On-chip beam rotators, adiabatic mode converters, and waveplates through low-loss waveguides with variable cross-sections by Sun, B, Morozko, F, Salter, PS, Moser, S, Pong, Z, Patel, RB, Walmsley, IA, Wang, M, Hazan, A, Barré, N, Jesacher, A, Fells, J, He, C, Katiyi, A, Tian, Z-N, Karabchevsky, A, Booth, MJ