Tuning light matter interaction in magnetic nanofluid based field induced photonic crystal-glass structure by controlling optical path length

TL;DR

This study demonstrates how optical path length influences light-matter interaction and structural ordering in magnetic nanofluid-based photonic crystals, enabling tunable photonic device development.

Contribution

It reveals the role of optical path length in controlling structural order and disorder in magnetic nanofluid photonic crystals, a novel approach for tunable photonic materials.

Findings

Debye diffraction rings indicate 3D hexagonal crystal formation

Structural disorder can be tuned by field strength and nanoparticle parameters

Different optical path lengths produce distinct diffraction patterns

Abstract

The ability to control the light matter interaction and simultaneous tuning of both structural order and disorder in materials, although are important in photonics, but still remain as major challenges. In this paper, we show that optical path length dictates light-matter interaction in the same crystal structure formed by the ordering of magnetic nanoparticle self-assembled columns inside magnetic nanofluid under applied field. When the optical path length (L=80 {\mu}m) is shorter than the optical (for wavelength, {\lambda}=632.8 nm) coherence length inside the magnetic nanofluid under applied field, a Debye diffraction ring pattern is observed; while for longer path length (L=1mm), a corona ring of scattered light is observed. Analysis of Debye diffraction ring pattern suggests the formation of 3D hexagonal crystal structure, where the longitudinal and lateral inter-column spacings are 5.281 and 7.344 microns, respectively. Observation of speckles within the Debye diffraction pattern confirms the presence of certain degree of structural disorder within the crystal structure, which can be tuned by controlling the applied field strength, nanoparticle size and particle volume fraction. Our results provide a new approach to develop next generation of tunable photonic devices, based on simultaneous harnessing of the properties of disordered photonic glass and 3D photonic crystal.