SBIR-STTR Award

It is proposed to employ diffractive waveplate optical elements in an energy web architecture in the atmosphere or in space. Such optical elements may also be referred to as geometric phase optical elements or Pancharatnam-Berry Phase optical elements. Such diffractive elements have the potential to be orders of magnitude lighter than comparable refractive or reflective conventional optical elements, and are therefore worth considering for applications in which weight is a major factor. Calculations show that the total active birefringent material weight for a 3.5 meter diameter beam deflector/recollimator fabricated with such diffractive waveplate technology would weight only about 67 grams, i.e. the weight of the active birefringent material would be negligibly small. The Phase I program would address some of the major barriers to such employment of diffractive waveplate technology, including the maintenance of diffraction-limited performance for the large apertures needed for long-range transmission between relay elements of the energy web.

The Phase 2 work would allow us prototyping and delivering a beam steering system for energy web by optimizing the materials, the components, and the architecture of the relay nod. the objectives of the work are: 1. Developing cycloidal diffractive waveplates (CDWs), the planar geometrical phase analog of a prism, with enhanced optical properties with respect to efficiency and functionality that better meet multiple application requirements such as the need for steering bi-chromatic beams, controlling stray light, and minimizing wavefront errors; 2. Optimizing architectures of planar beam steering systems adapted to coherently as well as spectrally combined high energy laser beams; 3. Enhancing the steering system for line-of-sight jitter control of full aperture beams; 4. Maximizing efficiency and field of regard; 5. Developing material basis and improved fabrication processes for up to 8” aperture CDWs, including CDWs possessing optical power; 6. Fabricating and delivering a fully functional prototype system tested and characterized with low-power laser beams, and ready for high energy laser tests. While DARPA has taken over the challenge of using planar diffractive optics to enable critical application earlier (DARPA MOIRE, DARPA Extreme), this is the first time when the technology is adequate to meet challenging application requirements due, particularly, to the maturation of the fourth generation of optics. The Phase 1 of the project has allowed us to show the feasibility of dramatic SWaP reduction and enhancing the ultralight beam steering system with features such as polarization-independent wide angle steering, low-sensitivity to jitter typical to all-transmissive optics, automatic reduction of stray beams to low power density levels, refocusing the high energy laser between relays without compromising weight and size, and providing full aperture wavefront controls. The Phase 2 work will use low-profile off-the-shelf-actuators for prototype development. The development will lay the grounds for next generation energy web relay systems.