  An inertial sensor design is proposed in this paper to achieve high
sensitivity and large dynamic range in the sub-Hz frequency regime. High
acceleration sensitivity is obtained by combining optical cavity readout
systems with monolithically fabricated mechanical resonators. A
high-sensitivity heterodyne interferometer simultaneously monitors the test
mass with an extensive dynamic range for low-stiffness resonators. The
bandwidth is tuned by optical feedback cooling to the test mass via radiation
pressure interaction using an intensity-modulated laser. The transfer gain of
the feedback system is analyzed to optimize system parameters towards the
minimum cooling temperature that can be achieved. To practically implement the
inertial sensor, we propose a cascaded cooling mechanism to improve cooling
efficiency while operating at low optical power levels. The overall system
layout presents an integrated design that is compact and lightweight.
