1. Are the electrodes on the crystal faces transparent? How I could remove electrodes from a crystal? 

We make water-carbon electrodes along tetragonal C-axis and they are not transparent. To obtain monodomain state we apply to electrodes the electric field of 6-8 kV/cm. 
Electrodes can be removed by water (put the sample in a glass with water). 

2. What is the value of the r33 coefficient for Ce:SBN crystals? 

  Coupling coefficients for Ce:SBN crystals can be different for each crystal, aproximate values are following: 

• for SBN:61:Ce - r33=255pm/V;
• for SBN:75:Ce - r33=700pm/V;
• for SBN:61:Ce:La - r33=1000pm/V, the values were measured at 633nm wavelength.

3. Have you measured other photorefractive properties of cobalt-doped strontium barium niobate crystals? 

Our crystals has high photorefractive sensitivity (S = 39 cm2 J-1 ) and short optical response times (τ = 140 ms for I = 1 W cm-2 ).