Transcript Slide 1

RECHARGING PROCESSES OF ACTIVE IONS AND RADIATION DEFECTS
IN SOME LASER CRYSTALS DOPED WITH RE AND TM
S.M. Kaczmarek1, G. Boulon2, T. Tsuboi3
– Institute of Physics, Szczecin University of Technology, 48 Al. Piastow, 70-310 Szczecin
- Physical Chemistry of Luminescent Materials, Claude Bernard /Lyon 1 University, UMR, France
3 - Faculty of Engineering, Kyoto Sangyo University, Kamigamo, Kita-ku, Kyoto 603-8555 , Japan
1
2
Solid state laser systems based in space are exposured to charged particles: electrons, protons,
high energy cosmic rays, and bremsstralung photons. All these forms of radiation can damage the
laser by ionizing constituent atoms in the gain medium.
Content
1. Introduction
2. Garnets: YAG (pure, Nd, Cr, Er, Yb), YAP (Er, Pr, Nd), GGG (Nd, pure)
3. Galates: SrLaGa3O7 (Cr, Co, Dy), SrGdGa3O7 (Cr), Mg2SiO4 (Cr)
4. Perovskites: LiNbO3 (pure, Cr, Cu, Fe, Yb, Yb+Nd, Yb+Pr)
5. Fluorides: CaF2 (Yb, pure), LiLuF4 (Yb), YLiF4 (Yb), KY3F10 (Yb)
BaY2F8 (Yb)
6. Li2B4O7 (pure, Mn, Co) single crystals and glasses (pure, Mn)
7. Conclusions
YAG 20 MeV
1.0
20
440
16
YAG
0.5
4
15
1
2
K [1/cm]
K [1/cm]
0.0
-0.5
YAG
255
-1.0
5
8
4
0
10
1E14
1E15
1E16
-2
Protons fluency [cm ]
5
1 - 10 Gy
2 - 1473 K nitrogen 0.5h
213 nm
258 nm
305 nm
476 nm
12
K [1/cm]
300
13
5
3
-1.5
-2
1 - 3*10 cm
14
-2
2 - 1.3*10 cm
15
-2
3 - 1.13*10 cm
16
-2
4 - 1.113*10 cm
5 - 1673 K 2h air
2
0
208
1
-2.0
200
400
600
800
1000
200
1200
400
600
800
1000
Wavelength [nm]
Wavelength [nm]
Nd:YAG (1at.%) 20 MeV
3.0
0.75
K [1/cm]
1.0
0.00
4
2.5
10
Nd:YAG
255 nm
385 nm
300 nm
650 nm
-0.25
1
2
10
3
10
4
10
5
10
6
10
7
1
400
500
600
6
700
Wavelength [nm]
0.5
4
2
-1
1
-2
1.0
3
0
1E13
5
3 4
2
1
4
0.0
1E14
1E15
1E16
Protons fluency [nm]
5
Oxygen atmosphere
2
3
4
1-10 Gy, 2-10 Gy, 3-10 Gy
5
6
7
4-10 Gy, 5-10 Gy, 6-10 Gy
o
7-1400 C 3h air
300
2.0
1
8
1.5
Gamma dose [Gy]
2
7
1
-0.75
6
4 35
-0.5
-1.0
200
3
-0.50
0.5
0.0
0.25
K [1/cm]
YAG:Nd 1%
7
K [1/cm]
0.50
1.5
1 - 258 nm
2 - 273 nm
3 - 352 nm
4 - 586 nm
2
2
K [1/cm]
2.0
800
900
1000
1100
12
-0.5
1
-1.0
3
2
-1.5
100
200
2
13
2
1 - 5*10 protons/cm , 2 - 3,5*10 protons/cm
14
2
15
2
3 - 1,35*10 protons/cm , 4 - 1,135*10 protons/cm
16
2
16
2
5 - 5*10 el./cm , 1 MeV, 6 - 1,1135*10 protons/cm
7 - 1673 K 3h air
300
400
500
600
700
800
Wavelength [nm]
900
1000
1100
1200
- The shape of the additional absorption is almost of the same type for pure YAG and
doped with Nd for all types of the irradiation: g-rays, electrons and protons,
- Three at least color centers one can recognize: Fe3+ , Fe2+ and F-type with maxima at: 255,
276, 300, 385 (440 pure YAG) nm, respectively. For crystals annealed in the air additional 586
nm band is observed. With an increase of the g-dose from 102 to 107 Gy, fluencies of
electrons from 1014 to 1016 particles/cm2 and of protons from 1012 to 1016 particles/cm2,
values of AA bands became higher and higher.
-The dependence of the additional absorption on the irradiation dose shows a tendency
to a saturation in case of g-rays.
- Protons fluency dependence of the additional absorption exhibits characteristic shape
with minimum at about 1014 protons/cm2. Such non-monotonic dependence is characteristic
for color centers rather than for Frenkel ones. For the latter centers, a monotonic, linear with
proton fluency dependence is observed.
- It seems that for electrons, ionization fraction is lower than for protons
- Annealing in the air leads to the increase in Fe3+ ions content in the crystals. Annealing in the
air at 673K for 3h seem to be high enough to receive
starting optical properties of g-irradiated crystals
- Annealing in hydrogen give almost the same shape
of the additional absorption as in case of g-irradiation
- Lower susceptibility to electron and g-irradiation
2
1
2
reveal Nd:YVO4 single crystals
1
0,50
Nd: YVO4 (1at. %)
YVO4
0,2
5
1 - g 10 Gy
6
2 - g 10 Gy
1 - g 10 Gy
5
2 - g 10 Gy
6
0,25
-1
K [cm ]
0,1
0,00
0,0
-0,1
400
600
800
Wavelength [nm]
1000
-0,25
400
600
800
Wavelength [nm]
1000
60
120
1
Nd:YAG (L=45,63mm, =4mm)
50
o
1 - 1400 C 3h in air
3
2 - g 10 Gy
2
80
Optical output [mJ]
Optical output [mJ]
100
5
3 - g 10 Gy
o
4 - 1200 C N2+H2
5
5 - g 10 Gy
60
4
3
40
5
40
2
30
1
5
Nd:YAG (1at.%) - g 10 Gy
20
o
after anneal. at 1200 C 1h N2+H2
L=45,63mm,=4mm
pump of 25 J
10
20
0
0
0
10
20
30
40
50
0
Pump energy [J]
10
20
30
40
50
Pump pulses [number]
Nd:YAG laser
- All forms of the irradiations: exposure to 60Co gamma rays, over threshold electrons (1 MeV)
and high energy (20 MeV) protons and annealing in hydrogen create almost the same damage
centers which reduce optical output by absorbing of laser emission.
