TABLE OF CONTENTS | 5.1 | The bandgap of the Hg 1 ? xCd xTe alloy is given by the expression  Calculate the composition of an alloy which gives a cutoff wavelength of (a) 10 m; (b) 5.0 m. | |||||
| 5.2 | Calculate the cutoff wavelength for a GaAs detector. If the cutoff wavelength is to be decreased to 0.7 m, how much AlAs must be added to a GaAs? Assume that the bandgap of Ga 1 ? xAl x is given by 
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| 5.3 | Calculate the absorption coefficient for GaAs for photons with energy 1.8 eV. Calculate the fraction of this light absorbed in a GaAs sample of thickness of 0.5 m. | |||||
| 5.4 | An optical power density of 1 W/cm 2 is incident on a GaAs sample. The photon energy is 2.0 eV and there is no reflection from the surface. Calculate the excess electron-hole carrier densities at the surface and 0.5 m from the surface. The e-h recombination time is 10 ?8 s. | |||||
| 5.5 | The performance of a silicon detector is poor for photons of wavelength 1.0 m, but are quite good for photons of wavelength shorter than 0.4 m. Explain this observation by examining the bandstructure of silicon. | |||||
| 5.6 | In long-distance fiber optics communication, it is important that photons with energy with low absorption in the fiber be used. The lowest absorption for silica fibers occurs at 1.55 |
