Tunable wavelength filters using polymer long-period waveguide gratings based on metal-cladding directly defined technique
Wang Ji-Hou, Chen Chang-Ming †, Zheng Yang, Wang Xi-Bin, Yi Yun-Ji, Sun Xiao-Qiang, Wang Fei, Zhang Da-Ming
       

(color online) Relations between the core thickness b and TM mode effective refractive indices of (a) the core and (b) the cladding for the resonant wavelength.