A novel Raman spectrum detection system based on an integrated optical biosensor

Abstract

In recent years, there has been a growing demand for hand held and miniaturized spectroscopic Raman systems that can be employed in the field to distinguish and quantify different analytes. In this paper, a novel and integrable system to detect a Raman spectrum is presented. We present the system principle, sensor design, experimental set-up and primary measurement results. In a conventional Raman setup, the four important components are: a light source, sensor, spectrometer and detector. We utilize a tunable laser as light source in the new Raman detecting system to replace the spectrometer by scanning the pump wavelength. A Raman sensor based on silicon nitride platform which has small size and high signal-background ratio is demonstrated in this paper to enable the excitation and the collection of the Raman signal using a plasmonic slot waveguide structure. Besides the tunable laser and the Raman sensor, there are two basic devices in our system, a narrow band-pass filter and a power detector. In this work, the Raman signal of the measured molecule 4-nitrothiophenol (NTP) is obtained by scanning the pump wavelength from 735 nm to 786 nm. The light source and detector in our experiment are implemented by discrete components. Silicon photonics promises the integration of a complete on-chip Raman spectroscope where the tunable laser, detector, sensor and filter can be integrated in a millimeter sized chip. We analyze the primary results measured by the discrete devices and discuss the feasibility of the on-chip integration in the end.