A convergentdivergent nozzle for a gas turbine engine has a throat portion of non-constant radius of curvature varying from an upstream high value to an intermediate low value and then to a downstream high value. One embodiment of the current regulating device uses the temperature of the fluid in the electrolysis chambers to control the widths of the pulses delivered to the electrolysis chambers to regulate production. The signal light passes through a point of inflection in the center of the circuit, subsequently propagate clockwise from the interior to exterior of the circuit, and then exit output waveguides.