Solid immersion

Spot size reduction of an optical beam is generally limited if focussing in air is considered due to the NA limit of unity. If the angular spectrum of the waveguide mode field comes close to or exceeds this limit, two ways can be eonsidered. The first one is to widen the mode field by a 2D-taper in such a way that it comes close to a diameter which is available with focus formation in air. The second one is to focus in a high index lens material, and to attach the lens to the lO-chip, finally, just similar to what is achieved with a solid immersion lens. The principal geometry is shown in figure 15. 

I. Ichimura, S. Hayashi, and G. S. Kino, High-density optical recording using a solid immersion lens, Applied Optics 36, 4339-4348 (1997). 

The heat values are markedly higher for the polar solid immersed in polar liquids they also vary considerably with the functional group of the liquid. For Graphon, however, the heats are almost unaffected by the structural features of the wetting liquid. This nonpolar solid, despite the presence of a small amount of hydrophilic sites on its surface 0), interacts with the liquids primarily through London dispersion forces. Because of the additive nature of these forces, each adsorbed molecule tends to lie flat on such a surface 40). In the case of a polar molecule the functional group is oriented somewhat away from the nonpolar surface toward the liquid. 

Our approach to the thermodynamics of adsorption and immersion remains simple, although rigorous, and close to the experiment. This is why the thermodynamic treatment of the energetics of immersion in Section 5.2 is confined to the simple system of a solid immersed in a pure liquid. Similarly, in Section 5.3 consideration is given only to the adsorption from binary solutions. The thermodynamic nomenclature and definitions proposed here are consistent with the recommendations of IUPAC (Everett, 1972, 1986). 

STM can also be applied to solids Immersed in liquids, with obvious relevance to colloid science. Examples include deposited Langmulr-Blodgett films, electrode surfaces and graphite in oll K However, a Langmulr-Blodgett lipid film can easily be pierced by the tip if the force becomes too high. The force required to displace one lipid molecule in such a layer can in principle be computed from membrane models and is probably of the order of a few tenths of a nanonewton. 

Experiments with solids immersed in cell culture media, with and without living cells present, convincingly demonstrate the absolute condition that protein-dominated films accumulate at the solid-liquid boundaries prior to cell adhesion. The reality and speed of this spontaneous, adsorptive event are documented by using infrared-transmitting, multiple internal reflection plates as the immersed solid with care to prevent film transfer from gas-liquid interfaces. 

At the start it is well to examine what is meant by a surface. Subconsciously we may think of a surface as the exterior of a material body. However, a surface is actually a boundary because where the mass of one body ends the mass of another begins. Consider a solid immersed in a liquid. Here the surface of the solid faces a corresponding surface of the liquid the region enclosed by these two surfaces we know as an interface, and it is within this interfacial region that adsorption occurs. 

Past strategies for increasing the storage capacity of optical disks were based on a reduction of A and an increase in NA, as can be seen from Table 12.1. In principle, a reduction in the spot size can be achieved with the aid of solid immersion lenses. This as yet not practically exploited technique, operating with a hemispherical or a Weierstrass superspherical lens placed near the recording medium (< 100 nm), yields a reduced spot size, S, as is evident from Eqs. (12-2) and (12-3), respectively, where n denotes the refractive index of the lens [8],... 

Fig. 7 Solid-immersion micropshere superlens, (a) planar design with high-index microsphere embedded in transparent layer, (b) hemisphere-top design which reduces total internal refection (TIR) effect of planar surface, (c) lab prototype produced at Bangor University, and (d) imaging example showing 40 nm lines can be clearly imaged.

Figure 7 shows two designs of coverslip-form solid-immersion micropshere superlens we have proposed, a flat-top design (Fig. 7a), and a hemisphere-top design (Fig. 7b), both having a thickness similar to standard coverslip which is small enough for the superlens to be directly inserted into the gap between conventional microscope s objective lens and sample. The hemisphere-top curved surface in the design Fig. 7(b) is used to reduce the effect of total internal reflection from a flat surface. 

Higher resolution can be achieved this is because in this design the solid immersion mechanism contributes to the resolution enhancement, as the working wavelength in the near-field region is scaled down by a factor of n (refractive index of solid immersion material). As shown... 

The new lens is also less sensitive to the environment change owing to encapsulation which separates microspheres and the environment. The solid-immersion design has great commercial potential which will be discussed in the outlook session below. 

I. Introduction and types of drag. In Chapter 2 we were concerned primarily with the momentum transfer and the frictional losses for flow of fluids inside conduits or pipes. In this section we consider in some detail the flow of fluids around solid, immersed objects. 

The Reynolds number for a given solid immersed in a flowing liquid is... 

In a number of instances adsorption of polar compounds from dilute solutions passes through a region in which the surface is covered by a closely packed monolayer of the polar solute. The author discovered in 1966 that most non-porous metal oxides adsorb preferentially n-butanol from n-heptane with the formation of such a monolayer. The integral heat produced during the formation of the monolayer correlated very well with the specific areas of the metal oxides measured by the BET(Na) method [26], The specific surface areas of these solids could be effectively measured by a single point method, in which a sample of the solid immersed in n-heptane was flooded with a 2 gl > solution of n-butanol producing a heat of n-heptane displacement which was proportional to the total surface area of the sample. 

The behaviour of diluted solutions is related to the relation between the viscosity and the chain characteristics (structure, configuration, conformation, etc). Usually, the polymer solutions are treated as two-phase systems, consisting from mechanical elements, the macromolecules, immersed into a continuous media, the solvent. For long time, it was considered that the solvent acts to the polymer macromolecules in the same manner in which a fluid exerts forces about a small particle suspended in it. However, the extension of this model to the polymer solution is not adequate since, the ratio between the dimensions of macromolecules and those of solvent molecules essentially differs by that between the dimensions of a solid immersed particle and solvent molecules. On the other side, the flexible macromolecules, randomly coiled, can not be assimilated with the solid particles and therefore the typical relations applied to solid suspensions in liquids can not be used in this case. 

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