α-BBO

α-BBO, high temperature phase of BaB2O4, is an excellent birefringent crystal, which has been successfully grown in our laboratory.  It is characterized by large birefringent coefficient and wide transmission-window ranged from 189nm to 3500nm.  The high chemical stability and medium hardness of α-BBO make it easy to be fabricated into many kinds of fine optical components, such as prisms, optical isolators.  Therefore, in many cases, the calcite, YVO4, TiO2 etc. can be replaced by α-BBO.  Especially, compared with natural calcite crystal, whose practical applications are often limited due to its optical in-homogeneity, small size and cleavability,α-BBO has high optical quality and large size (in diameter of 40-50mm and length of 25-35mm).

Specifications of α-BBO
Diameter max 40~50mm
Length max 25~35mm
Surface Quality 20/10 Scratch and Dig
Beam Deviation <3 arc min.
Optical Axis Orientation +/-0.5°
Flatness λ/4 @ 632.8 nm
Transmission Wavefront Distortion <λ/2 @632.8 nm
AR-coating R<0.5%
Basic Properties of α-BBO
Transparency Range: 189 - 3500 nm, See Transparency Curve

Transparency Curve of α-BBO

Density: 3.85 g/cm3
Therm-Optic Coefficients:
dno/dT = -9.3 x 10-6/ ℃
dne/dT = -6.6 x 10-6/ ℃
Damage Threshold:
at 1064nm 1GW/cm2 
at 355nm 500 MW/cm2
Optical Homogeneity: Δn ≈10-6/cm
Mohs Hardness: 4.5
Hygroscopic Susceptibility: Low
Thermal Expansion Coefficients (in the range of 25 ℃– 900 ℃)αa= 4 x 10-6/K, αc= 36 x 10-6/K
Linear Absorption Coefficients: α <0.005 cm-1 from 300nm to 2300nm
Refractive Indices, Birefringence (Δn = ne - no) and Walk-off Angle at 45º (ρ):
at 1064μm ne= 1.58462, no = 1.65790       Δn =-0.073282 ρ =-4.9532º 
at 532nm ne = 1.60206, no = 1.67755       Δn =-0.075491  ρ =-5.0407º 
at 266nm ne = 1.67190, no = 1.76171 Δn=-0.089805 ρ =-5.6926º