High efficiency gas laser with axial magnetic field and tunable

Abstract

A gas discharge laser includes a cylindrical symmetric discharge tube, having a prescribed gas therein at a low pressure, centered within a microwave-resonant cavity immersed in an axial magnetic field. Appropriate mirrors, optically aligned with a longitudinal axis of the discharge tube, are positioned at each end of the plasma column, one of which is partially transmissive. A pair of Brewster windows, or a pair of flat windows with antireflective coatings, one at each end of the discharge tube, are interposed between the mirror and discharge tube. Electromagnetic energy in the microwave range, e.g., greater than 1 GHz, is injected into the cavity and made to resonate in an appropriate mode. A large portion of the resonating energy is coupled into the discharge tube, causing a plasma to be created and maintained. The axial magnetic field confines the plasma to the center regions of the discharge tube, away from the walls, so as to form a plasma column. Sufficient energy to maintain a population inversion is imparted to the plasma column by the resonant electromagnetic energy. To the electromagnetic energy that propagates in the cavity, the configuration resembles a coaxial transmission line, with the plasma column functioning as the center conductor. The dominant loss of such coaxial cavity is to the plasma, thereby efficiently applying microwave power to the plasma.