Optical Materials

α-BBO Optical Crystal

Alpha-BBO is a birefringent optical material for polarizers and beam displacers, with a stated transparency range of 189–3500 nm. Its centrosymmetric structure suppresses second-order nonlinear conversion; it must be distinguished from beta-BBO.

Properties, applications and specifications

α-BBO Optical Crystal reference illustration

High Temperature form BBO ( a -BaB 2 O 4 ) is a negative uniaxial crystal. It has large birefringence over the broad transparent range from 189 nm to 3500 nm. The physical, chemical, thermal and optical properties of a-BBO crystal are similar to those of b-BBO. However, the nonlinear optical properties of a-BBO crystal is vanished due to the centric symmetry with its crystal structure. It is not recommended to use for NLO processes.

Alpha-BBO can replace calcite, TiO 2 and LiNbO 3 in Glan-Taylor and Glan-Thompson polarizers and walk-off beam splitters. Its UV transmission, mechanical properties and damage resistance are useful for UV and high-power polarization optics. Reference configurations also include Glan-Laser polarizers and beam displacers.

1. Basic Properties of a -BBO

Sellmeier equations: (l in mm) :
no2=2.7359+0.01878/(l2-0.01822)-0.01354l2
ne2=2.3753+0.01224/(l2-0.01667)-0.01516l2

Refractive Indices, Birefringence ( D n = n e - n o ) and Walk-off Angle at 45 o ( r ):
at 1.0642 m m n e = 1.5379, n o = 1.6579 Dn =-0.073282 r = -4.9532°
at 0.5321 m m n e = 1.5534, n o = 1.6776 Dn =-0.075491 r = -5.0407°
at 0.2660 m m n e = 1.6114, n o = 1.7617 Dn=-0. 089805 r = -5.6926°

Source consistency note: the listed refractive indices and birefringence do not satisfy the stated relation Δn = nₑ − nₒ. For example, nₑ = 1.5379 and nₒ = 1.6579 do not yield the listed Δn = -0.073282. The original entries are retained; confirm the refractive-index and Δn values before using this table for optical design.

Applications of a -BBO Please refer to Polarizer for the applications of a-BBO

Specifications of a -BBO

Surface Quality	20/10 Scratch and Dig
Beam Deviation	<3 arc min.
Optical Axis Orientation	+/-0.5°
Flatness
Transmission Wavefront Distortion	< L /2 @632.8 nm
AR-coating	R<0.5%

Reference-unit note: legacy unit typography is retained in the detailed values. Confirm wavelength units, density units and drawing tolerances when defining an order.