Observation of topologically enabled unidirectional guided resonances

Area of Science:

• Photonics
• Topological Physics
• Optoelectronics

Background:

• Unidirectional radiation is crucial for optoelectronic devices like lasers and antennas.
• Current unidirectional emitters often require bulky and lossy mirrors, hindering performance and fabrication.
• Controlling light emission directionality is a key challenge in optical engineering.

Purpose of the Study:

• To theoretically propose and experimentally demonstrate a new class of resonances for unidirectional radiation.
• To investigate the topological nature of these resonances.
• To achieve high-quality, single-sided light emission without mirrors.

Main Methods:

• Theoretical modeling of photonic crystal slabs to identify unique resonance conditions.
• Experimental fabrication and characterization of photonic crystal slabs.
• Far-field polarimetry measurements to confirm topological properties and emission directionality.

Main Results:

• Demonstration of 'unidirectional guided resonances' in photonic crystal slabs that emit light to only one side.
• Observation of topological characteristics arising from the interaction of polarization topological charges in momentum space.
• Achieved high single-side radiative quality factors (up to 1.6 × 10^5) in the telecommunication regime.

Conclusions:

• Unidirectional guided resonances offer a mirrorless approach to control light emission directionality.
• The topological nature of these resonances provides a robust mechanism for optical field control.
• This work enables the development of energy-efficient grating couplers and antennas for advanced optical applications.