Regenerated grating produced in a multimaterial glass-based photosensitive fiber with an ultrahigh thermal regeneration ratio by Yang, Hang Zhou, Paul, Mukul Chandra, Das, Shyamal, Dhar, Anirban, Qiao, Xue Guang, Nazal, Nurul Asha Mohd, Lim, Kok Sing, Ahmad, Harith