ObjectiveThe squeezed states can not only verify the fundamental principles of quantum physics, but also have important applications in the field of quantum information processing. In the field of quantum communications, the speed and fidelity of communication depend on the squeezing degree of the squeezed states. A degenerated optical parametric amplifier (DOPA) is efficient approach on the production of the squeezed states. In the paper, a coherent feedback controlled cascaded DOPA on the squeezing enhancement is discussed.MethodsBase on quantum Langevin equation, the input-output relation of the quadratures noise of the output field can be obtained. The output of the first DOPA is seeded to the second DOPA. Then, the noise of the light from the second DOPA can also be obtained. Further, the output of the second DOPA is partially feed back to the input of the first DOPA through a beam splitter. Based on the input-output relation of the beam splitter, the noise formula of the coherent feedback controlled cascaded DOPA is acquired.Results and DiscussionsBased on the noise formula, the dependence of squeezing from the coherent feedback controlled cascaded DOPA on feedback intensity, the phase delay of the feedback loop, pump parameter, the propagation loss of the feedback loop is numerically simulated and presented in the paper. These results show that the squeezing can be significantly enhanced with a certain parameter range.ConclusionsThis paper discusses a cascaded DOPA with coherent feedback, which uses a beam splitter as a feedback controller to feed the squeezed light output from the cascaded DOPA back to the input port. Our research results show that within a certain range of feedback intensity and specific feedback phase, coherent feedback can further enhance the quantum squeezing characteristics of the output light field from a cascaded DOPA. The paper has also studied the dependence of squeezing enhancement effect on system physical parameters. The research results of this paper can provide theoretical reference for improving the squeezing of the squeezed light for the short-wavelength range, laying the foundation for their application in quantum communication and quantum information fields.