Analysis on propagation properties of the eigenmodes in nonplanar ring resonators Dong Li, Jianlin Zhao, Dandan Wen and Yajun Jiang Eur. Phys. J. Appl. Phys., 63 3 (2013) 30501 Published online: 03 September 2013 DOI: 10.1051/epjap/2013130114