Semiconductor laser device

A semiconductor laser device comprising:

• a semiconductor laser array in which a plurality of active layers that emit laser lights with a divergence angle θS>4° in a slow axis direction are arranged in the slow axis direction;
• a collimating lens that collimates the laser lights emitted from each of the active layers in a plane perpendicular to the slow axis direction;
• a first optical element that reflects first partial lights advancing to one side in the slow axis direction from among each of the laser lights emitted from the collimating lens by a first reflecting surface and returns the first partial lights to each of the active layers via the collimating lens;
• and
• a second optical element that reflects a part of the mode lights of a plurality of mode lights of second partial lights advancing to the other side in the slow axis direction from among each of the laser lights emitted from the collimating lens by a second reflecting surface and returns the part of the mode lights to each of the active layers via the collimating lens,
• wherein the first optical element is disposed such that the first reflecting surface forms a first angle equal to or greater than 2° and less than θS/2 with respect to a plane perpendicular to an optical axis direction of the active layers, and
• the second optical element is disposed such that the second reflecting surface forms a second angle greater than −θS/2 and equal to or less than −2° with respect to the plane perpendicular to the optical axis direction of the active layers,
• wherein the second optical element is disposed in an optical path of zeroth-order mode light from among the plurality of mode lights of the second partial lights to reflect the zeroth-order mode light by the second reflecting surface and to return the zeroth-order mode light to each of the active layers via the collimating lens,
• the second optical element is formed to have a width smaller than the width of the second partial lights, and
• the second optical element is disposed substantially in the center in the width direction of the optical path of the second partial lights.