High speed laser sensing

laserphotodiode

I have the following setup…
A laser-pointer pointing downwards at an angled 45 degree mirror which is rotating at about 600-2200rpm on a high speed electric motor.
As the mirror rotates the laser dot is reflected outwards around the room and moves sideways along the walls of the room in a large circle.
I want to be able to detect this laser dot when it passes a point with an optical sensor on the wall but the speed at which the laser moves means it doesn't focus on a photodiode with a circuit long enough to saturate it and turn it on.

The main solutions I've researched so far have been avalanche photodiodes and transimpedance amplifiers to increase the sensitivity and response time however I haven't found many reference circuits built for similar applications; I'm also concerned about other light setting it off but one problem at a time I suppose!

Can anyone recommend an area to research or material that would be worth reading or if possible a circuit solution to the issue that might be of use?

Many thanks for any help offered

Best Answer

While I don't know all the design or budgetary constraints of your problem, from the technical point of view it should be very doable. I would find a narrow bandpass optical filter (with the center of the band at the wavelength of the laser) that I would place in front of my optical detector to filter out all the stray light. While APD (or even a PMT) would give you the best results, optical PIN diode (check Hamamatsu diodes) would suffice for your application. You just need to follow it with a good quality amplifier.

As to the research material, I would look up stuff on the design of flow cytometers or other flouresence detection systems. These instruments are able to detect much weaker optical signals at a rate of 10k events/second.