Re: Different results of PhC waveguides by using triangular lattice and rectangular lattice

On Nov 24, 2009, at 3:15 PM, JiangjunZheng wrote:
> The half of the modes I means that by using the rectangular lattice,  
> the number of the waveguide modes is smaller than that by using  
> triangular lattices. Could you please help me checking the following  
> codes? It uses the rectangular lattice. It should be very simple for  
> you. For W1, the results are different for the triangular and  
> rectangular lattices, too.


For one thing, you don't say what your triangular lattice code looks  
like; maybe you have bugs there.  You also don't say how you are  
counting waveguide modes.

For another thing, remember that the boundary conditions are  
periodic.  If you take your structure and imagine repeating it  
periodically in the lateral directions, you'll see that the two  
lateral sides of your unit cell don't match up. This means that you  
effectively have an additional line defect at the edge of your  
rectangular supercell, which is not what you want.  You need to add  
another half a period to each side in the lateral direction to make  
them match.

Steven