line-defect waveguide

Sir,



I have to design a structure with SOI as substrate and Si layer over it 
with air holes etched.my aim is to achieve slow light .



I have used extension code available on net for Dispersion calculation. I 
am having trouble understanding the output of the extension code.I tried 
running the code with some changes according to my ctl file I am getting 
outputs attached in file named group index. please guide as I am getting 
confusing(-ve group index values)  results.if u can provide an email 
address iwould like to mail my results and ctl file