The activity of Applied Photonics - Materials & Devices is focused on the photonics technology engineering combining current advances of novel functional materials and photonics platforms and techniques towards the study of optical phenomena as well as the design and implementation of customized and novel devices for a range of challenging applications.
The group has strong links with industry and other international academic partners and research networks in Europe, with a number of research collaborations in different disciplines ranging from defence and industrial applications to biomedical diagnostics. The main distinctive research directions within this activity are:
Mr. Dimitris Dimas, Photonics Training Internship, PRISMA Electronics S.A.
Mr. N. Aspiotis
Prof. M.N. Zervas, Prof. P.G.R. Smith, Prof. R.W. Eason, Dr. S. Mailis, University of Southampton, Optoelectronics Research Centre, Southampton, UK
Prof. Kyriacos Kalli, Nanophotonics Research Laboratory, Department of Electrical Engineering / Computer Engineering and Informatics, Cyprus University of Technology - CUT, Cyprus
Prof Theodora Krasia Christoforou, Department of Mechanical and Manufacturing Engineering, University of Cyprus, Cyprus
Prof N. Vainos, Materials Science Department, University of Patras, Greece
Prof. D. Hatziavramidis, Chemical Engineering Department, National Technical University of Athens -NTUA, Greece
Dr. Efrosyni Themistou, School of Chemistry and Chemical Engineering, Queen's University Belfast, Belfast, UK
Prof. Jun Lyu, Institute of Polymer Materials, Key Laboratory of Advanced Technologies of Materials, Southwest Jiaotong University, China
Financial Support & Supporting Networks
Project WelCOM 09SYN71-856 "Wireless Sensors for Engineering Asset Life Cycle Optimal Management" funded by the National Strategic Reference Framework NSRF 2007-2013/Hellenic General Secretariat for Research and Technology GSRT. http://welcom-project.ipet.gr/ (PI: C. Riziotis)
Project SESAMO (A-0931-RT-GC-EDA): “Sensors for Structural Monitoring” – funded by European Defence Agency-EDA. (PI: G. Kakarantzas)
Project Polynano KRHPIS 447963, "Novel Multifunctional Nanostructured Materials and Devices" funded by the National Strategic Reference Framework NSRF 2007-2013/Hellenic General Secretariat for Research and Technology GSRT. (PI: E.I. Kamitsos)
Project NANOMACRO: "Functional Self-assembled Nanostructures from Block Copolymers and Proteins", GSRT (PI Dr. S. Pispas)
1. Development of Low Cost and Autonomous Photonic Sensors
Our current research interests in this engineering area focus on the development of low cost photonic sensors with operational characteristics that can be applied in a variety of current and emerging applications in infrastructures monitoring and also predictive maintenance and assets' management.
This is a challenging area of sensors technology with a high anticipated impact in a variety of applications. The research activity lies in the design and development of suitable devices by photonics engineering in combination with novel functional nanostructured materials. Additionally the use of special micromachining tools based on excimer and femtosecond lasers enable the modification of optical fibers or the fabrication of free space diffraction gratings for customised sensing architectures.
I. Polymer Optical Fibers for Sensors development
Coupling the sensing and monitoring flexibility offered by photonics technologies, with the data transmission flexibility of wireless networking provides opportunities to develop hybrid wireless sensor solutions for wireless condition monitoring architectures and maintenance management or maintenance support strategies.
Use of Plastic Optical Fibers-POF in combination with laser based rapid prototyping and novel functional nanostructured materials is proposed as a viable approach for developing an integrated customizable photonics platform of low circuitry complexity and cost, combining desired characteristics such as reliability, operational autonomy and safe operation in presence of high electromagnetic fields or even in potentially explosive/flammable environments. Such wireless sensing nodes with integrated prototype photonic sensors have been developed by NHRF in collaboration with industrial partners like PRISMA Electronics S.A. in the frame of the R&D project WelCOM.
Fig. Schematic illustration of the incorporation of a liquid level photonic sensor in a Zigbee based Wireless Sensor Network
D. Dimas, S. Katsikas, A.C. Boucouvalas, and C. Riziotis, (2011), “Wireless-enabled photonic sensor for liquid level and distributed flood monitoring”, Proceedings of the 24th International Conference on Condition Monitoring and Diagnostic Engineering Management, COMADEM 2011, 30 May-1 June, Stavanger, Norway, ISBN: 0954130723.
I.a. Polymer Optical Fibers for Physical Sensing
Diverse application areas ranging from critical defence applications to heavy machinery manufacturing industry, focusing on both production facilities assets monitoring, as well as on the end-products have been considered in various projects.
Successful customization has demonstrated efficient, robust sensors for strain monitoring of energetic propellant materials used in solid rocket motors -SRMs of guided missiles. Also there have been implemented miss/displacement and strain measurement sensors and systems in heavy machinery production lines and mechanical parts.
