FLUORESCENCE OF Pr3+ AND Dy3+ IN LaMgAl11O19 SINGLE CRYSTALS

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FLUORESCENCE OF Pr3+ AND Dy3+ IN LaMgAl11O19 SINGLE CRYSTALS

B. Viana, P. Derouineau, J. Barrie, A. Lejus, B. Dunn, O. Stafsudd, D. Vivien

To cite this version:

B. Viana, P. Derouineau, J. Barrie, A. Lejus, B. Dunn, et al.. FLUORESCENCE OF Pr3+ AND

Dy3+ IN LaMgAl11O19 SINGLE CRYSTALS. Journal de Physique Colloques, 1987, 48 (C7), pp.C7-

509-C7-511. �10.1051/jphyscol:19877121�. �jpa-00226939�

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JOURNAL DE PHYSIQUE

C o l l o q u e C7, s u p p l e m e n t a u n 0 1 2 , Tome 4 8 , d e c e m b r e 1 9 8 7

FLUORESCENCE OF p r 3 + AND D Y ~ + IN LaMgAl110L9 SINGLE CRYSTALS

B. VIANA, P. DEROUINEAU, J. B A R R I E * , A.M. LEJUS, B. DUNN*

0. STAFSUDD* a n d D. VIVIEN

Chimie Appliquee de 1'Etat Solide, CNRS-UA 302, ENSCP,

11, Rue Pierre et Marie Curie, F-75231 Paris Cedex 05, France

" ~ e p a r t m e n t of Materials Science and Engineering, University of California, Zos Angeles, CA 90024, U. S. A.

A b s t r a c t

LaMgAlllOlg doped w i t h pr3+ could lead t o a material l a s i n g i n t h e v i s i b l e range. For lamp pumping it is necessary t o s e n s i t i z e t h e fluorescence ( f o r example by ~ y ~ + ) . O p t i c a l p r o p e r t i e s have been determined by absorption, d i f f u s e r e f l e c t a n c e , fluorescence s p e c t r o s c o p i e s as w e l l as f l u o r e s c e n c e decays on 2 kinds o f m a t e r i a l s : s i n g l e doped crystals LaJal-xLn#gAlllolS (Ln = p r , ~ y ) and codoped ones L~l-x~yPrXDyyMgAlllOlg. I n s i n g l e doped m a t e r i a l a s t r o n g

fluorescence quenching occurs. I n codoped c r y s t a l s , w h i l e f l u o r e s c e n t l e v e l s of

~ y a r e i n resonance w i t h pr3+ a b s o r p t i o n l e v e l s , t h e r e ~ + is no s e n s i t i z a t i o n o f t h e pr3+ fluorescence

.

I n t r o d u c t i o n

Figure 1

Energy l e v e l s o f pr3+ and Dy3+ i n

~ ~ l - . & n ~ g A l l l o l g (Ln

-

^{P r o r}^Dy⁾

LaMgAlllOlg i s a w e l l known l a s e r h o s t f o r i o n s such as ~ d ~ + , cr3+,

~ i( 1, ~2, 3 +)

.

^{W i t h}pr3+ i o n s t h i s m a t r i x could l e a d t o a m a t e r i a l l a s i n g i n t h e v i s i b l e range ( 4 ) . F l u o r e s c e n t l e v e l s o f pr3+ i o n s are 3 ~ 0 ( i n t e n s e ) and 'D2 (weak). As t h e r e is o n l y a

f e w l e v e l s above t h e f l u o r e s c e n t ones, l a s e r e x c i t a t i o n i n t o t h e s e l e v e l s is t h e u s u a l way t o pump a pr3+ a c t i v a t e d l a s e r . Lamp pum- p i n g i s up t o now very d i f f i c u l t . However t h i s pumping could be performed v i a a s e n s i t i z a t i o n o f pr3+ f l u o r e s c e n c e by o t h e r i o n s which p r e s e n t U.V. and v i s i b l e

l i n e s such as D ~ i o n s . These ~ + i o n s r e v e a l on t h e one hand s t r o n g a b s o r p t i o n s l e a d i n g t o energy l e v e l s above t h e 3 ~ 0 one, and on t h e o t h e r hand f l u o r e s c e n t l e v e l s i n resonance with pr3+

a b s o r p t i o n ( s e e f i g . 1 ) :

- +942

-

6 ~ 1 3 / 2 ~ 3 * emission with Ha

-

^pr3+a b s o r p t i o n t o s e n s i t i z e t h e

f l u o r e s c e n t l e v e l

-

4 ~ 9 / 2

-

^6~15/2^~ ^y ^emission^~ ⁺

with 3 ~ 4

-

3 ~ o - 2 ~ r 3 + a b s o r p t i o n t o s e n s i t i z e t h e 3p0

f l u o r e s c e n t l e v e l .

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19877121

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J O U R N A L DE PHYSIQUE

Materials

Two series o f c r y s t a l s have been obtained from t h e molten s t a t e

(Tf = 1850 O C ) by t h e flame f u s i o n method : L~l-xL~gA1llO1g (Ln = P r o r Dy) and

~l-x-yPr~yMgAlllOlg. There is a t o t a l s o l u b i l i t y o f pr3+ i n t h e m a t r i x

( 0 ^4;x 6 1 ) while i t i s l i m i t e d t o y

<

0.2 f o r

&+.

