  From fundamental discovery to practical application, advances in the optical
and quantum sciences rely upon precise control of light-matter interactions.
Systems of coupled optical cavities are ubiquitous in these efforts, yet design
and active modification of the hybridized mode properties remains challenging.
In this Letter, we demonstrate the ability to thermally control the degree of
hybridization in a heterogeneous photonic molecule composed of a ring resonator
strongly coupled to a nanobeam photonic crystal cavity. Combining theory and
experiment, we show that the composition of the resulting super-modes can be
actively tailored and we derive temperature-dependent analytic expressions for
the super-mode profiles, frequencies, and volumes. This work illustrates the
potential for actively tunable, designer photonic properties using
heterogeneous optical cavity devices.
