Abstract
Researchers at the University of Central Florida have developed a method of stabilizing external cavity QCL system alignment by exploiting changes in QCL impedance that occur with changes in alignment and optical feedback. An electrical error signal determined by the changes in QCL impedance can correct a loss of optical alignment, from changes in cavity length and mirror orientation, caused by temperature changes and vibrational or environmental noise sources.
Rapid and accurate detection of trace gases and vapors at parts-per-billion mixing ratios is critical in applications from environmental monitoring to military objectives and homeland security. Conventional analytical instruments tend to be bulky, expensive, limited to the detection of a single analyte?or require advanced training to distinguish and identify the characteristic signals of multiple analytes?are sensitive to vibrations, and have high power requirements.
The new technology for gas sensing is capable of detecting multiple analytes under the same technical principle with low power requirements and at low cost, based on intracavity laser absorption spectroscopy (ICLAS), and applicable to any chemical vapor except homopolar diatomic molecules and noble gases.
Dynamic alignment of QCL-based external cavity systems can improve the process and quality of results in applications including remote gas leak detection, pollution monitoring, medical diagnostics, industrial process controls, petrochemicals, automotive, real-time combustion control, homeland security, military applications, explosives detection, and chemical warfare agent detection.
Technical Details
By analyzing changes in optical feedback, observed as changes in QCL impedance, the UCF technology produces an error signal that can be used to stabilize the QCL system alignment. A measurement of the QCL's compliance voltage is used to determine the QCL's impedance in real time and produce a signal, conditioned and analyzed with signal processing techniques to become an error signal. The error signal is sent to electromechanical and electro-optical controls and devices (for example, galvanometer-mounted and/or piezo-controlled mirror mounts and supports), which are adjusted using known noise cancelling techniques to ensure optimized alignment for improved QCL system performance.
Benefit
Higher signal-to-noise ratioPrevents slow signal drift due to misalignmentLow power requirementsLow-cost methodDetects multiple analytesMarket Application
Gas sensors using QCL-based external cavity systems
