The Integrated Photonic Devices Group, led by Professor James Wilkinson, was established in early 1990 to meet the demand for optical device functions of increasing complexity and parallelism. Planar photonic devices are exploited in applications as diverse as telecommunications, tuneable and short-pulse miniature laser light sources, diagnostics in medicine, the environment and food processing, and early-warning sensors for biological agents. We exploit surface science, waveguide engineering, laser physics and microstructure technology to realise robust mass-producible integrated optical circuits, to further the monolithic integration of diverse devices, and to develop novel materials processing for optoelectronic devices.
The group is currently active in the fields of novel optical microresonators and their application in environmental sensing, mid-infrared waveguides for biomedical sensing, waveguide based Raman sensing, fluorescence-based optical biosensors, optofluidic integration for bioanalysis, integrated microflow cytometers, Terahertz interactions with proteins, waveguide lasers and amplifiers, all-optical signal processing and on-chip lasers for silicon photonics, nonlinear optics, and microstructured dielectric films and materials.
The group runs the Integrated Photonics cleanroom facility for optical, electronic and microfluidic device fabrication. Processes include photolithography, dip-pen nanolithography, thin-film deposition by sputtering, ion-beam deposition and evaporation, reactive ion and wet etching, ion-exchange and diffusion to 2300oC, surface metrology and scanning electron microscopy.
The group has also established an advanced mid-infrared waveguide characterisation and spectroscopy suite including many tunable laser sources (OPO and QCL based), thermal imaging cameras and detectors in the 2-13µm wavelength range. The group’s optical characterisation labs include tunable titanium sapphire and diode lasers, waveguide characterisation apparatus, optical spectrum analysers, high-sensitivity electrical impedance spectroscopy, and flow-injection analysis for biosensors.
There is increasing interest in low-cost photonic circuits for mass-market applications such as fibre-to-the-home. For this dream to be realised, materials and fabrication processes suitable for all-optical photonics must be devised. All-optical processing requires high third-order nonlinearity (power dependent refractive index), gain, storage and frequency-manipulation functions, in on-chip photonic circuits. Silicon itself has problems with nonlinear absorption in the appropriate power and wavelength regime, but heavy metal oxides, such as Ta2O5 and Nb2O5 which can be integrated with silicon, are attractive for a wide range of optical functions, especially all-optical switching and gain. We are exploring these materials for advanced device functionality exploiting third order nonlinearity, electro-optic control using induced second order nonlinearity in amorphous platform and doping with active materials for waveguide amplifiers and lasers, and incorporating them in silicon photonics.
Continuous monitoring and detection of accidental leakage of toxic gases produced by industries, especially in developing countries, requires highly sensitive detection systems with detection limits of the order of parts per billion (PPB). Optical microresonators in which light recirculates about one million times and interrogates the environment every round-trip potentially allows the detection down to the single molecule level. This project exploits novel hybrid fiberised polymer microresonators on tapered silica optical fibres. The polymer will be doped with selective supra-molecular compounds to entrap specific toxic gases, giving the device both high sensitivity and very high specificity for analyte gases. The resonance wavelength shift on interaction with entrapped gas molecules will provide a sensitive measure of the number of molecules entrapped. Complementary sensing techniques such as molecular fingerprint detection of trace toxic gases using highly sensitive evanescent field Mid-IR spectroscopy utilising waveguides with caged supra-molecular compounds doped polymer layer as superstrates will also be investigated.
The following projects are all supported by the ERC. For further information, please visit the WIPFAB project pages.
Mid-infrared absorption spectroscopy is the most widely used technique for detecting the molecular signatures of an unknown sample using their fingerprint absorption. Waveguide evanescent field based spectroscopy can detect analytes at very low concentrations using their absorption fingerprints, potentially offering high sensitivity and selectivity over a wide range of compounds without labelling. The ideal molecular “fingerprint” region for biochemical analysis is dominated by the Mid-IR spectral region from 2μm - 13μm. We are exploring novel Mid-IR waveguide based integrated photonic devices to realise photonic lab on-chip platform for biomedical diagnostic applications, for example to lung-surfactants in infant respiratory distress syndrome and analgesics taken in overdose, and basic investigations on stem-cells. Specifically, this involves the fabrication and characterisation of waveguides (using novel Mid-IR materials) and waveguide based devices such as ring resonators, on-chip sources and interferometers for integrated Fourier Transform spectroscopy, and their integration. The project also involves electromagnetic modelling of devices to design photonic circuit layouts and optimise performance.
In collaboration with the School of the Environment, Tsinghua University, we are realising highly specific highly sensitive biosensors based on fluorescent immunoassay to detect up to 32 pollutants rapidly and simultaneously on a single chip. Our novel chip designs will be combined with aptamer-based recognition chemistries and detection protocols studied at Tsinghua University. Aptamer-based biosensing exhibits high sensitively, fast kinetics, high selectivity, and facile synthesis. Compact silicon-compatible optical waveguide multisensors offer a powerful combination of mass-manufacturability and ease-of-use with stability and high surface sensitivity. This collaboration is expected to result in highly sensitive, highly specific, compact, robust and reusable integrated photonic devices suitable for bioassay of environmental contaminants, such as antibiotics in water bodies.
Highly specific, sensitive sensors interfaced with portable, easy-to use, low-cost instruments are needed for rapid point-of-care infection diagnostics, leading to better targeted therapy, shorter time to treatment and reduced morbidity. We aim to realise a generic, flexible, compact sensing platform with high sensitivity and selectivity, building upon our recent work on waveguide-enhanced Raman spectroscopy (WERS) to realise a sensor chip which shows surface enhancements comparable to those of surface enhanced Raman spectroscopy (SERS) with improved application flexibility and manufacturability. These will be applied to the rapid detection of infectious diseases in collaboration with Chemistry and Medicine, and will have wide application in the diagnosis of disease and in environmental monitoring and security. The research ranges from basic investigation of light-matter interactions in organised layers at surfaces to device design, and instrumentation & signal processing.
Flow cytometry is an important tool for medicine and biology with applications from clinical diagnosis to investigations of fundamental cell biology. However, traditional flow cytometers are expensive, bulky and complex to operate. Miniaturised flow cytometers would offer advantages over traditional devices, being compact, cheap and mass producible and would offer the user ease of operation and portability. Miniaturisation also brings the potential for interrogating small particles with much higher sensitivity. We are integrating optical components with the fluidics and have demonstrated a microcytometer on a chip with fluorescence and multi-angle scattering detection. Collaboration with Medicine and the Institure for Life Sciences has identified the characterisation of microvesicles in blood as biomarkers as an important application where this approach may offer data on small particles while being mass-manufacturable. We are presently testing new fluidic and optical designs for fluidic and optical focussing with nanoscale particles.
Proteins are dynamic macromolecules, exhibiting quasi-harmonic oscillations over the terahertz frequency range and the electromagnetic absorption behaviour of proteins—termed protein electrodynamics—presents opportunities for new modalities of medical diagnosis. Protein dynamics probed by narrow-band terahertz radiation may provide label-free spectroscopy for attaining true biological specificity. In a collaborative study with Terahertz device researchers in the ORC, in Physics & Astronomy and at Samsung, we have identified suitable biological targets for examining the On-chip micro flow cytometer effects of narrowband THz radiation on protein function. We have conducted broadband THz characterisation of PTFE microfluidics and of biological buffer solutions, and are now conducting protein studies in a microflowcell.
Michael Zervas, Periklis Petropoulos, David Shepherd, Dan Hewak, Gilberto Brambilla, Sakellaris Mailis, James Gates, Peter GR Smith, Goran Mashanovich, Graham Reed, David Thomson, Jacob Mackenzie, Peter Horak, Marco Petrovich.
Profs Phil Bartlett (Chemistry), Prof Anne Tropper & Dr Vasilis Apostolopoulos (Physics & Astronomy), Prof. Tony Postle, Dr Nicola Englyst & Dr Jude Holloway (Medicine), Dr Jonathan West (Medicine/FEE), Prof Martin Charlton & Dr Harold Chong (ECS), Prof. John Chad (Centre for Biological Sciences).
Prof Olav Hellesø & Dr. Balpreet Ahluwalia (UiT Tromsø), Prof Francesc Diaz & Dr M. Cinta Pujol (URV Tarragona), Dr Marc Dussauze & Dr Thierry Cardinal (U. Bordeaux), Prof Yasutake Ohishi (Toyota Technological Institute), Prof Marc Sorel & Dr Steven Neale (U. Glasgow), Prof Hanchang Shi & Dr Xiaohong Zhou (Tsinghua University), Prof. Prem Bisht & Dr. Balaji Srinivasan (IIT Madras), Dr. Shivakiran Bhaktha (IIT Kharagpur), Prof Kyoungsik Yu (KAIST), Dr Amol Choudhary (U. Sydney), Prof Roel Baets (U. Gent), Dr Alessia Pasquazi & Dr Marco Peccianti (U. Sussex).
Oclaro (UK), Aviospace (Italy), Blue Industry & Science (France), [dstl] (UK), SIME Diagnostics (UK)
Please contact Professor James Wilkinson or Dr. Senthil Ganapthy if you would like any further information about the work of our Integrated Photonic Devices group or would be interested to work with us.