Optics & Photonics News - July/August 2012

Meyer and his colleagues at Iowa State, Spectral Energies LLC and the U.S. Air Force Research Laboratory (AFRL) built the system around a narrow-linewidth pulsed fiber laser as the master oscillator. The researchers used an electro-optic modulator in a burst-mode laser to reduce unwanted amplified spontaneous emission. Finally, the system relied on diode-pumped solid-state amplifiers instead of flashlamp-pumped amplification; the former has about 10 times the efficiency of the latter, according to Meyer.

To demonstrate what the laser system can do, the team performed planar laser-fluorescence imaging of a mixture of formaldehyde in a methane-air flame illuminated by the laser. At that time, the system was still using a combination of diode-pumped and flashlamp-pumped amplifiers. The researchers caught 10-ms-long, 200-image sequences with

Iowa State Univ., Spectral Energies LLC and the U.S. AFRL 10-ms sequence showing the combustion of formaldehyde in a methane-air environment.

laser pulse energy of up to 150 mJ at

1,064.3 nm, as reported in the Optics Letters paper. Since submitting the article, the researchers switched the remaining flashlamp-pumped amplifiers to their diode-pumped counterparts and realized 30-ms-long sequences.

Any kind of gas-phase spectroscopy would benefit from this type of burst-mode laser, says Meyer. It also could be used to pump an optical parametric oscillator to study other types of intermediate chemical species in the combustion process.

Meyer’s team included Mikhail Slipchenko and Sukesh Roy of Spectral Energies, James Gord and Stephen Danc-zyk of AFRL and Iowa State doctoral student Joseph Miller.