Dear Mahdi Vazvani,
What is the rise time of a photodetector?
The rise time is equivalent to the response speed of the device. It is defined as the time required for the photodetector output signal to change from 10% to 90% of the peak level. A good rule of thumb is to choose a photodiode with a rise time that is one fifth of the laser pulse width to be measured.
How can we measure the laser pulse duration less than pS?
Pulse durations down to roughly 10 ps can be measured with the fastest available photodiodes in combination with fast sampling oscilloscopes. For the measurement of shorter pulse durations, streak cameras can be used.
How is laser pulse measured?
The pulse duration, which is typically in the nanosecond regime, can be directly measured with a fast photodetector. The pulse energy may be measured directly (e.g. with a pyroelectric detector). In some cases with repetitive operation, it is calculated from the average power (from a power meter) and repetition rate.
Why are femtosecond lasers important?
Femtosecond lasers exhibit excellent capability in performing three-dimensional processing in transparent materials, especially glass, which makes them a powerful tool for micromachining optical fibers.
How is laser pulse duration calculated?
For a fixed average power, the higher the repetition rate, the lower the energy per pulse. For a CW or pulsed laser that is fired for a known and finite amount of time, you will need to multiply the average power of your source by that time, which is often called “Pulse Duration”.
How do you calculate pulse duration?
Wave number ν (cm− 1) is connected with the wavelength λ (cm) of generated radiation by the equation ν = 1 / λ. Pulse width (duration) τ is given by the temporal length of laser pulse; that is, the time during which the laser actually emits energy.
Why are rise and fall times different?
Since electrons travel more quickly than holes in most semiconductors, the electron response results in a fast rise and fall time component, but the slower holes continue to contribute current after the electron current has been collected. This leads to a “tail” on the falling edge.
Dear Mahdi Vazvani,,
Here below are some auxiliary data:
https://www.ophiropt.com/laser--measurement/knowledge-center/article/14047
https://datascience.iq.harvard.edu/files/mazur/files/rep_595.pdf
https://lia.scitation.org/doi/10.2351/7.0000549
Usually something like tens-hundreds of psec laser is sufficient..
e.g.
http://photek.mintbig.com/products/pulsed-laser.html
https://www.picoquant.com/products/category/picosecond-pulsed-sources
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