A package for hermetically sealing a semiconductor laser which outputs
light having a wavelength of 1.1 .mu.m or more is filled with a gas
containing an oxidizing gas such as oxygen or ozone. The oxidizing gas in
the package oxidizes hydrogen in the package to prevent hydrogen
embrittlement of electrodes that applies stress on electrodes and to
suppress variation in the emission wavelength which would otherwise result
from the application of stress.
