banie siriwardena <b3824855 <at> gmail.com> writes: > > > Hello All, > > Im trying to calculate the effective refractive index of a mode, and for this Im using the (display group velocities) function. > > One of the velocity outputs of my simulation is > > velocity:, 2, #(-4.90451745978336e-6 -4.90681942731539e-6 0.912710199555404), #(-4.80093195197473e-5 -4.8009048331541e-5 0.91561875483683), #(1.31121732587251e-5 1.30097505968729e-5 0.118793068102301), #(3.30328251620264e-4 3.30323377140027e-4 -0.300956120203374), #(4.63721694288894e-4 4.63785289361192e-4 -0.304113410536935), #(3.42546127623946e-7 -3.23401587667056e-7 0.0272995328645365), #(1.21167087607205e-4 1.24729489218949e-4 0.026147706220866), #(9.11879799925218e-4 9.14055080695155e-4 0.238485996216362) > > My waveguide is 3D, with the propagation in the z direction. So I have selected only the propagation velocity in the z direction (vz) (The 3rd component of any set of velocities) and used this to calculate the effective index as (1 / vz). (Since vz is in units of c and the effective index is c/ velocity inside the medium). But this gives me values of 1.1, 1.5 etc, where as the expected refractive index values are around 3.6 (This is a GaAs waveguide). > > Im getting the same results when I try to calculate effective index as k-z / k0. > > I have a feeling that Im getting the units of 'k' and 'group velocity' wrong. > Can you please let me know how to interpret my results and how to correctly calculate the effective index? > > Thank you very much.
Dear Banie, have you solved the problem? Dear Prof. Johnson, Dear all, Merry Christmas and Happy New Year to you all. I am running mpb 1.5, using libctl 3.2.1 and Guile 1.8.8. The group velocity computed using find-k command in strip.ctl example (supplied with the latest version of MPB) is 0.22638186725781. This implies the effective index of 1/0.22638186725781=4.4173. The problem is that the maximum refractive index (Si waveguide) used in this example waveguide is 3.45. How the effective index can be larger than the maximum refractive index? best wishes pavel > > > _______________________________________________ > mpb-discuss mailing list > mpb-discuss <at> ab-initio.mit.edu > http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/mpb-discuss _______________________________________________ mpb-discuss mailing list mpb-discuss@ab-initio.mit.edu http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/mpb-discuss
