A laser includes: a substrate; a first reflector including pairs of high and low refractive index layers; an active region forming a resonator; a second reflector including an emission surface and pairs of high and low refractive index layers; an extending region thicker than oscillation wavelength, extending the length of the resonator, and including a conductive semiconductor material; a confining layer including a high refractive index region and a surrounding low refractive index region; and an additional film allowing the oscillation wavelength to transmit therethrough. The first and second reflectors, the extending region, and the active region determine a reflection band including resonance wavelengths, in one of which oscillation occurs. The additional film includes central and outer circumferential portions having different thicknesses to suppress resonance in the high refractive index region and the extending region. The central and outer circumferential portions overlap the high and low refractive index regions, respectively.