End device of optical waveguide and optical filter

An end device for an optical waveguide, which is formed on a semiconductor substrate and surrounded by a clad layer, wherein the end device is provided at a longitudinal end of a main waveguide portion of the optical waveguide, comprising:

• a converting portion for converting a condition of light confinement from a strong condition to a weak condition in a direction to an outside end of the converting portion;
• a bending structure portion connected to the outside end of the converting portion and formed in an arc shape on a plane parallel to a surface of the semiconductor substrate;
• and
• an intermediate extension portion formed between the converting portion and the bending structure portion for changing a direction of light transmitted from the converting portion,
• the bending structure portion being connected to the outside end of the converting portion through the intermediate extension portion,
• wherein the converting portion is formed in a taper shape having a first waveguide width and a second waveguide width, wherein the second waveguide width is smaller than the first waveguide width and a waveguide width of the converting portion is gradually decreased from the first waveguide width to the second waveguide width in a direction from the longitudinal end of the main waveguide portion to the outside end of the converting portion, and
• wherein the intermediate extension portion has a larger curvature radius than the bending structure portion.