SBIR Phase II: Low Cost On-Chip Photonic Crystal Slot Waveguide Absorption Spectrometer for Highly Sensitive, Continuous,In-Situ,Remote Specific Detection of Multiple VOC in Water

This Small Business Innovation Research (SBIR) Phase II project proposes to develop a low cost packaged near-infrared on-chip silicon absorption spectrometer for simultaneous and specific detection of multiple volatile organic compounds in water (ground water, waste water and drinking water). In phase I, the volatile organic compound xylene was successfully detected in water at 100 parts per billion through near-infrared absorption signatures, on chip with 300 micron long photonic crystal slot waveguides which represents the best results in device sensitivity and in miniaturization. The device combines slow light effect in photonic crystal waveguides with highly concentrated optical field intensity in a low index slot at the center of the photonic crystal waveguide. The photonic crystal slot waveguide proposed herein provides a factor of 1000 reduction in interaction length compared to conventional waveguides leading to enhanced optical absorption by analytes in the optical path. Transmission is measured from multiple waveguides covering the entire near-infrared wavelength range, and absorbance determined by measuring transmission differences in the presence and the absence of any volatile organic compound analytes of interest. The miniature spectrometer will enable massively parallel identification and high throughput analysis. The broader impacts of this research are the enabling of continuous, remote, in-situ monitoring and unique identification of multiple volatile organic compounds (VOCs) in groundwater, drinking water, and waste water, with high sensitivity and specificity, a facility that is not available commercially at present. The integrated silicon platform ensures low cost production in high volume. From commercial standpoint, the United Nations Environment Program estimates the global water market to expand to $660 billion from the current $250 billion by 2020. The proposed photonic crystal slot waveguide device can be expected to occupy a significant position in this market. The generalized design of the proposed versatile technology implies possible implementation in multiple areas of in-situ analyte sensing, detection, and spectroscopy such as control of food, air, and water quality and health, in a lab-on-chip platform with low cost of ownership. Through continuous, in-situ and remote monitoring, the prototype developed from this research will eliminate the lag time that currently exists in industrial water monitoring, sometimes extending to few months as in VOC monitoring of rivers and lakes, thereby enabling early warning of spurious leaks and spills instead of after-the-fact damage control and mediation and thus enhance environmental and national security.