Two waveguide layers in lithium niobate crystal formed by swift heavy Kr ion irradiation
Liu Taoa), b) , Huang Qingc) , Zhao Jin-Huad) , Kong Wei-Jina), b) , Liu Penge) , Zhang Liane) , Zhou Yu-Fane) , Yu Xiao-Feie) , Wang Leie) , Wang Xue-Line)† 
