Reconfigurable Frequency-Selective Resonance Splitting in Chalcogenide Microring Resonators

This paper reports a method to enable, for the first time, reconfigurable control of resonance splitting of one or multiple arbitrarily selected azimuthal orders in a microring resonator. This is accomplished by inscribing Bragg gratings in photosensitive Ge23Sb7S70 chalcogenide microring resonators via a novel cavity-enhanced photoinscription process, in which injection of light at the targeted C-band resonance frequency induces a spatially varying refractive index change. The so formed Bragg grating precisely matches the selected resonance order without introducing optical losses. Long-term room temperature stability of the photoinscribed Bragg gratings has been verified in darkness and during operation with reduced optical power levels. The Bragg gratings can be reconfigured by first erasure with flood illumination of visible light at 561 nm and subsequent reinscription. We also report controlled splitting of multiple resonances by inscribing superimposed Bragg gratings.