Investigation of the internal field in photorefractive materials and measurement of the effective electro-optic coefficient

Space-Charge Waves in Sillenites: Rectification and Second-Harmonic Generation

“…(Table 9.1). It is important to note that the reduction in the internal electric field obtained from measurements of rectification (E int = E 0 /(1 + q) = 0.59 E 0 for BGO and E int = 0.52 E 0 for BSO) is surprisingly close to the data reported in [25], where it was found that E int = 0.6 E 0 for BSO. This can mean that the factor q ≈ 0.7 is quite a typical value for BSO and BGO, and many data obtained from measurements in a permanent external field must be corrected by a factor 1/(1 + q) ≈ 0.6.…”

“…If holographic experiments are performed in the presence of an applied electric field, one more factor can be very important. As is often discussed, the internal field in sillenites is lower (for instance, by a factor of 0.6 [25]) than the expected internal field corresponding to the applied voltage. This is due to various screening effects caused, for instance, by the influence of contacts (or contact areas) or inhomogeneous illumination of the sample [26].…”

“…In addition to the electrooptic effect, the 23-point group permits natural activity and piezoelectric effect in the sillenites. Typically, the optical activity plays a [5] 47 [134] at f = 1 KHz n 0 2.54 [5] at λ = 633 nm, 2.52-2.53 [25] at λ = 633 nm, 2.87-2.51 [5] at λ = 400-700 nm 2.54 [5] at λ = 633 nm, 2.5476 [133] at λ = 632.8 nm 2.25 [134] 2.68 at λ = 488 nm, 2.56 [133] at λ = 630 nm [137] at λ = 600 nm 6.9 deg T −1 mm −1 [137] at λ = 500 nm ρ, deg/mm 60.2 [135] at λ = 450 nm, 20.5 [135] at λ = 650 nm, 21.2 [25] at λ = 630 nm, 25 [4] 23 [137] at λ = 600 nm 60.9 [135] at λ = 450 nm, 19.5 [135] at λ = 650 nm, 25 [4] 23 [137] at λ = 600 nm, 102 [137] at λ = 500 nm, 6.3 [134] 5.3 [7] at λ = 630 nm, 2.3 [7] at λ = 1060 nm, 6.3 [136] at λ = 633 nm, 11.9 [136] at λ = 514.5 nm, 7 [137] at λ = 600 nm, 42 [137] at λ = 400 nm, 6.49 [26] at λ = 630 nm Band gap, eV 3.25 [11,16] 3.1 [138] Trap density, cm [151] the data were not confirmed by other authors * the data were obtained from holographic experiments detrimental role since it reduces diffraction efficiency [27]. However, for a specific geometry (reflective grating with wave vector K//[111] the existence of optical activity has a positive aspect since it allows the use of orthogonally polarized beams [28].…”

“…For instance, in [106] two-wave mixing gain measurements were used to detect the resonance in the 10 kHz range under an AC applied field in BGO. (The theory of high-frequency SCW in square wave and sine wave alternating fields is presented in [25].) In [131], the so-called holographic time-of-flight technique was used to determine the electron mobility in BSO.…”

Oscillating holograms recorded in photorefractive crystals by a frequency detuned feedback loop

“…So, in theory, 0 Ϸ E D / E E Ϸ 0.027͑Ϸ1.5°͒ should produce a stationary hologram, which is in agreement with the experimental value considering that electrical charges associated with the photorefractive centers may accumulate near the electrodes and thereby act to screen the externally applied field E E , increasing the theoretical 0 value. 36 …”