Re: measuring the pulse length of a nanosecond laser
- From: John McMillan <j.e.mcmillan@xxxxxxxxxxxxxxxxxxxxx>
- Date: Mon, 30 Apr 2007 10:05:04 +0100
In article <1177689223.353838.195260@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
meto <metelek83@xxxxxxxxxxx> wrote:
Hello
I want to measure the pulse length of a nanosecond laser(at 532nm Nd-
Yag) with a photodiode.
I could not find the correct photodiode to measure it.
Our lasers beam length is approximately 4-5 nanoseconds but I don't
know the exact length and I wanna learn it.
Can you suggest me a detector anf manufacturer for measuring it.
If you have another idea to measure the pulse width can you let me
know?
Thanks
This isn't a trivial measurement. After you've converted your light
pulse to an electrical signal with your photodiode, you have to measure
the width of the electrical signal. If its 4ns then to get a good
measurement with an oscilloscope you'll need a 2GHz bandwidth machine.
You might get away with 1GHz, check the risetimes of the instrument.
You might be able to work on the signal with fast discriminators and a
time-to-digital converter (TDC) but setting up without a fast scope is
likely to be a problem.
There is a very clever technique for measuring the widths of nanosecond
light flashes - called the single-photon technique, also known as
"time correlated single photon counting".
It uses devices whose time response is comparable with the light
flash being measured - and samples over many flashes to derive
the shape.
The original paper is
Bollinger L M and Thomas G E 1961 Measurement of the
time dependence of scintillation intensity by a delayed coincidence
method
Rev. Sci. Instrum. 32 1044-50
If you put Bollinger Thomas photon into google or similar you'll find
lots of info.
.
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