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Forum: Processes Involving Optical Photons
Re: Question how to add complex refrative index for a dielectric-dielectric surface
Date: 11 Apr, 2014
From: Gumplinger Peter <Gumplinger Peter>

Hi,

>  I am simulating a surface composed by a dielectric material with really small
> imaginary part,

I am afraid, the current code in G4 does not handle the situation where a dielectric material has an imaginary part and the 'finish' is defined as polished or ground.

I must suggest that you either ignore the imaginary part and define this 'Window's material (I presume we are talking about the 'Window' volume) as a dielectric with only a real index of refraction.

As an experiment - don't know if it'll work - you could, in addition to the above, but instead define the surface LiquidScintillator with Window as finish '...frontpainted' and give the surface's MPT the real and imaginary index.

> and a photocathode, which is also a dielectric material,

Originally in G4, only 'metal' surfaces are presumed to have a non-ignorable imaginary part. From the Application Dev. Man.:

The reflectivity off a metal surface can also be calculated by way of a complex index of refraction. Instead of storing the REFLECTIVITY directly, the user stores the real part (REALRINDEX) and the imaginary part (IMAGINARYRINDEX) as a function of photon energy separately in the G4MaterialPropertyTable. Geant4 then calculates the reflectivity depending on the incident angle, photon energy, degree of TE and TM polarization, and this complex refractive index.

Please, see how the photocathode is defined in this example:

http://www-geant4.kek.jp/lxr/source/examples/extended/optical/LXe/src/LXeMainVolume.cc#L244

In any case you want the photocathode to be dielectric_metal. The above 'experiment' may work and you may not have to ignore the tiny imaginary part for the window.

I am actually surprised why your photons not already vanish at the LiquidScintillator and Window interface. You must have define this surface as what?

(It may be possible for me to change the code so that the program also looks for a imaginary index for a dielectric material.)

Peter

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1 Question: Re: how to add complex refrative index for a dielectric-dielectric surface   (cyuchiash - 13 Apr, 2014)
(_ Feedback: Re: how to add complex refrative index for a dielectric-dielectric surface   (Gumplinger Peter - 14 Apr, 2014)
(_ Question: Re: how to add complex refrative index for a dielectric-dielectric surface   (cyuchiash - 15 Apr, 2014)
(_ Feedback: Re: how to add complex refrative index for a dielectric-dielectric surface   (Gumplinger Peter - 15 Apr, 2014)
(_ None: Re: how to add complex refrative index for a dielectric-dielectric surface   (cyuchiash - 20 Apr, 2014)
(_ Feedback: Re: how to add complex refrative index for a dielectric-dielectric surface   (Gumplinger Peter - 22 Apr, 2014)
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