This review describes the current state-of-the-art of photorefractive polymers for holography. The analysis of this rich field begins with a brief historical perspective followed by descriptions of prevailing physical models relating basic parameters of the polymer constituents to the bulk response of the final device. Methods for probing these responses and the underlying phenomena are discussed followed by an overview of the recent holographic applications of photorefractive polymers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 193–231

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/polb.23412

Photorefractive polymers for holography

Review on tabletop true 3D display

Photorefractive polymers have been extensively studied for over two decades and have found applications in holographic displays and optical image processing. The complexity of these materials arises from multiple charge contributions, for example, leading to the formation of competing photorefractive gratings. It has been recently shown that in a photorefractive polymer at relatively moderate applied electric fields the primary charge carriers (holes) establish an initial grating, followed by a subsequent competing grating (electrons) resulting in a decreased two-beam coupling and diffraction efficiencies. In this paper, it is shown that with relatively large sustainable bias fields, the two-beam coupling efficiency is enhanced owing to a decreased electron contribution. These results also explain the cause of dielectric breakdown experienced under large bias fields. Our conclusions are supported by self-pumped transient two-beam coupling and photocurrent measurements as a function of applied bias fields at different wavelengths.

Achieving enhanced gain in photorefractive polymers by eliminating electron contributions using large bias fields

AFOSR [FA9550-10-1-0207]; National Science Foundation through CIAN NSF ERC [EEC-0812072]; Office of Naval Research [N00014-14-1-0505]

Diffraction response of photorefractive polymers over nine orders of magnitude of pulse duration.

Enhanced photoconductivity and trapping rate through control of bulk state in organic triphenylamine-based photorefractive materials

The time dynamics of self-pumped reflection gratings in a commonly used photorefractive polymer PDCST:PVK:ECZ-BBP:C60 with no additional electron sources or traps is investigated. While holes are normally the mobile charges and responsible for grating formation, our experimental observations, analyzed using multi-exponential fitting curves, show evidence of electrons in addition to holes as charge carriers, particularly above an applied field of 40 V/μm. The dependence of effective carrier mobilities on the applied electric field, deduced from experimental results, show stronger field dependence of electron mobility at high electric fields. At an applied field of 70 V/μm, electron and hole mobilities become approximately equal, and the contribution of electrons on grating formation becomes significant.

/pdf/time-dynamics-of-self-pumped-reflection-gratings-in-a-2uz1ijyqyl.pdf

Time dynamics of self-pumped reflection gratings in a photorefractive polymer

The complexity of photorefractive polymers arises from multiple contributions to the photo-induced index grating. Analysis of the time dynamics of the two-beam coupling signal is used to extract information about the charge species responsible for the grating formation. It has been shown in a commonly used photorefractive polymer at moderate applied electric fields, the primary charge carriers (holes) establish an initial grating which, however, are followed by a subsequent competing grating (electrons) that decreases the two-beam coupling efficiency. We show by upon using higher applied bias fields, gain enhancement can be achieved by eliminating the electron grating contribution and returning to hole gratings only.

S. H. Buller

Papers

Achieving enhanced gain in photorefractive polymers by eliminating electron contributions using large bias fields

Time dynamics of self-pumped reflection gratings in a photorefractive polymer

Enhanced gain dynamics in photorefractive polymers