| Passive
q-switching has become widely used technique in solid state lasers development.
The application of saturable absorbers simplifies considerably laser design,
makes it more compact and cheap. The saturable absorbers became successfully
applied in diode pumped microchip lasers. |
|
Cr+4:YAG passive Q-switch |
|
Cr+4:Y3Al5O12
or Cr+4:YAG - is a material that can be
used as an active media for CW, pulsed or self mode-locked tunable NIR
solid-state lasers with tunability range 1340 - 1580 nm as well as a media
for Q-switching in lasers with operating wavelength at 950 - 1100 nm.
It is particularly useful in practical applications because of convenient
absorption band of Cr+4around 1 mm which
gives possibilities to pump it by regular Nd:YAG lasers. A saturation
of absorption in the band at 1060 nm is useful for application in small
sized Nd:YAG oscillators with flash lamp or laser diode pumping instead
of based on dye or LiF:F-center passive Q-switches. Using the Cr+4:YAG
crystal the self mode-locking (KML) regime is achievable. It gives an
opportunity to build the laser source with pulse duration shorter then
100 fs at 1450 - 1580 nm.
Finally, its high thermal and radiation stability as well as excellent
optical and mechanical properties will give you an opportunity to design
reliable devices based on the crystal.
Technical Specifications:
| Wavelength,
nm |
950 - 1100
nm |
| Initial transmittance,
% |
15 - 90 |
| Initial absorption
coefficient, cm-1 |
0.05 - 3.00 |
| Aperture, mm |
5 - 12 |
| Contrast |
> 8 - 10 |
| Optical length,
mm |
1 - 40 |
| Damage threshold,
J/cm2 |
> 4 |
| Long-term stability |
> 15 years |
|
|
|
GSGG : Cr4+ passive Q-switch |
|
|
Gadolinium-scandium-gallium garnet doped with chromium and magnesium
GSGG:Mg:Cr4+ is a material for passive
Q-switching in 1 µm region. The valence state of chromium ion
Cr4+ is provided by use of charge
compensator. The crystals are grown by Zchochralski method in argon-oxigen
atmosphere. Crystals of GSSS:Mg:Cr possessing the contrast parameter
close to the one of YAG:Cr4+ have
some advantages such as: possibility to provide necessary initial
transmission at less thickness (typical thickness is about 1mm),
transparency in the visible range which simplifies the alignment
procedure. |
SPECIFICATION:
| Initial transmission
|
5 - 95 % |
| Absorption index
at the wavelength of 1.067 µm |
0.2-10 cm-1 |
| Contrast |
6 - 7 |
| Thickness |
0.5 - 5 mm |
| Diameter |
6 - 9 mm |
| Relaxation time
of the exited state (4A2
→ 4T1(4F)
absorption) |
200 ns |
Application: for short-pulse
lasers of IR spectral range
Publications:
R.Buzelis, A.Dementiev,
E.Kosenko, E.Murauskas, F.Ivanauskas, M.Radziunas "Determination of
absorption cross sections of Cr4+:GSGG and Cr4+:YAG passive Q-switches
at the generation wavelength of Nd:YAG laser", Lithuanian Journal of
Physics, 37(4), pp 291-298, 1997
|
|
|
YAG:V3+ passive Q-switch |
|
|
The crystals of Yttrium-Aluminum Garnet doped with three-valence
vanadium V3+ in tetrahedral position
suggest efficient q-switching for lasers operating in 1.3 µm
region. The absorption band between 1.0 - 1.5 µm is attributed
to 3A2
→3T2
transition of V3+ ion in tetrahedral
position of garnet lattice. The crystals are grown by oriented crystallization
method. Concentration of V3+ in tetrahedral
position is controlled by growth and annealing conditions.The efficient
q-switching of lasers operating at 1.3 micron has been obtained
with a number of active mediums such as YAG:Nd, YVO4:Nd,
KGd(WO4)2:Nd
under flash-lamp and laser diode pumping. |
SPECIFICATION:
| Initial transmission
|
5 - 95 % |
| Contrast |
5 - 6 |
| Thickness |
0.5 - 5 mm |
| Diameter |
5 - 7 mm |
| Ground-state
absorption cross-section at 1.32 µm |
7.3 x
10-18 cm2 |
