Planar polymer waveguides with a graded-index profile resulting from intermixing of methacrylates in closed microchannels - Missinne, J; Misseeuw, L; Liu, X; Salter, P; Van Steenberge, G; Adesanya, K; Van Vlierberghe, S; Booth, M; Dubruel, P (Optical Materials, 2018)