The United States of America As Represented by the Director of the

The United States of America As Represented by the National Security

Timothy E Dimmick

Duane Anthony Satorius

An inexpensive and accurate wavemeter for measuring the wavelength of monochromatic light is described. The device uses the wavelength dependent phase lag between principal polarization states of a length of birefringent material (retarder) as the basis for measuring the optical wavelength. The retarder is sandwiched between a polarizer and a polarizing beamsplitter and is oriented such that its principal axes are non-orthogonal to the axis of the polarizer and the principal axes of the beamsplitter. As a result of the disparity in propagation velocities between the principal polarization states of the retarder, the ratio of the optical power exiting the two ports of the polarizing beamsplitter is wavelength dependent. If the input wavelength is known to be within a specified range, the measurement of the power ratio uniquely determines the input wavelength. The device offers the advantage of trading wavelength coverage for increased resolution simply through the choice of the retarder length. Implementations of the device employing both bulk-optic components and fiber-optic components are described.

Polarization interferometer apparatus using the polarization dependent

The present invention is a wide field of view electro-optic detector and locator of coherent light of unknown wavelength that includes a collecting optic that collimates incoming optical radiation, a common-path electro-optic polarization interferometer placed at an exit pupil plane, an imaging optic, a detector array placed one focal length away from said imaging optic, an image processor that processes the incoming signal in a manner that is independent of the phase of the modulation signal, and an output device. The preferred collecting optic includes a first lens, a field lens, and a collimating lens. The preferred interferometer includes a first polarizer, a liquid crystal variable phase modulator, a fixed phase retarder, and a second polarizer.

Wide field of view coherent light detector and locator

A fiber optic wavelength measuring apparatus using the wavelength dependent nature of a fused fiber coupler to measure the wavelength of light propagating in an optical fiber. The input light is coupled, using a fused fiber coupler, of the type commonly used as wavelength division mutiplexers, into two fibers and the light in these two fibers is then measured using a pair of fiber coupled photodiodes. The ratio of the optical power of light in the two fibers corresponds to the wavelength of the input light. Hence it is possible to perform precise real-time measurement of the wavelength of light in a fiber with a compact, inexpensive, and field rugged apparatus.

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Glenville, PA, United States of America

Timothy E Dimmick