Terbium Gallium Garnet(TGG) is the right crystal material for Farady devices(Rotator and Isolator).The Farady rotator is made up of a TGG rod contained in a special designed magnet.The polarization of a light beam passing through the rotator makes rotation. The direction of rotation is only dependent on the direction of the magnetic field and not on the direction of propagation of the light beam to pass through in one direction only. With a combination of excellent properties,such as large verdet constant, low light loss, high thermal conductance and high light damage threshold,TGG is the unique material for Farady devices.It is widely used for YAG lasers and Ti:sapphire tunable lasers, ring lasers, etc.

Physical Properties

9.OPTICAL CRYSTAL

CaF2

CaF2 is a crystal,which has good transmission from 170nm to 7800nm.It’s slightly soluble in water and susceptible to thermal shock.CaF2 is commonly in IR components such as windows,Lenses and prisms.

l Transmission Range:170nm-7800nm

l Thermal Expansion Coefficient:18.85*10-6/K

l Density:3.18g/cm³

Sapphire

    Sapphire  is a single crystal aluminum oxide(AL2O3).It is one of the hardest materials .Sapphire has good transmission characteristics over the visible,and near IR spectrum.It exhibits high mechanical strength,chemical resistance,thermal conductivity and thermal stability.It is often used as window material in specific field such as space technology where scratch or high temperature resistance is required.

Physical Properties

Silicon(si) Crystals

Silicon(Si) is commonly used as a substrate  material for infrared reflectors and windows in the 1.5um-8um region.The strong absorption band at 9um makes it unsuitable for CO2 laser transmission applications but it is frequently used for laser mirrors because of its high thermal conductivity and low density.Silicon is also a useful transmitter in 20um range.

Physical Properties