Basic optics

A reader unfamiliar with any optics should consult a textbook for more information. Jenkins and White [1] is a comprehensive college level text, Martin [2] and Lipson and Lipson [3] are more detailed and technical. Spencer [4] provides an elementary introduction to microscope optics and optical microscopy texts and several references already cited in Chapter 2 (refs 3-11 there) are also useful sources. All of these describe light optics and light microscopy, but TEM texts tend to assume this knowledge and are more advanced. 

The velocity v and wavelength A of the wave will be changed during passage through matter. 

Matter slows down light and electrons and the refractive index n can be defined as  

The optical path length of a wave in a material of thickness t is nt. The material contains ntlX wavelengths as would a path of length nt in vacuum. The optical path difference A due to the presence of this material is then (m - l)t, and the phase difference produced is (2n/A)A. Table 3.1 shows how the optical properties of polystyrene depend on the incident radiation. The refractive index for electrons is taken to be that for carbon (see section 3.1 of ref. 5), corrected for the lower density of polystyrene. 

If the phase of the wave can be calculated from its phase at nearby points and times, the radiation 

Matter slows both light and electrons, decreasing their wavelength A the refractive index, n is defined as  

When an object scatters coherent waves, interference produces a variation in intensity as a function of their direction, the diffraction pattern of the object. An object with regular periodicity d in one dimension has a pattern with maximum intensity when the angle between incident and scattered radiation, 0 takes the values given by  

If the phase of the wave can be calculated from its phase at nearby points and times, the radiation is coherent, monochromatic and parallel light, for example, is coherent. The phase and amplitude of completely incoherent light vary randomly in space and time. When two coherent waves of amplitudes a and b come together they interfere with each other. The result is a wave of intensity (a + bf if they are exactly in phase (constructive interference) and intensity (a - bf if they are completely out of phase (destructive interference). In general the waves must be added by vector sum rules. Incoherent waves interfere momentarily, but over any period of observation the phase effects average out. The resulting average intensity is the sum of the intensities of the two waves, a + b ). 

When an object scatters coherent waves, interference between waves scattered from different 

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There are several types of optical waveguides - planar waveguides and cylindrical waveguides (optical fibers). Basic optical waveguide geometries are shown in Figure 1. 

I. Hamburg and C.G. Granvist, Evaporated Sn-doped ln203 films basic optical properties and applications to energy-efficient windows, J. Appl. Phys., 60 R123-R159, 1986. 

The reflectivity of a solid can also be determined after establishing the boundary conditions for the electromagnetic radiation at the interface between the solid and the vacuum. In the simple case of a solid in a vacuum, and considering normal incidence of light, it is well known from basic optics texts that... 

FIG. 1.19 Basic optical principle governing the operation of an optical microscope (a) the geometry on which the resolving power d of a microscope is based (b) detail showing how light from both sources must be intercepted by the lens to become part of the image. 

Laser Doppler velocimetry is a powerful technique for the in situ measurement of fluid velocities. The basic optical configuration for the measurement is shown in Figure 6.1. The velocity measurement is made at the intersection of two laser beams that are focused to a point in the flow. The use of laser radiation is essential since the light must be monochromatic and coherent. This is required since the intersection of the two beams must create an interference pattern within the fluid. Such a pattern is shown in Figure 6.2, where two plane waves intersect at an angle 2(J). The two waves will have the following form [55] ... 

Figure 23 is a representation of the use of composite lenses for such work. The special distance values Ll, lu and l2 relate to the focal points in composite lenses H and H the focal distance is/0. The basic optical parameters in the image sensing systems A, B, and C are calculated as follows ... 

There is no doubt that a better understanding of the fundamental optical transitions and their dynamic processes will provide important information for improving material quality as well as for the design and optimisation of the optoelectronic devices based on GaN. However, systematic studies are still needed in order to understand fully the basic optical processes in nitrides, while time-resolved PL measurements can provide unique opportunities for such studies. 

Without doubt, however, the greatest difference between the two is that the sophisticated electronics of the newer instrument enable it to be directly connected to an Infrared Data Station , a microcomputer system which can smooth spectra, produce an average spectrum from a number of scans, subtract one spectrum from another, or reformat a spectrum. In addition, it is possible to identify possible structural features of an unknown compound and to match the spectrum against a reference library stored on magnetic disks, to facilitate a rapid identification of unknowns3). It is interesting to note that the basic optical specifications of the two instruments are not all that dissimilar ... 

The basic optical setup was shown in Fig. 12 [90]. The spectra were recorded on a commercially available spectrometer equipped with an external PM setup. The photoelastic modulator modulated the polarization of the IR light at a fixed frequency. Demodulation was performed with a lock-in amplifier and a low-pass filter. After the IR beam passes through the polarizer and modulator, it is focused on the sample, then focused on an mercury-cadmium-telluride (MCT) detector cooled by liquid nitrogen. 

II. REMARKS ON BASIC OPTICAL PROPERTIES OF LOW-DIMENSIONAL ORGANIC SOLIDS... 

In Section II we describe some applications for refractive-index recording materials, with particular emphasis on the basic optical concepts and the required material characteristics. 

To produce a high-resolution lattice image of a crystal, at least two beams must be allowed to pass through the aperture in the back focal plane of the objective lens. The basic optical principles involved in this imaging mode are discussed in Chapter 1. However, a number of factors not discussed there influence high-resolution TEM images these are the main concern of Chapter 6. 

The first chapter provides an introduction to the basic physics of OLEDs and surveys the various topics and challenges in this field. It includes a description of the basic optical and transport processes, the materials used in some of the OLEDs that have studied extensively to date, the performance of various blue-to-red OLEDs, and a brief outlook. 

In this section, we describe the basic optical properties of spheres, elHpsoids and coated particles and colloid thin films. Predictions based on these equations will be compared with rationally designed materials in Sects. 3-6. 

Equation (14) can be used to model hollow particles, as well as core-shell particles. It describes the basic optical effects associated with changes in the medium refractive index and the effects of different core-shell thicknesses (Sect. 4.1). Note that these equations are limited by the fact they are predicated upon dipole models and work accurately only for particles such that kRless than 30-40 nm in total size. 

The magnetic permeability p is nearly unity at optical frequencies for most materials. The basic optical characteristics of the phase are defined by p, n, and k, or, alternatively, by p, s, and s". Both sets are used in the analysis of experimental results. 

Because of basic optical principles, the light injected into the fiber must belong to a geometrical acceptance cone in order to be guided within the core. This condition is given by the numerical aperture, defined as NA = sint ni = ( i — with 0, the maximum angle of the cone, and n and 2 the refractive indices of the core and cladding, respectively. Numerical apertures are usually between 0.1 and 0.3 for telecommunication applications, with the refractive index of pure silica equal to 1.4586 at sodium D-line. 

Single-molecule techniques have found their initial applications in living cells. These experiments are related to time-resolved microscopy in that they use the same basic optical systems and TCSPC devices. A combination of singlemolecule spectroscopy and FLIM may expand the capabilities of biological microscopy considerably. 

When the alkaloids are treated at moderate temperatures with acetic anhydride, basic optically active 0-acetyl derivatives are formed, but at the boiling point of the reagent dehydration takes place and optically inactive A-acetyl derivatives are formed as the result of ring scission. Mercuric acetate removes two hydrogen atoms (27) forming new colorless bases which yield intensely colored salts and which can be reduced to the original alkaloids without change of optical activity. 

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