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Birefringent Crystals

The Yttrium Orthovanadate (YVO4) is a positive uniaxial crystal grown with Czochralski method. It has good mechanical and physical properties and is ideal for optical polarizing components because of its wide transparency range and large birefringence. It is an excellent synthetic substitute for Calcite (CaCO3) and Rutile (TiO2) crystals in many applications including fiber optic isolators and circulators, beam displacers, Glan polarizers and other polarizing optics, etc.

Main properties of YVO4 crystal

Crystal SymmetryZircon Tetragonal, Space Group D4h
Transmittance Range400-5000nm
Crystal Cella=b=7.12Å, c=6.29Å
Mohs Hardness5
Hygroscopic SusceptibilityNone
Thermal Expansion Coefficientαa=4.43×10-6/K αc=11.37×10-6/K

Themal Optical Coefficient

∥c:5.23 W/m/K, ⊥c:5.10 W/m/K

Refractive Indices, Birefringence (Δn=ne-no) and Walk-off Angle at 45°(ρ)n0=1.9500 ne=2.1554 Δn=0.2054 ρ=5.72°@1300nm
n0=1.9447 ne=2.1486 Δn=0.2039 ρ=5.69° @1550nm
Sellmeier Equations (λ in μm)no2=3.77834+0.069736/(λ2-0.04724)-0.0108133λ2

Specifications of YVO4 Beam displacers 

Dimensional TolerancesW(±0.05mm)xH(±0.05mm)xL(±0.1mm)
Wavefront Distortion<λ/8@632.8nm
Surface Quality10-5 S/D
Acurracy of Oriention≤0.5°
AR-coatingR<0.2%@1550+/-40nm or 1310+/-40nm



Calcite is a negative uniaxial crystal that has high birefringence, wide spectral transmission and availability in reasonably sized rhombs. Although a fairly soft crystal and easily scratched, Calcite is an ideal material for use as visible wavelengths and near IR polarizers such as Glan Taylor, Glan Thompson and Glan Laser.

Main Properties of Calcite Crystal

Transmittance Range350-2300nm
Mohs Hardness3
Hygroscopic SusceptibilityLow
Thermal Expansion Coefficientαa=24.39×10-6/K αc=5.68×10-6/K
Crystal ClassNegative uniaxial with no=na=nb, ne=nc

Refractive Indices, Birefringence (Δn=ne-no)

and Walk-off Angle at 45°(ρ)

n0=1.6629 ne=1.4885 Δn=-0.1744 ρ=6.32° @630nm
n0=1.6557 ne=1.4852 Δn=-0.1705 ρ=6.20° @1300nm

Sellmeier Equations (λ in μm)


Specifications of Polarizers 

Dimensional Tolerances+/-0.1mm
Surface Quality10-5 S/D
Acurracy of Oriention≤0.5°
Beam Deviation<3'
AR-coatingSingle MgF2


High temperature form of BBO (α-BaB2O4) is a negative uniaxial crystal. It has large birefringence over a broad transparent range of 190nm to 3500nm. The physical, chemical, thermal and optical properties of α-BBO are similar to those of β-BBO. However, the nonlinear optical properties of a-BBO crystals are nonexistent due to the centric symmetry with its crystal structure. α-BBO crystal is not recommended for NLO processes.

Main Properties of Calcite Crystal

Transmittance Range190-3500nm
Mohs Hardness4.5
Hygroscopic SusceptibilityLow
Thermal Expansion Coefficientαa=4×10-6/K αc=36×10-6/K
Optical HomogeneityΔn=10-6/cm
Linear Absorbtion Coefficient0.05%/cm-1@300-2300nm

Themal Optical Coefficient

Damage Threshold1 GW/cm2 @1064nm, 500 MW/cm2 @532nm
Refractive Indices, Birefringence (Δn=ne-no) and Walk-off Angle at 45°(ρ)no=1.7617 ne=1.6719 Δn=-0.0898 ρ=-5.6926° @266nm
no=1.6776 ne=1.6021 Δn=-0.0755 ρ=-5.0407° @532nm
no=1.6579 ne=1.5846 Δn=-0.0733 ρ=-4.953° @1064nm

Specifications of YVO4, α-BBO and Calcite Polarizers


LiNbO3 (LN) crystal is widely used as frequency doublers for wavelength greater than 1000µm and optical parametric oscillators (OPOs) pumped at 1064 nm and quasi-phase-matched (QPM) devices. Due to its unique electro-optical, photoelastic, piezoelectric and non-linear properties, Lithium Niobate is widely used in a variety of integrated and active acousto-optical devices. The material is Czochralsky grown and poled along Z-axis.

Main Properties of LN Crystal

Crystal StructureTrigonal, Space Group R3c, Point group 3m
Transmittance Range420-5200nm
Absorption Coefficient~0.1%/cm at 1064nm
Melting Point1253ºC
Mohs Hardness5
Hygroscopic SusceptibilityNone
Thermal Conductivity Coefficient38 W/m/K at 25ºC
Thermal Expansion Coefficient (at 25ºC)∥a:2.0×10-6/K, ∥c:2.2×10-6/K
Themal Optical Coefficientdno/dT=-0.874x10-6/K at 1.4μm
dne/dT=39.073x10-6/K at 1.4μm
Refractive Indicesn0=2.232 ne=2.156 @1064nm
n0=2.220 ne=2.146 @1300nm
Sellmeier Equations (λ in μm)no2=4.9048+0.11768/(λ2-0.004750)-0.027169λ2

Specifications of LN Wedges 

Dimensional Tolerances+/-0.05mm
Surface Quality10-5 S/D
Acurracy of Oriention≤0.5°
Wedge Angle Tolerances+/-0.1°

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