Calculating Light Intensity in Diffraction Orders

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Discussion Overview

The discussion revolves around calculating the intensity of light produced by diffraction orders when a laser beam interacts with a diffraction grating. Participants explore how to estimate the percentage of light intensity in the zeroth and first diffraction orders, considering the complexities involved in the calculations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about calculating the intensity of light in the zeroth and first orders of diffraction, seeking a rough percentage figure without needing exact calculations.
  • Another participant suggests that intensity is related to the square of the amplitude of the wave and asks if the amplitude can be calculated based on where the maximum occurs.
  • A different participant expresses uncertainty about calculating amplitude but notes that if the zeroth and ±1 orders account for 100% of the light, there may not be a general rule for the intensity percentages between these orders.
  • One participant mentions that the answer may depend on the blaze angle of the grating, indicating a variable factor in the calculations.
  • Another participant acknowledges the need for more specific information about the grating, suggesting that the blaze angle might be optimized for a particular wavelength, affecting the intensity distribution.
  • One participant offers a method to calculate the interference pattern and suggests squaring the amplitude at specific points, while also referencing external resources for further learning.

Areas of Agreement / Disagreement

Participants express varying levels of uncertainty regarding the calculations and factors influencing light intensity in diffraction orders. There is no consensus on a specific method or outcome, and multiple views on the dependencies of intensity calculations remain present.

Contextual Notes

Limitations include the lack of specific details about the grating and laser, as well as the dependence on factors such as the blaze angle and wavelength, which are not fully resolved in the discussion.

u0362565
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Hi,

I was wondering how you can calculate the intensity of light produced by diffraction orders. If say a laser was incident on a diffraction grating and this split the zeroth and +-1 orders what percentage of the light intensity is within the zero and first orders and how can you work this out? I'm only looking for a rough percentage figure i don't actually need to calculate exact figures, i imagine that is possible if details of the grating/laser were known..

Many thanks
 
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No i don't think i can, i know the power at the output of the laser cavity and the wavelength but I'm not sure how i could calculate the amplitude. However if the laser incident on the grating is only split into zero and +-1 orders and that constitutes 100% of the light then there isn't a general rule of thumb for what approximate light intensity percentage the zeroth would contribute relative to the -+1 orders?
Thanks
 
That's interesting I've not come across blazing before, I think I need more specific info about the grating to work this out, the grating transmits multiple wavelengths so perhaps the blaze angle is optimised for one wavelength only and the rest are a compromise.
Thanks
 
You can calculate the interference pattern, then you square the amplitude of the wave of the point you want. There are very good videos on youtube that teach how to do that. Search for single slit diffraction and double.
Sorry I cannot help more, I am very very busy right now =(
 
Ok thanks i'll take a look. Thanks for your help!
 

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