|
Presented is a novel optical system using Cis-Trans photoisomerization where nearly every molecule of a mirror
substrate is itself an optically powered actuator. Primary mirrors require sub-wavelength figure (shape) error in order to
achieve acceptable Strehl ratios. Traditional telescopy methods require rigid and therefore heavy mirrors and reaction
structures as well as proportionally heavy and expensive spacecraft busses and launch vehicles. Areal density can be
reduced by increasing actuation density. Making every molecule of a substrate an actuator approaches the limit of the
areal density vs actuation design trade space.
Cis-Trans photoisomerization, a reversible reorganization of molecular structure induced by light, causes a change in the
shape and volume of azobenzene based molecules. Induced strain in these "photonic muscles" can be over 40%. Forces
are pico-newtons/molecule. Although this molecular limit is not typically multiplied in aggregate materials we have
made, considering the large number of molecules in a mole, future optimized systems may approach this limit
In some π-π* mixed valence azo-polymer membranes we have made photoisomerization causes a highly controllable
change in macroscopic dimension with application of light. Using different wavelengths and polarizations provides the
capability to actively reversibly and remotely control membrane mirror shape and dynamics using low power lasers,
instead of bulky actuators and wires, thus allowing the substitution of optically induced control for rigidity and mass.
Areal densities of our photonic muscle mirrors are approximately 100 g/m2. This includes the substrate and actuators
(which are of course the same). These materials are thin and flexible (similar to saran wrap) so high packing ratios are
possible, suggesting the possibility of deployable JWST size mirrors weighing 6 kilograms, and the possibility of
ultralightweight space telescopes the size of a football field. Photons weigh nothing. Why must even small space
telescopes weigh tons? Perhaps they do not.
|
