Integrated optical structures include a first wafer layer, a first insulator layer directly connected to the top of the first wafer layer, a second wafer layer directly connected to the top of the first insulator layer, a second insulator layer directly connected to the top of the second wafer layer, and a third wafer layer directly connected to the top of the second insulator layer. Such structures include: a first optical waveguide positioned within the second wafer layer; an optical coupler positioned within the second wafer layer, the second insulator layer, and the third wafer layer; and a second optical waveguide positioned within the third wafer layer. The optical coupler transmits an optical beam from the first optical waveguide to the second optical waveguide through the second insulator layer.