Fig. Schematic of Solid Rocket Motor based guided missile system, with an illustrated crack of solid propellant that need to be productively monitored for efficient maintenance.
Fig. Incorporation of polymer optical fibers in the core of solid energetic propellants for strain monitoring
Fig. Demonstration of successful monitoring of strain in SRMs by embedded Polymer Optical Fibers
I.b. Wireless Enabled Polymer Optical Fiber Sensors for Chemical and Biological Sensing
Polymer Optical Fibers is an ideal photonic platform enabling fast and efficient customization for engineering and design of sensing devices. Surface modification by means of laser micromachining and also sensitization by using a variety of inorganic or organic sensitive materials have been employed as tools for customizable sensors development for a variety of chemical and biological applications.
Sensors' customization by proper functionalization of POFs' surface with novel diblock amphiphilic polymers leaded to multiagent sensors allowing the detection of a wide variety of measurands, like toxic aromatic hydrocarbons- benzene and toluene, ammonia, relative humidity levels and specific proteins such as lysozyme, which find applications in industrial or environmental monitoring and chemical and food industry. Specific polymers' properties and high glass transition temperature enabled the formation of stable overlayers and thus robust sensors with additional characteristics of fast response, high operational reversibility and also reusability in successively different testing agents, making their use affordable even as disposable sensors, due to sensing heads' extremely low cost.
Fig. Processing and functionalization of polymer optical fiber for the formation of sensitive sensing heads
Fig. A prototype POF based sensing head connected to battery operated Fiber Optic Driving Circuit Board
In collaboration with our industrial partner PRISMA Electronics S.A. it was possible to complete the integration of the POF based optical sensor in a Wireless Sensing Node ready for operation in a wireless sensor network in the frame of the Project WelCOM.
Fig. Wireless Sensing Node with integrated fiber optic chemical sensor, operating with the ZigBee protocol. (in collaboration with PRISMA Electronics S.A.)
L. Athanasekos, D. Dimas, S. Katsikas, S. Pispas, N. Vainos, A.C. Boucouvalas and C. Riziotis, “Laser microstructuring of polymer optical fibres for enhanced and autonomous sensor architectures”, Procedia Engineering 25, (2011) pp. 1593-1596.
L. Athanasekos, M. Vasileiadis, A. El Sachat, N.A. Vainos, C. Riziotis, “ArF excimer laser microprocessing of polymer optical fibers for photonic sensor applications", Journal of Optics, 17, (2015) 015402.
Sensors' customization demonstrated also efficient biochemical monitoring of industrial-grade lubricants/coolants' aging in metal polishing/finishing heavy machines with great anticipated personnel health protection and also economic impact.
Fig. Fiber optic sensors have been successfully employed for the aging monitoring of commercially available coolants in heavy duty industrial metal polishing machines in a collaboration with Kleemann S.A., in the framework of the project WelCOM
A. El Sachat, A. Meristoudi, C. Markos, A. Papadopoulos, S. Katsikas, and C. Riziotis, "Characterization of industrial coolant fluids and continuous ageing monitoring by wireless node-enabled fiber optic sensors", Sensors MDPI, 17, 568 (2017).
II. Free Space Diffraction Based Remote Optical Sensors
Further to optical fiber based sensors, certain applications often require a remote point sensing operation due mainly to specific restrictions of the surrounding environment under monitoring.
Fig. Soft lithography techniques, namely, modified solvent assisted micro molding (m-SAMIM) and modified micro molding in capillaries (m-MIMIC) for the fabrication of high quality diffraction gratings onto appropriate substrates.
We have developed laser based techniques for the low cost production of diffraction based sensors by soft lithography techniques such as SAMIM and MIMIC, by proper tailoring using appropriate photonic sensitive materials. The developed gas sensors were successfully tested in the detection of ammonia and aromatic hydrocarbons (benzene, toluene) achieving a relative low detectable analyte concentration. The obtained results confirm the efficient and low cost implementation of point gas sensors for a variety of analytes. By further optimization of the fabrication technique for the diffraction gratings and by employing also customizable sensitive materials, this sensing approach could attract a lot of interest in various environmental and industrial applications.
N. Aspiotis, A. El Sachat, L. Athanasekos, M. Vasileiadis, G. Mousdis, N. Vainos, and C. Riziotis, (2013) "Diffractive Ammonia Sensors based on Sol-Gel Nanocomposites Materials" Sensor Letters, 11(8), (2013) pp.1415-1419
New alternative materials have also recently studied for the development of fluorescent based gas sensors with remote interrogation capability. Electrospun nanofibrous materials with embedded fluorescent agents have been employed for the demonstration of ammonia sensing those materials offer large area due the 3D fibrous network that can enhance their responsivity.
