Subwavelength Quasi-Periodic Array for Infrared Antireflection.

Area of Science:

• Materials Science
• Optics and Photonics
• Nanotechnology

Background:

• Infrared antireflection is crucial for enhancing the performance of infrared detector systems.
• Zinc sulfide (ZnS) is a common material used in optical systems, but its surface properties require optimization for infrared applications.

Purpose of the Study:

• To propose and demonstrate a novel method for fabricating subwavelength quasi-periodic arrays (SQA) on ZnS for infrared antireflection.
• To investigate the tunability of SQA properties, such as depth, and their impact on infrared transmittance and hydrophobicity.
• To evaluate the effectiveness of the fabricated SQA in improving infrared imaging quality.

Main Methods:

• Fabrication of SQA on ZnS substrate using double-pulse femtosecond laser micro-machining.
• Tuning of SQA depth by adjusting pulse energy and pulse delay.
• Simulation of optical field intensity distributions using rigorous coupled-wave analysis (RCWA).
• Evaluation of infrared imaging quality using a self-built infrared detection system.

Main Results:

• A uniform SQA with approximately 30 million holes over a 2 × 2 cm² area was fabricated rapidly.
• Double-pulse laser machining effectively suppressed surface plasma shielding, enabling deeper arrays.
• SQA depth was tunable, allowing regulation of infrared transmittance spectra and hydrophobicity.
• RCWA simulations confirmed the modulation effect of array depth on optical field intensity.

Conclusions:

• Double-pulse femtosecond laser micro-machining is an effective technique for fabricating ZnS SQAs for infrared antireflection.
• The fabricated SQAs demonstrate tunable optical and surface properties, leading to improved infrared detector performance.
• The developed method shows promise for enhancing infrared imaging systems.