PRIMES LDS software is a well known tool for M2 measurements for laser beams. Anyone working with the software? Want to know the reason for taking multiple planes to measure M2. When we want to take a final result, which plane should be looked in to? If we are measuring a closer to a single mode beam, does each plane should give a Gaussian intensity distribution?
I haven’t used the PRIMES beam profiler before, but generally the divergence and spot size (=BPP) is closely related to the beam quality. Just taking a single plane of measurement and fitting a Gaussian on it won’t tell much about the divergence. It might give a close enough value for close Gaussian beams but what if you have higher order modes involved (rings, spots etc) in your beam profile?
In a extreme case if you have a multimode laser with flat-top beam profile, a single measurement will be rather useless without the caustics / divergence.
Thanks, In my case the M2 value is closer to 1.2. I have noticed a donut like shape in one plane but other planes show Gaussian like profiles. What is the reason for that? So far we have concluded that it might be due to some aberrations of the lens, but I would like to know more.
That’s hard to say exactly why you see a donut shape. It could be the laser or the optics too. Some Chinese high average power lasers use not very well process controlled LMA fiber and it can happen that the fiber supports other than the ground mode and some of the light leaks into it. If this is the case, you might be able to increase the amount of light in the donut mode by bending the fiber more.
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