Optical microspheres

Hanumegowda, N. M. White, I. M. Oveys, H. Fan, X., Label free protease sensors based on optical microsphere resonators, Sens. Lett. 2005, 3, 315 319... 

Laine, J.-P., Tapalian, Fl.C., Little, B.E., and Haus, FI.A., 2001, Acceleration sensor based on high-Q optical microsphere resonator and pedestal antiresonant reflecting. Sensors and... 

Song, L., Ahn, S., and Walt, D. R. (2006). Fiber-optic microsphere-based arrays for multiplexed biological warfare agent detection. Anal. Chem. 78,1023-1033. 

Adams EW, Ueberfeld J, Ratner DM, O Keefe BR, Walt DR, Seeberger PH. Encoded fiber-optic microsphere arrays for probing protein-carbohydrate interactions. Angew. Chem. Int. Ed. 2003 42 5317-5320. 

Gorodetsky ML, Savchenkov AA, Ilchenko VS (1996) Ultimate Q of optical microsphere resonators. Opt Lett 21 453 55... 

Gorodetsky ML, Ilchenko VS (1999) Optical microsphere resonators optimal coupling to high-Q whispering-gallery modes. J Opt Soc Am B 16 147-154... 

Direct observation of molecular diffusion is the most powerful approach to evaluate the bilayer fluidity and molecular diffusivity. Recent advances in optics and CCD devices enable us to detect and track the diffusive motion of a single molecule with an optical microscope. Usually, a fluorescent dye, gold nanoparticle, or fluorescent microsphere is used to label the target molecule in order to visualize it in the microscope [31-33]. By tracking the diffusive motion of the labeled-molecule in an artificial lipid bilayer, random Brownian motion was clearly observed (Figure 13.3) [31]. As already mentioned, the artificial lipid bilayer can be treated as a two-dimensional fluid. Thus, an analysis for a two-dimensional random walk can be applied. Each trajectory observed on the microscope is then numerically analyzed by a simple relationship between the displacement, r, and time interval, T,... 

Dhas NA, Zaban A, Gedanken A (1999) Surface synthesis of zinc sulfide nanoparticles on silica microspheres sonochemical preparation, characterization, and optical properties. Chem Mater 11(3) 806-813... 

Fig. 5.2 Hemispherical prism coupling scheme. The microsphere is in a V groove channel for the solvent and analyte. Left, polar view showing input and output coupling. Right, equatorial view illustrating how precessed light is collected at the drop port. Reprinted from Ref. 3 with permission 2008 Optical Society of America...

Fig. 5.5 Experimental setup. The diode laser is frequency scanned by one waveform generator, while the other controls the modulation. The light couples from a tapered fiber into and back out of microsphere WGMs, and the throughput is detected. A polarizing beamsplitter (PBS) separates throughput of the two polarizations. A diode pumped solid state laser can be used as an external heat source for the microsphere, and the vacuum chamber allows control over the ambient pressure. Reprinted from Ref. 5 with permission. 2008 International Society for Optical Engineering...

Fig. 13.1 Photonic sensors that are either based on MNF sensing ((a),(b), (d), (e), (f)) or use MNF for the input and output connection (c), (g) (j). (a) straight MNF sensor with surrounding evanescent field (b) straight MNF sensor coated with bio or chemical layer and surrounding evanescent field (c) generic structure of MNF based optical sensor with surrounding evanescent field (d) straight MNF sensor (e) MNF loop resonator (MLR) sensor (f) MNF coil resonator (MCR) sensor (g) MNF/microsphere sensor (h) MNF/microdisk sensor (i) MNF/micro cylinder sensor (j) MNF/microcapillary sensor (k) a sensor composed of an MNF coupled to a series of microcylinders (optical fibers)...

An MNF/microcylinder sensor exploits WGMs resonances in a cylinder (optical fiber), which are excited by an MNF. The arrangement of an MNF and a cylinder is shown in Fig. 13.li. As opposed to the WGM in a microsphere and microdisk considered in Sect. 13.3.1, the beam launched from the MNF into the cylinder spreads along the cylinder surface and eventually vanishes, even if there is no loss. The theory of resonant transmission of the MNF/microcylinder sensor was developed in Ref. 18. The resonant transmission power of this device can be modeled by a self-interference of a Gaussian beam that made n turns along the cylinder circumference ... 

Here n5 and nm are the refractive indices of the microsphere and ambient medium, respectively, and R is the microsphere radius. To determine An and t from this equation, it is sufficient to measure AA for two wavelength, ly1 and A. In Ref. 36, this was done for A[ = 760 nm and A[ = 1,310nm. As the result the authors optically characterized a hydrogel nanolayer with 110-nm thickness and an extremely small excess refractive index of 0.0012, which was formed in situ in an aqueous environment. 

Fig. 13.22 (a) MNF/microsphere tool for surface sensing, (b) Transmission power dependence on the position of the microsphere at the diffraction grating surface. Comparison of two measure ments of the same grating region shows the reproducibility of measurements. Reprinted from Ref. 42 with permission. 2008 Optical Society of America... 

MNFs, optical cylinders, disks, and microspheres can be assembled in more complex multifunctional sensing structures. One of the suggested structures is... 

Fig. 13.26 (a) Set of parallel MNFs and parallel microcylinders coupled to each other, (b) Two microspheres coupled to an MNF (from Ref. 38). (c) Two microcapillaries coupled to an MNF imbedded in a low index polymer. Reprinted from Ref. 69 with permission. 2008 Optical... 

Sumetsky, M. Dulashko, Y. DiGiovanni, D. J., Optical surface microscopy with a moving microsphere, In Nanophotonics Topical Meeting, OSA, Uncasville, 2006... 

Figure 5.17 Stability of optical encoding towards oligonucleotide reagents. Organosilica microspheres covalently labelled with ATTO 550 dye are stable towards each of the reagents used in phosphoramidite oligonucleotide synthesis. In contrast, optically encoded polystyrene-divinylbenzene (DVB) beads are unstable in most steps, in particular those involving dichloromethane and tetrahydrofuran. (Reproduced from ref. 28, with permission.)...

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