Semiconductor laser device, and image forming apparatus

A semiconductor laser device comprising:

• a semiconductor laser chip having a first light-emitting surface which is formed on one end face of said semiconductor laser chip and outputs a plurality of front beams from a plurality of light emitting portions, and a second light-emitting surface which is formed on another end face opposite to said first light-emitting surface and outputs a plurality of back beams from a plurality of light emitting portions, corresponding to the plurality of front beams;
• and
• back beam detection means formed to face said second light-emitting surface and having a plurality of photodetection portions for independently detecting the plurality of back beams output from said second light-emitting surface, said back beam detection means being in contact with said second light-emitting surface of said semiconductor laser chip,
• wherein said back beam detection means comprises (i) a first semiconductor layer of a first conduction type having a surface facing said second light-emitting surface, (ii) a second semiconductor layer of a second conduction type provided by implanting a donor into a region of a surface of said first semiconductor layer opposite to the surface facing said second light-emitting surface to form a pn junction with said first semiconductor layer, said region having an area smaller than said first semiconductor layer within a plane parallel to said second light-emitting surface, and (iii) a pair of electrodes formed respectively on surfaces of said first and second semiconductor layers opposite to surfaces facing said second light-emitting surface, and
• wherein one of said pair of electrodes is used in common with the plurality of photodetection portions.