Quantum noise reduction in a passive optical bistable system with a coupled linear external cavity

We study the quantum noise in the output field of an optical bistable device with a coupled linear external cavity when the input light is a coherent field. Unlike a normal passive optical bistable device, if only the parameters of this system are chosen property (i) the reduction of quantum noise of the output field can be obtained not only near to the bistability turning points but also far away from the turning points; (ii) in some operating points the quantum noise reduction can be obtained for all frequency. © 1995.