# Laser pulse

## Main Question or Discussion Point

What does it mean by laser pulse 10 nanosecond?

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Integral
Staff Emeritus
Gold Member
How many different things could it possibly mean? Such pulses are usually generated by a "Q switch". Here is what Wikipedia has to say.

Claude Bile
It is the duration of the pulse, typically measured as the full-width half maximum in the time domain (i.e. the length of time it takes for the pulse to go from half its peak intensity to the peak intensity and back to half its peak intensity).

Lasers are sometimes described as 'nanosecond', 'picosecond' or 'femtosecond' lasers. These terms are in reference to the duration of the pulses these lasers emit.

Claude.

Mk
touqra said:
What does it mean by laser pulse 10 nanosecond?
Or maybe you think a laser beam is a continuous stream of light, its not. The laser machine sends out chunks of beam, but so many so fast (1x10-7 in your case).

Danger
Gold Member
Mk said:
Or maybe you think a laser beam is a continuous stream of light, its not.
Yeah. You almost have to consider it to be a photonic machine gun. The pulse duration can be equated to the length of a bullet, and the pulse frequency to the firing rate. That's the reason that you can get such enormous energy density in a laser; if you take a couple of hours to pump 5 megawatts into a capacitor bank, then release it in a millisecond chopped into some picosecond pulses...

Danger said:
Yeah. You almost have to consider it to be a photonic machine gun. The pulse duration can be equated to the length of a bullet, and the pulse frequency to the firing rate.
Do you mean the pulse frequency, as in the frequency, calculated as:

$$frequency = \frac{lightspeed, c}{duration, 10ns}$$

Last edited:
ZapperZ
Staff Emeritus
This is EXACTLY an example where if you do not put your question in its proper context, you will not get the answer to your question. Please put some effort to elaborate where you are reading or using such a thing. This will tell the rest of us the relevant "frame of reference" where your question is applied.

From my perspective, it is simply a time duration of the laser. In fact, I use laser pulses 8 to 10 ps long. This is the length in time of each laser shot that hits a photocathode.

Zz.

Danger
Gold Member
touqra said:
Do you mean the pulse frequency, as in the frequency, calculated as:

$$frequency = \frac{lightspeed, c}{duration, 10ns}$$
No; sorry about the confusion. As Zapper said, it's really very basic. The duration, which your original question was about, is how long the laser fires for one particular pulse. The frequency that I referred to is simply how many of those pulses are fired per second.

Danger said:
snip...That's the reason that you can get such enormous energy density in a laser; if you take a couple of hours to pump 5 megawatts into a capacitor bank, then release it in a millisecond chopped into some picosecond pulses...
Just to be clear for the original poster's sake and the sake of people who may not know different, I believe that you mean that you would pump some number of joules (maybe 5 megajoules) into a capacitor bank rather than pumping 5 megawatts into it (unless you have a 5 MW power supply that you use to charge the bank and that's what you meant).

Danger
Gold Member
Geoff St. Germaine said:
(unless you have a 5 MW power supply that you use to charge the bank and that's what you meant).
That is what I meant. Thanks for the reminder not to use sloppy language here.