Multimode interference coupler, multi-layer optical planar waveguide using the same and method of manufacturing the same

A method of manufacturing a multi-layer optical planar waveguide, comprising the steps of:

• (a) forming a lower core layer at a given portion of a substrate;
• (b) coating a cladding material on the entire structure;
• (c) etching the cladding material so that a portion of a lower core layer at a region where a multimode interference coupler will be formed, thus forming a lower clad layer;
• (d) coating a core material on the entire structure;
• (e) etching the core material to form a multimode interference coupler and all upper core layer;
• and
• (f) coating the cladding material on the entire structure to form an upper clad layer.

A method of manufacturing a multi-layer optical planar waveguide, comprising the steps of:

• (a) forming the lower core layer at a given portion of a substrate;
• (b) coating the cladding material on the entire structure;
• (c) etching the entire cladding material down to the top of the lower core layer;
• (d) coating the core material on the entire structure;
• (e) etching the core material down to the top of the lower core layer remaining the multimode interference coupler region;
• (f) coating the cladding material on the entire structure;
• (g) etching the cladding material down to the top of multimode interference coupler region;
• (h) coating the core material on the entire structure;
• (i) etching the core material to form a multimode interference coupler and an upper core layer;
• and
• (j) coating the cladding material on the entire structure to form an upper clad layer.

A method of manufacturing a multi-layer optical planar waveguide, comprising the steps of:

• (a) Forming a lower core layer at a portion of a glass substrate using ion-exchanged method;
• (b) coating photoresist polymer the refractive index of which is changed by means of UV light on the entire structure;
• (c) forming an upper core layer at a portion in the photoresist polymer;
• (d) forming an upper clad layer on the entire structure;
• (e) locating a metal mask on the upper clad layer corresponding to a region where a multimode interference coupler will be formed;
• and
• (f) illuminating an UV light on the entire structure to form the multimode interference coupler and a lower clad layer in the photoresist polymer.