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Figure 1: LED construction
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Working Principle of LED
LED consists of a state and p state. When the current is passed through the LED the electrons from one side gets excited and tries to go to the next state lose photon and comes back to the original state. This photon is the light produced by the LED. The color produced by the LED depends on the wavelength of the lights produced.
The greatest advantage of using the LED is its tendency to be turned on and off rapidly. This allows creating different pulses of the source. The amount of light produced by the LED depends on the current flowing through it. The more the current, the range of amount of light produced is high. However, more current might also destroy the LED due to the excessive heat produced by it.
Working principle of Laser
Figure 2: Laser System
A laser is an optical oscillator, which can be made out of a solid, liquid or gas. It contains two with mirrors at both ends: one is totally reflecting and the other only partially. To make it work, the material is excited or "pumped," with an energy source such as light or electricity.
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The spectral response of the light detector determines its sensitivity to different wavelengths in light spectrum. Thus, to increase the sensitivity, the spectral of source and the detector are matched.
Working principle
The photo diode is connected in revearsed bias way. It operates by converting signals that hit the junction to a voltage or current. The junction uses and illumination window with an anti-reflect coating to absorb the light photons. The result of the absorption of photons is the creation of electron hole pairs.
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