Intensity characterization of laser pulses

  • #1
LuL
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I am using the fluroescence spectroscopy technique to obtain the fluorescence spectrum of exposed neuroblasts to uv radiation (355 nm) from a Nd:YAG source and I need to characterize the radiation pulses of the laser. Specifically, I use a spectrometer (Avantes brand) with integration time of 250 ms, to obtain the average intensity (a.u.) in a specific number of pulses, I modify the average of scans. I'm supposed to get fluctuations in intensity but I get a decay. I understand that the spectrometer detects less energy because I expose the sample less time to radiation. Then I can not find a way to get the fluctuations of intensity in the different numbers of pulses. Standard deviation. I'm really confused
 

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  • #2
Charles Link
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For the laser, I suggest you measure the pulses without a spectrometer. Silicon photodiode detectors should be commercially available and the output can be displayed on an oscilloscope. You may need something such as an integrating sphere to attenuate the signal, with the detector placed a good distance from the output port of the integrating sphere. To see what the individual pulses are doing, you can see the results, and take many readings from the oscilloscope.
 
  • #3
LuL
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Thank you very much for the reply. But I do not have an integrating sphere.
 
  • #4
Charles Link
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Thank you very much for the reply. But I do not have an integrating sphere.
You can also use a diffuse surface, and scatter the laser off of it. You may get some specular reflection along with the diffuse scattering. In any case, a diffuse plate can make a good attenuator. Most lasers are too bright to aim them directly at a photosensor.
 

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