Optical photo detectors
Department of General Sciences
College of Basic Education / Haditha - Anbar University
Optical detectors have been used in many types of electro-optical and electronic circuits, as they are considered one of the most important industrial technologies, including their use in televisions, automatic door opening, communications, electric elevators, computers, thermal imaging cameras, laser printers, and high analysis capacity.
The great development in the technology of manufacturing reagents was clearly reflected in the field of their use, as the research trend began to focus on photo detectors nanowires, because the reagents had taken an important part of nanotechnology.
The need to manufacture optical detectors appears through the use of vacuum technology in the field of semiconductors, where the focus has been placed on developing methods for preparing optical detectors to be suitable for use in various fields, and working on finding physical methods through which a voltage barrier can be formed to allow metal contact with semiconductors. Through the current transmission through the depletion layer. Optical detectors depend in their work on the availability of charge carriers in semiconductors that stimulate electrons and move them from the valence band to the conduction band.
The process of forming the voltage barrier is through the important role played by the levels in the semiconductors.
There are several conditions and requirements that must be met in optical detectors:
1- High quantum efficiency, when there is a high response to the received signal.
2- High sensitivity in relation to the wavelength used.
3- The noise levels should be as low as possible.
4- The response time should be short in order to obtain an appropriate bandwidth.
5- Low cost
6- Small size to fit the fiber sizes.
There are several types of optical detectors:
1- PN photo diode
2 - P-I-N photo diode
3- Phototransistors
4- Avalanche photo diode (APD).