Issues related to the development of direct detection, long-range CO2 DIAL systems for chemical detection and identification are presented and discussed including : data handling and display techniques for large, multi-lambda data sets, turbulence effects, slant path propagation, and speckle averaging. Data examples from various field campaigns and CO2 lidar platforms are used to illustrate the issues.

A combined experimental and computational approach utilizing tunable CO(2) lasers and chemometric analysis was employed to detect chemicals and their concentrations in the field under controlled release conditions. We collected absorption spectra for four organic gases in the laboratory by lasing 40 lines of the laser in the 9.3-10.8-mum range. The ability to predict properly the chemicals and their respective concentrations depends on the nature of the target, the atmospheric conditions, and the round-trip distance. In 39 of the 45 field experiments, the identities of the released chemicals were identified correctly without predictions of false positives or false negatives.

A combined experimental and computational approach utilizing CO2 infrared gas lasers and chemometric multivariate analysis was employed to detect chemicals and their concentrations in the open atmosphere under controlled release conditions. Absorption spectra of four organic gases were collected in the laboratory by lasing 40 lines of a Synrad 15 W CO2 laser in the 9.3 to 10.8 micron range. Several chemometric calibration models were constructed based on this IR data using the Partial Least Squares computational technique. The chemometric models were used to analyze in near real time the field DIAL data acquired over this exact wavelength range at round trip distances of 7 and 13 km. It will be shown that the ability to predict the chemicals and their respective concentrations depends on a variety of factors. In 39 of the 45 experiments, the identities of the released chemicals were correctly identified without predictions of false positives or false negatives. Under the best field conditions, we achieved predictions of absolute concentrations within 30% of the actual values.

The techniques utilized to study the surface and bulk properties of KTiOPO4 (KTP) were Rutherford backscattering (RBS), particle induced x-ray emission (PIXE), secondary ion mass spectrometry (SIMS), optical absorption and emission spectroscopy, and controlled laser damage. RBS and SIMS results provide strong evidence for potassium ion and titanium ion migration from the bulk to the electrode surface under an applied DC voltage. Optical measurements suggest the presence of Ti3+ ions in pristine, EC and PC damages KTP. Catastrophic damage was induced models will be presented to rationalize the RBS, PIXE and SIMS data for the impurities, and a damage mechanism consistent with the findings of the laser damage and optical absorption and emission experiments will be discussed.

The UV Laser Damage Program has been in existence at Los Alamos for over five years. Recently, the damage laboratories have been upgraded by using a computer system to control and monitor testing parameters, and to display and store the damage data. The system was designed around already existing testing equipment merged with an IBM-XT for cost effectiveness. The damage fluence is set by a programmable beam attenuator configured in a closed-loop control system with the computer and an energy meter. A matrix of damage sites is set up at the test plane such that the operator can move the sample sequentially between sites or pick sites at random. To aid the operator in choosing test fluence values, a damage plot may be generated on the monitor or on a high resolution plotter. By automating the Laser Damage Laboratory with a computer, consistent results can be achieved over a short testing time.

In a series of experiments incorporating 351-nm pulselengths of 9, 26, 54, and 625 ns, it was found that laser damage thresholds increased as (pulselength)X, and that the exponent averaged 0.36 and ranged, for different samples, from 0.23 to 0.48. Similar results were obtained when only catastrophic damage was considered. Samples included Al2O3/SiO2 in both AR and HR multilayers, HR's of Sc2O3/SiO2 and HfO2/SiO2, and an Al-on-pyrex mirror; 9-ns thresholds were between 0.2-5.6 J/cm2. When these data were compared with a wide range of other results — for wavelengths from 0.25 to 10.6 μm and pulselengths down to 4 ps — a remarkably consistent picture emerged. Damage thresholds, on average, increase approximately as the cube-root of pulselength from picoseconds to nearly a microsecond, and do so regardless of wavelength or material under test.

The need for improved means of beam attenuation in uv optical damage experiments has led to the development of a new reflective attenuator using conventional multilayer dielectric optics. The device has low insertion loss even for unpolarized beams, high damage resistance, continuously variable attenuation, and a large clear aperture. Also discussed is a transmissive version of this device which uses standard reflectors or edge filters. Either version lends itself well to computer automation.

A laser damage test facility is described which employs in-line beam diagnostics and a real-time video monitoring system. Testing at three excimer laser wavelengths is accomplished at 35 pps with a nominal 10-ns pulsewidth. The test spotsize (1/e/sup 2/ diameter) is typically 0.6 mm. Samples have consisted primarily of multilayer dielectric reflectors composed of a variety of materials. In particular, the best results - is congruent to 3 J/cm/sup 2/ at 248 nm, is congruent to 5 J/cm/sup 2/ at 308 nM, and is congruent to 8 J/cm/sup 2/ at 351 nm - have been obtained consistently for coatings utilizing ThF/sub 4/, Al/sub 2/O/sub 3/, or Sc/sub 2/O/sub 3/ as the high-index component. Significant improvement has resulted from the use of non-quarterwave designs at 248 and 308 nm. Also presented are preliminary 248 nm test results for LiF - both single crystal and press-forged - and KD*P.