- Gamma irradiation lowers the slope efficiency of pulsed laser. After subsequent pulses the
output energy of the laser increases to the level, which comes out from the thermal equilibrium of
rod being the heated by pumping pulses, and, air cooled. This increase of the laser energy after
subsequent pumping pulses suggests that UV contained in the pump spectrum causes heating up
the rod and accelerates those relaxation processes which decrease the AA.
5
a)
1
b)
4+
20
6
2
4
Cr:YAG
6
K [1/cm]
3
3
8
1
10
7
400
600
800
1000
6
K [1/cm]
0
200
6
-1
K, K [cm ]
8
10
3+
Cr and Cr : YAG
4
0
2
1 - Absorption AG
5
2 - K g 10 Gy
o
3 - K 1100 C 3 h in air
5
4 - K g 10 Gy
o
5 - K 1200 C in N2+H2
-10
5
278 nm
4
2
1E13
6
4
1E14
1-Absorption after 1200 C N2+H2
13
1
4
5
2
4+
3+
Cr
Cr
3+
Cr
4+
Cr
13
7 - K 10 protons/cm
2
1
4+
Cr
2
2-10 protons/cm
13
2
3-1.1*10 protons/cm
13
2
4-2.1*10 protons/cm
14
2
5-1.21*10 protons/cm
15
2
6-1.121*10 protons/cm
16
2
7-1.1121*10 protons/cm
o
-20
1E16
-2
o
7
3
2
6 - Absorption after 1200 C in N2+H2
1E15
Protons dose [cm ]
6
0
200
400
600
800
200
1000
400
600
1000
Wavelength [nm]
Wavelength [nm]
200
0
800
100
200
300
400
500
600
700
800
900
300
400
500
600
700
800
900
1000 1100
3.0
1000 1100
2
2.5
1.5
Cr,Tm,Ho:YAG
6
1
10 Gy
2
1400 C
5
3
g 10 Gy
2.0
1
3+
Er:YAG 33%
1673 K 3h
5
10 Gy
4
300
385
K [1/cm]
H6
0.5
K [1/cm]
650
2
3
Cr
4
A2
3
1.5
3+
3+
Tm
4
T1
3
Cr
A2
3
H6
0.0
F4
1.0
1
0.5
0.0
-0.5
3+
4
-0.5
o
Tm
3
3
F2, F3
 [1/cm]
1.0
4
T2
Cr,Tm,Ho: YAG
6
1 - g 10 Gy
2 - 530 C
5
3 - g 10 Gy
0
3
-1.0
o
255
2
-1.0
-2
-1.5
200
300
-1.5
0
100
200
300
400
500
600
700
800
900
1000 1100
 [nm]
-4
400
600
Wavelength [nm]
800
500
600
700
 [nm]
Er:YAG
200
400
1000
Cr,Tm,Ho:YAG
800
900
1000 1100
1200
Er:YAG
5
after g 10 Gy of "as-grown" crystal
150
o
after annealing at 800 C 3h in air
o
5
after annealing at 1400 C in air and g-irradiation g 10 Gy
o
after annealing at 400 C 3h in air
Optical output [mJ]
120
90
Cr, Tm, Ho: YAG
1at.%, 5.7at.%, 0.36at.%
Lrod=67,3mm, Lres=255mm
rod=4mm, p=700ms
60
Cr,Tm,Ho:YAG
30
0
120
140
160
180
200
220
Pump energy [J]
- The obtained results point to the direct influence of the color centers on the processes of
formation of the inverse population of the energy levels of Er: YAG, Cr, Tm, Ho: YAG (positive)
lasers. Gamma irradiation leads to the formation of color centers which transfer energy of
excitation to excited laser level and also to an increase in active impurity concentration and thus
luminescence intensity.
-The type of introduced CC strongly depends on the starting defect structure determined by
Growth conditions or annealing in the reducing or oxidizing atmosphere (see Cr:YAG AA spectra)
- Changes in the active dopant concentration are observed after all the types of irradiations: g-rays
electrons and protons in Cr:YAG and Cr,Tm,Ho:YAG crystals
- From AA of proton irradiated crystals there can be distinguished two dose ranges: (1) fluencies
less than 5*1014 cm-2 where recharging effects dominate and, (2) fluencies larger than 5*1014 cm-2
where the presence of Frenkel defects is expected.
