Porous Polymer Waveguides and Ring Resonators CNF

Label-free optical biosensors are particularly interesting because of their ability to tightly confine light while avoiding complications often associated with label dependent detection. However, many traditional optical biosensors often store the majority of their optical energy in the waveguide core, leaving only the evanescent field to interact with biomolecules. In this work we develop nanoporous polymer waveguides and ring resonators which allow increased interactions between core energy and biomolecules. Initial results indicate a 20% increase in device sensitivity between control and porous devices. Summary of Research: Significant research efforts have been made at developing advanced biosensing technology over the last few decades yet the amount of commercialized technology hasn’t increased significantly. Devices have been developed based on optical, mechanical, and electrical methods of signal transduction, and have been optimized on the nanoscale [1­4]. Optical devices are of particular interest because of their ability to detect minute quantities, as far down as ten attograms [3]. Many of these current devices rely on fabrication techniques and materials developed in the semiconductor in­ dustry, and face difficulties associated with wide­ spread fabrication and the cost of devices. Recently, others have investigated the feasibility of using non­ traditional nanofabrication techniques and materials to reduce costs and make devices that are easier to mass produce [2]. How ever, many of these cheaper polymer devices aren’t capable of matching the sensitivity of their Si counterparts. In this work we investigate how the sensitivity of polymer optical biosensors can be increased to match that of silicon devices and how polymers can provide other advantages in optical biosensing, including robustness and flexibility. Specifically, we use nanoimprint lithography as an alternative to traditional techniques and create porous polymer waveguides and ring resonators where biomolecules can interact directly with the core waveguide energy. Because the energy in the waveguide core is many Figure 1: (A) A Ring Resonator is shown coupled to a bus waveguide. (B) and (C) show porous waveguides forming the resonator, yet solid waveguides composing the bus waveguide far from the ring. This technique allows increased interactions at the measurement site while not increasing losses throughout the entire bus waveguide.