Generation optical

Literature quotes more complex expressions for this term, taking into account multiple reflections at the front and at the back surface, real spectral dependences of reflection coefiicient and (possibly) finite surface recombination rates at detector surfaces. For instance, in the case described by (1.8) optical generation becomes 

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As with metal-semiconductor contacts, the electric field in the space charge, which is given by the diffusion voltage Fd and the width of the space-charge region W, separates optically generated electron-hole pairs. W is given by 41> ... 

Radical 44 is generated by electron transfer from the parent pyrimidine to the optically generated (308 nm laser pulse) triplet states of anthroquinone-2,6-disulfonic acid. The experimental method detects transient species in the time range of 40 ns to 10 ps after the laser pulse. At pH = 1.0, the primary cation radical is the only radical found 40 ns after the pulse. The spectrum of this radical disappears at a time shorter than 1.0 ps after the pulse. A second spectrum observed 5 ps after the pulse, is attributed to radical 46, which was thought to form by net OH- addition to C6 of the cation radical. At pH = 7.0, the N3... 

Optical Generation of Hydrated Electrons from Aromatic Compounds... 

Fig. 15. (a) Schematic Er excitation model, showing the electronic band structure of Si nanocrystall-doped Si02 and the Er 4f energy levels. An optically generated exciton (dotted line) confined in the nanocrystal can recombine and excite Er3+. (b) Schematic representation of SiC>2 containing Er (crosses) and nanocrystals (circles). The nanocrystals that couple to Er (filled circles) show no exciton luminescence (redraw after (Kik and Polman, 2001)). 

Nelson KA, Miller RID, Lutz DR, Fayer MD. Optical generation of tunable ultrasonic waves. I Appl Phys 1982 52(3) 1144-1149. 

Rogers JA, Maznev AA, Banet MJ, Nelson KA. Optical generation and characterization of acoustic waves in thin films fundamentals and applications. Ann Rev Mater Sci 2000 30 115-157. 

The number of carriers collected (in an external circuit, for example) versus those optically generated defines the quantum yield (C>), a parameter of considerable interest to photochemists. The difficulty here is to quantify the amount of light actually absorbed by the semiconductor since the cell walls, the electrolyte and other components of the assembly are all capable of either absorbing or scattering some of the incident light. Unfortunately, this problem has not been comprehensively tackled, unlike in the situation with photocatalytic reactors involving semiconductor particulate suspensions where such analyses are available [204-207]. Pending these, an effective quantum yield can still be defined. 

Within inorganic photorefractive crystals the optical generation of carriers is associated usually with the oxidation of defect and impurity states within the optical band gap of the crystal, such as iron impurity within lithium niobate crystals, as in Figure 9. 

Figure 2.8 shows the experimental set-up. An above-band-gap, short laser pulse is used to optically excite electron-hole pairs with excess energy. The time evolution of the electron distribution is followed by the use of a second short laser pulse with sufficient photon energy to place the excited electrons above the electron affinity of the semiconductor. The optical generation of the carriers again is not selectively at the surface region of interest—but the probed states are. 

Basseras P., Gracewski S. M., Wicks G. W. and Miller R. J. D. (1994), Optical generation of high-frequency acoustic waves in GaAs/Al cGai cAs periodic multilayer structures , J. Appl. Phys. 75, 2761-2768. 

An optically generated x-ray mask is itself one of the key features of LIGA, producing the necessary high contrast with a thick (>10 pm) gold absorber on materials membrane consist of low atomic number elements [27], The absorber mask is patterned using polymethyl methacrylate (PMMA) resists exposed by electron-beam lithography (e-beam) or from an intermediate mask that relies on an e-beam exposure... 

The permittivity of a vacuum Eq has SI units of (C /J m). The specific conductivity (Tc (l/( 2-m)) couples the electric field to the electric current density by J= OcE. From the relations described in (6b), it becomes evident that optically generated gratings correspond to spatial modulations of n, , or Xg. The parameters AA, , and Xg are tensorial. This means that the value of Xg depends on the material orientation to the electric field (anisotropic interactions). In general, P and E can be related by higher-rank susceptibility tensors, which describe anisotropic mediums. The refractive index n, and absorption coefficient K, can be joined to specify the complex susceptibility when K (Xp) 471/Xp such that... 

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