EKSMA - Nonlinear and Laser Crystals

Barium Nitrate – Ba(NO₃)₂

Ba(NO₃)₂ crystals are used as the substitution of laser radiation frequency converters based on organic dye solution. This greatly improves the devices’ performance characteristics.

Also the Ba(NO₃)₂ crystals are used as Stimulated Raman Scattering (SRS) converters that provide non-linear conversion of frequency radiation of laser due to the stimulated Raman scttering effect. They can be used as frequency converters in tunable lasers for extention of tuning range.

Ba(NO₃)₂ crystals are free from bubbles and inclusions. The optical uniformity of Ba(NO₃)₂ crystals is comparable with the quality of barium and calcium fluoride crystals. Transmission band is from 0.35 µm up to 1.8 µm. The crystals can be used in the range from 1.8 µm up to 2.4 µm as optical filters.

Achieved radiation conversion efficiencies into first and second Stock’s are ~60% and ~20 % respectively at 532 nm pump.

MATERIAL PHYSICAL AND LASER PROPERTIES

Crystal symmetry	cubic, P2₁3
Lattice constant	a = 0.811 nm
Density	3.25 g/cm³
Mohs hardness	2.5-3
Stoke's shift	1048 cm^-1
SRS-amplifications increment	11 cm/GW
Optical uniformity relative parameter ∆n/cm	(3+7) × 10^-6
Optical losses µ(λ), cm^-1 (at λ = 1.06 µm)	< 0.005
Optical quality ∆n	< 5 × 10^-6
Anomaluos birefrigence in some areas not exceed	5 nm/cm
Refractive indices λ = 0.5461 µm n = 1.5756 λ = 2.00 µm n = 1.5452 λ = 1.064 µm n = 1.5551 λ = 2.50 µm n = 1.5399

STANDARD PRODUCT SPECIFICATIONS

Surface quality	40/20 scratch/dig
Flatness	λ/4 @ 633 nm
Damage threshold	10 J/cm2 @ 532 nm (in the volume) 4 J/cm2 @ 532 nm (at the surface)
Maximum dimensions	10×10×10 mm
Ba(NO₃)₂ Stokes @ pump	1064 nm	532 nm
1 Stoke	1197 nm	563 nm
2 Stoke	1369 nm	598 nm
3 Stoke	1599 nm	638 nm
4 Stoke	1924 nm	684 nm
1 Anti-stoke	957 nm	503 nm

Please contact EKSPLA for non-standard specifications.
Comparing Ba(NO₃)₂ and KGW crystals for Raman applications, Ba(NO₃)₂ is more effective in case of ns pulses, KGW and KYW crystals - in case of ps.

Optical transmission of Ba(NO₃)₂ crystal

Crystals for Stimulated Raman Scattering

EKSPLA offers new materials - undoped KGW, KYW and Ba(NO₃)₂ which have attracted much interest as most suitable for stimulated Raman scattering (SRS). These crystals can be used as frequency converters in tuneable lasers for extension of tuning range.

The potassium gadolinium tungstate KGd(WO₄)₂ or KGW single crystal is a new and very promising material for optical and laser applications. Because of its low structure symmetry and high c³-nonlinearity KGW offers unusual wealth of properties.

Attractive spectral characteristics for diode pumping
The broad pump bandwidth centered at 810 nm allows operation at wider range of temperature and a range of laser diode specifications. Together with their high peak cross section a direct pump geometry is possible. That makes way for construction of chip lasers which can be manufactured in large volume at low cost.

Efficient Stimulated Raman Scattering /SRS/
The ultralow-threshold SRS made possible the construction of so called stringer: a simultaneous generator of a string of lines – the common Nd and a few Stokes lines with selected string bran-ching ratio. The first Stokes line from the second Nd transition ⁴F_3/2 —>⁴I_13/2 fall just in 1.54 µm – the most promising wavelength for laser applications in inhabited areas. The Nd:KGW Raman amplifiers, four wave mixing and phase conjugate mirrors, etc., are undergoes to intensive research.

High conical refraction
The high conical refraction angle is due to the high birefringence and unusual equidistant values of the refractive indexes of KGW. Discovered 160 years ago, the conical refraction effect can find a real application in polarization optics with the introducing on the market of non doped KGW. This effect could be used jointly with lasing c³-nonlinearity properties of KGW in the development of new laser/SRS schemes.

Stokes generation wavelengths in KGW crystal with oscillation efficient 901.5 cm^-1 and Ba(NO₃)₂ crystal are given in the table below.

Stokes	KGW pumped at		Ba(NO₃)₂ pumped at
Stokes	532 nm	1064 nm	532 nm	1064 nm
1 Stoke	558	1177	563	1197
2 Stoke	588	1316	598	1369
3 Stoke	621	1494	638	1599
4 Stoke	658	1726	684	1924
1 Antistoke	507	970	503	957