ABSTRACT
Microsphere-based biosensors have been attracting the attention of the photonics community due to their high sensitivity, selectivity and implementation. Microspheres, with their high quality-factor (Q-factor) morphology dependent resonances, are very sensitive to refractive index and size changes. The perturbation of the microsphere morphology dependent resonances can be used for the detection of biomolecules. Adsorption of different biomolecules on the surface of microspheres causes a change of effective size and refractive index leading to the shift of resonance wavelengths. A biosensor, based on this phenomenon, can detect a single molecule sensitively depending on the configuration that needs to be designed and optimised. Silica with a refractive index of 1.5, which is very close to that of bimolecular agents, is a suitable photonic material to use for biosensing applications. The transverse electric and transverse magnetic elastic scattering spectra at 90 degrees and 0 degrees are calculated at 1.55 microm with the associated shifts after adding a layer on it. 90 degrees scattering is used to monitor the scattered signal, whereas 0 degrees scattering is used to monitor the transmission signal.
Subject(s)
Biopolymers/analysis , Biopolymers/chemistry , Biosensing Techniques/methods , Models, Chemical , Nanotechnology/methods , Photometry/methods , Silicon Dioxide/chemistry , Biosensing Techniques/instrumentation , Computer Simulation , Computer-Aided Design , Equipment Design , Light , Microspheres , Nanotechnology/instrumentation , Photometry/instrumentation , Refractometry/instrumentation , Refractometry/methods , Scattering, RadiationABSTRACT
A Fabry-Perot microcavity is used for the enhancement and inhibition of photoluminescence in hydrogenated amorphous silicon nitride. The amplitude of the photoluminescence is enhanced 4 times, while its linewidth is reduced 8 times with respect to the bulk hydrogenated amorphous silicon nitride. The transmittance, reflectance, and absorptance spectra of the microcavity were also measured and calculated. The calculated spectra agree well with the experimental ones.
ABSTRACT
Morphology-dependent resonances of microspheres sitting upon an index-matched single-mode fiber half-coupler are excited by a tunable 753-nm distributed-feedback laser. Resonance peaks in the scattering spectra and associated dips in the transmission spectra for the TE and TM modes are observed. We present a new model that describes this interaction in terms of the fiber-sphere coupling coefficient and the microsphere's intrinsic quality factor Q(0). This model enables us to obtain expressions for the finesse and the Q factor of the composite particle-fiber system, the resonance width, and the depth of the dips measured in the transmission spectra. Our model shows that index matching improves the coupling efficiency by more than a factor of 2 compared with that of a non-index-matched system.
ABSTRACT
Morphology-dependent resonances (MDR's) of solid microspheres are excited by using an optical fiber coupler. The narrowest measured MDR linewidths are limited by the excitation laser linewidth (<0.025 nm). Only MDR's, with an on-resonance to off-resonance intensity ratio of 10(4), contribute to scattering. The intensity of various resonance orders is understood by the localization principle and the recently developed generalized Lorentz-Mie theory. The microsphere fiber system has potential for becoming a building block in dispersive microphotonics. The basic physics underlying our approach may be considered a harbinger for the coupling of active photonic microstructures such as microdisk lasers.
ABSTRACT
The relative intensities of glare spots in the image of an electrodynamically trapped aerosol droplet are measured experimentally with an aerosol particle microscope and calculated theoretically. The theoretical calculations are in good agreement with these experiments and indicate that the intensities of these spots are extremely sensitive to the imaginary part of the refractive index. Experimentally, we obtain the molecular absorption spectrum of an impurity within a droplet by recording the spectrum of an individual glare spot produced by broadband illumination.
ABSTRACT
Two-dimensional fluorescence, lasing, and stimulated Raman scattering images of a hollow-cone nozzle spray are observed. The various constituents of the spray, such as vapor, liquid ligaments, small droplets, and large droplets, are distinguished by selectively imaging different colors associated with the inelastic light-scattering processes.
