Mitigation of photon background in nanoplasmonic all-on-chip Raman sensors

In the quest for a more compact and cheaper Raman sensor, photonic integration and plasmonic enhancement are central. Nanoplasmonic slot waveguides exhibit the benefits of SERS substrates while being compatible with photonic integration and mass-scale (CBIOS) fabrication. A difficulty in pursuing further integration of the Raman sensor with lasers, spectral filters, spectrometers and interconnecting waveguides lies in the presence of a photon background generated by the excitation laser field in any dielectric waveguide constituting those elements. Here, we show this problem can be mitigated by using a multi-mode interferometer and a nanoplasmonic slot waveguide operated in back-reflection to greatly suppress the excitation field behind the sensor while inducing very little photon background. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement