Disorder-Induced Light Confinement in Photonic Crystals as a Platform for Efficient Optical Sensing

Abstract

Abstract:We demonstrate optical sensing with disorder-induced confined light on silicon nitride photonic crystal waveguides. For a refractive index change of ≈0.38, we measure 14 nm wavelength shifts of an optical resonance 0.4 nm broad.OCIS codes: (350.4238) Nanophotonics and photonic crystals; (280.4788) Optical sensing and sensors; (300.6280) Spectroscopy, fluorescence and luminescence IntroductionOptical sensing is of preeminent importance for a variety of applications [1]: it can enable detection of harmful or desired contaminants, it can confirm that expected reactions have taken place and can be used for quantitative analysis of the processes under study.To this end, several kind of devices have been developed; in particular they have been based on plasmonic resonances [2] that have the advantage of relatively easy production and high yield, and photonic crystal cavities [3] that posses much sharper spectral resonances (and therefore higher sensitivity), but suffer from low scalability due to the highly engineered fabrication process required.To overcome this issue, we follow a different approach and show that multiple scattering on unavoidable fabrication imperfections can be used as a platform for efficient light confinement in disordered photonic crystal waveguides. By using imperfections as a resource, we show that several high-quality optical cavities spontaneously appear along a fabricated photonic crystal waveguide operating at room temperature [4]. Such an approach represents a route for scalable, high quality optical sensors.