Measurement of the photorefractive grating phase shift in a polymer by an ac phase-modulation technique

Abstract

The complex coupling constant of a photorefractive polymer was measured as a function of an applied electric field by use of a modified ac phase modulation technique. We determined that both a photorefractive index grating and a nonphotorefractive absorption grating were present. The electric field dependencies of the amplitude and the phase of the photorefractive gain coefficient were accurately described by standard photorefractive theory. The accuracy of the photorefractive phase shift as measured by this phase-modulation technique was Ϯ1°near phase shifts of 90°and Ϯ3°near phase shifts of 45°.

Organic Photorefractives: Mechanisms, Materials, and Applications

“…To measure the phase shift Φ, a simple experimental technique based on translating the grating with respect to the interference pattern at a rate much faster than the response rate of the material has been developed. ,, The required fast displacement of the grating with respect to the intensity pattern can be accomplished either by the direct movement of sample or by changing the relative phase of the two writing beams (which translates the interference pattern). The sensitivity of the measurement can be further improved by ac phase modulation and lock-in detection . The 2BC technique in conjunction with phase shift measurements has been widely utilized to assess material parameters such as the PR trap density and electro-optic nonlinearity. ,,,,, …”

“…The sensitivity of the measurement can be further improved by ac phase modulation and lock-in detection. 101 The 2BC technique in conjunction with phase shift measurements has been widely utilized to assess material parameters such as the PR trap density and electrooptic nonlinearity. 46,49,50,85,102,103…”

Photorefractive Binary System Based on Ferroelectric Liquid Crystals

“…The PR nature of the obtained gratings was confirmed performing two different types of experiments: two-beam coupling 2 and direct phase shift measurements. [43][44][45] As already outlined in the Introduction, two-beam coupling detects possible energy exchanges between two beams interfering on a medium, and thus it is the technique of choice to assess the photorefractive nature of a hologram. As shown in Figure 10, in two-beam coupling experiments a large energy exchange between the two writing beams was obtained, with beam coupling ratios γ 1 ∼ 1.18 and γ 2 ∼ 0.72, the highest ever measured in PR FLCs.…”

<title>Edge enhancement in photorefractive polymer</title>

“…The photorefractive effect of inorganic materials has been examined theoretically and experimentally for more than 30 years. Since the discovery of the organic system with very large photorefractive response, research on organic material has been increasing [1][2][3][4][5][6]. Many applications of organic photorefractive materials have been reported [7], however application of organic material to optical information processing is now developing [8,9].…”