Adaptive Control of Necklace States in a Photonic Crystal Waveguide

Resonant cavities with high quality
factor and small mode volume
provide crucial enhancement of light–matter interactions in
nanophotonic devices that transport and process classical and quantum
information. The production of functional circuits containing many
such cavities remains a major challenge, as inevitable imperfections
in the fabrication detune the cavities, which strongly affects functionality
such as transmission. In photonic crystal waveguides, intrinsic disorder
gives rise to high-Q localized resonances through
Anderson localization; however their location and resonance frequencies
are completely random, which hampers functionality. We present an
adaptive holographic method to gain reversible control on these randomly
localized modes by locally modifying the refractive index. We show
that our method can dynamically form or break highly transmitting
necklace states, which is an essential step toward photonic-crystal-based
quantum networks and signal processing circuits, as well as slow light
applications and fundamental physics.