1,721,027 research outputs found
Leaky waveguides for low κ-measurement: From structure design to loss evaluation
No full textFor high quality optical coatings the knowledge of the losses of the deposited materials is essential. A precise measurement of low Im(n+i )≤ 10-6 at an intended operation wavelength and with low intensity can be achieved in waveguide configurations, whereby leaky waveguide configurations allow one to analyze losses of high- and low-index media of H-L-stacks as well due to resonances in the angle-dependent reflection curve. Numerical investigations reveal that different leaky wave schemes, e.g. Bragg-, Bloch- and Antiresonant-Reflecting waveguides, comply differently with practical requests. Loss figure evaluation requires peculiar attention due to measurement accuracy and ambiguities, thus suitable constraints for layer data and a proper merit-function construction have to be used
Effect of thickness disorder on the performance of photonic crystal surface wave sensors
Get PDFWe investigated experimentally and numerically the robustness of optical sensors based on Bloch waves at the surface of periodic one-dimensional photonic crystals. The distributions of sensor characteristics caused by the fabrication uncertainties in dielectric layer thicknesses have been analyzed and robustness criteria have been set forth and discussed. We show that the performance of the surface wave sensors is sufficiently robust with respect to the changes of the photonic crystal layer thicknesses. Layer thickness optimization of the photonic crystal, carried out to achieve low limit of detection, leads to an improvement of the robustness of the surface wave sensors that is attributed to Bloch states lying deeper in the photonic band gap.We investigated experimentally and numerically the robustness of optical sensors based on Bloch waves at the surface of periodic one-dimensional photonic crystals. The distributions of sensor characteristics caused by the fabrication uncertainties in dielectric layer thicknesses have been analyzed and robustness criteria have been set forth and discussed. We show that the performance of the surface wave sensors is sufficiently robust with respect to the changes of the photonic crystal layer thicknesses. Layer thickness optimization of the photonic crystal, carried out to achieve low limit of detection, leads to an improvement of the robustness of the surface wave sensors that is attributed to Bloch states lying deeper in the photonic band gap
From 23rd European Society for Animal Cell Technology (ESACT) Meeting: Better Cells for Better Health Lille, France. 23-26 June 2013
Get PDFFirst published by BioMed Central:
Kloke, Lutz ; Schimek, Katharina ; Brincker, Sven ; Lorenz, Alexandra ; Jänicke, Annika ; Drewell, Christopher ; Hoffmann, Silke ; Busek, Mathias ; Sonntag, Frank ; Danz, Norbert ; Polk, Christoph ; Schmieder, Florian ; Borchanikov, Alexey ; Artyushenko, Viacheslav ; Baudisch, Frank ; Bürger, Mario ; Horland, Reyk ; Lauster, Roland ; Marx, Uwe : Automated substance testing for lab-on-chip devices : From 23rd European Society for Animal Cell Technology (ESACT) Meeting: Better Cells for Better Health Lille, France. 23-26 June 2013. - In: BMC Proceedings. - ISSN 1753-6561 (online). - 7 (2013), suppl. 6, P28. - doi:10.1186/1753-6561-7-S6-P28
Effects of reabsorption due to surface concentration in highly resonant photonic crystal fluorescence biosensors
No full textPhotonic crystal enhanced fluorescence biosensors have been proposed as a novel immunodiagnostic tool, due to the increased fluorescence excitation rates and angular redistribution of the emission. Among these, purely dielectric one-dimensional photonic crystals (1DPC) sustaining Bloch surface waves (BSW) at their truncation edge, have recently attracted much interest. We report for the first time on the time resolved experimental study of the effects of excess reabsorption of the BSW coupled fluorescence in the near infrared range around 800 nm. Temporally and angularly resolved measurements of the BSW coupled fluorescence emission permit to put into evidence a strong reabsorption of the fluorescence emission when using highly resonant 1DPC. The results suggest that, when designing 1DPC sustaining BSW for quantitative diagnostic assays, it is necessary to choose a compromise quality factor, to exploit the features arising from the electromagnetic field enhancement while avoiding reabsorption
Direct competitive assay for HER2 detection in human plasma using Bloch surface wave-based biosensors
