Faraday Crystals

KTF – Potassium Terbium Fluoride

Comparison of Products
Composition	TGG Tb₃Ga₅O₁₂	KTF KTb₃F₁₀
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%

Applications
Faraday Rotators and Isolators
Advantages
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:	[111]
Extinction Ratio (over 2/3 clear aperture):	30 dB
Verdet Constant (632nm):	-134RadT^-1m^-1
Verdet Constant (1064nm):	-40RadT^-1m^-1
Thermal Conductivity:	7.4Wm^-1K^-1
Refractive Index:	1.95
Nonlinear Index, n_2:	8.0
Figure of Merit, V/a:	27
Figure of Merit, V/n_2:	5