Diode laser source for DIAL methane measurements in coal mines
Thesis/Dissertation
·
OSTI ID:5604295
A study was conducted to determine if room-temperature injection lasers could be used as the source for a DIAL methanometer for coal mine applications. Prior DIAL measurements of methane were reviewed and the measurement technique was explored in a general way. The absorption spectroscopy of methane was then examined in detail and found to contain an appropriate absorption feature near a wavelength of 1.65 ..mu..m provided the spectral width of the light source was approximately 0.2 cm/sup -1/. Also the operating characteristics of broad area high optical output InGaAs/InP injection lasers were examined. A detailed calculation of the requirements for a diode laser DIAL measurement of methane in a coal mine was then performed. It was found that broad area LnGaAs/InP injection lasers were suitable in most respects for coal methane measurements. The exception was the diode laser spectral bandwidth. It was found to be some 400 times too large. The second task was the design and fabrication of an external grating cavity to reduce the bandwidth of the injection lasers. The optical design of an off-axis parabolic mirror grating cavity was developed. Geometric optics was used to determine the physical parameters for an external cavity which would produce the desired spectra bandwidth of 0.2 cm/sup -1/. The fabrication and performance of this external resonator source is described. Measurement of the source linewidth showed it to be two to three times larger than the design value. An explanation of the resultant bandwidth based on coupled model theory is presented.
- Research Organization:
- Oregon Graduate Center, Portland (USA)
- OSTI ID:
- 5604295
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
01 COAL, LIGNITE, AND PEAT
012000* -- Coal
Lignite
& Peat-- Mining
ABSORPTION SPECTROSCOPY
ALKANES
COAL MINES
DESIGN
GAS ANALYSIS
HYDROCARBONS
LASERS
LINE WIDTHS
MEASURING INSTRUMENTS
MEASURING METHODS
METHANE
MINES
MINING
ORGANIC COMPOUNDS
PERFORMANCE TESTING
SPECTROSCOPY
TECHNOLOGY ASSESSMENT
TESTING
UNDERGROUND FACILITIES
UNDERGROUND MINING
012000* -- Coal
Lignite
& Peat-- Mining
ABSORPTION SPECTROSCOPY
ALKANES
COAL MINES
DESIGN
GAS ANALYSIS
HYDROCARBONS
LASERS
LINE WIDTHS
MEASURING INSTRUMENTS
MEASURING METHODS
METHANE
MINES
MINING
ORGANIC COMPOUNDS
PERFORMANCE TESTING
SPECTROSCOPY
TECHNOLOGY ASSESSMENT
TESTING
UNDERGROUND FACILITIES
UNDERGROUND MINING