenses have been measured at foci as far as 56 µm into the microfluidic channel
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