Optical apparatus and methods of manufacture thereof An optical apparatus (20) for evanescently coupling an optical signal across an (interface (30) is described. The optical apparatus (20) comprises a first substrate (22) and a second substrate (24). The optical signal is evanescently coupled between a first waveguide (26) formed by laser inscription of the first substrate (22) and a second waveguide (28) of the second substrate (22). The first waveguide (26) comprises a curved section (34) configured to provide evanescent coupling of the optical signal between the first and second waveguides (26, 28) via the interface (30).