Iron garnets have long been known for their high Faraday rotation. Yttrium Iron Garnet (YIG) and Bismuth-substituted rare earth iron garnets (Bi:RIG or BIG) are excellent materials that exhibit a large Faraday effect paired with good transparency.  These iron garnets, however, cannot be grown as large single crystals; their growth is accomplished through epitaxy of magnetic garnet films on garnet substrates. The result is a single crystal thick film growth that can be used as a Faraday rotator in optical isolators and optical switches.

Enter Saint-Gobain Crystals garnet substrates.   Our garnets are ideal for use in epitaxy processing of magnetic garnet films.  They can withstand harsh epitaxy environments and because we perfectly regulate their composition, they ensure excellent control and reproducibility of the lattice parameter.  In turn, the ensuing iron garnet thick films are at the core of a wide variety of magnetic and optical devices including memory, display and signal processing, magnetic field imaging sensors and optical communications applications such as optical isolators and circulators.

Products Available

Saint-Gobain Crystals manufactures Gallium based garnet crystals, with a high level of crystalline perfection, by the Czochralski process using computerized pulling machines.
A proprietary process of double sided polishing has been developed and allows us to offer polished substrates that exhibit superior flatness and surface quality. 

GGG Wafers (Gadolinium Gallium Garnet - Gd₃Ga₅O₁₂ - lattice parameter = 12.383A) offers a very close lattice match to YIG (12.376A). 

SGGG (Substituted Gadolinium Gallium Garnet - (CaGd)₃(MgZrGa)₅O₁₂ - lattice parameter = 12.497A) offers an improved match to Bismuth-substituted rare earth iron garnets. 

With its even larger lattice parameter (12.509A), NGG (Neodymium gallium garnet - Nd₃Ga₅O₁₂) is used for the growth of larger Bismuth content BIG films. 

Main Characteristics

Garnet substrates are usually supplied in the (111) direction, however special orientations like (100) and (110), non standard thicknesses and compositions may be supplied on request.

Polished substrates are core and facet free. 

Substrate edges are rounded.  

Dislocation density measurements are made by visual inspection after a chemical etching process. 

Diameters:  
SGGG: up to 4"
GGG:   up to 3"
NGG:   up to 2"