Mechanophotonics:

 

Is it possible to build photonic circuits out of molecular crystals and polymer particles?

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Our research group precisely aims to achieve that using rigid/flexible crystals and dye-doped polymer particles to guide, trap, modulate, split, polarize and lase light at the microdomain - a new research field, namely, Organic Photonic Integrated Circuits (OPICs). We take an interdisciplinary approach by combining Chemistry, Physics and Materials Sciences to accomplish this goal and beyond.

 

To realize OPICs, our group invested more than a decade in designing, creating, micromanipulating and understanding basic photonic microcomponents viz. waveguides, resonators, modulators, lasers, as tools from custom-made molecule/polymer-based solid structures.

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Our research journey towards OPICs started with discovering "Passive Organic Optical Waveguides" [Angew. Chem. Int. Ed. (2012), 51, 3556; Adv. Opt. Mater. (2013),1, 305; Adv. Mater. (2013), 25, 2963]- crystals that could guide laser light up to several microns both in linear and (naturally) bent geometries. Later, we also found a way to trap the wide band fluorescence (FL) within organic microstructures, so-called optical resonators to convert FL signal into a tunable multimodal band. Particularly, we reported the first organic chiral (R & S) resonators displaying Circular Dichroism in the non-linear optical (NLO) signal [J. Mater. Chem. C (2017), 5, 12349].  Using photo-responsive organic microcrystal passive waveguide, our group developed a unique optical experiment to modulate guided light intensity and propagation time (delay lines) using two laser beams [Adv. Opt. Mater. (2015), 3, 1035]. Production of ultra-thin organic surfaces is technologically imperative to realize potential up-conversion organic-lasers. Our group has done that by fabricating nonlinear optical microcavities, producing enhanced second harmonic generation (SHG) signal [Adv. Mater. (2017), 29, 1605260].

 

We reported our first successful mechanical micromanipulation operation to "lift" a crystal waveguide using an atomic force microscope (AFM) cantilever in 2014 [J. Mater. Chem. C (2014), 2, 1404]. Later, a report on mechanical "cutting" of a microcrystal cavity followed [Adv. Opt. Mater. (2016), 4, 112]. We found that unlike bulk 1D macrocrystals, the "elastic" microcrystals behave more like "plastic" on the substrate due to substrate-crystal adhesive interactions paving a way for a stable OPICs. As a result of this important finding, we invented more micromechanical operations to mechanically bent, move, split, transfer and integrate microcrystal waveguides and cavities towards OPICs- using a technique known as Mechanophotonics [Angew. Chem. Int. Ed. (2020), 59, 13821; Small (2021), 17, 2100277]. In the same year, we reported the first OPIC component - a 2x2 directional coupler made entirely from two flexible (plastic-like) organic crystals (Chemistry Views News) to split the light into two signals [Angew. Chem. Int. Ed. (2020), 59, 13852]. As a result of this innovative approach, several homo and heterocrystal OPICs possessing directional-specific and mechanism-selective [passive/active/energy transfer] photonic properties were constructed by combining chemically/electronically different crystal-waveguides and –ring resonators with very high precision [Adv. Opt. Mater, (2021), 9, 2100550; Adv. Funct. Mater. (2021), 31, 2100642].

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Crystal-photonics Foundry:

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FIB milling has been employed to machine perylene crystal resonators into different geometry and size for the first time. The fabrication of disk- and rectangular-shaped photonic resonators is a proof-of-principle experiment that can also be applied to other molecular crystals. The presented technique can be used directly to fabricate circular-, ring-, rod-shaped, and any possible geometries to create photonic modules such as resonators, waveguides, lasers, interferometers, and gratings, couplers, modulators and photonic crystals suitable for the fabrication of PICs. As the geometry and dimension of the molecular crystals can be precisely controlled down to microscale during the milling process, this technique can also be applied to the industrial-scale production of organic crystal photonic modules for PICs.

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Examples of Organic Flexible Crystal Photonic Circuit Components: