Photorefractive performance of a CdSe/ZnS core/shell nanoparticle-sensitized polymer

Sub-Millisecond Response Time in a Photorefractive Composite Operating under CW Conditions

Extensive study of photorefractive polymeric composites photosensitized with semiconductor nanocrystals has yielded data indicating that the inclusion of such nanocrystals enhances the charge-carrier mobility, and subsequently leads to a reduction in the photorefractive response time. Unfortunately, the included nanocrystals may also act as a source of deep traps, resulting in diminished diffraction efficiencies as well as reduced two beam coupling gain coefficients. Nonetheless, previous studies indicate that this problem is mitigated through the inclusion of semiconductor nanocrystals possessing a relatively narrow band-gap. Here, we fully exploit this property by doping PbS nanocrystals into a newly formulated photorefractive composite based on molecular triphenyldiamine photosensitized with C₆₀. Through this approach, response times of 399 μs are observed, opening the door for video and other high-speed applications. It is further demonstrated that this improvement in response time occurs with little sacrifice in photorefractive efficiency, with internal diffraction efficiencies of 72% and two-beam-coupling gain coefficients of 500 cm⁻¹ being measured. A thorough analysis of the experimental data is presented, supporting the hypothesized mechanism of enhanced charge mobility without the accompaniment of superfluous traps. It is anticipated that this approach can play a significant role in the eventual commercialization of this class of materials.

Nanoparticle-Based Photorefractive Polymers

Photorefractivity has attracted intense attention owing to its ability to spatially modulate the refractive index under non-uniform light illumination. In particular, photorefractive polymers are appealing materials as they enable the high non-linear performance that underpins many areas of photonics. The incorporation of nanoparticles into photorefractive polymers shows an enormous potential owing to the broad spectroscopic tuning range and the high photogeneration efficiency, which are inaccessible to traditional photorefractive materials. This article reviews the recent developments in the field of nanoparticle-doped photorefractive polymers. The merit and functionality of these hybrid materials are summarized and future challenges are discussed. The application of nanoparticle-doped photorefractive polymers under two-photon excitation is also described, which facilitates a promising new area of high-density optical data storage, the third-generation of optical data storage.