1.0
30
Yb:YAG
5%
7%
10%
15%
20%
25%
30%
20
15
380
0.5
630
0.0
-0.5
K [1/cm]
Absorption coefficient [1/cm]
25
320
255
-1.0
-1.5
20%
7%
30%
10
YAG:Yb
5
g 10 Gy
-2.0
5
-2.5
0
850
900
950
1000
1050
Yb:YAG
10
7%
20%
30%
I Abs YAG:Yb 5%
YAG:Yb
K [1/cm]
5
0
1030
915
-5
968
-10
900
1000
Wavelength [nm]
300
400
500
600
700
Wavelength [nm]
Wavelength [nm]
942
-3.0
200
- Important in diode pumped high power laser
systems: used sometimes in orbital space missions,
ranging systems
- Important for solar neutrino detection: a prompt
electron plus a delayed gamma-signal is the signature
of a neutrino event: scintillator is designed to work in the
strong external fields of ionizing radiation
- Due to both requirements it is important to study the
ionizing effects in Yb:YAG crystals
- The changes after g-irradiation are mainly related to the
charge exchange Fe3+- Fe2+, F-type centers and Yb2+
ions arising as an effect of recharging of Yb3+ ions from
pairs
234
12
401
315
10
6
K [1/cm]
5
8
Er:YAP
2
303
10
320
4
8
204
4
6
2
4
1E14
3
1E15
1E16
Protons fluency [cm
-2]
1
0
385
430
4
K [1/cm]
K [1/cm]
6
4
234 nm
315 nm
401 nm
8
1
YAP:Nd 1.2%
5
g 10 Gy
1073 K for 3h air
1473 K for 0.5h hydrogen
5
10 Gy nitrogen
1473 K with respect to AG
2 244
5
0
-2
-6
2
-8
100
200
300
-2
YAP:Er_50%
5
g10 Gy
673 K 3h air
14
2
10 prot/cm
15
2
10 prot/cm
16
2
10 prot/cm
-4
400
500
600
700
800
2
-4
900
1000
315
100
1100
200
300
400
247
12
8
1
8
YAP:Pr 0.05%, 3%
5
g 10 Gy 0.05% Pr
5
g 10 Gy 3% Pr
673 K for 3h air 3% Pr
5
g 10 Gy nitrogen 3% Pr
385
4
2
303
6
358
1
4
K [1/cm]
K [1/cm]
2 260
10
303
2
Pr:YAP
4
0
0
248
300
400
-12
100
700
Wavelength [nm]
900
1000
1100
800
900
1000
1100
YAP:Pr_0.05at.%
5
g 10 y
1673 K for 2h air
1473 K for 0.5 h hydrogen
1473 K for 1h hydrogen
1473 K for 1.5h hydrogen
487
3
-6
-10
600
800
-2
3
500
700
385
-8
200
600
2
-4
-2
100
500
Wavelength [nm]
Wavelength [nm]
6
Nd:YAP
3
-6
5
4
200
300
400
500
600
700
Wavelength [nm]
800
900
1000
1100
YAP
- Important in developing of LD pumped lasers, promising as fast scintillators that exhibit very
short fluorescence decay with time constant 1-100 ns,
- Growth atmosphere (inert) leads to the presence of oxygen vacancies; there are present also
uncontrolled dopants in the crystal and cation vacancies,
- Changes after gamma and proton irradiations are mainly related to the charge exchange of Fe2+
, Fe3+ (234-260, 303-315 nm), cation vacancies and F-type centers (385 nm) [F+ →Vo+e-,
F→Vo+2e-],
- Annealing in the air at 673 K for 3h is enough to receive starting optical absorption of the crystal,
annealing in the air at 1073 K introduce additional defects (430 nm band); annealing in the air at
1673 K introduce some additional defects (260, 358, 487 nm), annealing in hydrogen at 1473 K
fully clear (bleaching) the crystal,
- YAP crystals seem to be resistant to proton irradiation especially for doping with Er; saturation
one can observe in the AA change as a function of proton fluency,
- Increase in Pr3+ concentration from 0.5 to 3% leads to the three fold decrease in the value of AA,
- Generally there are not observed distinct changes in the valence states of active dopants in the
crystal.
Nd:GGG
- Three main centers arises after g-irradiation: 255, 340 and 465 nm being attributed to:
the presence of Ga and O vacancies as well as Fe ions (255 nm), Ca2+F+ complex centers
and hole O- centers (340 nm), and, F-centers (465 nm). Annealing in the air increase an
amount of Fe3+ ions and new one 400 nm centers are creating. UV irradiation forms only first
two centers but of the same intensity. Protons less influence the crystal than YAP and YAG.
345 nm
0.4
0.2
K [1/cm]
0.0
-0.2
-0.4
Nd:GGG 1.2%
UV 150 W 1 min after 1400 C 2h
-0.6
-0.8
200
300
400
500
600
700
800
Wavelength [nm]
Nd:GGG
30
3
2
Gd3Ga5O12 (GGGC1)
gamma and protons
ABS AG
6
10 Gy
12
-2
10 cm
13
-2
5.56*10 cm
14
-2
1.556*10 cm
16
-2
10 cm
255
K [1/cm]
0,4
465 nm
0,2
400
20
1
0
200
400
600
800
0,0
Nd:GGG 1.2%
3
10 Gy
5
10 Gy
6
10 Gy
-0,4
15
1
0
1000 1200
Wavelength [nm]
-0,2
25
1673 K 2h air
2
K [1/cm]
K [1/cm]
340 nm
K, K [1/cm]
0,6
=440 nm
10
1E10
1E11
5
1E13
1E14
1E15
1E16
-2
Protons fluency [cm ]
0
Gd3Ga5O12
-5
-0,6
1E12
255 nm
200
400
600
800
Wavelength [nm]
1000
1200
-10
200
300
400
Wavelength [nm]
500
600
6
70
30
24
2
20
1
16
12
2
8
4
5
12
4
3
350 nm
9
6
3
800 nm
0
20
4
20
15
40
28
25
K [1/cm]
3
0
1E13
15
1E13
1E14
1E15
SrLaGa3O7:Dy (1 at. %)
10
1E16
13
200
400
600
0
800
1000
Wavelength [nm]
5T -5E
2
2
4
0
300
1200
1223 nm, Co3+
5
400
5
6
1
500
600
14
2
1
8
40
-2
SrLaGa3O7:Co (2wt.%)
5
1 - g 10 Gy
6
2 - g 10 Gy
o
3 - 1100 C in the air
o
4 - 1050 C in oxygen
-4
-6
1500
2
=600 nm
2
3
1000
14
1-AG, 2-10 protons/cm , 3-2*10 protons/cm
15
2
16
2
4-1.2*10 protons/cm , 5-1.12*10 protons/cm
2
4
500
700
4
4
1
16
Wavelength [nm]
60
1
2000
Wavelength [nm]
2500
3000
K, K [1/cm]
Addidional absorption K [1/cm]
2
15
3
1
SrLa(Gd)Ga3O7
3
14
1 - 2*10 , 2 - 1.2*10 , 3 - 1.12*10 , 4 - 1.112*10
5
1
4
2, 3, 5
0
1E16
-2
-2
Fluence [cm ]
10
1E15
Protons dose [cm ]
2
1E12
4
1E14
6
0
4
3
500
600
700
800
900
20
K [1/cm]
K [1/cm]
50
1
K [1/cm]
60
1 - 373 nm, 2 - 300 nm, 3 - 276 nm, 4 - 450 nm
30
K [1/cm]
80
SrLaGa3O7:Cr (0.05at.%)
1-AG
12
2
2-10 protons/cm
13
2
3-1.1*10 protons/cm
14
2
4-1.11*10 protons/cm
15
2
5-1.111*10 protons/cm
16
2
6-1.1111*10 protons/cm
4
2
0
1E12
5
1
1E13
1E14
1E15
-2
Proton fluency [cm ]
0
3, 4
2
SrGdGa3O7:Cr
-20
200
400
600
Wavelength [nm]
800
1000
1E16
SLG, SGG
- They appear to be promising active laser materials. They exhibit, however, strong changes in
absorption and luminescence spectra under irradiation by ionizing particles.
