Laser spectroscopic trace chemical sensors for environmental sensor networks and portable medical devices
So, Stephen G.
Tittel, Frank K.
Doctor of Philosophy thesis
This thesis represents the development of the first laser spectroscopy based trace-gas sensors with sensor characteristics which simultaneously satisfy low cost, handheld footprint, low power, and long term autonomous operation while still providing part-per-billion detection sensitivity and negligible interference to enable trace gas sensor networks and wearable sensors. In order to realize these demanding criteria, this work describes the development of a complete laser spectroscopic sensor platform from the ground up to determine all of the tradeoffs inherent to photonic chemical sensing, and presents a sensor platform with a configuration to meet as many application requirements as possible. Specifically, complete photonic sensor integration and design optimization (e.g. digital signal processing, low power analog, digital control technology, high speed digital design, efficient programming, infrared laser technology, mechanical design) provides sensor characteristics which are significantly improved over the current sensor technology. These sensors can permit the portable deployment of trace gas sensors and enable applications previously unattainable with any other gas sensing method. A performance comparison of the various different types of sensors measured according to these new metrics of cost, size, power consumption in addition to standard metrics (such as sensitivity and specificity) will provide a complete description of advantages and disadvantages of each trace gas sensing technique. Performance characteristics of an open-access handheld sensor platform also provide the baseline for comparison in terms of all of these new criteria. This work will also detail the development path of each major sensor component to allow new technologies to update the original modules. This thesis also describes a scalable network of high sensitivity trace gas sensors, something which has not been achieved to-date. Additionally, issues such as variable-power consumption sensor management and gas sensor data harvesting and analysis will be addressed. Several new applications will be described which may be performed with the optimized sensors which were difficult to perform previously. Finally, this thesis will extrapolate future optimal sensor configurations based on current research in MEMS, photonics, networking, integration, and sensing and will conclude with a discussion of the impact of the various advances achieved in this work.
Chemistry, Analytical; Engineering, Electronics and Electrical; Physics, Optics