Beta barium borate 5110180 224155875 2008-07-07T15:59:18Z 132.163.53.18 Added (for λ in microns) to Sellmeier equations '''Beta barium borate''' ('''β-barium borate''', '''BBO''' or '''β-BaB<sub>2</sub>O<sub>4</sub>''') is a crystal frequently used for frequency mixing and other [[nonlinear optics]] applications. It has a wide transmission range, from approximately 200 nanometres to beyond 3 micrometres, and is used particularly for its transparency in the deep ultraviolet. BBO has a trigonal [[crystal system]], belongs to [[crystallographic point group]] 3m, and belongs to the crystallographic [[space group]] R3c. BBO has strong negative uniaxial [[birefringence]] and can be phase-matched for type I (''ooe'') [[Second harmonic generation|second harmonic generation]] from 409.6–3500 nm. The temperature sensitivity of the indices of refraction is low, leading to an unusually large (55°C) temperature phase-matching bandwidth. The crystal is mildly [[hygroscopic]]. β-Barium borate differs from α-barium borate in the positions of the barium ions within the crystal. Both phases are birefringent, however the α phase, which exists above 925 C, possesses centric symmetry and thus does not have the same nonlinear properties as the β phase.<ref name=Nikogosyan /> ==Physical properties== *Lattice parameters: ''a''=''b''=1.253 nm, ''c''=1.272 nm, ''Z''=6 *Melting point: 1095±5°C *Phase transition temperature: 925±5°C *Mohs hardness: 4.5 *Density: 3.85 g/cm<sup>3</sup> ==Optical properties== *Refractive index, 1064 nm: <math>n_o=1.65, \quad n_e=1.54 </math> *Refractive index, 532 nm: <math>n_o=1.67, \quad n_e=1.55 </math> *Refractive index, 266 nm: <math>n_o=1.75, \quad n_e=1.61 </math> *Transparency range (> 0.5 cm<sup>-1</sup>): 198–2600 nm<ref name=Nikogosyan /> *Thermo-optic coefficients:<ref name=Nikogosyan>{{cite journal| author=D. N. Nikogosyan | title=Beta Barium Borate (BBO)| journal=Applied Physics A| volume=52 | pages=359--368}}</ref> :*<math>\frac{\partial n_o}{\partial T}= -9.3 \times 10^{-6} / \mathrm{^\circ C} </math> :*<math>\frac{\partial n_e}{\partial T} = -16.6 \times 10^{-6} / \mathrm{^\circ C} </math> *Nonlinear optical coefficients: <ref name=Dmitriev>{{cite book| author= V.G. Dmitriev, G. G. Gurzadyan, and D. N. Nikogosyan | title=Handbook of Nonlinear Optical Crystals, 3rd edition| publisher=Springer | date=1999| isbn=0342-4111}}</ref> :d<sub>22</sub> = 2.3 pV / m. :d<sub>31</sub> = -0.16 pV / m. *High damage threshold of 10 GW/cm<sup>2</sup> for 100 ps pulse-width at 1064 nm. ===Sellmeier equations (for λ in microns)=== *<math>n^2_o(\lambda)</math> = 2.7359+0.01878/(λ<sup>2</sup> - 0.01822)-0.01354 λ<sup>2</sup> <ref name=Kato>{{cite journal| author=Kato, K. |journal = IEEE Journal of Quantum Electronics | volume=22| number = 7 | date=1986|title= Second-harmonic generation to 2048 Å in β-BaB<sub>2</sub>O<sub>4</sub> | pages= 1013--1014|doi= 10.1109/JQE.1986.1073097}}</ref> *<math>n^2_e(\lambda)</math> = 2.3753+0.01224/(λ<sup>2</sup>-0.01667)-0.01516 λ<sup>2</sup> <ref name=Kato /> ==References== <references /> ==External links== *{{cite web |url=http://www.photox.co.uk/bbo.htm |title=BBO Crystal ß-Barium Borate |accessdate=2006-10-23 |work=Photox Optical Systems website }} [[Category:Nonlinear optical materials]] [[Category:Crystals]] [[de:Beta-Bariumborat]]