Photorefractive Materials for Dynamic Optical Recording. Jaime Frejlich

The dashed line is the spectrum of th...Figure 2.9 Intrinsic semiconductor: Fermi level for an intrinsic semiconductor...Figure 2.10 Doped semiconductor: Fermi level pinned at the position of the dop...Figure 2.11 Doped semiconductor: Fermi

and quasi‐stationary Fermi levels upo...Figure 2.12 Recombination centers.Figure 2.13 Traps.Figure 2.14 Schematic representation of a material with one center (one single...Figure 2.15 Under the action of light (of adequate wavelength) electrons are e...Figure 2.16 In this example, under the action of light, electrons and holes ar...Figure 2.17 Under nonuniform light, negative charges (in this case, we assume ...Figure 2.18 Photochromic effect and the band‐transport model. On the left side...Figure 2.19 Schema for the crystal samples: undoped

(labeled BTO‐J40), lead‐...Figure 2.20 Crystal samples.Figure 2.21

(left) and

:Fe (right) crystal samples showing the [010] and c‐...Figure 2.22 Average photovoltaic current density measured along axes [010] and...Figure 2.23 Polarization‐dependent photovoltaic photocurrent for both BTeO and...Figure 2.24 Photocurrent (

)

, for undoped

as a function of the angle

. Th...Figure 2.25 Photovoltaic current versus light intensity

(uniform

nm laser ...Figure 2.26 Photovoltaic current versus light intensity (uniform

nm laser in...Figure 2.27 Photovoltaic current versus light intensity (uniform

nm laser in...Figure 2.28 Average photovoltaic current density data, measured along the c‐ax...Figure 2.29 Light‐induced absorption spots produced in the center of an undope...Figure 2.30 Photochromic relaxation time for

as a function of inverse absolu...Figure 2.31 Transmitted versus incident power (both measured in the air) for a...Figure 2.32 Light‐induced Schottky barrier at the illuminated transparent cond...Figure 2.33 Schema of a photorefractive BTO crystal plate between two conducti...Figure 2.34 Cross‐section schema of the ITO‐sandwiched BTO plate indicating th...Figure 2.35 ITO sandwiched 0.81 mm thick BTO crystal plate with electrodes wir...Figure 2.36 Measured photocurrent data referred to Fig. 2.35 with

,

and

i...Figure 2.37 Photovoltaic‐based current data (

,

and

) computed from curves ...

      3 Chapter 3Figure 3.1 Photoactive centers inside the Band Gap. There are filled traps

(...Figure 3.2 Under the action of light the electrons are excited from the traps ...Figure 3.3 The charge distribution produces a space‐charge electric field modu...Figure 3.4 The electric field modulation may produce deformations in the cryst...Figure 3.5 If the photoconductive material is also electro‐optic, that is to s...Figure 3.6 Holographic setup: A laser beam is divided by the beamsplitter BS, ...Figure 3.7 Generation of an interference pattern of fringes.Figure 3.8Figure 3.8 Light excitation of electrons to the CB in the crystal.Figure 3.9Figure 3.9 Generation of an electric charge spatial modulation in th...Figure 3.10Figure 3.10 Generation of a space‐charge electric field modulation.Figure 3.11Figure 3.11 The electric field modulation produces a index‐of‐refra...Figure 3.12Figure 3.12 The recorded grating can be read using one of the recor...Figure 3.13Figure 3.13 The grating is erased during reading.Figure 3.14 Until all recording is erased.Figure 3.15 Space‐charge electric field grating being recorded by the

‐shifte...Figure 3.16 Space‐charge electric field without an externally applied field fo...Figure 3.17 Simulated recording (from 0 to 20 au) and erasure (from 20 to 50 a...Figure 3.18 Index‐of‐refraction modulation arising in the crystal volume. The ...Figure 3.19 Schematic description of running hologram generation in photorefra...Figure 3.20 Plot of

for the assumed parameters:

m,

m,

,

rad/s,

and

Figure 3.21 Plot of

from Eq. 3.85 for the same parameters referred to in Fig...Figure 3.22 Plotting of Q as a function of

(

‐axis) and

(

‐axis) for

V/m...Figure 3.23 Plotting of Q as a function of K, from Eq. 3.91, for typical value...Figure 3.24 Plotting of

(continuous curve),

(long dashing curve) and

(sh...Figure 3.25 One‐species/two‐valence/two‐charge carrier model contributing to c...Figure 3.26 Two‐species/two‐valence/two‐charge carrier model contributing to c...Figure 3.27 Hole‐electron competition on different photoactive centers under t...Figure 3.28 Short circuit schema using conductive silver glue to electrically ...

      4 Chapter 4Figure 4.1 Reading the recorded hologram with one of the recording beams.Figure 4.2 Recording a fixed volume index‐of‐refraction hologram that is phase...Figure 4.3 Bragg condition where

and

are the incident beam and the diffrac...Figure 4.4 Amplitude coupling in two‐wave mixing: in this example, the weaker...Figure 4.5 Phase coupling in two‐wave mixing: the pattern of fringes and assoc...Figure 4.6 Numerical plotting of

versus the normalized time

, from Eq. 4.80...Figure 4.7 Numerical plotting of

versus the normalized time