研究目的
To develop an optical security device that combines phase and amplitude control to integrate holograms into a colour print for enhanced anti-counterfeiting applications.
研究成果
The holographic colour prints successfully combine phase and amplitude control to display colour images under white light and multiple holographic projections under laser illumination, offering enhanced optical security for anti-counterfeiting. The monolithic integration and use of a single material enable potential mass-manufacture via nanoimprint lithography. Future work could explore pixel-level control of additional light properties for further security applications.
研究不足
The fabrication process is time-consuming (6-8 hours for a 1.44 mm square print), and the pixel design has a minimum feature size of several hundred nanometers, which may limit resolution. Phase-amplitude coupling effects were present but minimized. The prints are passive devices and require external illumination for verification.
1：Experimental Design and Method Selection:
The study designed holographic colour pixels integrating structural colour filters and phase plates to control both phase and amplitude of light. A modified Gerchberg-Saxton algorithm was used for iterative optimization of holographic projections and colour image formation.
2：Sample Selection and Data Sources:
Samples were fabricated using direct laser writing on glass substrates with a negative-tone photoresist. Transmission spectra and optical micrographs were collected from various pillar array colour filters.
3：List of Experimental Equipment and Materials:
Equipment includes a femtosecond pulsed IR laser for direct laser writing, high numerical aperture immersion microscope objective, and MATLAB for design algorithms. Materials include a cross-linked polymer photoresist and glass substrates.
4：Experimental Procedures and Operational Workflow:
The fabrication process involved rastering the laser spot to create phase plates and point exposures for pillar arrays, with patterning done in write-fields and stitched together. Holographic projections were verified under laser illumination, and colour images under white light.
5：Data Analysis Methods:
Transmission spectra were measured and averaged, and holographic fidelity was assessed through visual inspection and efficiency measurements.
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