A gas laser emits an output laser beam from a low pressure region to a region having a higher pressure. This is done through an opening in the side of a laser device. Under normal circumstances, the provision of such an opening would incur a flow of air from the high pressure side, externally of the laser device, to the low pressure side within the device. To prevent this, an aerodynamic window is placed in a passageway leading from said opening in the laser device through which the laser beam passes. A gas flow is passed across said passageway which will provide a flow segment having a pressure differential across the segment which is equal to that between the low and high pressure regions. When such an aerodynamic window is used in an aircraft and the aircraft experiences changes in altitude, the pressure differential across the flow segment changes. By using a multi-element nozzle array to provide the aerodynamic window flow, where each element of the array contains its own supply valve, changes in pressure differential are accommodated by throttling the individual elements.
A multiple shock aerodynamic window for use within a laser system. The aerodynamic window provides separation between the pressure within the laser cavity and the ambient pressure adjacent thereto. Making up the aerodynamic window is an entrance duct and a capture duct situated transverse to a laser beam output passageway leading from the laser cavity. A wedge-shaped element is located in the entrance duct, partially protruding into the passageway. A diffuser vane is located in the capture duct. Upon the passing of a supersonic flow of gas through the entrance duct at least two shock waves are generated at the wedge-shaped element and cross the passageway.The diffuser vane intersects at least one of the shock waves thereby substantially reducing flow separation in the capture duct. In addition, the entrance wall of the capture duct may be inclined at an angle of approximately 16.degree. in order to assist the diffuser vane in the reduction of flow separation in the capture duct.
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.
