Re: How to set k-points in piperiod pc waveguide?

"Steven G. Johnson" <[email protected]>
Newsgroups gmane.comp.science.photonic-bands
Message-ID <[email protected]>
On Feb 20, 2009, at 4:02 AM, [email protected] wrote:
>   I design a PC waveguide , but the period of waveguide is not equal  
> to the period of crystal .When i calculate the mode of  the  
> waveguide , how to set the k-point ?
>

If the periods are commensurate, then the period should be the least  
common multiple of the two periods.

If the periods aren't commensurate (i.e. one is not a rational  
multiple of the other), then you don't really have a "waveguide"  
because you don't have translational symmetry.

The "k" is only meaningful with respect to the actual period of the  
structure (if any), which is the least common multiple (if any).  "k"  
comes from periodicity (via Bloch's theorem).  See e.g. our book ab- 
initio.mit.edu/book

Steven
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