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Nanoporous Solid-Liquid core waveguides were prepared by UV induced surface modification of hydrophobic nanoporous polymers. With this method, the index contrast (δn = 0.20) is a result of selective water infiltration. The waveguide core is defined by UV light, rendering the exposed part of a nanoporous polymer block hydrophilic. A propagation loss of 0.62 dB/mm and a bend loss of 0.81 dB/90° for bend radius as low as 1.75 mm was obtained in these multimode waveguides.

We present an efficient method for functionalizing the large polymer-air interface of a gyroid nanoporous polymer. The hydrophilicity of nanoporous cross-linked 1,2-polybutadiene is tuned by thiol-ene photo-grafting of mercaptosuccinic acid or sodium 2-mercaptoethanesulfonate. The reaction is monitored by FT-IR, UV-Vis, contact angle, and gravimetry. Overall quantum yields are calculated for the two thiol-ene "click" reactions in nano-confinement, neatly revealing their chain-like nature. Top-down photolithographic patterning is demonstrated, realizing hydrophilic nanoporous "corridors" exclusively hosting water. The presented approach can be relevant for many applications where, e.g., high control and contrast in hydrophilicity, chemical functionality or refractive index are needed.

In this work we demonstrate an efficient and cleanroom compatible method for the fabrication of solid–liquid core waveguides based on nanoporous polymers. We have used thiol-ene photo-grafting to tune and pattern the hydrophilicity of an originally hydrophobic nanoporous 1, 2-polybutadiene. The generated refractive index contrast between the patterned water-filled volume and the surrounding empty hydrophobic porous polymer allows for light confinement within the water-filled volume—the solid–liquid core. The presented fabrication process is simple and fast. It allows a high degree of flexibility on the type and grade of surface chemistry imparted to the large nanoporous area depending upon the application. The fabrication does not need demanding chemical reaction conditions. Thus, it can be readily used on a standard silicon lithography bench. The propagation loss values reported in this work are comparable with literature values for state-of-the-art liquid-core waveguide devices. The demonstrated waveguide function added to the nanoporous polymer with a very high internal surface area makes the system interesting for many applications in different areas, such as diagnostics and bio-chemical sensing.

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