Light Escalators in Optical Circuits Between Thick and Thin Waveguides

The invention relates to photonic circuits, in particular to photonic circuits where light is escalated transferred between optical waveguides which are coupled to photonic devices. A first waveguide (33a) on a silicon substrate (34) is provided having a first thickness and a first refractive index. A tapered second waveguide (32) having a second thickness less than the first thickness and a second refractive index higher than said first refractive index is deposited on the first waveguide. At least one layer of an optically active material (31) comprising a photonic device is deposited on the first waveguide adjacent to the second waveguide. The photonic device is interfaced with the wide end of the tapered second waveguide to provide an optical coupling, and the opposite narrow end of the tapered second waveguide is interfaced on top of the first waveguide to provide adiabatic light transfer between said first and second waveguides.