Semiconductor laser device

Abstract

A quantum cascade laser device includes a QCL element and a package. A light-emitting window through which laser light emitted from the QCL element passes is provided on a side wall of the package. The light-emitting window includes a small-diameter hole, a large-diameter hole larger than the small-diameter hole, a counterbore surface having an annular shape that connects the small-diameter hole and the large-diameter hole, and a window member disposed inside the large-diameter hole. An incident surface of a window member includes a first region in which an anti-reflection film is provided, and a second region metallized and formed in an annular shape to be separated from the first region and to surround the first region. The second region is joined to the counterbore surface through a solder member.