Submount, submount assembly, and submount assembling method

A light-emitting device comprising:

• a base;
• a fusion-bonding material layer formed on a first surface of the base;
• and
• a semiconductor light-emitting element including a waveguide fixed on the first surface, an axis line of the waveguide is inclined at and angle of θWG, and made of a semiconductor material with a refractive index nLE,
• wherein at least one alignment mark is formed in the fusion-bonding material layer, the alignment mark having an axis line of the alignment mark that is an extension direction of the alignment mark or a straight line connecting two of the alignment marks, the axis line of the alignment mark being aligned at an angle relative to an axis line of the base,
• wherein the alignment mark is aligned at an angle θSM=sin−1[nLE·sin(θWG)/n0], where a refractive index of a light-transmitting medium in proximity to the outside of the light-incident/emission end surface of the semiconductor light-emitting element is no, θWG is an inclination angle of an axis line of the waveguide, and nLE is a refractive index of the semiconductor material of the waveguide,
• wherein the fusion-bonding material layer has a laminate structure including a first fusion-bonding material layer and a second fusion bonding material layer formed in order from the first surface side, and
• wherein the alignment mark is configured from an opening formed in the first fusion-bonding material layer that exposes a portion of the second fusion-bonding material layer underneath.