- Color centers, which appeared after g and proton irradiation (290 nm), shift the short-wave
absorption edge towards the longer wavelengths by a few hundreds nm. They are probably
attributed to the Ga2+ centers that are formed according to reaction Ga3+ + e- Ga2+ with a spin
S=1/2, g|| = 1.9838(5) and g = 2.0453(5). The second type center arises in the AA spectrum at
about 380 nm and is attributed to F-centers.
- In Cr and Co doped SLG and SGG crystals beside the above CC, recharging of chromium and
cobalt ions is observed after both types of the irradiation
Forsterite and YAG:Cr
- Gamma irradiation recharges both Cr3+ and Cr4+ ions, moreover, there arises color centers,
observed between 380 nm and 570 nm, that may participate in energy transfer of any excitation
to Cr4+ giving rise to Cr4+ emission. The g-irradiation leads to increase in intensity of excitation
spectra. The 380 nm additional absorption band is assigned probably to Cr6+ ions of 3d0
configuration or more probably to O-- hole centers and/or F-centers. The 570 nm band may be
assigned to F+ color centers,
- In the absorption spectrum of g-irradiated crystal we observe 275 nm additional band that may
be interpreted as a valence change of Si4+ ions due to capture of electron coming from ionization
of an O2- ion,
- If conditions of optimal Cr doping content and optimal oxygen partial pressure can not be satisfied,
one can deal with annealing in O2 to increase of Cr4+ emitting centers and, after that, with
g-irradiation of the crystal
- The observed behavior of the absorption spectrum of YAG:Ca, Cr annealed in the air crystal
under influence of g-irradiation suggests that g-irradiation ionizes only Cr ions.
12
1
8
8
8
6
4
2
0
1000
2
2000
3000
4000
5000
Wavelength [nm]
4
Forsterit
1-0,3%
2-0,6% anneal.
in O2
2
6
Additional absorption after:
3 - annealing in O2
4 - g-irradiation
12
8
K [1/cm]
Mg2SiO4:Cr (0.6wt.%)
1 - "annealed in the air"
5
2 - g 10 Gy
3 - K [1/cm]
Absorption coefficient
16
Absorption coeffiicient [a.u.]
Absorption coefficient [1/cm]
Cr: Mg2SiO4 and Y3Al5O12
3
4
4
0
4
1
300
400
500
600
700
800
900 1000 1100
Wavelength [nm]
2
0
3
300
400
500
600
700
800
900
1000
1100
0
200
1200
Wavelength [nm]
70000
5
1 - em=1160 nm after g 10 Gy
2 - em=1200 nm
800
1000
60000
1
50000
PL [a.u.]
60000
50000
2
40000
1200
Mg2SiO4:Cr 0.6wt.%
1400
4+
5
70000
EXCITATION [a.u.]
600
Wavelength [nm]
Mg2SiO4:Cr 0.6%
80000
400
40000
g 10 Gy
1 - ex=455 nm
2 - ex=657 nm
10000
annealed
3 - ex=632 nm
1
5
1 - ex=610 nm after g 10 Gy
2 - ex=840 nm after g 10 Gy
2a - ex=850 nm only annealed
5
3 - ex=990 nm after g 10 Gy
2a
6000
2
1
4000
3
2
30000
Y3Al5O12:Cr
5
8000
PL [a.u.]
-4
200
2000
30000
0
700
20000
800
900
1000
1100
1200
1300
1400
Wavelength [nm]
20000
10000
10000
3
0
0
200
300
400
500
600
Wavelength [nm]
700
800
900
800
1000
1200
Wavelength [nm]
1400
1600
1500
1600
1700
8
3,5
3,0
LiNbO3 (NR1)
LiNbO3 (pure)
g - irradiation
2,5
5
2,0
o
LiNbO3
5
1 - 10 Gy
6
2 - 10 Gy
1,0
0,5
0,0
-0,5
-1,0
2
6
7
2
3 - 10 Gy
K, K [1/cm]
K [1/cm]
1,5
7
1 - K, annealing at 800 C after g 10 Gy
13
2
2 - K, 10 prot/cm
15
2
3 - K, 10 prot/cm
16
2
4 - K, 10 prot/cm
3
1
4
annealing
6
0.8
4
0.4
o
6
o
7
o
2
1
5 - after 10 Gy at 800 C
-2,0
6 - after 10 Gy at 800 C
600
0.0
1E13
4
-2,5
400
515 nm
0.6
0.2
5
4 - after 10 Gy at 400 C
-1,5
1.0
800
2
0
300
1000
1E14
1E15
1E16
-2
Fluence [cm ]
3
400
500
Wavelength [nm]
600
700
800
900
Wavelength [nm]
LN:Fe
20
6.0
4.5
4.0
5
0
400
15
3.0
1
2.5
2.0
3
600
1073 K
15
2
10 prot/cm
AG
16
2
10 prot/cm
10
1.0
4
0
400
0.5
500
600
700
800
Wavelength [nm]
0.0
-0.5
-1.0
4
10
482 nm
12
8
550 nm
1
2
600
800
Wavelength [nm]
1000
482 nm
500 nm
6
4
2
0
1
1E13
3
1E14
1E15
1E16
-2
Fluence [cm ]
2
0
400
10
8
6
4
2
2
12
1 - K, 800 C
13
2
2 - K, 10 prot/cm
15
2
3 - K, 10 prot/cm
16
2
4 - K, 10 prot/cm
1000
Wavelength [nm]
5
1.5
800
LN1121 (LiNbO3:Fe - 0.1at.%)
o
20
K [1/cm]
K [1/cm]
3.5
10
14
K [1/cm]
5
1 - 10 Gy
6
2 - 10 Gy
7
3 - 10 Gy
13
4 - 10 prot
AG
5
673 K after 10 Gy
6
673 K after 10 Gy
7
1073 K after 10 Gy
K, K [1/cm]
5.0
15
LiNbO3:Fe 0.1 at.% - LN1121
K [1/cm]
5.5
400
500
600
Wavelength [nm]
700
800
Additional absorption bands in Cu:LiNbO3 single crystals after g-irradiation
