  We introduce a passively-aligned, flexure-tuned cavity optomechanical system
in which a membrane is positioned microns from one end mirror of a Fabry-Perot
optical cavity. By displacing the membrane through gentle flexure of its
silicon supporting frame (i.e., to ~80 m radius of curvature (ROC)), we gain
access to the full range of available optomechanical couplings, finding also
that the optical spectrum exhibits none of the abrupt discontinuities normally
found in "membrane-in-the-middle" (MIM) systems. More aggressive flexure (3 m
ROC) enables >15 microns membrane travel, milliradian tilt tuning, and a
wavelength-scale (1.64 $\pm$ 0.78 microns) membrane-mirror separation. We also
provide a complete set of analytical expressions for this system's
leading-order dispersive and dissipative optomechanical couplings. Notably,
this system can potentially generate orders of magnitude larger linear
dissipative or quadratic dispersive strong coupling parameters than is possible
with a MIM system. Additionally, it can generate the same purely quadratic
dispersive coupling as a MIM system, but with significantly suppressed linear
dissipative back-action (and force noise).
