Semiconductor laser module

A semiconductor laser module comprising:

• a semiconductor laser outputting a laser light, output from an output facet side of a waveguide having a refractive index waveguide structure, via a lens system, the waveguide having, from a rear facet side opposite to the output facet and in an order of, a first narrow portion formed to be identical in width, a wide portion formed to be wider than the first narrow portion, a second narrow portion formed to be narrower than the wide portion, a first tapered portion being formed between the first narrow portion and the wide portion and increasing in width toward the wide portion, and a second tapered portion being formed between the wide portion and the second narrow portion and decreasing in width toward the second narrow portion, a width of the second narrow portion being within 2.0 μm to 5.0 μm, an inclination angle θ indicated as θ=arctan [(ΔW/2)/Lt2] being equal to or smaller than 0.6 degrees in a case where ΔW indicates a difference between a width of the wide portion and a width of the second narrow portion of the waveguide and Lt2 indicates a length of the second tapered portion, Ln2≧106θ−0.00681 (where 0.47<θ≦0.60), Ln2≧317θ−100 (where 0.32<θ≦0.47), and Ln2>0 (where θ≦0.32) holding true in a case where Ln2 indicates a length of the second narrow portion, and a length of the first narrow portion of the waveguide being equal to or greater than 30% of a cavity length defined by the output facet and the rear facet;
• a package enclosing the semiconductor laser and having a portion having a first coefficient of thermal expansion and an opening passing and extending through an outer wall thereof;
• a ferrule, passing through the opening at the portion of the package, extending so that a gap is formed between the ferrule and the package, having a second coefficient of thermal expansion smaller than the first coefficient of thermal expansion, and having a path having a predetermined inner diameter and extending in a longitudinal direction;
• a glass solder, filling the gap between the ferrule and the portion of the package, being compressed by the portion due to a difference between the first and the second coefficients of thermal expansion, and forming a hermetic sealing between the ferrule and the portion of the package;
• the optical fiber passing and extending through the ferrule to align with the semiconductor laser and having an outer diameter smaller than an inner diameter of the path extending in the longitudinal direction by equal to or smaller than 50 μm;
• and
• an adhesive hermetically sealing the optical fiber in the path extending in the longitudinal direction.