Mesoscopic self-collimation along arbitrary directions and below the light line

Area of Science:

• Photonics
• Condensed Matter Physics
• Materials Science

Background:

• Self-collimation (SC) and mesoscopic self-collimation (MSC) are phenomena in photonic crystals enabling waveguiding without confinement structures.
• Previously, wide angular acceptance for SC and MSC was limited to high-symmetry directions due to flat isofrequencies.

Purpose of the Study:

• To numerically demonstrate mesoscopic self-collimation (MSC) with large angular acceptance along arbitrary, non-high-symmetry directions in photonic crystals.
• To propose a method for identifying these non-trivial collimation directions and frequencies.

Main Methods:

• Numerical simulations of photonic crystals with double periodicity.
• Analysis of isofrequency surfaces to identify non-trivial collimation phenomena.
• Exploration of tailoring collimation direction and frequency via crystal design.

Main Results:

• Demonstration of mesoscopic self-collimation (MSC) with large angular acceptance in arbitrary directions.
• Development of a method to find non-trivial collimation directions and frequencies.
• Identification of MSC solutions below the light cone.

Conclusions:

• Mesoscopic self-collimation (MSC) is not restricted to high-symmetry directions.
• The proposed method allows for precise control over collimation direction and frequency.
• These findings facilitate the design of complex photonic integrated circuits using combinations of MSC, high reflection (HR), and anti-reflection (AR) elements or active materials.