Efficient and stable coupling to nanophotonic waveguides and resonators in stringent environments

Area of Science:

• Nanophotonics
• Quantum Optics
• Optical Engineering

Background:

• Coupling light to nanophotonic structures is essential for quantum optics and sensing.
• Constrained environments, such as those found in cryostats, pose significant challenges for efficient light coupling.
• Existing methods often struggle with stability and performance in demanding conditions.

Purpose of the Study:

• To explore new methods for coupling light to nanophotonic structures in constrained environments using conical optical fibers.
• To demonstrate efficient and stable light coupling to on-chip nanophotonic devices.
• To achieve high coupling efficiencies for applications in quantum optics and sensing.

Main Methods:

• Utilized single-sided conical fiber tapers for initial coupling to on-chip nanophotonic bus waveguides immersed in liquid.
• Employed a face-to-face configuration of two conical fibers to couple light directly into whispering gallery disk resonators.
• Operated and tested the system within a vibrating pulse tube cryostat at low temperatures.

Main Results:

• Demonstrated efficient light coupling to a nanophotonic bus waveguide with a single-sided conical fiber taper.
• Achieved highly efficient coupling, exceeding 90%, using two conical fibers joined face to face for whispering gallery resonators.
• Confirmed the stability of the two-conical-fiber coupling method within a vibrating cryostat.
• Validated performance in the telecom band and near-infrared (around 900 nm).

Conclusions:

• Conical optical fiber techniques offer a robust solution for light coupling in challenging and constrained environments.
• The developed methods significantly enhance coupling performance, meeting requirements for advanced quantum optics and sensing experiments.
• These advancements address previous signal-to-noise ratio limitations in stringent experimental settings.