Semiconductor laser device

A semiconductor laser device comprises: a semiconductor laser including laser resonators for emitting laser beams forward and backward oppositely along a plurality of parallel axes; a photodetector including a plurality of photodetector elements for detecting intensities of the laser beams emitted backward; and a waveguide located between the semiconductor laser and the photodetector for guiding the backward emitted laser beams to the corresponding ones of the photodetector elements, the waveguide including a plurality of guide grooves for guiding the backward emitted laser beams.