Get PDFThe overexpression and/or amplification of the HER2/neu oncogene has been proposed as a prognostic marker in breast cancer. The detection of the related peptide HER2 remains a grand challenge in cancer diagnosis and for therapeutic decision-making. Here, we used a biosensing device based on Bloch Surface Waves excited on a one-dimensional photonic crystal (1DPC) as valid alternative to standard techniques. The 1DPC was optimized to operate in the visible spectrum and the biosensor optics has been designed to combine label-free and fluorescence operation modes. This feature enables a real-time monitoring of a direct competitive assay using detection mAbs conjugated with quantum dots for an accurate discrimination in fluorescence mode between HER2-positive/negative human plasma samples. Such a competitive assay was implemented using patterned alternating areas where HER2-Fc chimera and reference molecules were bio-conjugated and monitored in a multiplexed way. By combining Label-Free and fluorescence detection analysis, we were able to tune the parameters of the assay and provide an HER2 detection in human plasma in less than 20 min, allowing for a cost-effective assay and rapid turnaround time. The proposed approach offers a promising technique capable of performing combined label-free and fluorescence detection for both diagnosis and therapeutic monitoring of diseases
Combined label-free/fluorescence platform based on Bloch surface waves biochips for cancer biomarker detection
No full textA biosensor platform based on Bloch Surface Waves and operating in angular interrogation mode is applied to the detection of a clinical biomarker (HER2-neu/ERBB2) related to breast cancer initiation/progression. Preparing regions for specific recognition of different proteins as well as a reference on the biochip enables to correct the signal for nonspecific effects. Additionally, label-free analysis and surface wave enhanced fluorescence detection can be applied and compared directly on the platform. Cell lysates with high and low expression levels of ERBB2 are analyzed. Comparing the signals of such ERBB2 positive and negative samples estimates the limit of detection at 1.7 ng/mL. This is well below the threshold of 15 ng/mL set by the FDA for clinically useful ERBB2 detection in human serum, demonstrating that 1DPC-based biochips are attractive candidates for breast cancer detection/monitoring
A novel technique based on Bloch surface waves sustained by one-dimensional photonic crystals to probe mass transport in a microfluidic channel
Get PDFWe report on the use of an optical sensing platform based on Bloch surface waves sustained by one-dimensional photonic crystals as a novel optical tool to probe in real time the fluid flow at a boundarywall of a microfluidic channel under dynamic conditions. Understanding how fluid flow interacts withwall surfaces is crucial for a broad range of biological processes and engineering applications, such as sur-face wave biosensing. The proposed platform provides nanometric resolution with respect to the distancefrom the boundary wall sensor’s surface. Here, for the first time, we report on the experimental inves-tigation on the temporal evolution of the interface between two fluids with different refractive indicesunder convective and diffusive conditions. The temporal evolution of the fluids interface in proximity ofthe wall is recovered. From the data analysis, the diffusion coefficients of glucose and glycerol in waterare measured and found in good agreement with the literature. Tuning the one-dimensional photoniccrystals geometry and the Bloch surface wave’s dispersion has the potential to probe the fluid flow in anextremely wide range of distances from the microfluidic channel wall
Cavitation bubble wall pressure measurement by an electromagnetic surface wave enhanced pump-probe configuration
Get PDFWe report on the measurement of the pressure associated with a shock wave within a very thin layer (100 nm) in proximity of a boundarysurface. In the experiments, the shock wave was emitted by a cavitation bubble generated by a pulsed pump laser in water. We developed apump-probe setup based on the detection of the light scattered at the surface of a one-dimensional photonic crystal, which was purposelydesigned to sustain a surface electromagnetic wave in the visible range and to enhance the optical response. In order to better understand thephenomenon, we implemented numerical simulations to describe the light scattering intensity distributions through a modified Rayleigh’smethod. We report, with a LoD of about 0.1 MPa, the measurements of the pressure at a surface in the presence of a laser-induced cavitationbubble generated at different distances from the surface and for different pulse energies
Label-free monitoring of human IgG/anti-IgG recognition using Bloch surface waves on 1D photonic crystals
Get PDFOptical biosensors based on one-dimensional photonic crystals sustaining Bloch surface waves are proposed to study antibody interactions and perform affinity studies. The presented approach utilizes two types of different antibodies anchored at the sensitive area of a photonic crystal-based biosensor. Such a strategy allows for creating two or more on-chip regions with different biochemical features as well as studying the binding kinetics of biomolecules in real time. In particular, the proposed detection system shows an estimated limit of detection for the target antibody (anti-human IgG) smaller than 0.19 nM (28 ng/mL), corresponding to a minimum surface mass coverage of 10.3 ng/cm2. Moreover, from the binding curves we successfully derived the equilibrium association and dissociation constants (KA = 7.5 × 107 M−1; KD = 13.26 nM) of the human IgG–anti-human IgG interaction
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