Page 66 - Photonics Essentials an introduction with experiments

Photodiodes

60 Photonic Devices

= 0.62 m or 620 nm. The LED is capped with a lens so that the
light is emitted in a circular cone of 20°, as shown in the figure
below. The LED is emitting 10 –4 watts. Your detector is a silicon
photodiode with quantum efficiency at
= 620 nm = 0.75, and di-
mensions 0.3 cm × 0.3 cm
a. At 1 meter from the LED, what is the optical power intercept-
ed by the photodiode?
b. What is the responsivity of the photodiode in amps/watt?
c. What is the photocurrent generated by the photodiode? (As-
sume: R = 100 .)
L
d. What would be the photocurrent 10 meters away?

Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.