Page 57 - Photonics Essentials an introduction with experiments
P. 57
Photodiodes
Photodiodes 51
80
60
40
External quantum efficiency (%) uncoated detector
20
Ga 0.47 In 0.53 As/InP
T = 295 K
10
absorption edge
of Si filter
4
2
1
1.0 1.2 1.4 1.6 1.8
Optical Wavelength (microns)
Figure 3.7. Measured absorption spectrum of a GaInAs photodiode at room tempera-
ture.
Figure 3.8. Light of intensity I(x) is incident on an absorbing medium such as a photodi-
ode. At position x + x, the intensity is less because some photons have been absorbed.
The number of photons absorbed is proportional to the number of photons present.
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