Optimization of band gap of photonic crystals fabricated by holographic lithography X.-L. Yang, L.-Z. Cai, Y.-R. Wang, C.-S. Feng, G.-Y. Dong, X.-X. Shen, X.-F. Meng and Y. Hu EPL, 81 1 (2008) 14001 Published online: 22 November 2007 DOI: 10.1209/0295-5075/81/14001