5
5
Additional absorption
with a dose of 10 Gy at 300K and 77K
6
5
1
5
4
3
2
1
4
0
3
K [1/cm]
4
5
2
4
16
2
3
300
1
400
500
600
700
800
900
1000
1100
3
2
1
4
0
5
-1
LN:Cu
-2
15
-2
10 cm
14
-2
10 cm
"as grown"
+
F and F centers
15
-2
1.2*10 cm
K [1/cm]
Cu:LiNbO3, g 10 Gy at 300K
1-0.03 at. %, f.a.e.-320nm
2-0.05 at. %, f.a.e.-370nm
3-0.06 at. %, f.a.e.-370nm
4-0.07 at. %, f.a.e.-370nm
5-0.1 at. %, f.a.e.-380nm
7
LiNbO3:Cu (0.06at.%)
20
5
Cu:LiNbO3 g 10 Gy at 77K
1-0.03 at. %
2-0.05 at. %
3-0.06 at. %
4-0.07 at. %
5-0.1 at. %
Absorption coefficient [1/cm]
5
3
10
2+
Nb polaron
5
2
Cu decrease
4+
0
400
600
800
1000
change in defect structure
1
0
-3
300
350
400
450
500
550
600
650
700
500
1000
1500
2000
Wavelength [nm]
2500
3000
3500
4000
4500
5000
5500
6000
420
nm
Wavelength
[nm]
8
LiNbO3:Cu (0.06 at.%)
1-absorption of "as grown" crystal
13
2
2-10 protons/cm
14
2
3-10 protons/cm
14
2
4-2*10 protons/cm
15
2
5-1.2*10 protons/cm
16
2
6-1.12*10 protons/cm
25
15
1
4
2
12
=450 nm
10
6
8
0
400
-2
0
-4
1E13
1E14
1E15
1E16
1
2, 3, 5
4
-2
Fluence [cm ]
500
600
0
4
5
3
5
2
4
4
9*10 Gy
673 K 3h
5
10 Gy
LN:Cu
b)
K [1/cm]
K, K [1/cm]
20
LiNbO3:Cu 0.1% "Z"
6
K [1/cm]
a)
700
800
Wavelength [nm]
900
1000
-6
1100
-8
350
400
450
500
550
Wavelength [nm]
600
650
700
LN:Cr
10
8
1
465 nm
K [1/cm]
8
2
6
K, K [1/cm]
4
3
6
1
4
4 12
13
14
15
16
1,0x10 1,0x10 1,0x10 1,0x10 1,0x10
2
-2
Fluence [ cm ]
0
-2
1-K, AG
14
2
2-K, 10 protons/cm
14
2
3-K, 2*10 protons/cm
15
2
4-K, 1.2*10 protons/cm
16
5-K, 1.12*10
6-outside the proton beam
5
6
LiNbO3:Cr (0.3%) FAE=350 nm
-4
400
600
800
Wavelength [nm]
1000
- OH- absorption do not exclude substitution of both octahedral sites: Nb and Li in all of the
investigated crystals, especially in case of Pr doping,
- Annealing at 400oC and 800oC discover two different initial optical states,
- It had been observed rather unexpectedly that classical thermal annealing can lead to a
decrease in optical homogeneity in the majority of cases. It may be attributed to generation of an
internal electric field by the pyroelectric effect, and to the electrooptic effect involved thereafter.
The secondary electrons which are homogeneously generated by gamma or proton irradiation in
the investigated crystals are believed to increase the optical homogeneity, also by canceling this
field. Birefringence dispersion seems to be a good key parameter in manufacture of e.g. retardation
plates, 2nd harmonic generators or polarizers,
- In the additional absorption of LINbO3 single crystals irradiated with gamma and protons there
arises at least two additional bands peaked at about 384 (F-type color centers ) and 500 nm (Nb4+ Nb4+ bipolarons ). After annealing process additional absorption arises near 650 nm (polarons Nb4+),
- One can observe changes in the concentration of TM active ions (Fe 2+, Cu2+ and Cr3+) after the
Irradiations (recharging of active ions),
-In fluency dependence of additional absorption at least three regions are seen. First one for fluencies
below 1014 cm-2 (recharging effects), second one for fluencies between 1014 and 5*1014 cm-2 (mutual
interaction of the cascades from different proton trajectories) and third one over 5*1014 cm-2 (Frenkel
defects),
- Polarimetric measurements have shown that LN:Cu crystal exhibit strong susceptibility to proton
irradiation. Even for such small fluencies as 10 13 cm-2 the observed changes in polarimetric image
and BRD coefficient are very significant.
Cu:LiNbO3 (0.06at.%)
Annealed
1013 prot cm-2
Cu:LiNbO3 (0.07at.%)
1015 prot cm-2
Protons: Cu: LiNbO3 wafers
1013 prot cm-2
3
LN:Yb
K [1/cm]
K [1/cm]
LiNbO3:Yb 1%
1
370 nm
gamma 10 Gy
0.8
2
1 - LN
2 - LN:Yb (1%)
3, 4 - LN:Nd, Yb (0.3%, 0.5%)
0.6
3
0.4
1
0.2
2
5
gamma 10 Gy
0.0
500 nm
-0.2
0
500
600
LN codoped
700
800
900
1000
1100
500
1000
1500
2000
2500
3000
Wavelength [nm]
Wavelength [nm]
7000
LN:Nd,Yb (0.3wt.%,0.5wt.%) FAE=320 nm
LN:Yb (1wt.%) FAE=320 nm
LN:Pr,Yb (0.5wt.%,0.8wt.%) FAE=355 nm
LN:Pr,Yb (0.1wt.%,0.8wt.%) FAE=320 nm
LN:Er,Yb (1wt.%,0.5wt.%) FAE=320 nm
LN FAE=320 nm
LiNbO3:Pr (1at.%) FAE=360nm
LiNbO3:Er (0.3at.%) FAE=320 nm
2.0
1.8
1.6
1.4
Intensity [a.u.]
