A primary constraint in the major photonic integration platform of Silica-on-Silicon, especially when combined with fabrication approaches like Direct Laser Writing is the optical waveguides' low refractive index contrast, leading thus to limitations for efficient coupling with currently available state-of-the-art single photon emitters such as semiconductor nanowires with quantum dots (NWQD). We propose and demonstrate a novel approach to drastically enhance the light coupling between silica based Laser-written channel waveguides and NWQDs, by incorporating an optical microsphere in their intermediate space. It is demonstrated that the induced photonic nanojet action of a suitably designed microsphere illuminated by the NWQD, excites efficiently the channel waveguide's modes and can enable light coupling to a degree even above 50%. The proposed method is reasonably robust to imperfections and misalignments and could be implemented by current state-of-the-art micro/nano patterning techniques. It is anticipated that the practical implementation of the method will allow the integration of multiple quantum emitters in silica based hybrid integrated circuits thus enabling their scalability towards for quantum computing and sensing applications.
High quality poly(methyl methacrylate) (PMMA) thin nanocomposite films doped with different concentration of silver (Ag) nanoparticles are demonstrated. SEM and TEM confirmed the presence of Ag-PMMA nanocomposites with excellent dispersion of Ag nanoparticles into the PMMA matrix and nanoparticles with an average size of 9 nm. By using a direct Laser writing system with a continuous wave 405 nm diode Laser source the films were exposed, allowing the formation of hole-like or linear patterns in the sub 200nm regime, using a 280nm FWHM sized laser spot, demonstrating, for the first time, the potential for sub-diffraction limit laser processing in such 2-material composite systems.
The development of a low complexity fiber optic based protein sensor by functionalizing the surface of silica optical fibers using block copolymers having both hydrophobic poly(methyl methacrylate) (PMMA) and hydrophilic poly[2- (dimethylamino)ethyl methacrylate] (PDMAEMA) blocks is presented here. The amphiphilic thiol-functionalized PMMA117-b-P(DMAEMA17-st-TEMA2) and vinyl-sulfone PMMA117-b-P(DMAEMA17-st-VSTEMA2) block copolymers designed and synthesized in this work contain a cationic hydrophilic PDMAEMA block that can electrostatically bind selected oppositely charged proteins and also appropriate functional groups for reversible or non-reversible protein binding, respectively, leading to a refractive index change of the overlayer and hence, enabling the sensing. The developed PMMA117-b-PDMAEMA16-based platform has been evaluated for bovine serum albumin (BSA) sensing, exhibiting linear response to detected BSA concentrations.
The integration of Plasmonic Nano-Resonators (PNRs) to optical fibers tips with thin metallic claddings forming plasmonic slot nano-resonators (PSNRs) is presented. It is shown that the placement of the PSNR at the cut-off radius of the fiber tip for a specific wavelength where the group velocity tends to zero and light slows down leads to an optimization of field's enhancement. Enhancement factors greater than 3x105 were calculated through Finite Element Method (FEM) simulations by placing the PSNR at the cut-off radius and by changing the geometrical characteristics in order to identify optimal conditions for loss minimization that can find many practical applications in nano-optics and sensing.
The development of plasmonic devices for sensing applications can offer high sensitivity and a dramatic improvement to
the detection limits due to the high field enhancement at the metal surfaces. The platform proposed here is a tapered
hybrid microfiber comprising a metal core and a glass cladding. The existence of a glass cladding not only serves as a
mechanical host for the metal core, but also provides ease of handling regarding the tapering process. The advantages of
this composite material system over pure metal tips are the absence of impurities and the multiple excitation of the
plasmon modes due to the total internal reflection at the glass/air interface. The improved field enhancement at the apex
of these tapered microwires was calculated through Finite Element Method (FEM) simulations. Enhancement factors up
to 104 were theoretically observed for this type of tapered microwires. The use of different metals having different
melting points and thermal expansion coefficients as well as different glass thicknesses can lead to an optimization of the
tapering process conditions in order to achieve tapered microwires with the desirable geometrical characteristics.
A grid acting as a spatial reference and calibration aid, fabricated on glass cover slips by laser micromachining and attached on the carrier microscope slide, is proposed as a visual aid for the improvement of microscopy diagnostic procedure in the screening of cytological slides. A set of borderline and also abnormal PAP test cases -according to Bethesda 2014 revised terminology- was analyzed by conventional and grid based screening procedures, and statistical analysis showed that the introduced grid-based microscopy led to an improved diagnosis by identifying an increased number of abnormal cells in a shorter period of time, especially concerning the number of pre- or neoplastic/cancerous cells.
Lately the demand for in situ and real time monitoring of industrial assets and processes has been dramatically increased. Although numerous sensing techniques have been proposed, only a small fraction can operate efficiently under harsh industrial environments. In this work the operational properties of a proposed photonic based chemical sensing scheme, capable to monitor the ageing process and the quality characteristics of coolants and lubricants in industrial heavy machinery for metal finishing processes is presented. The full spectroscopic characterization of different coolant liquids revealed that the ageing process is connected closely to the acidity/ pH value of coolants, despite the fact that the ageing process is quite complicated, affected by a number of environmental parameters such as the temperature, humidity and development of hazardous biological content as for example fungi. Efficient and low cost optical fiber sensors based on pH sensitive thin overlayers, are proposed and employed for the ageing monitoring. Active sol-gel based materials produced with various pH indicators like cresol red, bromophenol blue and chorophenol red in tetraethylorthosilicate (TEOS), were used for the production of those thin film sensitive layers deposited on polymer's and silica's large core and highly multimoded optical fibers. The optical characteristics, sensing performance and environmental robustness of those optical sensors are presented, extracting useful conclusions towards their use in industrial applications.
