Liquid core waveguides by UV modification of nanoporous polymer

Liquid core waveguides are fabricated from a self-assembled nanoporous polymer, with a porosity of 40%. The high porosity results in an effective refractive index of 1.26 for visible light, i.e. below the refractive index of aqueous solutions. However, since the polymer is hydrophobic, fluids to not initially penetrate into the pores. We show that the inner surface of the pores can be rendered selectively hydrophilic by exposing them to ultraviolet light thorough a photo mask¹. As liquids infiltrate the exposed regions and replace air, the refractive index is raised to 1.42, and thus these areas can function as liquid core waveguides. Fig. 1 illustrates this principle.