Tunable Mid IR focusing in InAs based semiconductor Hyperbolic Metamaterial

Area of Science:

• Metamaterials
• Optics
• Semiconductor Physics

Background:

• Noble metals (gold, silver) used in mid-infrared (mid-IR) metamaterials exhibit high losses and limited tunability.
• Doped semiconductors offer a promising alternative with lower losses and inherent tunability.
• Achieving negative real permittivity is crucial for realizing mid-IR hyperbolic metamaterials (HMMs).

Purpose of the Study:

• To theoretically demonstrate super focusing using an all-semiconductor planar HMM.
• To explore the use of InAs heterostructures for mid-IR applications.
• To investigate the tunability and resolution of the proposed HMM structure.

Main Methods:

• Theoretical demonstration of super focusing using a single slit integrated with a doped InAs/InAs HMM.
• Coupling incident light to high wave vectors within the HMM modes.
• Analysis of the effect of doping concentration and substrate refractive index on focusing performance.

Main Results:

• Sub-diffraction focusing achieved in the mid-IR wavelength range.
• Tunable operation demonstrated by varying the doping concentration of InAs.
• Focusing resolution adjustable from 4.64 μm to 19.57 μm, with a maximum resolution of 0.045λ at 19.57 μm.
• The influence of substrate refractive index on enhancing focusing resolution was analyzed.

Conclusions:

• The proposed all-semiconductor planar HMM based on InAs heterostructures enables efficient super focusing in the mid-IR.
• The structure offers wide tunability by adjusting doping concentration, overcoming limitations of noble metal-based metamaterials.
• The all-single-material design eliminates lattice mismatch issues, facilitating fabrication.