Photonic Crystal Slot Waveguide Spectrometer for Monitoring of Volatile Organic Compounds in Groundwater and Hazardous Pollutants in Air

In this program, Omega Optics, Inc. and the University of Texas, Austin, propose a novel lab-on-chip photonic crystal slot waveguide infrared spectrometer for detection and spectroscopic analysis of BTEX hydrocarbons (benzene and toluene) in water and greenhouse gas (carbon dioxide) in air. The device utilizes the unique dispersive properties of slow light photonic crystal waveguides together with electric-field intensity enhancement in narrow slot waveguides to achieve a factor 2000 reduction in absorption length for the spectroscopic measurement of absorption spectra of analytes, specifically hydrocarbons in water and greenhouse gases. The versatility of the proposed method enables the realization of a novel in situ on-chip miniature absorption spectroscopy instrument. This SBIR Phase I project aims to develop a commercially viable, 100 micron long silicon lab-on-chip photonic crystal integrated infrared spectrometer for sensing and spectroscopic identification of hazardous materials and pollutants in the environment, specifically volatile organic compounds (VOCs) in drinking water and hazardous air pollutants (HAPs). Defect engineered photonic crystals, with submicron dimensions, have already demonstrated high sensitivity to trace volumes of analytes; exact identification of analyte through spectroscopic signature, however, has not been demonstrated. Omega Optics, Inc. proposes a photonic crystal slot waveguide device that combines slow light effect in photonic crystal waveguides with large optical field intensity in a low index 80 nm slot at the center of the photonic crystal waveguide. The photonic crystal slot waveguide provides a factor of 2000 reduction in interaction length compared to conventional waveguides leading to enhanced optical absorption by analytes in the optical path. By measuring absorption differences in presence and absence of analyte, absorption spectrum of the analyte is determined. The method eliminated the need for labeling for analyte identification. The CMOS compatible platform will ensure high-volume and low-cost production of devices. The potential commercial application of the versatile miniature spectrometer is for any chemical spectroscopy discipline where massively parallel sensing, identification and high-throughput analysis are desired, such as quality control of analytical solutions, food and beverages, petroleum, groundwater, and trace detection and identification of gases.