An audio amplifier circuit comprises a voltage-gain amplifier and a current-gain amplifier in series between an input node and an output node. The semiconductor laser includes a semiconductor substrate, a semiconductor laminated structure containing a p-n junction, on the semiconductor substrate, and an electrode on the semiconductor laminated structure and joined to the submount via the solder. Each of the select gates 3a-3i, created by the division, is formed in a comb-like shape in which, when viewed from the direction of a normal line to a plane, a plurality of comb teeth extend from a common line. 2\u22661\u2212W\xb7\u03b8Pt\u22660.