Temperature Tunable 4D Polymeric Photonic Crystals

Photonic crystals owe their multitude of optical properties to the way their structure creates interference effects. It is therefore possible to influence the photonic response by acting on their physical structure. In this article, tunable photonic crystals made by elastic polymers that respond to their environment are explored, in particular with a physical deformation under temperature variation. This creates a feedback process in which the photonic response depends on its physical structure, which itself is influenced by the environmental changes. By using a multi-photon polymerization process specifically optimized for soft responsive polymers such as Liquid Crystalline Networks, highly resolved, reproducible, and mechanically self-standing photonic crystals are fabricated. The physical structure of the 3D woodpile can be tuned by an external temperature variation creating a reversible spectral tuning of 50 nm in the telecom wavelength range. By comparing these results with finite element calculations and temperature induced shape-change, it is confirmed that the observed tuning is due to an elastic deformation of the structure. The achieved nanometric patterning of tunable anisotropic photonic materials will further foster the development of reconfigurable photonic crystals with point defects acting as tunable resonant cavities and, more in general, of 4D nanostructures.

Automated summary

This article explores tunable photonic crystals made from elastic polymers that respond to their environment, particularly with physical deformations under temperature changes. The physical structure of these crystals can be adjusted by external temperature variations, resulting in a reversible spectral tuning. By comparing the experimental results with calculations and temperature-induced shape changes, it is confirmed that the observed tuning is due to elastic deformations. The achievement of nanometric patterning of tunable anisotropic photonic materials will contribute to the development of reconfigurable photonic crystals and 4D nanostructures.