Label-free biosensor based upon a vertically emitting distributed feedback laser

Firstly, a novel fabrication strategy combining a nano-replica molding technique and a horizontal dipping technique has been demonstrated for the fabrication of solid state organic distributed feedback laser (DFB) biosensors. The combined techniques enable the organic DFB laser to be uniformly fabricated over large surface areas upon a flexible plastic substrate, with an approach that is compatible with roll-based manufacturing. Secondly, laser pump threshold from a distributed feedback (DFB) structure, based upon a second order grating in a dye-doped polymer, has been efficiently reduced by implementing a resonant optical pumping scheme. The proposed scheme couples the excitation laser light into a resonant mode and takes advantage of the intensified electromagnetic field. For a Bragg grating having a periodicity of 400 nm, a Rhodamine 590 doped polymer laser operates at 584 nm and concurrently supports a resonance mode at 532 nm which is the excitation laser wavelength. Pumped under the resonant condition, the DFB laser exhibits a pump threshold reduction of 25-fold. In addition, the resonant optical pumping technique also enhances the light conversion efficiency by a factor of 23. This technique improves the performance of organic DFB lasers. Finally, we demonstrate that a dielectric nanorod structure could be used to enhance the label-free detection sensitivity of the vertically emitting distributed feedback laser biosensor (DFBLB). We show that the use of the nanostructured film results in a three-dimensional volume overlap between the DFBLB resonant mode and the region in which the biomolecule adsorption can occur. This modification in device design results in a ~6.6?? increase in detection sensitivity while maintaining a narrowband output