Terbium Gallium Garnet(TGG)，as a magneto-optical crystal, is an optimum material for Faraday devices (Rotator and Isolator) in the range from 400nm-1100nm, excluding 470-500nm.The Faraday rotator consists of a TGG rod contained inside a special designed magnet. The rotation sense of the polarization of a light beam passing through the rotator only depends on the direction of the magnetic field and not on the direction of propagation of the light beam. The optical isolator is a Faraday rotator set between two suitably aligned polarizers which allows a light beam to pass through in one direction only. TGG has a combination of excellent properties such as large Verdet constant, low light loss, high thermal conductance and high light damage threshold which makes it a unique material for Faraday devices particularly suitable for YAG lasers and Ti: sapphire tunable lasers, ring lasers and seed injected lasers.
Crystal Parameters:
| Chemical Formula | Tb3Ga5O12 |
| Lattice Parameter | a=12.355Å |
| Growth Method | Czocralski |
| Density | 7.13g/cm3 |
| Mohs Hardness | 8.0 |
| Melting Point | 1725oC |
| Refractive Index | 1.954 at 1064nm |
| Thermal Conductivity | 9.4×10-6oC-1 |
| Verdet Constant | 0.12min/Oe.cm at 1064nm |
Standard TGG rod specification:
| Crystal rod parameters: | |
| Orientation | [111] within 5 degrees |
| Wave front Distortion(Measured at 633nm) | < 1/8 wave total |
| Extinction Ratio | > 30dB |
| Dimensional Tolerances: | |
| Diameter | +0.00mm/-0.05mm |
| Length | +0.2mm/-0.2mm |
| Chamfer | 0.13mm (+0.00mm,-0.08mm) at 45º +/- 5º |
| End Configuration: | |
| Flatness | < 1/10 wave at 633nm |
| Parallelism | < 1 minutes of arc |
| Perpendicularity | < 1 degree |
| Scratch-dig | 10-5 per MIL-O13830A |