Fig. Demonstration of use of nanofibrous grids for remote gas detection
A. Petropoulou, K. Christodoulou, T. Krasia Christoforou, C. Riziotis, "Evaluation of fluorescent nanocomposite grids and membranes based on polymeric electrospun nanofibres towards ammonia sensing", 5th International Conference on Materials and Applications for Sensors and Transducers, IC-MAST, September 27-30, 2015, Mykonos, Greece.
This activity is focused on the design, analysis and implementation of waveguide and Bragg grating based integrated optical circuits. A number of active and ongoing research collaborations have lead to date to various implementations of such optical components with anticipated important applications in sensors and lab-on-chip and biomedical devices.
I. Analysis Design and Implementation of Integrated & Bragg Grating Based Optical Devices
Analysis and design of waveguide and Bragg grating based optical components with exact Normal Mode Theory and computational techniques like Finite Difference Time Domain (FDTD) and Finite Element Method (FEM) as well as variational optimization and computational intelligent optimization techniques. Fabrication of optical components with direct laser inscription technique.
Fig. Design of Bragg grating based Optical Add Drop Multiplexers for WDM networks
Fig. Planar Integrated Bragg grating based optical sensors
Fig. Design of optical cross-couplers for development of ultra dense integrated optical circuits
F.R.Mahamd Adikan, C.B.E. Gawith, P.G.R. Smith, I.J.G. Sparrow, G.D. Emmerson, C. Riziotis, H. Ahmad, “Design and demonstration of direct UV-written small angle X-Couplers in silica-on-silicon for broadband operation”, Appl. Opt. 45, 6113 (2006).
The group has also experience on the study and implementation of waveguides and optical components in different material systems, like Ga:La:S, oxide glasses, polymers, Lithium Niobate with various potential functionalities that can lead to applications like lasers development, electrooptic devices, nonlinear resonators etc.
Fig. Waveguide based devices and structures in a number of different material platforms
A.K. Mairaj, C. Riziotis, A.M. Chardon, P.G.R. Smith, D.P. Sepherd, D.W. Hewak, “Development of channel waveguide lasers in Nd3+-doped chalcogenide (Ga:La:S) glass through photoinduced material modification”, Applied Physics Letters, 81, 3708, (2002).
S. Mailis, C. Riziotis, I.T. Wellington, P.G.R. Smith, C.B.E. Gawith, R.W. Eason, "Direct ultraviolet writing of channel waveguides in congruent lithium niobate single crystals", OSA Optics Letters, 28, 1433(2003)
C. Riziotis, T.J. Sono, S. Mailis, and R.W. Eason, "Design considerations for quasi-phase-matching in doubly resonant Lithium Niobate hexagonal micro-resonators", Journal of Optics (submitted)
II. Novel Integrated Optical Platforms for Enhanced Functionality
The research on the exploitation of novel optical platforms such as the "Flat Fibre" platform (ORC, Southampton) has lead to the demonstration of waveguide components (ring and disk resonators, Mach Zehnder Interferometers, Bragg gratings etc) combined with the functionality of inscribed microfluidic channels that can result by ongoing collaborative research (ORC, CUT) to lab on chip devices for a variety of application like point of care diagnostics.
Fig. The Flat Fibre photonic platform
Fig. Structures and optical components inscribed by femtosecond Laser on Flat Fibres. The structures could be filled and functionalised with sensitive materials for integrated sensors development.
K. Kalli C. Riziotis, A. Posporis, C. Markos, C. Koutsides, S. Ambran, A.S.Webb, C. Holmes, J.C. Gates, J.K. Sahu, P.G.R. Smith,"Flat fibre and femtosecond laser technology as a novel photonic integration platform for optofluidic based biosensing devices and lab-on-chip applications: current results and future perspectives", Sensors and Actuators B. Chemical", 209 (2015).
C. Riziotis,"Novel integrated photonic platforms towards lab-on-chip based point of care diagnostics", in 4th International Congress on Biophotonics (ICOB 2015), and COST Action BM1401 "Raman for Clinics" Joint Meeting, Florence, Italy; 18-20 May 2015 (Invited Talk).
C. Riziotis, K. Kalli, C. Markos, A. Posporis, C. Koutsides, C. Riziotis, A.S.Webb, J.K. Sahu, C. Holmes, J.C. Gates, P.G.R. Smith, "Flexible glass flat-fibre chips and femtosecond laser inscription as enabling technologies for photonic devices", Proceedings of SPIE Photonics West 2014. SPIE OPTO Conference, 1-6 February 2014, The Moscone Center, San Francisco California, USA. Proc. SPIE 8982 Optical Components and Materials Conference XI, 89820G-89820G-8 (2014)
This activity is focussed on the engineering of optical fibers at the micro and nano scale for nonlinear and plasmonic devices with enhanced sensitivity.
Indicatively there have been demonstrated results on nonlinear enhancement by ultra fine tapered optical fibres for Super Continuum generation for lasers development.
Fig. Supercontinuum generation in tapered optical fibers
G. Antonopoulos, P. Velanas, C. Riziotis, G. Kakarantzas,"Hybrid silica nanowires with a highly nonlinear glass thin coating", IEEE Proceedings of Spatiotemporal Complexity in Nonlinear Optics (SCNO), Proc. IEEE SCNO 2015, 1-3 (2015).
Also there have been studied plasmonic devices on ultrafine tapered metal coated silica fibers for light nanofocussing that can find various applications such as in biosensing and Surface Enhanced Raman Scattering SERS.
Fig. Optimization of nanoresonators on fibre plasmonic tips for light nan focusing
A. Petropoulou, M. N. Zervas, and C. Riziotis, “Study and optimization of tapered plasmonic waveguides for light nanofocusing”, 11th International Conference of Computational Methods in Sciences and Engineering, (Invited Talk)
A. Petropoulou, M.N. Zervas, and C. Riziotis, "Design optimization of gold-coated fiber tips with embedded plasmonic slot nano-resonators ", Journal of Optics 19, 055002 (2017)
A new promising composite fiber platform based on metal core -silica cladding material system (in collaboration with ORC/Southampton) has been studied theoretically and engineered by means of fiber tapering for plasmonic and nonlinear applications. Also metal microspheres trapped in the silicate enclosure have been fabricated in a controllable manner during the tapering process and have been demonstrated as they can find applications as microresonators incorporated in the optical microfibers.
Fig. Hybrid metal-silicate composite microfires and fabrication of plasmonic fibers tips and metal microspheres incorporated in glass silicate enclosure.
4. Photonic Techniques for Biomedical Applications
Combining group's expertise with practical needs from medical diagnostic and biomedical area has lead also to a number of ongoing collaborations in applications like pancreatic islet/cell transplantation, antibiotic delivery, lab-on-chip applications, diagnostic microscopy etc.
In the last example it has been implemented the design and engineering of novel structures with high anticipated use in a number of microscopy based diagnostic techniques such as cytological PAP-Test. Cervical screening based on Papanicolaou (PAP) Test has been proved to be an efficient practice for preventing cervico-vaginal cancer in High Risk Human Papilloma Virus infected women. Introduction of liquid based process combined with automatization and digital image analysis has led to a more reliable diagnosis compared to conventional management of the slides. However, microscopy based diagnosis in Cytology is characterized by a variety of parameters, including specimens’ adequacy, inhomogeneous/discontinuous cell density, fixing/staining procedure quality, and also screeners’ experience and observation ability. Our group introduce a novel real-time screening aid and platform improving diagnosis in Pap -Test slides.
The proposed solution (patent pending) provides a customizable spatial grid with sequentially ordered and indexed segments than can be attached in different possible ways to the carrier platform (e.g. microscope slide) and can act as a calibration and orientation aid during the screening process. Such grids were developed by a number of technical means and also by Femtosecond Laser Micromachining technique on commercially available borosilicate glass based cover slips.
A set of difficult-borderline diagnostic PAP-Test cases were comparatively analyzed by conventional and grid based screening procedures, respectively. Statistical analysis showed that grid based microscopy led to a dramatically updated diagnosis by identifying a significantly increased number of abnormal cells in a shorter (4 instead of 5 min) screening time per slide compared to conventional microscopy, especially concerning the number of detected neoplastic/cancerous cells.
The grid can be fabricated and integrated in different platforms such as in solid glass cover slips, flexible polymers stripes and thin shelf-adhesive transparent tapes that could be attached afterwards on top of the slides. The grid can be applied both in pathology and also in cytology diagnostic cases such as ASCUS/ASC-H/LGSIL/HGSIL/AGC/INSITU ADENOCA/ADENOCA as well as in "In Situ Hybridization"- ISH techniques, and Immunocytochemistry-Immunohistochemistry (ICC-IHC) protocols for assessment of immunostained cell characteristics.
This is the first described application of this real-time diagnostic tool in PAP-Test screening and in collaboration with medical diagnostic labs we strongly support its introduction in routine cytology as a significant improvement in detecting specific abnormal cells modifying also the final diagnosis in borderline cases.
Fig. Demonstration of grids on PAP-Test slides
C. Riziotis, and E. Tsiambas, "Reference and Callibration Grid For Improved Real Time Detection of Biological Entities in Microscopy Diagnostic Techniques", Hellenic Industrial Property Organization, Patent No# 1008931 (16/7/2015).
E. Tsiambas, C. Riziotis, I. Mavrikos, E. Armatas, E. Patsouris, "Novel techniques for morphometrical and geometrical analysis in abnormal cervical smears (Pap test slides)", J. Bal. Un. Oncology -JBUOΝ (vol. 22, no. 4 2017)