400
90000
80000
6000
5000
4000
3000
2000
70000
60
80 100 120 140 160 180 200 220
Wavenumber [1/cm]
60000
1.2
PL [a.u.]
Absorption coefficient [1/cm]
7
1.0
1.0
0.8
as grown
ex = 920 nm
LN (1% Er, 0.5% Yb)
LN (0.3% Nd, 0.5% Yb)
LN (0.5% Pr, 0.8% Yb)
LN (0.1% Pr, 0.8% Yb)
LN (1% Yb)
LT (0.3% Nd, 0.5% Yb)
50000
40000
30000
0.6
20000
0.4
10000
0.2
0.0
0
2840
2860
2880
Wavelength [nm]
2900
2920
960
980
1000
1020
1040
Wavelength [nm]
1060
1080
1100
LN:Yb, Pr
ZY
ZX
- In the co-doped crystals or crystals with large dopant concentration, two kinds of Yb3+ ions may
be present, one is Yb3+ accompanied by nearby rare-earth ion – perturbed Yb3+, the other is
Yb3+ located far from the rare-earth ion – isolated,
- The same kind of the CC arises in LN crystals doped with RE ions (384 and 500 nm). Irradiation
of the LN:Yb and LN:Yb, Pr crystals reveal IR AA suggesting the presence of Yb pairs,
- Yb3+ ion is substituted for Li+ ion with small ionic radius of 0.74 nm, while Pr3+ ion with large ionic
radius of 1.013 nm is substituted for Nb5+ ion with much smaller ionic radius of 0.64 nm,
- The peak position of the sharp line cantered at 980 nm is different among LN crystals doped
with rare-earths, its intensity strongly depends on the temperature,
- From the angular variations of the EPR spectra it results Yb3+ ions of C1 symmetry arise in the
crystal (170Yb , 173Yb ), temperature dependence of EPR signal shows maximum at low
temperatures (6K) suggesting pair presence of RE ions.
Absorption and emission spectra after g-irradiation
for Ca0.995Yb0.005F2.005 crystallized by simple melting
36
50
30
32
1,0
0,8
2
20
0,6
4
A
D
3
28
K, K [1/cm]
40
24
CaF2:Yb 5at.%
1-K
4
2 - K g 10 Gy
5
3 - K g 10 Gy
C
20
2
16
12
B
0,4
1
8
0,2
10
0,0
200
0
300
400
500
600
700
800
900
4
1000
3
12
200
1
0
300
400
500
600
700
800
900
200
1000
400
Excited with 357 nm light
at room temperature
300
200
100
400
250
300
350
Wavelength [nm]
Wavelength [nm]
emission intensity (arb. units)
K, K [1/cm]
F
CaF2
1 - K, "as-grown"
5
2 - K, g 10 Gy
CaF2: Yb (30wt.%)
3 - K, "as-grown"
5
4 - K/10, g 10 Gy
420
440
460
480
500
520
wavelength (nm)
540
560
580
600
400
450
Absorption spectra under hydrogen processing
for Ca0.995Yb0.005F2.005 crystallized by simple melting
5
G
F
emission intensity (arb. units)
8.0x10
CaF2:Yb at 290K
3+
1: as-grown, Yb 5at%
3+
2: as-grown, Yb 0.5at%
3+
3: H2-annealed, Yb 5at%
4: K
-1
3+
Excitation
for 980 nm emission
5
6.0x10
5
4.0x10
Emission
by 261 nm excitation
5
2.0x10
6
4
K [1/cm]
4
D
C
2
0.0
200
4
400
500
600
700
800
900
1000
1100
0
200
B
300
400
500
600
700
800
2
900 1000 1100
5
F
3
x5
1
0
300
400
500
600
700
Excitation Sp. for 980 nm emission at RT
5
3+
10 Gy g-rayed CaF2:5 at%Yb
1.2x10
Wavelength [nm]
800
wavelength (nm)
900
1000
1100
1.4
1: as-grown crystal
2: H2-annealed crystal
3: g-rayed crystal
5
1.0x10
E
1.2
emission intensity (arb. units)
A
2
200
300
wavelength (nm)
emission intensity (arb. units)
absorption coefficient (cm )
6
H2-annealed CaF2:Yb
4
8.0x10
4
6.0x10
D
4
4.0x10
C
1.0
2
0.8
3
1
0.6
0.4
0.2
0.0
940
960
980 1000 1020 1040 1060 1080 1100 1120 1140
wavelength (nm)
4
2.0x10
A
0.0
220
240
260
280
300
320
340
wavelength (nm)
360
380
400
420
EPR spectra:
CaF2:Yb3+ 5%
- Annealed in hydrogen and g-irradiated CaF2:Yb crystals show the presence of additional UV
bands characteristic of Yb2+ absorption,
- AA intensity value has been observed much higher for g-irradiated crystal and strongly
dependent on the gamma dose,
- Different are mechanisms of Yb2+ creating under g-irradiation and annealing in hydrogen.
The latter favors Yb2+ isolated centers by reduction of Yb3+ ions located at Ca2+ lattice sites
whereas the former favors Yb2+ centers being neighboring to Yb3+ ions when one Yb3+ ion pair
captures a Compton electron. As compared to the annealed crystal, g-irradiation does not
change the position of Yb3+ ions being converted to Yb2+ one in CaF2 lattice. In case of the
annealing in hydrogen the cluster is probably destroyed under the influence of temperature
and Yb3+ ion being converted to Yb2+ one is shifted to lattice Ca2+ position.
- Temperature dependence of EPR spectra shows agreement with the Curie law for most of the
lines,
- EPR spectra show Yb3+ as isolated ions, but temperature dependence of the linewidth suggests
the presence of Yb3+ - Yb2+ interacting pairs after g-irradiation.
