No abstract
Public reporting burden for this collection of information is estimated to average 1 hour per response, including the gathering and maintaining the data needed, and completing and reviewing the collection of information. 09114. SUBJECT TERMS blue and ultraviolet solid state, fiber, diode and gas lasers, primary solid state crystalline and glass sources, fibere systems, GaN diodes, frequency converted lamp and diode pumped blue and uv lasers, nonlinear conversion materials for blude/uv generation from the infrared, optical parametric oscillators, upconversion techniques, high order harmonic generation, system applications, Here we describe a system consisting of an extended cavity laser electronically locked to a highfinesse (Av~ 6 kHz) cavity. The Pound-Drever-Hall technique 1 is used, with the side-bands applied at 30 MHz and a servo bandwidth of nearly 3 MHz. Repetitive locking and un-locking is accomplished by the use of high-speed analog switches at a number of positions in the feedback circuit.Cavity ring-down spectroscopy is often used to measure low levels of absorption in laboratory settings. The technique relies on the accurate determination of the exponential decay of power from a high-finesse cavity. If a difference in the decay time constant can be measured both with and with-out an intra-cavity absorber present, the loss due to the absorption over an effective path of tens of kilometers can be calculated. This results in exceedingly sensitive absorption measurements. In our work we have used a 25 cm long cavity with a ring-down time of 25 \is, which corresponds to a cavity finesse of 90,000 and an effective path length of about 15 km.Both pulsed and cw lasers are used by research groups in this field. Typically the ring-down event is digitized by a fast A/D board, and subsequently the decay time is extracted by a leastsquares fit to the data. Noise in the data can be reduced by averaging if each event has the same time constant, even if the individual decay traces begin from differing intensity levels. Consequently it is often systematic errors which limit the accurate measurement of the decay time. For instance pulsed lasers, depending on the bandwidth, will generally couple to many cavity modes. This leads to beating between modes and departures from an exponential decay. CW excitation has been recognized as superior to pulsed excitation, since the decay is from a single mode and high intensity levels are possible at the start of the ring-down. 2 The ideal lasers for ring-down instruments would be widely tunable, but also have sufficiently narrow linewidths so that most of the power could be locked to a narrow cavity.The cavity ring-down is measured in transmission by quickly switching the laser frequency off of the cavity resonance, instead of using an acousto-optic switch to divert the beam from the cavity. We are presently investigating the circumstances in which this approach results in an acceptable decay time measurement. The simplicity and cost of the system is significantly reduced by t...
Army technological areas. This approach leverages external expertise, facilities, and technologies in areas where the private sector has both the lead and the incentive to invest. 6 In January 1996, ARL launched the FedLab initiative, entering into cooperative agreements with industry and university partners to form three consortia: Advanced Telecommunications and Information Distribution, Advanced Displays and Interactive Displays, and Advanced Sensors. The dynamic feature of the FedLab concept is the cumulative effect of the shared resources, both people and facilities. FedLab members are applying more of their facilities and research talent than is funded by the program. ARL held its third annual Federated Laboratory Technology Symposium to showcase the progress and results of the effort. The symposium was highly successful and resulted in the transition of technologies to the United States Army Intelligence & Security Command (INSCOM) Land Information Warfare Activity and to Advanced Technology Demonstrations. Outreach ARL manages 20 Centers Of Excellence. Notable external partners include the Army High-Performance Computing Research Center (AHPCRC) at the University of Minnesota; the Institute for Advanced Technology at the University of Texas (Austin), which is doing hypervelocity phenomena work; and the Information Sciences Center at Clark Atlanta University, with its software engineering efforts. ARL also has cooperative agreements that support microelectronics, including one with the Johns Hopkins University and one with a consortium headed by the University of Maryland. Collaborative programs in materials research are conducted with Johns Hopkins, the University of Delaware, and the Michigan Molecular Institute. ARL has pursued an active Historically Black Colleges and Universities/Minority Institutions (HBCU/MI) program since the early 1980s. It has been designated by the Department of the Army as the AMC and Army lead for HBCU/MI oversight and proponency.
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