Photodetector applications

RCA ERMA" Photodetector, Application Note AN-4637 (RCA Electronic Components, Harrison, New Jersey 1971)... 

PHOTOVOLTAIC AND PHOTODETECTOR APPLICATIONS A MOLECULAR APPROACH TO HIGH EFFICIENCY PHOTOVOLTAIC CELLS USING PHOTOINDUCED ELECTRON TRANSFER... 

Another interesting property of the metal NP-ineorporated Ti02 is that the dark current of the electron-only device reduces when the eurrent is enhanced under UV excitation when compared to that of pristine Ti02 devices, as shown in Figure 7.8. This can enhance the dynamie range of the OSCs and shows potential for photodetector applications. 

The principle of optical triangulation has been known since the time of the early Greeks, and indeed optical triangulation has been used for hundreds of years in applications such as surveying, camera auto-focus and even smart-bombs. With the advent of low-cost, compact electro-optic components such as lateral-effect photodetectors, diode lasers and micro-optics, laser-based triangulation sensors can now be employed for applications that were, heretofore, considered uninspectable. 

Silicon is not as prominent a material in optoelectronics as it is in purely electronic applications, since its optical properties are limited. Yet it finds use as a photodetector with a response time in the nanosecond range and a spectral response band from 0.4 to 1.1 im, which matches the 0.905 im photoemission line of gallium arsenide. Silicon is transparent beyond 1.1 im and experiments have shown that a red light can be produced by shining an unfocused green laser beam on a specially prepared ultrathin crystal-silicon slice.CVD may prove useful in preparing such a material. 

Optoelectronic components produced by CVD include semiconductor lasers, light-emitting diodes (LED), photodetectors, photovoltaic cells, imaging tubes, laser diodes, optical waveguides, Impact diodes, Gunn diodes, mixer diodes, varactors, photocathodes, and HEMT (high electron mobility transistor). Major applications are listed in Table 15.1.El... 

The optode transduces the non-optical signal from the environment to the optical one, readable by the photodetector. Various indirect optical sensors and theirs applications are described in literature35. The optode can work as a chemical sensor that detects certain analytes in aqueous solutions or in air on chemical way. It means that changes in the environment cause the changes in the photosensitive material, which is immobilized in the optode matrix. These chemical changes influence the observed light intensity (for example, due to absorption) or one can analyze the intensity or time decay of luminescence. There are numbers of publications devoted to the family of optical chemical sensors36. 

The PCBM methyl ester can be used for coupling amine-containing ligands after removal of the methyl group and activation of the carboxylate using a number of different reaction strategies. Hummelen et al. (1995) successfully coupled cholestanol and histamine to the fuller-ene-PCBM derivative (after acid chloride formation) for use in fabrication of photodetectors and biological studies, respectively. For specific applications of PCBM-fullerenes, see Shaheen et al. (2001), Brabec et al. (2001), Yu et al. (1995), Mecher et al. (2002), Meijer et al. (2003), van Duren et al. (2004), and Anthopoulos et al. (2004). 

Because of its indirect bandgap, bulk crystalline silicon shows only a very weak PL signal at 1100 nm, as shown for RT and 77 K in Fig. 7.9. Therefore optoelectronic applications of bulk silicon are so far limited to devices that convert light to electricity, such as solar cells or photodetectors. The observation of red PL from PS layers at room temperature in 1990 [Cal] initiated vigorous research in this field, because efficient EL, the conversion of electricity into light, seemed to be within reach. Soon it was found that in addition to the red band, luminescence in the IR as well as in the blue-green region can be observed from PS. 

A photodetector with a suitable spectral response for the detection of the fluorescence emission. As mentioned above, the fluorescence of most Cr3+-activated materials consists of either the red R-lines or a broadband infrared emission with the peak wavelengths ranging from -750 to 1000 nm, or both emissions. Thus, the widely available, compact and inexpensive silicon PIN photodiodes are the most suitable photodetectors for these applications. In some particular circumstances, where high speed and high sensitivity of detection are required, a silicon-based avalanche diode could be the best alternative to the PIN photodiode, at small price premium ... 

As noted earlier, on-line process monitoring is among the application areas that can benefit most from the use of sensors provided they can be incorporated into portable systems. Electrochemical sensors are generally more suitable for these applications, even though optical sensors can also be readily adapted for this purpose (e.g. by using LEDs or photodetectors instead of conventional photometers) at the expense of somewhat degraded spectral resolution and sensitivity. 

Tristimulus colorimeters are used to measure color in certain food applications. They combine light source, filters, and photodetectors to reproduce the CIE Standard Observer response functions (Fig. F5.1.8). Colorimeters, having broad band-pass filters, do not measure the spectral data. Without spectral data they cannot offer the choice of either observer or... 

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