A semiconductor laser is disclosed with which a VCSEL can be constituted
with a simplified configuration for optical transmission at a
transmission rate higher than 10 Gbps. The semiconductor laser includes a
resonator including a first active region able to emit light in response
to current injection and a second active region able to emit light in
response to external excitation light. Multilayer film reflecting mirrors
sandwich the resonator from two opposite sides. The first active region
and the second active region generate light at a wavelength the same as
the resonance mode of the resonator.