Ultrathin photonic nanostructures, such as plasmonic and dielectric metamaterials and metasurfaces, have broad applications in electromagnetic wave manipulation, high resolution imaging, and computation. However, conventional production of these metastructures relies on precise nano-machining techniques that are difficult to manufacture over a product-relevant scale.
Nanoimprint lithography (NIL) is an alternative technique to conventional nanofabrication methods and is capable of large-area production due to its layer-by-layer printing process. NIL has been successfully demonstrated for a wide range of applications in polarizers, anti-reflection coatings, and absorbers. Recently, NIL printing on a single layer has been demonstrated for metastructures, but its fabrication of more complex structures, such as double-layer metastructures used in polarimetric imaging, has not yet been achieved.
Researchers at Arizona State University have developed novel method for co-designing functional multi-layered metastructures and their nanoimprint lithography (NIL)-based process integration. In this method, a layer of vertically coupled aluminum (AL) double gratings (VCDGs) are designed as a polarizer that shows greatly improved linear polarization extinction ratio compared to single-layer metal gratings. In initial tests, the NIL process successfully flattened the substrate surface, producing a smooth grating scaffold for VCDGs that enables multi-wavelength operation.
- Electromagnetic wave manipulation
- High-resolution imaging
- Beam steering & light focusing
Benefits and Advantages
- Scalable for larger applications
- Greatly improved linear polarization extinction ratio (LEPR over 10x in simulation, 3-4x in experiment) compared to single-layer metal gratings
- Optical performance and structural geometries of the VCDG polarizer are synergistically designed with other parts of NIL process
- Replaces conventional fabrication methods that require complex processes (e.g., SiO2 spacer deposition, electron beam lithography (EBL), plasma descum, chromium mask deposition, liftoff, SiO2 dry etching, Cr removal)
- Successfully flattens substrate surface, producing smooth grating scaffold for VCDGs
- Enables multi-wavelength operation (blue, green, red)