Bruce N. Perry

Controllable pulse compression in a multiple-pass-cell Raman laser

Pulse compression has been observed with the 16-microm multiple-pass-cell hydrogen Raman laser. The effect, which also leads to high quantum conversion of the pump radiation, has been analyzed and is a result of beam crossings inherent in the geometry of the device.

Stimulated Raman scattering with a tightly focused pump beam

We predict and experimentally measure the transverse spatial shapes, threshold, and ratio of Stokes to anti-Stokes radiation generated by stimulated Raman scattering of a focused Gaussian pump beam. The eigenmodes and the threshold of the scattered radiation are found to depend critically on the confocal parameter of the pump beam and the background dispersion.

Two‐photon electronic spectroscopy of Cs2GeF6:Mn4+

The spectrum of the d→d transitions of Mn+4 in Cs2GeF6 has been observed by means of two‐photon spectroscopy using a tunable infrared laser. The g→g two‐photon spectrum is fully allowed and therefore, shows the true electronic origins and symmetric vibrational sidebands without any interfering odd parity vibrations. The resulting spectra for each of the four electronic states studied (2Eg,2T1g,4T2g,a 4T1g), a 4T1g), are free of lattice mode and enabling mode complications and provide data for the analysis of Jahn–Teller effects, spin‐orbit coupling, and other dynamical processes at the impurity ion. In the 4T2g, state there is clear evidence both in the quenching of the origin quartet, and in the vibronic structure for both e‐ and t2‐type Jahn–Teller distortions. Each of the four states shows a specific, and a different mode of coupling to the lattice. Many other spectroscopic details are revealed, none of which were evident in the one‐photon spectra.

Carbon dioxide laser monitor for NH 3 in flue gas

An instrument was developed for the detection of NH3 in flue gas, exploiting a fortuitous spectral overlap between the ν2aQ(6,6) absorption line of NH3 and the R (18) emission line of the isotopic 13C16O2 laser. The system was developed for use with De–NOx processes, which convert harmful nitric oxides generated in utility and industrial furnaces into harmless nitrogen and water vapor by injection of NH3. The instrument detects unreacted NH3 in the flue gas down to concentrations of a few ppm with an accuracy of ∼10%. It can serve as an environmental monitor and as part of a feedback control system to adjust the upstream NH3 injection to the desired rate.