TGG (Terbium Gallium Garnet)


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/  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