Abstract: A laser is disclosed which includes a gain medium, a switch element, and a pulse controller. In one embodiment laser light of differing polarizations pass along respective paths and a pulsed laser output is generated via an electro-optical element. In another embodiment light of differing polarizations passes in differing directions through a cyclical path. The invention can make use of a prism-shaped polarizer having a polarization selection face and two further faces. Yet further initial pulses can be controlled to reduce energy, for example by progressively increasing the period or amplitude of successive pulses. As a result an efficient and high power laser apparatus is realized.

Abstract: A semiconductor laser module according to the present invention has a semiconductor laser element for outputting a laser beam and a package hermitically containing and sealing the semiconductor laser element. The package has a vent for introducing and/or exhausting a low heat conduction type gas into or from the package. The vent is hermetically sealed by swaging and welding the external end thereof after the low heat conduction type gas has been introduced into or exhausted form the package.