1. Photo Detectors

2. p-n Photodiodes
A reverse biased p-n junction consists of a region known as depletion region that is devoid of free charge carriers.
When light impinges on one side of such a p-n junction, electrons absorb light and make a transition from valence band to conduction band. Thus, electron-hole pair is created through light absorption.
The electrons and holes generated inside the depletion region accelerate in opposite directions due to the reverse bias.
This gives rise to a current flow in an external circuit and this current flow is known as the photocurrent.

3. p-n photodiodes

4. p-n photodiodes

5. p-n photodiodes

6. p-n photodiodes

7. p-i-n photodiodes

8. p-i-n photodiodes

9. Avalanche Photodiodes (APD)

10. Avalanche Photodiodes (APD)

11. Receiver Noise

12. Shot Noise

13. Thermal Noise

14. Thermal Noise

15. Noise in p-i-n Receivers

16. Noise in APD Receivers

17. Avalanche Photodiodes (APD)