Chip mode converter for light source isolation

A method of forming an optical device, comprising:

• forming a first pattern of photoresist material over a wafer that includes a bottom layer and a device layer disposed on the bottom layer by performing a photolithography process;
• forming a first waveguide and a second waveguide on the bottom layer by removing part of the device layer through an etching process using the first pattern of photoresist material as an etching mask;
• and
• forming a first material layer in an exposed portion of the bottom layer that surrounds the first and second waveguides,
• wherein the first waveguide has a first width and includes a body section and two or more tapering arm sections connected to the body section at a junction section, and each tapering arm section is connected to the body section through a bent section,
• wherein the second waveguide has a second width and includes a first end spaced apart from the junction section of the first waveguide by a first gap, wherein the second width is smaller than the first width.

An optical device, comprising:

• a plurality of unit optical devices;
• and
• a plurality of optical combiners configured to connect the plurality of unit optical devices in cascade,
• wherein each of the plurality of unit optical devices comprises:
• a first waveguide having a first width and including a body section and two or more tapering arm sections connected to the body section at a junction section, each tapering arm section connected to the body section through a bent section;
• and
• a second waveguide having a second width and including a first end spaced apart from the junction section of the first waveguide by a first gap.