| Ground-state
absorption cross-section at 1.06 µm |
3.0 x
10-18 cm2 |
| Relaxation
time of the exited state (3T2
→ 3A2
absorption) |
20 ns |
Application:
for short-pulse lasers of IR spectral range 1.06 - 1.4 µm
Publications:
A.M.Malyarevich,
I.A.Denisov, K.V.Yamashev, V.P.Mikhailov, R.S.Conroy, B.D.Sinclair,
"V:YAG - a new passive Q-switch for diode pumped solid state lasers",
Appl. Phys. B 67 (1998), p. 555
|
|
|
Passive Q-switch based on NANOSIZED CRYSTALS in glass ceramics |
|
|
The new saturable absorber is based on NANOSIZED CRYSTALS IN GLASS
MATRIX. It is transparent glass ceramics containing magnesium-aluminum
spinel nanocrystallites doped with tetrahedrally coordinated Co2+
ions. The material provides q-switching within the spectral interval
of 1200 - 1600 nm in particular for Yb-Er-glass laser (λ = 1.54
µm). Having the absorption cross-section of Co2+
at the wave length of 1.54 µm (transition 4A2
→ 4T1(4F))
significantly higher than emission cross-section of Er:glass, it
allows Q-switch operation without focusing radiation into the saturable
absorber. In comparison with single crystals the glass ceramics
is considerably cheaper. |
| The glass ceramics
technology is based on controlled nucleation and crystallization
of the glass and has several advantages over conventional powder-processed
ceramics as it uses glass preparation technique. They are: 1) ease
of flexibility of forming in glassy state, 2) uniformity of microstructure,
3) reproducibility of properties that results from starting glass.
|
SPECIFICATION:
| Initial transmission
|
5 - 95 % |
| Thickness |
0.5 - 10 mm |
| Diameter |
5 - 100 mm |
| Ground-state
absorption cross-section at 1.54 µm |
(3.2 ± 0.4)
x 10-19 cm2
|
| Excited-state
absorption cross-section at 1.54 µm |
(5.0 ± 0.6)
x 10-20 cm2
|
| Relaxation
time of the exited state (4A2
→ 4T1(4F)
absorption) |
450 ± 150 ns |
Publications:
Uk Kang, O.S.Dymshits,
A.A.Zhilin, T.I.Chuvaeva, G.T.Petrovsky, "Structural states of Co(II)
in b-eucryptite-based glass-ceramics nucleated with ZrO2", J. Non-Cryst.
Solids, 204, pp 151-157, 1996
|
|
|
Co+2:MgAl2O4 passive Q-switch |
|
Spinel
crystal is a material having high optical damage threshold and low optical
losses in 1.3 - 1.6 µm spectral range. Co2+-activated
MgAl2O4
(Co:MALO, Co:spinel) can be used as a media for passive Q-switch of lasers
which operate in the spectral range of 1.3 - 1.6 µm, for example 1.32
µm and 1.44 µm Nd:YAG lasers, 1.31 µm iodine lasers and especially
1.54 µm erbium glass lasers.
High enough absorption cross-section of Co+2
ions together with practical absence of excited state absorption makes
this material a very efficient passive Q-switcher (that does not require
intracavity focusing) for various types of erbium glass lasers, including
diode-pumped microchips.
Technical Specifications:
| Absorption
band, µm |
1.3 - 1.6 |
| Operating transition |
4A2
-4T1
(4F) |
| Absorption
cross-section at 1.54 µm, cm2 |
2 x 10-19 |
| Bleached state
lifetime at 300°K, ns |
200 |
| Dopant level,
cm-3 |
2 x
10-17- 3 x
1019 |
| Initial transmission,
% |
10 - 99 |
| Initial absorption
coefficient at 1.54 µm, cm-1 |
0.06 - 10 |
| Aperture, mm |
5 - 12 |
| Plate thickness,
mm |
0.2 - 5 |
| Co+2:MgAl2O4
passive Q-switch |
Cat.-No.: D-120-01 |
|
|
|
Solid
state Raman shifter |
|
New availabilities for frequency conversion
The Solid state Raman shifter RS-14 is an easy in operation device for
expansion of the tuning range of a Ti:Sapphire laser. In the Shifter are
used innovative technology Ba(NO3)2
crystals. The crystal unique properties, such as: optical homogeneity,
1047 cm-1 shift, wide transparency range
allows utilization of these crystals for frequency conversion (practically)
in any (360 to 1500 nm) spectrum regions.
