Optical apparatus including nested resonator

Apparatuses that include an input and output waveguide; and a nested resonator including at least an external loop and a nested loop positioned entirely inside the external loop, each loop independently having a length that supports a single resonant wavelength, the external loop further including: an input interface configured to couple energy between the input waveguide and the nested resonator, an output interface configured to couple energy between the nested resonator structure and the output waveguide, and an internal interface, the external loop and the nested loop configured to couple energy there between via the internal interface.