Improving the Angular Visibility of Photopolymer-Based Reflection Holograms for Sensing Applications

Area of Science:

• Holography
• Optical Sensors
• Materials Science

Background:

• Volume reflection holograms change color with stressors but suffer from narrow angular selectivity.
• This limits their practical use and interpretation by non-experts.

Purpose of the Study:

• To improve the visibility and interpretability of reflection hologram-based sensors.
• To develop a novel speckle holography technique for enhanced holographic sensors.

Main Methods:

• A new recording method combining speckle recording with Denisyuk geometry was developed.
• Speckle reflection gratings were created, acting as multiplexed gratings with varied spatial frequencies.
• Comparative studies assessed angular and wavelength selectivity against standard reflection gratings.

Main Results:

• Speckle reflection gratings showed doubled angular selectivity (4° vs 2°) and wavelength selectivity (8.6 nm vs 4.2 nm).
• The enhanced gratings effectively functioned as color-changing compressional pressure sensors (0.88-5.31 MPa).
• A prototype viewer was developed for easy observation of holographic sensors.

Conclusions:

• Speckle holography significantly improves the angular and wavelength selectivity of reflection holograms.
• This technique enhances the performance and accessibility of color-changing holographic sensors.
• The developed viewer facilitates non-expert use of these advanced optical sensors.