Faraday Crystals

Northrop Grumman SYNOPTICS is the world's leading manufacturer of synthetic crystals and optical components used primarily in the solid-state laser industry.

KTF – Potassium Terbium Fluoride

Comparison of Properties​​​
Composition TGG
Crystal structure cubic cubic
Transparency range (rad/Tm) 400 - 1500nm 400 - 1500nm
Verdet constant, 1064nm (rad/T•m) 39 36
Refractive index at 1064nm 1.944 ~1.5 (in process)
Density (g/cc) 7.2 5.86
Absorption at 1064nm ~0.16%/cm ~0.02%/cm
Thermo-optic coefficient (dn/dT)
17.9x10-6K-1 ~1x10-6/K
Nonlinear refractive index ~2x10-19m2/W ~1x10-20m2/W
Thermal conductivity (W/m•K) 7.4 1.67
Thermal expansion x 10-6°C-1 7.3 13.7
KTF - General Specifications​
Crystal axis orientation: <100> standard
<111> available
Diameter Tolerance: +0.000" / -0.002"
Chamfer: 0.005" ± 0.003" @ 45°
Barrel Finish: 55μinches
Perpendicularity: within 10arc minutes
Parallelism: 60arc-seconds or less
Rod End Face Flatness: within λ/10 wave at 633 nm wavelength
Surface Quality: 10-5
Wave Front Distortion: less than 1/4 wave per inch of length (measured at 633nm)
Standard Coating: Anti-Reflection with R < 0.25%
Data Sheet

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TGG (Terbium Gallium Garnet)

​Faraday Rotators and Isolators
TGG has twice the Verdet constant of a terbium-doped glass.​
Thermal conductivity is an order of magnitude greater than typical glass.
Optical losses are lower for TGG than Tb-doped glasses.​
Material Properties​​​
Formula: ​Tb3Ga5O12
Crystal Structure:
Extinction Ratio (over 2/3 clear aperture): ​30 dB
Verdet Constant (632nm): -134RadT-1m-1
Verdet Constant (1064nm): -40RadT-1m-1
Thermal Conductivity: 7.4Wcm-1K-1
Refractive Index: 1.95
Nonlinear Index, n2:
Figure of Merit, V/a: 27
Figure of Merit, V/n2:
Verdet Constant
Data Sheet