George M. Wood

Recent advances in efficient long-life, eye-safe solid state and CO2 lasers for laser radar applications

There is increasing interest in the comparative roles of CO2 and the more recently developed eye-safe solid-state lasers for long-life efficient laser radar applications. This paper assesses recent technology advances in each area and their roles in laser radar and especially Doppler lidar and DIAL development. The key problems in eye-safe solid-state lasers are discussed relating to the energy transfer mechanisms between the complicated energy level manifolds of the Tm,Ho,Er ion dopants in hosts with decreasing crystal fields such as YAG or YLF. One concerns optimization of energy transfer for efficient lasing through choice of dopant concentration, power density, crystal field and temperature, with the highly practical goal of minimal cooling needs. Another key problem, specific to laser radar and lidar, involves tailoring of energy transfer times to provide efficient energy extraction for short, e.g., Q-switched pulses used in DIAL and Dopper lidar. Special emphasis is given to eye-safe lasers in the 2 μm range because of the high efficiency applications to DIAL and (windshear) Doppler lidar and because they are well suited for Optical Parametric Oscillator frequency conversion into the important ≈ 4 to 5 μm DIAL range. The discussion of CO2 lasers concerns recent advances in Pt/Sn02 oxide catalysts and other noble metal/metal oxide combinations. Emphasis is given to the dramatic effects of small quantities of H20 vapor for increasing the activity and lifetime of Pt/Sn02 catalysts and to increased lifetime operation with rare isotope 12C18O2 lasing mixtures; iL-the 12C18O2 laser wavelengths in the 9.1 μm range are of special interest for space-based Doppler lidar such as the proposed Laser Atmospheric Wind Sounder.

Iterative and function-continuation Fourier deconvolution methods for enhancing mass spectrometer resolution

Mass spectrometer data in the form of ion current versus mass-to-charge ratio often include overlapping mass peaks, especially in low- and medium-resolution instruments. Numerical deconvolution of such data effectively enhances the resolution by decreasing the overlap of mass peaks. In this paper two approaches to deconvolution are presented: a function-domain iterative technique and a Fourier transform method which uses transform-domain function-continuation. Both techniques include data smoothing to reduce the sensitivity of the deconvolution to noise. The efficacy of these methods is demonstrated through application to representative mass spectrometer data and the deconvolved results are discussed and compared to data obtained from a spectrometer with sufficient resolution to achieve separation of the mass peaks studied. A case for which the deconvolution is seriously affected by Gibbs oscillations is analyzed.

Evaluation of catalyst for closed cycle operation of high energy pulsed CO2 lasers

Several catalyst materials have been tested for efficiency of converting CO and 02 to CO2 for use in a high energy CO2 laser. The composition of the gas mixtures was monitored by mass spectrometry and gas chromatography. A copper/copper oxide catalyst and a platinum/ tin oxide catalyst were used for closed cycle operation of a CO2 laser (0.7 joules/pulse), operating at 10 pulses per second.