May 30, 2015, Saturday, 149

Research:Polarization Gratings


Jump to: navigation, search

A polarization grating is a thin-film diffractive optical element which functions analogous to a Wollaston prism beam-splitter.

Ummm... Does light have polarization???

OK. I can make it better.

Polarization is the property of electromagnetic waves (i.e., light). It describes the direction of the electric field. Use of light polarization enables a large number of current technologies such as sunglasses, liquid crystal displays, 3D movie theaters (e.g., IMAX), etc. However, it is still challenging to control polarization of light.

A polarization grating is one kind of gratings which split light into multiple orders corresponding to their periodic patterns in materials. Unlike conventional gratings such as phase or amplitude gratings, polarization gratings change light polarization as well as directions (into diffraction orders). Diffraction is also sensitive to the polarization state of incident light. For a special type of polarization gratings, it is possible to convert a specific polarization (i.e., circular/linear polarization) from unpolarized light without loss. These unique properties of polarization gratings create great opportunities for improving existing technologies and lead to emerging technologies in displays, optical communications, biomedical imaging, and novel detectors.

In OLEG, we have ability to create high-quality polarization gratings using UV holography and photo-alignment of liquid crystals. For different applications, both electrically switchable LC polarization grating cells and reactive mesogen polarization gratings (thin polymeric films) are deliverable . We developed feasible processing methods using existing materials (commercially available) for maximizing commercialization of technologies. For the first step, we built a prototype of a projection display using polarization gratings as light modulator (HolobrightTM). This bright display will be presented at CES 2008 in Las Vegas. We also demonstrated the compact spectropolarimeter without polarizers and we are developing a compact, efficient spectrometer using tunable filters using polarization gratings. In addition, we invented achromatic polarization gratings with simple but unique structures. We expect that the broadband properties of the achromatic gratings expand the scope of applications.

OLEGers explore novel technologies from fundamental science to commercial applications.