Help with Dielectric Constants

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Discussion Overview

The discussion centers around the dielectric constants of TiO2 (rutile) as a function of wavelength, specifically focusing on the real and imaginary components. Participants explore the differences between these dielectric constants and single values found in reference materials, as well as their implications for simulations and calculations involving optical properties and waveguiding effects.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant seeks updated resources for the dielectric constants of TiO2 (rutile) and questions the completeness of existing references like Palik's book.
  • Another participant inquires about the specific wavelength or frequency range of interest, suggesting that a tensor dielectric constant may be necessary for simulations involving ordinary and extraordinary axes.
  • A participant expresses interest in the 300-500 nm range and questions whether a tensor dielectric function is required for calculating waveguiding effects, noting confusion over a website that provides indices of refraction in terms of ordinary and extraordinary axes.
  • One participant explains birefringence in the context of rutile, highlighting the differences in index of refraction based on polarization and the implications for light propagation through the crystal.
  • A suggestion is made to consult "the handbook of optical constants" for further information.

Areas of Agreement / Disagreement

The discussion reflects a lack of consensus on the necessity of using a tensor dielectric constant for specific applications, as well as differing opinions on the relevance of ordinary and extraordinary axes in the context of the participant's problem.

Contextual Notes

Participants express uncertainty regarding the appropriate use of dielectric constants in simulations and calculations, particularly in relation to the polarization of light and the geometry of the crystal. There are also references to varying definitions and contexts for dielectric constants in different sources.

excalibur313
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Hi Everyone,
I am trying to find the real and imaginary dielectric constants for TiO2 (rutile) as a function of wavelength. Could anyone suggest a good place to find something like this? Palik has a nice book but it is incomplete, so I'm not sure if there is something newer. Also, could someone help me sort out the difference between those dielectric constants and the single values that you sometimes find. (Like in the CRC) When is it appropriate to use one or the other? Also, I found a cool website that will calculate the ordinary and extraordinary ray- is this related or is it a different concept?
Thanks for your help!

PS- Also, I notice in Palik that they give values of n and k both parallel and perpendicular. For a FDTD calculation for trying to determine coupling with a metal nanoparticle, for example, what is more appropriate to use?
 
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What wavelength or frequency range are you interested in?

For simulation you'd need a tensor dielectric constant to capture the ordinary/extraordinary axes. Most FDTD codes aren't set up for this.
 
I'm interested in the 300-500 nm range. So do you mean that in order to theoretically capture ordinary/extraordinary axes you have to use a tensor dielectric function? Is that required when calculating waveguiding effects? I only mentioned it because when searching for dielectric constants online I cam across this website:
http://www.luxpop.com/
and I was confused why it gave the index of refraction in terms of ordinary/extraordinary axes. I hope that it is just extraneous to this particular problem.

I guess I was just hoping that I could enter in a table like they have for silicon or a metal where it has one n and k, but this seems like it would be more complicated. For what its worth, I would be pointing the plane wave light source right at the crystal so I wonder if that would allow me to only use one set of constants.

I appreciate the fast response!
 
Do you know what birefringence means?
In a crystal like rutile, which crystallizes in the tetragonal system, the index of refraction for a wave is different for whether it is polarized parallel or perpendicular to the four-fold axis. Hence an arbitrarily polarized ray is split into an ordinary and an extraordinary ray polarized parallel and perpendicular to the axis, respectively, for which also n and k are different. Only for a ray traveling along the optical axis, this splitting does not occur.
 
Try "the handbook of optical constants."
 

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