A boundary-controlled aerodynamic window positioned adjacent the exit aperture of a gas laser is transparent to the laser beam emitted from the cavity of the laser. The boundary-controlled aerodynamic window is formed by a high velocity gas flow directed by a duct across the exit aperture for the laser beam isolating the low pressure region of the cavity from the high pressure of the atmosphere. The exit aperture is enlarged and an auxiliary gas flow injected along the sidewall of the duct adjacent the exit aperture to expand the thickness of the boundary layer. In a second embodiment, particulate matter is fixedly attached to the sidewall of the duct to increase the roughness of the wall surface. A third embodiment uses a plurality of nozzles, each injecting gas with a predetermined velocity.

An improved spatial filter for operation with high power laser beams is provided wherein a first gas flow system and a second gas flow system cooperate to enclose a cavity therebetween capable of accommodating a filter having an aperture located therein for spatially filtering the beam. The first and second gas flow systems are adapted for providing a first aerodynamic window across a beam entrance and a second aerodynamic window across a beam exit to maintain a selected gas pressure within the cavity while providing a transmission path for a high power laser beam. The first and second aerodynamic windows are in optical line of sight communication with one another through the aperture in the filter.

A laser beam scanning apparatus, a device for stabilization of the beam intensity distribution, the device comprising an air turbulence generator disposed adjacent a portion of the laser beam optical path and adapted to provide forced air flow substantially thereacross, the forced air flow tending to eliminate variations in the index of refraction of the air layers in the optical path.

An apparatus adapted for providing an aerodynamic window having a cylindrical configuration with an annular cross section capable of enveloping annularly a cavity therein is disclosed. The apparatus includes an annular injector adapted for providing a flow of first gas therefrom through a gas path having an annular cross section, an annular collector disposed in a spaced apart relation with the annular injector and adapted for collecting gas flowing through the gas path wherein the annular collector, the annular injector and the gas path cooperate to enclose a cavity therebetween and a gas insertion means for providing a flow of second gas within the cavity. In one embodiment electrodes disposed within the cavity are adapted for enhancing the energy level of the recipient elements of the second gas, as for example by ionization, to produce a high intensity light source. First gas passing through the flow path produces an aerodynamic window having an annular cross section capable of maintaining second gas within the cavity at a desired pressure level.

This invention is a method and apparatus for refracting a laser beam. The beam can be collimated, focused, or expanded by passing it along the longitudinal axis of a volume of gas which has a radial pressure gradient. The pressure gradient causes a corresponding gradient in density and refractive index. Such a gradient can conveniently be established by the use of a gas vortex chamber. A vortex chamber will act as a negative lens. It can be located at or near the focal point of a focused laser beam as a collimating element. A gas vortex lens is useable at power densities above those which conventional optical materials can withstand.