  Quality factor plays a fundamental role in dynamic mode atomic force
microscopy. We present a technique to modify the quality factor of an atomic
force microscopy cantilever within a Fabry-P\'erot optical interferometer. The
experimental setup uses two separate laser sources to detect and excite the
oscillation of the cantilever. While the intensity modulation of the excitation
laser drives the oscillation of the cantilever, the average intensity can be
used to modify the quality factor via optomechanical force, without changing
the fiber-cantilever cavity length. The technique enables users to optimize the
quality factor for different types of measurements without influencing the
deflection measurement sensitivity. An unexpected frequency shift was also
observed and modelled as temperature dependence of the cantilever's Young's
modulus, which was validated using finite element simulation. The model was
used to compensate for the thermal frequency shift. The simulation provided
relations between optical power, temperature, and frequency shift.
