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© Dr. Rüdiger Paschotta
Last update: 2009-10-04
Quantum EfficiencyDefinition: percentage of input photons which contribute to a desired effect
The quantum efficiency (or quantum yield) is often of interest for processes which convert light in some way. It is defined as the percentage of the input photons which contribute to the desired effect. Examples are:
- In a laser gain medium, the pump process may require the transfer of laser-active ions from one electronic level (into which the ions are pumped) to the upper level of the laser transition. This pump quantum efficiency is the fraction of the absorbed pump photons which contributes to the population of the upper laser level. This efficiency is close to unity (100%) for many laser gain media, but can be substantially smaller for others. It may depend on factors like the excitation density and parasitic absorption processes.
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What are semiconductor diode laser describe with energy band diagram the construction and working of a semiconductor diode laser?
construction and working of semiconductor laser
What is the effect of temperature on photodiode?
photodiodes are basically reverse biased diodes with optical windows that allow like to shine on the PN junction. Like any diode, the leakage current (otherwise known as a photodiodes 'dark' current) increases exponentually with temperature in accordance to William Shockley's idea diode eqation. The other effect in a photo diode is the probability of a photon of a certain energy allowing an electron to cross the PN junction. This is known as the quantum efficiency of the photodiode. Because increasing temperatures increase the vibration of the silicon atoms, making them easier to be knocked loose by a photon. Thus the quantum efficiency of a photodiode will increase with tempature, as well as the thermally induced noise. photodiodes are basically reverse biased diodes with optical windows that allow like to shine on the PN junction. Like any diode, the leakage current (otherwise known as a photodiodes 'dark' current) increases exponentually with temperature in accordance to William Shockley's idea diode eqation. The other effect in a photo diode is the probability of a photon of a certain energy allowing an electron to cross the PN junction. This is known as the quantum efficiency of the photodiode. Because increasing temperatures increase the vibration of the silicon atoms, making them easier to be knocked loose by a photon. Thus the quantum efficiency of a photodiode will increase with tempature, as well as the thermally induced noise. photodiodes are basically reverse biased diodes with optical windows that allow like to shine on the PN junction. Like any diode, the leakage current (otherwise known as a photodiodes 'dark' current) increases exponentually with temperature in accordance to William Shockley's idea diode eqation. The other effect in a photo diode is the probability of a photon of a certain energy allowing an electron to cross the PN junction. This is known as the quantum efficiency of the photodiode. Because increasing temperatures increase the vibration of the silicon atoms, making them easier to be knocked loose by a photon. Thus the quantum efficiency of a photodiode will increase with tempature, as well as the thermally induced noise.
What kind of laser diode does a Casio projector use?
Most of the Casio projectors use a 445nm laser diode that is rated at 1 watt. The projectors have the diodes running at 600mw for life.
What does the nm in 650nm laser diode mean?
"nanometer" or billionths of a meter. 650 nanometers is the wavelength of the light produced by the diode.
What is the disadvantage of gunn diode?
Gunn Diodes are used in high frequency electronics. The advantages are increased efficiency and improved temperature stability while a disadvantage is the Gunn Diode can get burned out.
