Self-Nulling Beam Combiner Using No External Phase Inverter

A self-nulling beam combiner is proposed that completely eliminates the phase inversion subsystem from the nulling interferometer, and instead uses the intrinsic phase shifts in the beam splitters. Simplifying the flight instrument in this way will be a valuable enhancement of mission reliability. The tighter tolerances on R = T (R being reflection and T being transmission coefficients) required by the self-nulling configuration actually impose no new constraints on the architecture, as two adaptive nullers must be situated between beam splitters to correct small errors in the coatings.

The new feature is exploiting the natural phase shifts in beam combiners to achieve the 180° phase inversion necessary for nulling. The advantage over prior art is that an entire subsystem, the field-flipping optics, can be eliminated.

For ultimate simplicity in the flight instrument, one might fabricate coatings to very high tolerances and dispense with the adaptive nullers altogether, with all their moving parts, along with the field flipper subsystem. A single adaptive nuller upstream of the beam combiner may be required to correct beam train errors (systematic noise), but in some circumstances phase chopping reduces these errors substantially, and there may be ways to further reduce the chop residuals. Though such coatings are beyond the current state of the art, the mechanical simplicity and robustness of a flight system without field flipper or adaptive nullers would perhaps justify considerable effort on coating fabrication.

This work was done by Eric E. Bloemhof of Caltech for NASA’s Jet Propulsion Laboratory. For more information, contact This email address is being protected from spambots. You need JavaScript enabled to view it.. NPO-47027

White Papers

Linear Guides For The Next Generation Of Medical Machines
Sponsored by IKO
Bridging the Armament Test Gap
Sponsored by Marvin Test Solutions
Getting the Most Out Of Your Next Generation Digital Security Surveillance System
Sponsored by Adlink Technology
PICO Brochure
Sponsored by Nordson EFD
Estimating the Effort and Cost of a DO-254 Program
Sponsored by Logic Circuit
T&M Solutions for Software Defined Radios (SDR)
Sponsored by Rohde and Schwarz A and D

White Papers Sponsored By: