Fabricating Compact, Efficient Optical Waveguides

Scientists have demonstrated a new method for fabricating compact, low-loss optical waveguides in a polydimethylsiloxane (PDMS) slab.

A femtosecond writing laser initiates two-photon absorption in light-reactive monomers embedded in PDMS. Without potentially toxic photoinitiator compounds, two-photon absorption generates enough energy in the monomer molecules to initiate a chain polymerization reaction. The resulting polymerized waveguides have a higher refractive index (RI) than the surrounding PDMS and a more straightforward chemical structure than photoinitiator-fabricated waveguides, making them potentially valuable for biomedical applications.

The team used a host-guest system and optimized multiphoton laser direct writing to create its optical waveguides. The researchers chose PDMS as the “host” material because it is transparent over a broad spectral range and has excellent chemical and thermal stability. They chose phenylacetylene as the “guest” because it is a light-reactive monomer soluble in PDMS, polymerizes without the assistance of a photoinitiator, and has a high RI after polymerization.

They hope to improve their manufacturing process by optimizing the control system that minimizes material damage during laser writing. Researchers claim that with an optimized setup, they could create waveguides as thin as 1 m.

Biosensors, microfluidic flow cytometry, electro-elastic optical modulators, flexible optical circuit boards, wearable, and implantable photonic devices, and optical neuron stimulation are all possible applications for the waveguides.

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