Microstructuring of Polymer Optical Fibers-POF through surface modification with UV excimer laser radiation has been performed and studied. The laser modified surface cavities on fibers act as material receptors of exact volume allowing highly controllable and repeatable structures. The effect of Laser writing conditions on different etching characteristics of cladding and core materials of the fibres are presented. Ablated structures on the fibres are examined for optimised sensors' response characteristics. As a case study humidity and ammonia sensors are demonstrated by employing sensitive block copolymer materials on suitably micromachined segments of fibres.
The enhancement of nonlinear characteristics of a tapered fiber, which is covered with a thin layer of highly nonlinear glass, is theoretically studied in this work. The generation of a flat, octave spanning supercontinuum extending from 750 nm to 2750nm (at -20dB) has been numerically presented by considering the coupling of the proposed structure with a typical Yb laser able to emit ultrashort pulses. The physical processes behind the SC formation are described in the anomalous dispersion regions.
The potential of a new class of multifunctional photonic circuits is demonstrated by femtosecond laser micro-machining and inscription of micro-optical structures, such as ring and disk resonators, Mach-Zehnder interferometers, and microfluidic devices, in a flexible flat-fibre chip. Additional filling of surface channels with functional materials is employed towards sensing applications. Furthermore, direct write femtosecond-laser inscribed Bragg gratings were written in the Ge-doped core of flat-fibre enabling a number of relevant applications. The flat-fibre platform offers a unique degree of freedom by allowing surface and sub-surface devices to be integrated onto an a single optical chip with the potential for straightforward incorporation into integrated photonic circuits or optofluidic devices.
A low cost and low complexity optical detection method of proteins is presented by employing a detection scheme based on electrostatic interactions, and implemented by sensitization of a polymer optical fibers' (POF) surface by thin overlayers of properly designed sensitive copolymer materials with predesigned charges. This method enables the fast detection of proteins having opposite charge to the overlayer, and also the effective discrimination of differently charged proteins like lysozyme (LYS) and bovine serum albumin (BSA). As sensitive materials the block and the random copolymers of the same monomers were employed, namely the block copolymer poly(styrene-b-2vinylpyridine) (PS-b- P2VP) and the corresponding random copolymer poly(styrene-r-2vinylpyridine) (PS-r-P2VP), of similar composition and molecular weights. Results show systematically different response between the block and the random copolymers, although of the same order of magnitude, drawing thus important conclusions on their applications' techno-economic aspects given that they have significantly different associated manufacturing method and costs. The use of the POF platform, in combination with those adaptable copolymer sensing materials could lead to efficient low cost bio-detection schemes.
An efficient scheme for enhanced second harmonic generation in a nonlinear optical hexagonal microcavity by the combined mechanisms of total internal reflection and quasi-phase-matching is proposed. We demonstrate the operational principle by numerical simulation results showing resonance operation in a suitably designed hexagonal optical microresonator, revealing thus the operating feasibility of the proposed scheme in nonlinear material platforms such as Lithium Niobate. The fabrication of high optical quality hexagonal superstructures by chemical etching of inverted ferroelectric domains in this Lithium Niobate platform suggests a route for successful implementation. Design aspects, optimization issues and characteristics of the proposed device are presented.
We demonstrate femtosecond laser micro-machining and inscription of micro-optical structures, such as ring and disk resonators, Mach-Zender interferometers, and complex microfluidic devices, in a novel optical flat-fibre chip. In addition, we fill the channels with functional materials that can be used for sensing applications. Furthermore, direct write femtosecond-laser inscribed Bragg gratings are written in the Ge-doped flat-fibre core at 1547.8 nm. The flat-fibre chip offers a unique degree of freedom by allowing surface and sub-surface devices to be integrated onto an optical platform with the potential for straightforward incorporation into integrated photonic circuits or optofluidic devices.
A novel block copolymer material is applied successfully to a low cost Polymer Optical Fiber- POF for sensing
applications. The copolymer consists of two blocks, one hydrophilic and sensitive to polar substances and the other
hydrophobic and sensitive to hydrocarbons. Prediction of polymer's behavior in the presence of analytes has been
successfully verified experimentally. The existence of two different blocks allows for the detection of a wide variety of
agents and this response could be further engineered and enhanced by suitable adjusting the ratio of the two blocks.
Using methanol as polymer's solvent PMMA POF successfully coated without deteriorating its properties.
Functionalized U-bent POFs were employed as sensing tips overcladded with the sensitive material using a simple dip
coating technique. Due to material's high transition temperature (well above 120°degC) the overlayers were very stable
and environmentally robust. The developed sensors characterized and exhibited very fast response in ammonia,
humidity, toluene and benzene, with full operational reversibility.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.