Optofluidic gradient refractive index resonators using liquid diffusion for tunable unidirectional emission

Area of Science:

• Optofluidics
• Nanophotonics
• Materials Science

Background:

• Optofluidic resonators are crucial for biochemical detection and microscale lasers, leveraging unique liquid environments.
• Liquid diffusion is vital for optofluidic applications like gradient refractive index lenses but remains unexplored in resonators.
• Achieving unidirectional emission in conventional circular resonators is challenging.

Purpose of the Study:

• To introduce a gradient refractive index profile formed by liquid diffusion in annular channels into a circular resonator.
• To create a novel gradient-index resonator with tunable unidirectional emission.
• To explore the potential of this new resonator for sensing and light source applications.

Main Methods:

• Utilized liquid diffusion to create a gradient refractive index profile within annular channels of a circular resonator.
• Conducted simulations and experiments to analyze light intensity profiles and emission characteristics.
• Investigated the influence of refractive index difference, channel dimensions, and working wavelengths on emission.

Main Results:

• Successfully obtained a squeezed, non-rotationally symmetrical light intensity profile in the circular resonator.
• Demonstrated tunable unidirectional emission, a significant improvement over conventional resonators.
• Observed a squeezed light coefficient of approximately 1.8 with a 100 μm bending radius, resulting in a narrow 14-degree emission divergence angle.

Conclusions:

• The novel liquid gradient refractive index resonator provides a practical approach for optofluidic resonator emission.
• The squeezed light profile enables efficient unidirectional emission, suitable for future laser applications.
• This resonator shows significant potential for optofluidic sensing applications.