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We would like to implement a very fast beam limiting, so far google search shows that the common threshold ranges is in 1J/cm^2 or more, this could take seconds to activate as our laser ranges from 1 mW to 30 mW only.

Can you please suggest a low-threshold optical beam limiter, the most common one.

Or an easy method to fabricate such. I would be very grateful if you could give links and references.

Optical beam limiter: A material that does not permit the passage of laser when a certain intensity is reached. But when below certain intensity threshold it would allow laser to pass.

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  • $\begingroup$ A simple mechanical aperture with an electronic intensity measurement will do just that or you could directly modulate the laser. It is not clear to me why you need an active optical material for this purpose. $\endgroup$
    – CuriousOne
    Commented Sep 17, 2015 at 12:10
  • $\begingroup$ From the powers quoted, it sounds as though you might be trying to do this for laser safety reasons, to keep the beam automatically class 3R. Is this so, because this fact will impact on a correct answer. $\endgroup$ Commented Sep 17, 2015 at 13:07
  • $\begingroup$ @WetSavannaAnimalakaRodVance: Interesting observation. In that case, shouldn't we advise the OP to engineer the safety for the highest expected beam power rather than trying to engineer around the safety regulations? I can, for the life of me, not think of a reason to sacrifice beam quality for some savings on the safety side, which any form of beam modulation will do. Covering an experiment is easy and cheap, losing an eye is priceless. $\endgroup$
    – CuriousOne
    Commented Sep 17, 2015 at 13:34
  • $\begingroup$ We will use it to switch off our optical device when the intensity of the laser doubles (= 0.125mW of 1mW, other portion of the laser will go to other optical device). $\endgroup$
    – Jones G
    Commented Sep 17, 2015 at 17:14
  • $\begingroup$ @CuriousOne Aboslutely, that's why I want to know. ISO60825 talks about reasonably foreseeable conditions, and this would rule out trying to "detect and block" aside from in the most extreme cases when it is unavoidable and then you would use multiple redundant detection systems. The class 3R is one to be especially careful of, because an accidental viewing of class 3R, whilst temporarily blinding, seldom leads to permanent damage in a healthy retina with a healthy blink response. Class 3B often leads to permanent damage, so this is an especially important threshold we're talking about. $\endgroup$ Commented Sep 18, 2015 at 3:32

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