TGG

TGG


The magneto-optical crystal TGG (Terbium Gallium Garnet 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 polarizer which allow 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.

Advantages

- TGG has twice the Verdet constant of a terbium-doped glass.
- The thermal conductivity of crystalline TGG is an greater than a typical glass.
- Optical losses are lower for TGG than Tb-doped glasses.

 

- The combination of the above factors make TGG better suited to high average power applications. The principal limiting factor is thermally induced beam distortion. Beam distortion is less for TGG than Tb-doped glasses under the same power loading level. 
 

 

 Basic Properties

Chemical Formula                   Tb3Ga5O12                                                          
Lattice Parameter                   a=12.355Å                                         
Growth Method                     Czocralski Method                                     
Crystal Structure [111]
Verdet Constant (632 nm) -134 RadT -1m-1
Verdet Constant (1064 nm) -40 RadT -1m-1
Density                                7.13g/cm3                                                          
Mohs Hardness                       8
Melting Point                   1725oC                                                  
Refractive Index                     1.954 @1064nm                                     
Thermal Conductivity                 7.4 W cm-1 K-1                                           

TGG Verdet Constant  Curve

Capability

Common Specification
Orientation [111] ±15 arc minutes
Wave Front Distortion                          <Lambda/8 @ 633 nm                                
Extinction Ratio > 30dB
Diameter Tolerance +0.00mm/-0.05mm
Dimension Tolerance ±0.2mm
Flatness ≤Lambda/ 10@ 633nm
Surface Quality S/D 10-5
Parallelism < 10 arc seconds
Perpendicularity < 5 arc minutes
AR Coating R<0.2% AR @1064nm
Barrel Finish (10-6 inches) 55±5