In-plane emission manipulation of random optical modes by using a zero-index material

Area of Science:

• Photonics
• Materials Science
• Optical Engineering

Background:

• Controlling in-plane emission of random optical modes in disordered media is challenging.
• Zero-index materials (ZIMs) offer unique light manipulation properties due to their near-zero effective refractive index.
• Disordered structures, like those in random lasers, typically exhibit isotropic emission.

Purpose of the Study:

• To implement a ZIM to control and enhance the in-plane emission directionality of planar random optical modes.
• To maintain the intrinsic disordered features while improving light emission control.
• To explore the potential for on-chip integration of disordered optical devices.

Main Methods:

• Enclosing a disordered structure with a ZIM based on an all-dielectric photonic crystal (PhC).
• Analyzing light propagation in a near-zero refractive index medium.
• Investigating the effect of ZIM on emission directionality and divergence angle.

Main Results:

• Achieved a maximum output directionality enhancement factor of 30 (a 6-fold increase).
• Reduced the minimum divergence angle to approximately 3.5° for incoherent multimode superposition.
• Preserved random properties and slightly improved Q factors.
• Demonstrated robustness across various structural parameters and designs.

Conclusions:

• The ZIM-based method provides a novel and universal approach to manipulate in-plane emission directionality in disordered media.
• This technique enhances control over random optical modes, applicable to devices like random lasers.
• The method shows promise for on-chip integration with other functional devices.