Peak-to-peak linewidth changes continuously within 20 mT range for “as-grown” crystals,
while reveals distinct increase above 25 K for g-irradiated ones. It suggests strong ferromagnetic
coupling between neighbours Yb3+ and Yb2+ ions the latter being created due to Compton
electron capture. So, Yb3+ co-exists with Yb2+ after the Yb3+ - Yb2+ conversion under influence
of g-irradiation and/or annealing in hydrogen
Absorption spectra under g-irradiation
for other fluorides
LiLuF4 - undoped
1 - "as-grown"
5
2 - K 10 Gy
3 - K 903 K hydrogen with respect to gammas
4 - K 903 K hydrogen with respect to "as-grown"
5
5 - g 10 Gy with respect to hydrogen
2
6
5
K, K [1/cm]
4
80
40
BaY2F8:Yb (0.5wt.%)
1 - "as-grown"
5
2 - K 10 Gy
3 - K 903 K for 1h with respect to gamma
4 - K 903 K for 1h with respect to "as-grown"
5
5 - g 10 Gy with respect to hydrogen
2
2
4
-2
5
K, K [1/cm]
1
-4
3
-6
4
60
1
0
5
1 - K g 10 Gy
2 - K 903 K 1h hydrogen
with respect to gamma
3 - K 903 K 1h hydrogen
with respect to "as-grown"
5
4 - g 10 Gy with respect to hydrogen
1
100
3
2
YLiF4
120
K [1/cm]
8
3
0
-20
-40
2
-60
1
1
-80
4
0
20
-100
3, 4
-120
-8
200
400
600
800
-1
1000
200
400
600
800
1000
Wavelength [nm]
Wavelength [nm]
-2
3
-3
3,0
2,5
3
2,0
1,5
K, K [1/cm]
1,0
2
1
7
0,5
5
2-7
-0,5
-1,0
-1,5
600
800
1000
4
8
Wavelength [nm]
LiYF4:Yb 0.5% Yb
1 - "as-grown"
5
2 - K 10 Gy
3 - K hydrogen 903 K for 1h with respect to gamma
4 - K hydrogen 903 K for 1h with respect to "as-grown"
5
5 - g 10 Gy with respect to hydrogen
7
6
5
1
6
0,0
400
LLF:Yb, YLF:Yb
BYF:Yb, KYF:Yb
K, K [1/cm]
200
LuLiF4:Yb (0.5wt.%)
1 - "as-grown"
4
2 - K 10 Gy
5
3 - K 10 Gy
o
5
4 - K hydrogen 903 K for 1h with respect to 10 Gy
o
5 - K hydrogen 903 K for 5h with respect to "as-grown"
o
6 - K hydrogen 903 K for 1h with respect
to "as-grown"
5
7 - g 10 Gy withe respect to hydrogen
4
1
3
2
1
2
5
0
-2,0
4
-1
3
-2,5
-2
-3,0
-3
-3,5
200
400
600
Wavelength [nm]
800
1000
200
400
600
Wavelength [nm]
800
1000
LiLuF4 (5% Yb)
3,0
2,5
2,0
1,5
4
8
6
4
1
2
K [1/cm]
K [1/cm]
1,0
0,5
3
0,0
-0,5
2
-1,0
KY3F10 (5wt.%Yb)
1- as grown
5
2 - g 10 Gy
3 - 903 K H2 1h with respect to gamma
4 - 903 K H2 1h with respect to as-grown
10
5
1 - K g 10 Gy
2 - K with respect to gamma (903 K 5h)
3 - K with respect to "as-grown" (903 K 5h)
5
4 - g 10 Gy with respect to hydrogen
5
5
5 - g 10 Gy after H2
2
1
0
-2
4
-4
-1,5
3
2,3,4,5
-6
-2,0
1
-8
-2,5
-10
-3,0
200
400
600
800
1000
200
400
Wavelength [nm]
600
800
1000
Wavelength [nm]
Absorption spectra under g-irradiation
for other fluorides
14
KY3F10:Yb (20%)
4
8
1
6
4
K [1/cm]
8
5
1 - K g 10 Gy
2 - K 903 K 1h hydrogen
with respect to gamma
3 - K 903 K 1h hydrogen
with respect to "as-grown"
5
4 - g 10 Gy with respect to hydrogen
10
2
3
0
LiYF4:Yb (10wt.%)
1 - "as-grown"
5
2 - K 10 Gy
3 - K hydrogen 903 K for 1h
with respect to gamma
4 - K hydrogen 903 K for 1h
with respect to "as-grown"
5
5 - g 10 Gy with respect to hydrogen
6
K, K [1/cm]
12
-2
-4
4
2
2
-6
2
1
5
0
4
-8
-10
2,5
3
-12
3,4
-2
-14
200
400
600
Wavelength [nm]
800
1000
200
400
600
Wavelength [nm]
800
1000
Fluorides
- g-irradiation introduce some radiation defects:
LLF – 315 nm (F-centre), 240 nm and 380 nm (perturbed Vk centers, 520 nm (F2+ centers),
600 nm (N2 center)
YLF – 260, 330, 440, 505 and 640 nm, additionally 520 nm
CaF2 – 280, 380, 430, 560, 760 nm
- Doping with Yb generally reduce total induced absorption, the higher is Yb concentration, the
lower is induced absorption, the intensity of the F-center significantly decreases, new centre at
340 nm (Yb2+ centre) arises – competition of Yb3+ ions with F vacancies in capturing free
electrons arising after g-ray irradiation. Yb2+ centers induced in LLF, YLF, CaF2 and BYF
crystals doped with Yb3+ are related to Yb3+. Only Yb2+ centers in KYF arise at the expense of
the Yb3+ isolated centers.
Yb: CaF2 – 214, 225, 237, 257, 272, 310, 360 nm
- Conversion from Yb3+ to Yb2+ under annealing in reducing atmosphere is observed only for
middle ytterbium concentrations (5-10%), when isolated Yb centers dominate over Yb pairs,
gamma induced bands we associated with accompanied Yb2+ centers disappear after
annealing in H2 at 903 h for 1h but isolated ones arises
-- Curing influence of H2 annealing on point growth defects is clearly observed
-- Excitation of induced Yb2+ bands give rise to photoionization of of Yb2+ ions and electrons
in the conduction band to form the excited Yb3+ ions which emit IR Yb3+ luminescence.
