Skip navigation
Please use this identifier to cite or link to this item:
Full metadata record
DC FieldValueLanguage
dc.contributor.advisorWysocki, Gerarden_US
dc.contributor.authorWang, Yinen_US
dc.contributor.otherElectrical Engineering Departmenten_US
dc.description.abstractSensitive detection of trace gas molecules has various important applications in environmental science, medical diagnostics and homeland security. The invention of quantum cascade lasers (QCLs) has triggered development of compact, efficient and highly sensitive mid-infrared (mid-IR) spectroscopic techniques. This dissertation is primarily focused on Faraday rotation spectroscopy (FRS) for detection of gas-phase radicals, and new methods to perform broadband, high-resolution mid-IR spectroscopy. The developed techniques allow the sensor to reach quantum limit in the real-world settings. The noise in traditional FRS systems is typically far above the quantum shot-noise due to the strong laser noise at its spectral base-band. Here, a method employing heterodyne-enhanced FRS (H-FRS) is developed. Through optical heterodyning, the signal is shifted from the low frequency to radio frequencies (RF), where the noise is strongly suppressed, allowing significant improvement of the signal-to-noise ratio. An experimental demonstration of H-FRS was performed using a distributed feedback QCL and a mercury-cadmium-telluride photodetector. The cryogen-free system exhibited the total noise of 3.7 times higher than the quantum shot-noise. The complex optical design of H-FRS limits its application only to laboratory conditions. To overcome this issue a dual modulation FRS method that requires much simpler set-up and is capable of even higher performance than H-FRS is proposed. A prototype was built as a robust transportable system and was delivered to Cleveland Clinic for the first, proof-of-principle isotopic studies of nitric oxide metabolism in human body. The total noise observed in this system is only two times higher than the quantum shot-noise. A laser testing system for optimizing QCL chips is developed. The system allows for automatic optical alignment and characterization of the QCL chips in an external cavity QCL configuration. Thus it significantly improves the data quality and reduces the manufacturing cost. These studies led to a better understanding of operation of Fabry-Perot (FP) QCLs, and allowed for development of a mid-IR spectroscopy based on multi-heterodyne of two FP-QCLs. Molecular absorption profile is down-converted into the RF spectrum by the heterodyne process. Both a multi-mode spectral retrieval and a high-resolution spectral scan capability based on the RF signal analysis are demonstrated.en_US
dc.publisherPrinceton, NJ : Princeton Universityen_US
dc.relation.isformatofThe Mudd Manuscript Library retains one bound copy of each dissertation. Search for these copies in the <a href=> library's main catalog </a>en_US
dc.subjectBreath analysisen_US
dc.subjectNitric oxideen_US
dc.subjectQuantum cascade lasersen_US
dc.titleDevelopment of Novel Mid-Infrared Spectrometers based on Quantum Cascade Lasersen_US
dc.typeAcademic dissertations (Ph.D.)en_US
Appears in Collections:Electrical Engineering

Files in This Item:
File Description SizeFormat 
Wang_princeton_0181D_10833.pdf12.89 MBAdobe PDFView/Download

Items in Dataspace are protected by copyright, with all rights reserved, unless otherwise indicated.