Core-shell particles as efficient broadband absorbers in infrared optical range.

Area of Science:

• Nanophotonics and Metamaterials
• Infrared Optics and Spectroscopy

Background:

• Efficient broadband absorption of infrared radiation is crucial for many applications.
• Subwavelength structures offer unique optical properties but achieving broadband absorption remains a challenge.

Purpose of the Study:

• To demonstrate efficient broadband absorption of infrared radiation using subwavelength spherical dielectric particles with a metal layer.
• To provide analytical guidelines for designing such absorbers.

Main Methods:

• Mie theory and quasi-static approximation were employed to analyze particle configurations.
• Investigated the relationship between particle parameters, absorption cross-section, and scattering cross-section.
• Analyzed the role of surface plasmon modes in the metal shell.

Main Results:

• Achieved broadband infrared absorption with absorption cross-section reaching geometrical limits and significantly exceeding scattering.
• Identified a wide range of parameters for efficient absorption.
• Developed a simple analytical expression for absorption resonance, enabling quick identification of optimal configurations.
• Demonstrated the connection between absorption resonance and short-range surface plasmon modes.

Conclusions:

• Subwavelength dielectric particles with metal shells are effective broadband infrared absorbers.
• The findings provide practical guidelines for designing efficient, compact infrared absorbers.
• The study highlights the importance of surface plasmon excitation for enhanced absorption.