Observation of 4-ms response-time in a photorefractive polymer

Efficient photorefractive polymers hold great potential for optical data processing and storage and so have been a topic of intense investigations in recent years. Materials with nearly 100% diffraction efficiencies have been developed, but these have been generally characterized by much slower responses than their less efficient inorganic counterparts. In this report, we describe a 4-ms initial rise-time using a visible-transparent chromophore in a PVK-based polymer of T_g = 39°C for 48-V/μm bias projected along the grating vector and 250-m W/cm² writing beams. This fast component consistently accounts for 90% of the steady-state response and is analyzed as a function of bias field. We also present transient ellipsometry measurements of an orientational response significantly faster than the grating development, suggesting that chromophore alignment speed does not limit transient grating formation. We describe the role of such underlying property measurements in understanding photorefractive transient behavior, and prospects for further improvements.