Waveguide including first and second layers and manufacturing method thereof

A manufacturing method for a waveguide, the waveguide comprising:

• a core allowing light to propagate therethrough;
• and a cladding around the core, wherein
• the core is formed of a first dielectric material,
• the cladding is formed of a second dielectric material having a relative permittivity lower than that of the first dielectric material,
• the core includes a first layer and a second layer stacked in a first direction,
• each of the first layer and the second layer has a top surface and a bottom surface, and
• the top surface of the first layer includes a first region with which the bottom surface of the second layer is in contact, and a second region with which the bottom surface of the second layer is not in contact,
• the manufacturing method comprising:
• forming the core;
• and
• forming the cladding, wherein
• forming the core includes:
• a step of forming an initial first layer which later becomes the first layer, the initial first layer having a top surface including the first region and the second region;
• a step of forming an etching stopper layer on the second region of the top surface of the initial first layer;
• a step of forming an initial second layer on the initial first layer and the etching stopper layer;
• a first etching step of etching the initial second layer and the initial first layer so as to make the initial first layer into the first layer;
• and
• a second etching step of etching the initial second layer until the etching stopper layer is exposed, so as to make the initial second layer into the second layer.