Three-Stage Attenuation Using Glan-Thompson Prisms
Final rept. Oct 1991-Dec 1992
PHILLIPS LAB KIRTLAND AFB NM
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Conventional three-polarizer attenuators were developed in the 1960s and had accuracies limited to 0.001 transmittance unit. In 1971, Mielenz and Eckerle determined that at least ten times more accuracy could be obtained using two new types of attenuators which employed either a half-wave or a quarter-wave retardation plate, in conjunction with two sheet polarizers. The purpose of the current effort was to test the same concept using extremely high quality optical Glan-Thompson prisms, extremely precise automated stages, and an experimental setup designed to provide accurate measurement for high extinction ratios, to determine the feasibility of using a three-stage polarizer attenuator with laser beams in the 350- to 2500-nm range. This device would be used to calibrate experimental signals andor the transmittance of neutral density filters. The experimental results indicated that this attenuator could only provide uncertainties of 1 to 2 percent. The photometric accuracy was not tested with natural sources. However, this attenuator was useful in providing practical accuracies of a few percent over a wide dynamic range with a simple technique. It can be used to calibrate neutral density filters over a wavelength range from 350 to 2500 nm and an optical density range of nine orders of magnitude. Attenuation prisms transmittance, Three-polarizer.