Fast Laser Shutters With Low Vibratory Disturbances

NASA’s Jet Propulsion Laboratory, Pasadena, California

Tuesday, February 01 2005

Opposing cantilevered piezoelectric bending actuators balance each other to minimize vibration.

The figure shows a prototype vacuum-compatible, fast-acting, long-life shutter unit that generates very little vibratory disturbance during switching. This is one of a number of shutters designed to satisfy requirements specific to an experiment, to be performed aboard a spacecraft in flight, in which laser beams must be blocked rapidly and completely, without generating a vibratory disturbance large enough to adversely affect the power and frequency stability of the lasers. Commercial off-the-shelf laboratory shutter units — typically containing electromagnetcoil-driven mechanisms — were found not to satisfy the requirements because they are not vacuum-compatible, their actuators engage in uncompensated motions that generate significant vibrations, and their operational lifetimes are too short. Going beyond the initial outerspace application, the present vacuum compatible, fast-acting, long-life shutter units could also be used in terrestrial settings in which there are requirements for their special characteristics.

In designing these shutter units, unbalanced, electromagnetically driven mechanisms were replaced with balanced mechanisms that include commercial piezoelectric bending actuators. In each shutter unit, the piezoelectric bending actuators are configured symmetrically as opposing cantilever beams within a housing that contains integral mounts for lenses that focus a laser beam to a waist at the shutter location. In operation, the laser beam is blocked by titanium blades bonded near the free ends of the piezoelectric benders. The benders are driven by shaped electrical pulses with a maximum voltage differential of less than 60 V. Preliminary measurements indicate that rise and fall times are less than 1 ms.

This work was done by David Brinza, Donald Moore, Eric Hochberg, Tom Radey, and Albert Chen of Caltech for NASA’s Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Mechanics category.

The software used in this innovation is available for commercial licensing. Please contact Don Hart of the California Institute of Technology at (818) 393-3425. Refer to NPO-40151.