A semiconductor laser apparatus includes a substrate, a vertical-cavity
surface-emitting semiconductor laser diode (VCSEL) including a first and
second mirror layers of a first and second conduction types,
respectively, an active region between the first and second mirror
layers, a first and second electrode layers electrically connected with
the first and second mirror layers, respectively, and at least one Zener
diode including a first and second semiconductor regions of a first and
second conduction types, respectively, and a third and fourth electrode
layers electrically connected with the first and second semiconductor
regions, respectively. The second semiconductor region is formed in a
portion of the first semiconductor region and forms a PN junction with
the first semiconductor region. The VCSEL and the Zener diode are formed
on the substrate. The first and second electrode layers are electrically
connected with the fourth and third electrode layers, respectively.