Refractive index, change effective

Keywords Nanostructures Surface plasmon resonance Localized surface plasmon resonance Bio-molecular interactions Refractive index change Effective medium Thin films Biosensors Sensitivity Nanoparticles... 

Refractive Index. The effect of mol wt (1400-4000) on the refractive index (RI) increment of PPG in ben2ene has been measured (167). The RI increments of polyglycols containing aUphatic ether moieties are negative drj/dc (mL/g) = —0.055. A plot of RI vs 1/Af is linear and approaches the value for PO itself (109). The RI, density, and viscosity of PPG—salt complexes, which maybe useful as polymer electrolytes in batteries and fuel cells have been measured (168). The variation of RI with temperature and salt concentration was measured for complexes formed with PPG and some sodium and lithium salts. Generally, the RI decreases with temperature, with the rate of change increasing as the concentration increases. 

At concentrations greater than about 0.01 M, refractive index changes and the perturbing effect of solute molecules or ions on the charge distribution of their neighbours both affect the value of s. Positive or negative deviations may result. 

In this chapter, we will numerically analyze the effects of the HRI overlay on the cladding modes distribution with particular attention to its influence on the device sensitivity to the SRI changes and to the overlay refractive index changes. The structure to which we refer is depicted in Fig. 3.2. 

Here functions Qnt X), Qj(X), and QP(X) can be determined experimentally using calibration samples. If these functions are linear independent then the parameters Ank, A, and Ap can be uniquely determined from the variation of P /1, , n2,. .. /( . /. / considered as a function of X. In particular, the side effects, i.e., the temperature and pressure dependences, can be eliminated from the transmission spectrum. The sensing method based on this simple idea was applied in Ref. 69 for determination of microfluidic refractive index changes in two microcapillaries coupled to a single MNF illustrated in Fig. 13.26c. The developed approach allowed to compensate the side temperature and pressure variation effects. 

In Sect. 15.2 we concluded that refractive index variation in the aqueous cover media shifts the effective refractive index of the waveguide modes. Thus, by monitoring on-line the effective refractive index, the refractive index change can be followed. This is the basic principle of waveguide sensing. 

Various sensor arrangements depend on the actual way how the shift in the mode s effective refractive index is followed. In order to design a sensitive waveguide sensor and to quantify the refractive index changes, the effective refractive index has to be connected with the physical parameters of the waveguide. To this end, one needs to solve the Maxwell s equations using the appropriate boundary conditions10. 

The polyene chromophore (5.13), designed by Marder and utilised by Peyghambarian and co-workers, has specific features built into the structure that make it both an effective NLO chromophore for refractive index change and for it to... 

An applied electric field can also change a material s linear susceptibility, and thus its refractive index. This effect is known as the linear electro-optic (LEO) or Pocket s effect, and it can be used to modulate light by changing the voltage applied to a second-order NLO material. The applied voltage anisotropically distorts the electron... 

Temperature Sensing. As shown in Fig. 16, a layer of silicon (whose refractive index changes with temperature) is placed in the optical path in place of the evacuated cavity, as previously described. The second reflector (glass) is rigid. The effective path length thus changes with temperature. 

Figure 3 Refractive index change associated with the orientational enhancement effect. The arrows represent the direction of the total field Ej which is the sum of the applied and space-charge fields.

It may appear very tempting to apply the Forster s formalism to the question of electrolyte effects onto the lifetime. However, some features of this effect render the use of the Forster s theory difficult experiments with Eu have shown that the observed variations cannot be reproduced solely on the basis of the refractive index changes, a term included in the Forster s... 

In non-polar, isotropic crystals or in glasses, there is no crystallographic direction distinguished and the linear electro-optic effect is absent. Nevertheless a static field may change the index by displacing ions with respect to their valence electrons. In this case the lowest non-vanishing coefficients are of the quadratic form, i.e. the refractive index changes proportionally to the square of the applied field Kerr effect . 

Photochromic Effects. To estimate the maximum refractive-index change achievable with a photochromic transition, we consider separately the normalized index change (defined by eq. 12), and the net number density of the active species that undergoes the transition. 

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