  We investigate a coherent feedback squeezer that uses quantum coherent
feedback (measurement-free) control. Our squeezer is simple, easy to implement,
robust to the gain fluctuation, and broadband compared to the existing
squeezers because of the negative coherent feedback configuration. We conduct a
feasibility study that looks at the stability conditions for a feedback system
to optimize the designs of real optical devices. The feasibility study gives
fabrication tolerance necessary for designing and realizing the actual device.
Our formalism for the stability analysis is not limited to optical systems but
can be applied to the other bosonic systems.
