A Mechanophotonic Approach toward an Organic, Flexible Crystal Optical Interferometer

Abstract

Organic crystals are poised to be a potential alternative to conventional silicon and its derivatives due to their utilization as microscale photonic components like active and passive waveguides, ring-resonators, modulators, directional couplers, add-on filters, interferometers (IMs), and reconfigurable circuits. Among these, IMs are important for flexible organic photonic integrated circuits. Here, the design and synthesis of extremely flexible (E)-1-(((5-bromopyridin-2-yl)imino)methyl)naphthalen-2-ol (BPyIN) crystals are demonstrated. The interactions stabilizing the crystal packing and crystal-substrate adhesion dictate the elasticity and pseudo-plasticity, respectively. The extremely flexible BPyIN crystals disclose bending geometry-dependent optical modes in the fluorescence spectra. This understanding is extended for fabricating a fiber loop mirror (FLM)-like geometry using a BPyIN single crystal. Mechanophotonics approach facilitates the integration of FLM-like crystal with a doubly bent waveguide to construct a first-of-its-kind IM. The light propagating path-length-dependent optical interference within the IM is established. These proof-of-principle experiments illustrate the usefulness of mechanophotonics to fabricate miniature photonic devices beyond the traditional fabrication approach.