Unlike gaseous Raman shifters, there is no high pressure, complete safety
of operation, low input threshold powers - all this provides you with
additional ease of the usage.
The RS-14 provides highly efficient conversion of tunable radiation from
a Ti:Sapphire laser to tunable radiation of stimulated Raman scattering
at 1st, 2nd and 3rd Stokes components. The optimum conversion in the RS-14
is achieved at pump with a Ti:Sapphire laser operating in the wavelength
range from 815 to 900 nm. It allows to generate the tunable narrow-linewidth
radiation from 690 to 1245 nm at the output.
Used for radiation conversion Ba(NO3)2
crystal is located in the optimized cavity. Such an arrangement ensures
high efficiencies of the laser output conversion to the 1st or 2nd stokes
(30% or higher) along with a comparatively low output beam divergence
(1.5 mrad), enabling thus further non-linear conversion of radiation.
The diagram below illustrates the principle of the RS-14 operation.
The Ti:Sapphire pump wavelength range is divided into two Subranges.
Subrange I refers to the operational wavelength range 815-960 nm, while
Subrange II corresponds to the operational wavelength range 850-900
nm of Ti:Sapphire. By choosing Type I or Type II tunability range and
using one from the available 6 pairs of cavity mirrors, tunable radiation
with the parameters as follows can be established at the RS-14 output:
| For Ti:Sapphire
output from 815 to 860 nm (Subrange I), the RS-14 provides: |
| - 1st Stokes
component in the 890-950 nm range |
max. eff. appr.
35% |
| - 2nd Stokes
component in the 980-1050 nm range |
max. eff. appr.
30% |
| - 3rd Stokes
component in the 1090-1170 nm range |
max. eff. appr.
20% |
| For Ti:Sapphire
output from 850 to 900 nm (Subrange II), the RS-14 provides: |
| - 1st Stokes
component in 980-990 nm range |
max. eff. appr.
35% |
| - 2nd Stokes
component in 1030-1120 nm range |
max. eff. appr.
25% |
| - 3rd Stokes
component in 1160-1245 nm range |
max. eff. appr.
20% |
In the RS-14 are used 6 pairs of specially designed changeable cavity
mirrors. By changing one mirror pair for another, highly-efficient generation
of tunable radiation of the 1st, 2nd and 3rd Stokes components individually
or together can be established at the RS-14 output. Low alignment requirements
of the cavity mirrors together with ease of their replacement simplify
the laser alignment procedure for operation in the wavelength range desired.
Telescopic / focusing system that comes together with the converter, allows
the RS-l4 to be adapted to any pump laser.
Pumping sources and tunability ranges:
| Pump Laser
Type |
|
Input,
nm
|
Output,
nm, 1 stokes
|
Output,
nm, 2 stokes
|
| Nd:YAG |
|
1064
|
1197
|
1369
|
| Nd:YAG |
|
532
|
563
|
599
|
| Ruby |
|
694
|
748
|
812
|
| Ti:Sapphire |
from |
900
|
993
|
1109
|
| |
to |
1000
|
1117
|
1265
|
| Forsterite |
from |
1180
|
1346
|
1567
|
| |
to |
1340
|
1558
|
1869
|
We can complete the RS-14 Shifter with the following options:
- A set of mirrors to provide simultaneous generation of the 1st,
2nd and 3rd Stokes radiation components.
- Wide-band dichroic coating for expanding of the tuning range for
your Ti:Sapphire and Forsterite lasers.
- Telescopic system to ensure optimum power densities in a Ba(NO3)2
crystal.
- Second harmonic generator to expand the tunability range from 350
to 620 nm
- Tunable Ti:Sapphire Laser
- Tunable Forsterite Laser
|
