Gasdynamic light guide

The refractive index gradients in the gas flow in a radial flow convergent-divergent nozzle whose throat lies on the arc of a circle can create, in the neighborhood of the throat, a region capable of trapping and guiding light. Such a device, with a deflection angle of 90 degrees and a throat radius of 7.6 cm, is described. The shape, structure, and transmission characteristics of the light guiding region were investigated for a variety of nozzle conditions and light injection conditions. The data appear to form a consistent picture which gives a considerable degree of understanding of the light guiding region of this particular machine. Under optimum operating conditions, the transmission of the device was measured to be >0.996. The optical quality of this light guide was poor; however, there appears to be no fundamental limitation to developing gasdynamic light guides of much higher quality.