Photorefractive Crystals
Photorefraction is an effect of refractive index variation in the material
exposed to the light. This property makes it possible to create spatial
distribution of refractive index in the crystal and can be used in wide variety
of devices including spatial light modulators, optical memory, holography, phase
conjugation etc.
Most popular photorefractive crystals are Fe:LiNbO3 and crystals of Sillenite
structure Bi12MO20 (M = Si, Ge, Ti). These crystals have fortunate combination
of photorefractive, electrooptic and other properties making it promising
materials for optoelectronics.
Material Properties
| |
BSO |
BGO |
Fe:LiNbO3 |
| Crystal Symmetry |
Cubic, 23 |
Cubic, 23 |
Trigonal, 3m |
| Density, g/cm3 |
9.20 |
9.22 |
4.64 |
| Mohs Hardness |
5 |
4.5 |
5 |
| Melting Point, °C |
900 |
925 |
1255 (Tc=1140) |
| Transparancy Range, mm |
0.45 - 6 |
0.45 - 7 |
0.35 - 5.5 |
| Refractive Index at l=0.63 mm |
2.54 |
2.55 |
2.29 (no)
2.20 (ne) |
| Electrooptical Coefficient ,pm/V at l=0.63 microns |
5.0 (r41) |
3.5 (r41) |
32 (r33)
6.8 (r22)
10 (r31) |
| Dielectric Constant( low frequency) |
56 |
40 |
85 (e11)
30 (e33) |
NOTE
- Fe:LiNbO3 is available with various concentrations of Fe dopant from
0.005 to 0.1 mol.%. Crystals are grown from congruent melt.
- Finished elements are available in sizes (3-20)x(3-20)x(3-20) mm3. Wafers with
dia. up to 40 mm, or 30x30 mm square, 0.5 - 5.0 mm thick are available.
- Polish standard: 20/10 S/D, λ/4 flatness, parallelism <
2 arcmin
- Coatings available:
a) AR @ 514 nm, 532 nm or other on request
b) ITO conductive/transparent coatings
c) electrodes Cr + Au
- Other photorefractive crystals available from ELAN: doped BGO and BSO, BTO,
Fe:Ti:Ce:LiNbO3, crystals for UV photorefraction (LiTaO3, LiIO3, undoped
LiNbO3).
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