Light source comprising a plurality of semiconductor lasers mounted in one can and optical measurement instrument comprising such a light source

A living body measuring instrument having a sub-mount (4) on which plural light-emitting devices (1,2,3) oscillating at different wavelengths are mounted in proximity, one optical output monitoring device (9) that detects the optical outputs of these light-emitting devices, wherein said light emitting devices and said monitoring device are mounted on the same heat sink and are housed in one can-package, a light-receiving device that detects a signal from a living body, and a circuit that separates the optical output signals from the light-emitting devices, wherein at least one light-emitting device has a light-emitting layer including a In 1-x Ga x As y P 1-y quantum well layer and a barrier layer on a GaAs substrate, the strain µ satisfies 0.4%‰ µ‰ 1.4%, wherein y in the composition satisfies 0.10‰ y‰ 0.45, and the wavelength of the emitted light is from 700 nm to 760 nm.