Plate springs as coupling members can absorb deformation of an oscillator case
due to heat and do not transmit the deformation to two optical bases constituting
an optical resonator, and it is thereby possible to maintain an appropriate positional
relation between the optical cases. A harmful deformation force is produced due
to imperfect alignment deformation of bellows each of which is connected between
the oscillator case and each optical base. The plate springs can also suppress
the force acting on the two optical bases, and it is thereby possible to keep a
laser optical axis of a laser beam to be a fixed position.
