Method of manufacturing optical coupler, optical coupler, photoelectric conversion circuit module, and optical transceiver

A method of manufacturing an optical coupler, the method comprising:

• preparing a light-transmitting substrate having a first main surface and a second main surface aligned in a first direction and containing a third filler;
• applying a first photosensitive glass paste to the first main surface;
• arranging a grayscale mask formed in a binary pattern on the second main surface;
• emitting an ultraviolet ray to the second main surface to expose the first photosensitive glass paste;
• removing the grayscale mask from the second main surface and developing the first photosensitive glass paste;
• and
• removing the light-transmitting substrate from the first photosensitive glass paste developed and curing the first photosensitive glass paste, wherein
• a longest length of the third filler is larger than a wavelength of the ultraviolet ray.

An optical coupler comprising:

• a first glass part containing first glass and a first filler mixed in the first glass;
• and
• a second glass part that contains at least a second glass and is connected to the first glass part, wherein
• (1) the second glass part contains a second filler mixed in the second glass, and a content of the second filler contained in the second glass part is lower than a content of the first filler contained in the first glass part, or
• (2) the second glass part does not contain the second filler.

An optical coupler comprising:

• a first glass part;
• and
• a transparent part connected to the first glass part, wherein
• the first glass part contains glass and a first filler mixed in the glass,
• the transparent part contains a medium and a second filler mixed in the medium, and
• a longest length of the second filler is different from a longest length of the first filler.