Refraction total internal reflection

A feature of interest is the possibility of obtaining the condition of total internal reflection (TIR). Under this condition, the fundamental beam impinges on the interface from the liquid with the highest index of refraction yielding a SH intensity enhancement of more than a hundred times. Two TIR angles exist, given by the following relationships ... 

Fig. 9.1. Principle of total internal reflection. Light propagation and refraction in a system with different refractive indices separated with a smooth surface is shown. Left The incident light is entering from the high refractive index medium under an angle 61 which is less than the critical angle 0C. Right total internal reflection because the incident light angle 61 is larger than 6C.

Figure 14 illustrates an example of a structure that can provide enhanced fluorescence capture. It consists of a truncated cone, on top of which the fluorescent species is deposited. The cone angle, a, is chosen in order to cause total internal reflection of the emitted fluorescence (the angular distribution of which is calculated from the model) and is therefore dependent on the refractive indices of the cone material and the environment. The emitted fluorescence is reflected onto a detector positioned directly beneath the cone. 

Figure 2. Regular reflectance Replication of Snellius law for reflected and refracted radiation at interface in dependence on the refractive indices of the media adjacent to this interface, demonstrating total internal reflectance and evanescent field, exciting fluorophores close to the waveguide or even surface plasmon resonance.

The configuration most often used in SPR instruments relies on the phenomenon of total internal reflectance and was developed by Kretchmann (Fig. 8).71,73 Total internal reflectance occurs when light traveling from a medium of higher refractive index toward a medium of lower refractive index reaches the interface and is reflected back completely into the higher refractive index medium. An important side effect of total internal reflection is the propagation of an evanescent wave across the interface into the medium of lower refractive index. 

This type of mode can exist only under certain conditions related to the geometry of the microtube and the refractive indices of the three regions. By defining the incident and reflection angles at r = R and r R2 as 6t and 02, the light transmitted through the inner boundary and totally internal reflected at the outer boundary should satisfy the following three criteria ... 

Fig. 10.3 Total internal reflection in a three layer waveguide structure. n, (i C, F, S) indicates the refractive index of layer i of the waveguide structure, % > nc s dF is the thickness of the core layer...

The light can propagate along the fibre usually by totally internal reflection (TIR) as indicated in fig. 18. TIR is controlled by the angle of incidence and also by the refractive indices of the media involved in the propagation. 

When light is moving from a medium with a large refractive index to one with a smaller refractive index, the phenomenon of total internal reflection can occur when the refracted angle is 90° or more. In a... 

Optical effects due to refraction and total internal reflection have been observed in dye-loaded zeolite L crystals of 2.5 p,m length and 1.4 p-m diameter by means of an optical microscope equipped with polarizers, a narrow band, and cutoff filters [23]. An astonishing effect taking place in an Ox +-loaded crystal is seen in Fig. 15. Looking at the polarized red emission, a homogeneous intensity distri-... 

The luminous nonpolarized wings are due to part of the emission built up in the middle of the crystal. They can be understood when taking total internal reflection into account. Refraction of the emission from the object O at the zeolite L-air interface observed at an angle 2 is explained in Fig. 16a. The emission can appear between 0° and the critical angle for total reflection which is... 

As we reported in Section IV.A, refraction and total internal reflection can occur in dye-loaded zeolite L microcrystals. Therefore, a bundle of light rays in, for example, a POPOP-loaded zeolite composite can circulate inside the hexagon. If the emission can circulate often enough in the same volume and the loss of the zeolite L ring cavity is small enough, lasing should be possible. 

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