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When light encounters molecules in the air, the predominant mode of
scattering is elastic scattering, called Rayleigh scattering. This
scattering is responsible for the blue color of the sky; it increases
with the fourth power of the frequency and is more effective at short
wavelengths. It is also possible for the incident photons to interact
with the molecules in such a way that energy is either gained or lost
so that the scattered photons are shifted in frequency. Such inelastic
scattering is called Raman scattering.
New reliable and preferably all solid-state sources
of laser radiation in up-to-now uncovered spectral regions are highly
desirable due to the growing number of applications of such devices
in medicine, spectroscopy, defense, and research in general. Stimulated
Raman scattering (SRS) in solid state crystals has been recently
more widely employed for laser radiation frequency conversion. The
use of solid state SRS converters is advantageous due to high conversion
efficiency, no phase matching necessity, and easier handling compared
to gaseous and liquid Raman cells. Among the most efficient known
Raman crystals belong Ba(NO3)2 and KGd(WO4)2.
New Raman-active crystal - BaWO4 - was recently predicted
to be a promising Raman material suitable for a wide range of pumping
pulse duration from pico seconds to nano seconds.
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Barium
Nitrate 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 scattering
effect. They can be used as frequency converters in tunable lasers
for extention of tuning range, for production of additional emission
band combined with elements of doubling and summation of frequency,
as well as optical filter for wave band 1.8 - 2.4 µm.
MAIN PROPERTIES:
| Transmission
range, µm |
0.35
- 1.80 |
| Syngony |
cubic |
| Symmetry,
space group |
P213 |
| Lattice
parameter, Å |
8.11 |
| Density,
g/cm3 |
3.25 |
| Mohs
hardness |
2.5
- 3.0 |
| Refractive
indexes: |
- |
| at
0.5481 µm |
1.5758 |
| at
1.064 µm |
1.5551 |
| at
2.00 µm |
1.5452 |
| at
2.50 µm |
1.5399 |
| Stocks
frequency shift, cm-1 |
1047 |
| Relative
optical uniformity, ” n/cm |
(3
- 7) x 10-6 |
Optical uniformity
of Barium Nitrate crystals is comparable with the quality of Barium-
and Calcium-Fluoride optical crystals. Anomalous birefrigence in some
areas does not exceed 5 nm/cm. Barium Nitrate crystals ensure the
following characteristics of SHG-conversion for Nd-laser (0.53 µm):
- Radiation wavelength for 40-50 % conversion -
580 nm
- Radiation wavelength for 15 % conversion
- 600 nm
Achieved radiation conversion efficiences into first and second Stocks
are 60% and 19% respectively.
Potassium
Gadolinium Tungstate KGd(WO4)2 or KGW
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 an unusual wealth of properties.
Ultralow-threshold Stimulated Raman Scattering (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 branching ratio. The first Stokes line from
the second Nd transition 4F3/2 —>4I13/2 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 undergoing to intensive research.
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 introduction
to 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 wavelength in KGW crystal with oscillation 901.5 cm-1
and Ba(NO3)2 with oscillation 1048.6 cm-1:
|
Stokes |
KGW
pumped @532 nm
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KGW
pumped @1064 nm
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Ba(NO3)2
pumped @532 nm
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Ba(NO3)2
pumped @1064 nm
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1
Stoke
|
558
|
1177
|
563
|
1197
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2
Stoke
|
588
|
1316
|
598
|
1369
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3
Stoke
|
621
|
1494
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638
|
1599
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4
Stoke
|
658
|
1726
|
684
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1924
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1
Antistoke
|
507
|
970
|
503
|
957
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We supply elements
made from mentonied crystals with different cross-sections and dimensions.
| For
information about Solid State Raman Shifter please refer to
our page "LASER
COMPONENTS" |
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