In this work protective "sight glasses" for infrared gas sensors showing a sub-wavelength nanostructure with random
patterns have been fabricated by reactive ion etching (RIE) in an easy and comparable cheap single step mask-less
process. By an organic coating, the intrinsic water repellent property of the surface could be enhanced, shown by contact
angle and roll-off angle measurements. The "self-cleaning" surface property and chemical robustness towards aggressive
environments are demonstrated. FT-IR spectroscopy concerning the optical properties of these nanostructured silicon
windows revealed a stable anti-reflective "moth-eye" effect in certain wavelength ranges owing to the nanostructures.
The catastrophic optical mirror damage (COMD) effect is analyzed for 808 nm emitting diode lasers in single-pulse
operation. During each single pulse, both nearfield of the laser emission and thermal image of the laser facet are
monitored with cameras being sensitive in the respective spectral regions. A temporal resolution in the μs-range is
achieved. The COMD is unambiguously related to the occurrence of a 'thermal flash' detected by thermal imaging. A
one-by-one correlation between emission nearfield, 'thermal flash', thermal runaway, and structural damage is observed.
As a consequence of the single-pulse-excitation technique, the propagation of 'dark bands' as observed in photo- or
cathodoluminescence maps in the plane of the active region from the front facet is halted after the first pulse. Because of
the rapidness of the thermal runaway, we propose the single-pulse technique for testing the facet stability and the
intentional preparation of early stages of COMD; even for diode lasers that regularly fail by other mechanisms.
Measurements of gas temperatures and concentrations in combustion and industrial processes, where hot gases are produced, can be carried out using low resolution Fourier transform IR emission spectroscopy. An experimental setup is presented for measuring transmittance as well as emittance spectra of hot gases enclosed in a heated gas cell. It is shown that the measured emissivity of a CO2 and CO mixture at 673 compare well with the absorptivity measured of the gas sample. The influence of the spectral resolution on the detection limit of CO in our experimental setup at 673 K is discussed and illustrated with experimental results and calculations. It is concluded that the most precise CO concentration measurement is obtained at low spectral resolution from a single point in the spectrum. The gas temperature and water vapor content in the hot gas of a power plant boiler can be extracted from low resolution emission spectra which is illustrated with experiments carried out on a power plant.
Fourier transform infrared spectroscopy is a powerful tool for measuring the spectral radiation from flames and industrial processes. The effects on the spectrum from flame fluctuations occurring naturally during the measurement are analyzed briefly and illustrated by experiments and simulations. Results from applications on an oil flame, a pulverized coal flame, and a full- scale waste incinerator are described. The experiments show that important information about the composition and temperature of gas and solid temperatures might be extracted from the emission spectra. The practical and technical limitations of the technique and possible future applications are discussed.
Conference Committee Involvement (4)
Remote Sensing of Clouds and the Atmosphere XIV
31 August 2009 | Berlin, Germany
Remote Sensing of Clouds and the Atmosphere XIII
15 September 2008 | Cardiff, Wales, United Kingdom
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.