Metrology Tools and Processes Enable Commercial Grating Supply for HEL Weapons

S2909 — Production of MLD Gratings for Laser Weapon Systems

Objective

Multilayer dielectric (MLD) diffraction gratings, a key optical element in
many current and planned high energy laser (HEL) weapon systems, are
currently not available at the required performance level from a verified
commercial source. Lawrence Livermore National Laboratory (LLNL) is
currently the only source to fabricate MLD gratings for the DoD suitable for
spectral beam combining (SBC) HEL weapon systems. MLD gratings must
withstand high laser intensities, provide high diffraction efficiency with minimal
scatter over the spectral range of the laser sources, and exhibit minimal thermal
heating to minimize optical deformation. Performance in all of these areas must
be verified with specialized instruments and testing procedures to fully
characterize grating performance. This Electro-Optics Center (EOC) project will
develop the characterization tools and processes required to assess grating
performance and is the first phase in a group of grating projects aimed at
developing a commercial grating production capability for HEL weapon systems.

Payoff

Successful execution of this Capability Acceleration project will result in
documented grating characterization processes and measurement instruments to
permit independent assessment of commercial gratings against the performance
specification. It will then be available to support the development of a common
means of specifying a grating at a component level (versus the current approach – a
design spec supporting an overall system performance requirement). Navy, Army,
and the Office of the Se cretary of De fense are supporting follow-on projects that
will leverage the use of the instruments developed under this effort, and the EOC
expertise gained from characterizing the commercial and LLNL gratings. Grating
manufacturing requires very technical use of lithography and etching tools to achieve
the required performance levels. This project is providing critical characterization data
to support development of the commercial grating capability and verification of the
grating product prior to HEL insertion. With SBC grating procurements expected
to grow exponentially for HEL use, a commercial source greatly reduces supply risks.
Upon completion of the follow-on projects, a minimum of one commercial source
for HEL gratings is expected.

Implementation

The results from this project, including characterization processes,
measurement instruments, and expertise in characterizing HEL gratings, will
be implemented in follow-on HEL gratings manufacturing programs across
multiple services. This stringent characterization capability will be essential for
development of commercially supplied MLD gratings which are needed for future
deployment of HEL weapon systems on Navy DDG 51 Class destroyers and FFG
62 Class frigates.