Hi, I'm a newbie trying to learn from the book "Photonic Crystals" 2nd ed. (a True Masterpiece!). I have a simple question about how to interpret isofrequency diagrams like Fig. 14 & 15 of Chapter 10 (p. 222-225).

I expect that I can get the ordinary (reflective) Bragg condition: 2d cos(theta) = n lambda, [d = interplane distance = sqrt(2) * a etc] that is, if I fix the contour (omega = constant) and scan the incident angle (i.e., the dashed line in Fig. 14 Right), there should be a specific angle which satisfies the above condition and therefore gives a strong reflective peak (the opal color). I understand that the selected contour value in Fig. 14R (0.276) may be too low for the Bragg condition (we need a higher band), but nevertheless, I guess there must be a way to see such a general phenomenon via something similar to Fig. 14 (and the related discussion in the text). But I cannot see how to get this condition by looking at the isofrequency diagram or band contour plot. Could someone help me out? I'd appreciate it very much. Thanks! _______________________________________________ mpb-discuss mailing list mpb-discuss@ab-initio.mit.edu http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/mpb-discuss