Title of
Paper: High-Power Fiber
Sources for In Situ and Remote Detection of Trace Species
Principal
Author: Dahv Kliner
Abstract: Rare-earth-doped fiber lasers and
amplifiers are finding widespread use in applications requiring compact, rugged
optical sources with high beam quality. Single-mode (SM) fiber sources offer
the advantages of:
- high efficiency (we have demonstrated
39% electrical-to-optical efficiency);
- high-gain (~50 dB) and low-threshold
operation;
- diffraction-limited beam quality that
is insensitive to thermal or mechanical fluctuations, optical power level,
or aging of the laser system;
- continuous tunability;
- broad wavelength coverage in the
near-IR by selection of various rare-earth dopants;
- pumping with low-cost, reliable diode
lasers;
- room-temperature operation and no
significant cooling requirements; and
- scalability to high power (>100
W).
We are developing
pulsed and cw fiber sources for spectroscopic detection of trace species in the
IR and UV spectral regions. Current projects include development of a
high-sensitivity instrument for in situ detection of atmospheric SO2 by
laser-induced fluorescence and construction of a hand-held imager for stand-off
detection of CH4 using backscatter absorption gas imaging. Advances made in the
course of this research include:
- demonstration of a method to increase
the peak and average powers of fiber amplifiers by at least an order of
magnitude using multimode fiber, while maintaining the diffraction-limited
beam quality characteristic of SM fiber;
- development of
polarization-maintaining, double-clad, Yb-doped fiber, which allows
fabrication of fiber sources that maintain stable, linear polarization;
- construction of a compact, packaged,
narrow-linewidth (<1 MHz) fiber amplifier with >4 W cw output power;
- use of a fiber-pumped OPO based on
periodically poled lithium niobate to generate tunable radiation in the
3-micron region; and
- frequency-quadrupling of a pulsed
fiber source to generate UV radiation with high efficiency.
I will review
these developments and will discuss application of fiber sources to in situ and
remote detection of trace species throughout the atmosphere.