All t h e c r y s t a l s belong t o a magnetoplumbite l i k e s t r u c t u r e (hexagonal symmetry, space group P63/rmnc). They are rod-shaped and e%h&it a cleavage along (001). Optical i n v e s t i g a t i o n s were performed on t r a n s p a r e n t cleavage p l a t e l e t s .

O j t i c a l p r o p e r t i e s

O p t i c a l p r o p e r t i e s have been determined by absorption, d i f f u s e r e f l e c t a n c e , emission, e x c i t a t i o n and fluorescence decay measurements. For exemple f i g . 2 shows the f l u o r e s c e n c e spectrum o f pr3+ under arc xenon lamp e x c i t a t i o n . Fluorescence decays have been performed using a n i t r o g e n pulsed laser pumping dye l a s e r s ( a t 441 nm f o r pr3+ and 380 nm f o r Dy3+). I n t h e case o f

s i n g l e doped samples, decay p r o f i l e s are e x p o n e n t i a l s f o r both i o n s . L i f e t i m e s s t r o n g l y d e c r e a s e when t h e ^pr3+o r Dy3+ c o n c e n t r a t i o n s i n c r e a s e . For pr3+ i n

~ l - x P r ~ l l O l g , ^Tv a r i e s between 32 p s f o r x = 0.01 and 13 p s f o r x = 0.2. For DyJ+ _{i n}L ~ ~ - ~ D Y + ~ Z U ~ ~ O ~ ~ , T d e c r e a s e s from 905 ^pst o 765 ps when ^xi n c r e a s e s f r o m 0.02 t o 0.2. ^As t r o n g luminescence quenching occurs w i t h t h e c o n c e n t r a t i o n . T h i s is due t o the e x i s t e n c e o f a g r e a t number o f energy l e v e l s between the f l u o r e s c e n t l e v e l s and the ground s t a t e ones ( s e e f i g . l ) , o f f e r i n g s e v e r a l paths f o r s e l f quenching by energy t r a n s f e r between n e i g w u r i n g pr3+ o r ~ y 3 + i o n s .

1 ~ 2 - 3 ~ 4

F i g u r e 2

Fluorescence s p e c t r a o f pr3+

in L a l - ~ r ~ l 1 0 1 9

J(

I . , ,

#

480 MO 520 540 X(nrn)

I n t h e c a s e o f double doped samples, decays p r o f i l e s d o not p r e s e n t any non-exponential behaviour i n t h e same s c a l e time. pr3+ l i f e t i m e s are n o t

influenced by

&+

c o n c e n t r a t i o n . On t h e c o n t r a r y f o r h i g h pr3+ c o n c e n t r a t i o n , Dy3+ lifetimes d e c r e a s e r a p i d l y . For exemple, ^Tchanges from 905 p s t o 408 p s when pr3+ c o n c e n t r a t i o n v a r i e s f r o m x = 0 t o x = 0.25 i n

~ ~ ~ . g ~ - x P r ~ o . 0 2 M g A 1 1 1 0 1 g . This phenomenon is probably due t o a c r o s s - r e l a x a t i o n p r o c e s s between t h e two k i n d s o f ions, t h i s p r o c e s s a r i s i n g because o f t h e g r e a t number o f energy l e v e l s which e x i s t f o r each ion.

I n conclusion n e i t h e r pr3+ e x c i t a t i o n spectrum nor Dy3+ fluorescence have demonstrated that any energy t r a n s f e r f r o m D ~ t o ~ 3 ~ 0 + o r

-

^pr3+f l u o r e s c e n t l e v e l s o c c u r s . However decay p r o f i l e s o f ~ y r e v e a l t h e ~ + e x i s t e n c e o f s t r o n g i n t e r a c t i o n w i t h pr3+ involving non-fluorescent l e v e l s . Furthermore t h e p l o t t i n g of pr3+ fluorescence i n t e n s i t y v e r s u s

Ar+ ( A = 514.5 nm) CW e x c i t a t i o n power i n Dy3+ - pr3+ double doped samples d o not show any non l i n e a r e f f e c t which could be an i n d i c a t i o n o f energy t r a n s f e r v i a two photons a b s o r p t i o n ( i n 56 l e v e l s ).

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T h i s work demonstrates that while f l u o r e s c e n t l e v e l s of Dy3+ are i n resonance w i t h pr3+ a b s o r p t i o n l i n e s , there is no s e n s i t i z a t i o n o f t h e pr3+

fluorescence, n e i t h e r i n t h e 3 ~ 0 n o r i n the 1 ~ 2 energy l e v e l s . Other systems such as lW3+ or Sm3+-pr3+ might be more e f f i c i e n t . T h i s is a t p r e s e n t under s t u d y i n these l a b o r a t o r i e s .

References

( 1 ) M. LEDUC, L.D. SCHEARER, D. V N I E N , A.M. LEJUS, J.THERY I.E.E.E. J. Quantum E l e c t r o n

PE-22

713 (1986).

(2) B. VIANA, A.M. LE3US. D. VIVIEN, V. PONCON, G. BOULON J. S o l i d S t a t e Chem. ( i n p r e s s ) .

( 3 ) R. MONCORGE, T. BEDYAlTDU, D. VIVIEN, A.M. LFJUS J. Luminescence 35 199 (1986 ).

( 4 ) R. REISPELD, C.K. JORGENSEN

Lasers and e x c i t e d states o f r a r e earth S p r i n g e r Verlag ( 1977 )