Li2B4O7:Mn glass
10
15000
14000
4
1
4
3
10
0
250 500 750 1000 2500
2750
Wavelength [nm]
4
4
4
4
10000
T1(G)+( A1(G), E(G))
9000
4
4
E( D)
4
PL [a.u.]
K [1/cm]
20
1
4
E( G)
4
T2( D)
6000
8000
6000
4000
2
3000
1
4
2
4
T1( G)
2000
2
0
500
750
1000
2000 2250 2500 2750
200
250
Wavelength [nm]
300
350
400
500
450
550
0
450
600
Wavelength [nm]
500
550
600
650
700
750
Wavelength [nm]
300000
40000
250000
620 nm
200000
430 nm
Excitation [a.u.]
0
250
PL [a.u.]
K[1/cm]
6
12000
12000
30
Excitation [a.u.]
2
8
4
A1( G)
40
540 nm
150000
1 - em=620 nm
2 - em=540 nm
3 - em=430 nm
30000
20000
225 nm
10000
277
100000
411
374
50000
0
300
3
1
550
360
400
500
600
Wavelength [nm]
700
800
0
200
2
250
300
350
400
450
500
550
Wavelength [nm]
Changes in the absorption and emission spectra at the course of time
600
800
a)
b)
c)
EPR spectrum of LBO:Mn glass at room temperature: a – “as-grown” sample, b – irradiated with
gamma, and c - annealed at 400 oC in the air for 4h, n = 9.389 GHz
a)
b)
c)
L5
EPR spectrum of LBO: Mn crystal at room temperature along Z axis (Z||B): a) – a sample measured
before annealing treatment, b) – after irradiation with g-rays, c) – after annealing in the air at 673 K
for 4h
LBO:Co crystal
LBO:Mn crystal
225 nm
5
8
K [1/cm]
4
275 nm
24
Li2B4O7:Mn
3
20
2
5
0
500
4
1000
1500
2000
2500
3000
Wavelength [nm]
12
389 nm
8
5
Li2B4O7:Mn 1.2*10 Gy
2
LBO_Co g 1.5*10 Gy
1 wt.% Co
0,85 wt.% Co
0,5 wt.% Co
16
K [1/cm]
1
2
4
3
1
0
0
250
300
350
400
450
500
550
600
650
700
750
800
200
300
400
Wavelength [nm]
Pure glass
4
2,5
25
1-5.88*10 Gy
o
2-450 C in the air for 3h
4
3-10 Gy
6
4-10 Gy
15
10
4
5
3
1,5
-10
LBOS
glass
WAT
2
-15
1
1,0
0
-5
1-5.88*10 Gy
o
2-450 C
5
3-1.368*10 Gy
6
4-10 Gy
2,0
4
1
600
0,5
2
0,0
3
-0,5
-1,0
-1,5
LBOK1 single crystal
|| do osi wzrostu
WAT
4
-2,0
-2,5
-3,0
-20
-3,5
-25
-4,0
-30
-4,5
200
400
700
Pure single crystal
30
20
500
Wavelength [nm]
K [1/cm]
200
K [1/cm]
K [1/cm]
6
255 nm
600
800
Wavelength [nm]
1000
1200
200
400
600
Wavelength [nm]
800
1000
800
900
-The gamma irradiation cures the LBO:Mn crystal from the point defects, giving additional L5
EPR line attributed to Mn0B (Mno substituting for Li+ in off-centre position), Vk centres (225 and
370 nm AA bands), the same phenomenon is observed for LBO:Co crystal
- The gamma irradiation of the LBO:Mn glass cures the glass from point defects (lithium or
oxygen vacancies) ionising Mn1+, Mn2+ , and Mn3+ ions, leads to arising of the strong
additional absorption band (45 cm-1) on the FAE, centred at about 300 nm (B2+) and 575 nm
band assigned to Mn2+ , Mn3+ and F2+ centres,
- In Mn2+ doped “as-grown” LBO single crystals and glasses there arises oxygen, and, Li+
vacancies compensating Mn2+ substitution for Li+,
CONCLUSIONS
- For given growth conditions (growth method, purity of the starting material, growth atmosphere,
technological parameters) some definite sub-system of point defects appears in the crystal (e.g.
active ions, vacancies, antisite ions, active ions, uncontrolled and controlled impurities or interstitial
defects). At the end of the growth it is electrically balanced and is left in a metastable state. Some
external factors, like irradiation or thermal processing, may lead to the transition of this
sub-system from one metastable state to another. During this transition point defects may change
their charge state.
- Irradiation can induce numerous changes in the physical properties of a crystal ar a glass.
This may originate from atomic rearrangements which take place powered by the energy given up
when electrons and holes recombine non-radiatively, or could be induced by any sort of radiation
or particle bombardment capable of exciting electrons across the forbidden gap Eg into the
conduction band.
- Different type of treatments (annealing in reducing or oxidizing atmosphere, irradiation) differ in
producing of characteristic defects. They may be color centers, polarons, trapped holes,
Frenkel defects, recharged active, lattice or uncontrolled ions. In the absorption spectrum they
may be observed even in infrared. The type of the radiation defects arising in the crystal and
glasses strongly depends on wether the material was obtained or next annealed at oxidizing
or reducing atmosphere
- Fluency dependence of the additional absorption exhibit characteristic shape with maximum at
about 1014 protons/cm2, minimum at about 1015 protons/cm2 and further sharp rise for higher
fluencies. Such non-monotonic dependence is characteristic for color centers, rather than for
Frenkel centers. For the latter ones, a monotonic, linear with proton fluency dependence is seen.
The probable reason of the decrease in the region 2*1014 -1015 protons/cm2 could be mutual
interaction of the cascades from different proton trajectories.
- Irradiation and annealing treatments appear to be the effective tools of crystal change and
characterization. The observed in the absorption spectrum changes after ionizing radiation or
annealing treatment can have important influence on the performance of optoelectronic devices
applied in e.g. outer space. The obtained results point to the direct influence of color centers on
the processes of inverse population formation of many lasers.