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Forum: Processes Involving Optical Photons
Re: Question Optical Photons Spectrum (Dragos Constantin)
Re: Feedback Re: Optical Photons Spectrum (Gumplinger Peter)
Re: More Re: Optical Photons Spectrum (Gumplinger Peter)
Re: More Re: Optical Photons Spectrum (Gumplinger Peter)
Re: Idea Re: Optical Photons Spectrum (Benton Pahlka)
Date: 26 Jan, 2011
From: Dragos Constantin <Dragos Constantin>

Thank you Benton. I saw your previous posting as well and I have used your method from the start but I wanted to understand more what is going on here. A resolution of 1/nm is more than enough to correctly sample the emission spectrum. However, the sampling procedure gives me optical photons in regions where I should have no photons at all. I will post back once I am finished with my investigation.

Regards, Dragos

On Fri, 21 Jan 2011 23:21:27 GMT, Benton Pahlka wrote:

> Hi,
> 
> Just my two cents. For my simulations, I have text files that I read in
> for each optical property. Each file contains 500 data points, one for
> each integer wavelength (which I convert to from the energy), in a range
> from 200 nm to 700 nm (as this is the relevant range for my purposes). I
> read the files in and store them in an array. This produces very smooth
> output spectra for me.
> 
> Benton
> 
> On Fri, 21 Jan 2011 23:05:55 GMT, Gumplinger Peter wrote:
> 
> > I'll try to explain the photon energy sampling with words although a
> > simple graph would explain it much better and easier.
> > 
> > If you have a spectrum that is defined at discrete locations and you
> > want to sample from this spectrum, you have the two simplest choices:
> > 
> > (1) You can either brute force sample with the rejection method - slow -
> > or (2) you can resort to the faster integral method. The integral method
> > was chosen.
> > 
> > This means that you need to first integrate the spectrum and make a new
> > vector which is monotonically increasing and holds the integral of the
> > spectrum to the left of the bin in question. The (linear) integral of a
> > spectral bin F(x) is the width of the bin times the average y=f(x) at
> > the bin's edges.
> > 
> > During simulation a flat random number is taken from zero to the
> > integral vector's largest entry: Y_max=F(x_max). For this number (Y) we
> > now find the corresponding integral vector's left bin, x_i, then sample
> > x above the bin's lower limit, x_i, by linearly interpolating the
> > integral vector's entries at the bin edges, F(x_i) and F(x_i+1).
> > 
> > If you think about it, what that produces is a flat spectrum in x (the
> > photon energy) within the bin because the line connecting the bin's
> > edges Y_i=F(x_i) and Y_i+1=F(x_i+1) is a straight line.
> > 
> 

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