Physics Department Colloquium - “Diffractive Waveplates: Beyond Prisms, Lenses, and Q-Plates" by Dr. Gary Walsh, Research Electrical Engineer U. S. Army Combat Capabilities Development Command - Soldier Center, Natick MA

Monday, April 01, 2019
4:00 pm

Location:

Floor/Room #: 
109

Diffractive waveplate technology makes possible micron thin high quality optical elements. Through pattering the orientation of polymer liquid crystal films geometric phase optical elements are created that can be conformed to many surfaces such as flexible polymers. These components can be made to appear and disappear electronically, and possess polarization selection properties not seen in traditional optics. Lenses, prisms, and spiral phase plates are just a few of the elements that can be realized in this thin film technology. In this seminar diffractive waveplate technology is discussed along with advanced design methods that make possible the creation of complex optical systems that go beyond how this technology has traditionally been employed. Examples will include an angular momentum sorter which generalizes a log-polar transformation to separate both the orbital and spin angular momentum components of optical beams. Also arrays of singularities are presented in which vortex phase functions are summed together in phase to transform periodic and aperiodic point lattices into topological geometric phase elements that maintain the spatial frequency characteristic of the underlying lattice. This allows the vast field of diffraction from photonic arrays to be leveraged for shaping optical beams. A specific example of a golden angle spiral structure is given in which diffraction by geometric phase optics produce composite beams consisting of a small number of high order Bessel beams, encoding a dense spectrum of orbital angular momentum. This composition is demonstrated by numerical decomposition of theoretical diffraction and measured directly with the geometric phase angular momentum sorter. The advances presented in the design of specialty optics and optical systems with diffractive waveplate geometric phase elements demonstrate the impact that this thin film technology will have a future of optics.

 

Refreshments will be served in Olin Hall 118 at 3:30 P.M.

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