Grantee Research Project Results
2000 Progress Report: An Integrated Near Infrared Spectroscopy Sensor for In-Situ Environmental Monitoring
EPA Grant Number: R826190Title: An Integrated Near Infrared Spectroscopy Sensor for In-Situ Environmental Monitoring
Investigators: Levy, Roland A.
Institution: New Jersey Institute of Technology
EPA Project Officer: Aja, Hayley
Project Period: February 20, 1998 through February 19, 2001 (Extended to February 19, 2003)
Project Period Covered by this Report: February 20, 2000 through February 19, 2001
Project Amount: $322,230
RFA: Exploratory Research - Environmental Chemistry (1997) RFA Text | Recipients Lists
Research Category: Water , Air , Safer Chemicals , Land and Waste Management
Objective:
The integrated optical sensor developed in this study is a device that uses the principles of interferometry to monitor and determine in situ the concentration of numerous organic analyte species. It offers numerous advantages over conventional analytical techniques such as gas chromatography and mass spectrometry, including small physical size, geometric flexibility, environmental versatility, immunity to the electromagnetic interference, low loss for long-length sensing, and high sensitivity. This device has been designed to be mass-produced using standard silicon-based processes that result in low cost. The envisioned instrumentation that incorporates this sensor is expected to be portable, rugged, and suitable for real time monitoring of organics. The feedback from such a device combined with current optical fiber technology allows for the device to be used as a remote, in situ sensor.Progress Summary:
A fabricated device is shown from a top view in Figure 1. The sampling arm is separated a distance of 50 mm from the reference arm. The dimension of the shown interferometer is 3 mm in width by 2 mm in length. At both ends, the two Y-splitters are readily apparent.
Figure 1. Top view of the Mach-Zehnder interferometer.
One of the important criteria in the fabrication of the sensor is achievement of equal shapes of the sampling and reference arms so that light is equally split between them. A cross-sectional profile of a pair of adjoining arms (6 mm in width) is shown in Figure 2 and demonstrates the successful accomplishment of this geometrical goal.
Figure 2. Cross section of 6 mm ' 8mm waveguides.
When laser light (628.3 nm) is introduced at one end of the Y-splitter and allowed to emerge from both arms, Figure 3 indicates that an equal intensity is registered by the CCD camera. This provides the proof that the waveguides were properly designed and perfectly functional.
Figure 3. Equal intensity light emerging from adjoining arms of sensor.
To test the sensor's range of operation, a calculation was performed to relate the changes in refractive index relative to water as a function of ethanol concentration. From these changes, the normalized output intensity was established. The dependence of the normalized output intensity plotted as a function of refractive index change is seen in Figure 4. These results are important in establishing the correlation between output intensity of the sensor and ethanol concentration in the environment.
Figure 4. Normalized output intensity vs. refractive index change relative to water.
Future Activities:
We will continue development and testing of the integrated near infrared spectroscopy sensor and to test its effectiveness.Journal Articles:
No journal articles submitted with this report: View all 4 publications for this projectSupplemental Keywords:
air, water, VOC, environmental chemistry, monitoring, analytical, EPA Regions., Air, Scientific Discipline, Chemistry, Electron Microscopy, Environmental Chemistry, Engineering, Chemistry, & Physics, Mach-Zender interferometer, real time monitoring, environmental monitoring, infrared spectroscopy sensor, organic analyte species, waveguide surfaces, organic contaminants, remote sensing, sensor technologyProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.