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New dye lasers covering the visible spectrum
Volume24.A, number 5
PHYSICS LETTERS
Now we m a k e the u s u a l p l a s m a p h y s i c s a s s u m p tion that ~ << 1: the c h a r a c t e r of the e x a c t c o r r e l a tion function follows f r o m the p r o p e r t i e s of the B e s s e l function. F o r notational c o n v e n i e n c e we i n t r o d u c e the d i m e n s i o n l e s s v a r i a b l e z = x / 2 l . Then, j u s t a s f o r the t h r e e - d i m e n s i o n a l p r o b l e m , t h e r e a r e t h r e e d o m a i n s : Ca) z < exp(-1/E): g ( x ) ~ -1 + (eTz) 2~ (v is the E u l e r - M a s c h e r o n i c o n stant); (b) e x p ( - 1 / c ) < z < 1: g~x) ~ 2e In (e~z) + + O(E 2); (c) z > 1 : g(x) ~ -~ ~½z e - ~ e -2z. Region Ca) is w h e r e the r e p u l s i v e t w o - p a r t i c l e d y n a m i c s d o m i n a t e s the b e h a v i o r . Region (c) is the d is t a n t r e gion w h e r e the t w o - p a r t i c l e potential is s c r e e n e d out. The B a l e s c u - L e n a r d type of a p p r o x i m a t e s o l u tion is obtained by d i s c a r d i n g g(x) c o m p a r e d to unity on the l e f t - h a n d - s i d e in eq. (2). The c o n s e quent solution i s found d i r e c t l y f r o m (2): g ( x t a p p r o x i m a t e ) = -2E g o (x/l).
(6)
T h i s is what one could obtain f r o m the e x a c t s o lution (5) by taking the l i m i t E ~ 0. C l e a r l y such a l i m i t i n g p r o c e s s is not u n i f o r m l y valid, s i n c e it will m i s s the r e g i o n (a) that joins to the boundary condition g(0) = -1. The c o n s e q u e n t s i n g u l a r i t y at the o r i g i n (Ko(Y) ~ - l n y a s y --* 0) is a r e f l e c t i o n of this fact.
NEW
DYE
LASERS
COVERING
27 February 1967
F i n a l l y , f r o m eq. (5) we can by an i n t e g r a t i o n [3] get the equation of s t a t e f o r a t w o - d i m e n s i o n a l p l a s m a : P V = N k T {1 -½~). The s i m p l i c i t y of this r e s u l t is in c o n t r a s t to the t h r e e - d i m e n s i o n a l c a s e , which i n v o l v e s ~21n ~ and h i g h e r t e r m s in E. It is a p l e a s u r e to thank P r o f e s s o r Max K r o o k f o r s t i m u l a t i n g d i s c u s s i o n s . T h i s work was supp o r t e d in p a r t by the United States National S c i e n c e Foundation under Grant GK-65, and by the D i v i s i o n of E n g i n e e r i n g and Applied P h y s i c s , Harvard University.
References 1. R.Balescu, Phys. Fluids 3 {1960) 52; A. Lenard, Ann. Phys. (N.Y.) 3 (1960) 390. 2. R.L.Guernsey, Phys. Fluids 7 (1964) 792 and 1600. 3. E.A. Frieman and D.L.Book, Phys. Fluids 6 (1963) 1700. 4. G.L. Lamb and B. Burdick, Phys. Fluids 7 (1964) 1087. 5. G.N.Watson, Theory of Bessel functions, (Cambridge University Press, 1958). Note that as y ~ 0, yeKE(y) --* ½2£ F(e).
THE
VISIBLE
SPECTRUM
F. P. S C H A F E R , W. SCHMIDT and K. MARTH Physikalisch-Chernisches Institut der Universititt Marburg, Germany Received 31 January 1967
The operation of dye lasers in the wavelength range from 440 to 700 nm is reported. Dyes with widely differing chemical constitution were used.
The r e c e n t l y d e v e l o p e d dye l a s e r s [1-4] u s e the s t i m u l a t e d f l u o r e s c e n c e of o r g a n i c dye s o l u t i ons which a r e pumped by a giant p u l s e ruby l a s e r . Thus the w a v e l e n g t h r a n g e of dye l a s e r s is bounded t o w a r d s s h o r t e r w a v e l e n g t h s by the e x citation at 694 nm and t o w a r d s l o n g e r w a v e l e n g t h s by the a v a i l a b i l i t y of f l u o r e s c i n g dyes. Actually we h a v e o b s e r v e d dye l a s e r e m i s s i o n f r o m 720 to 1100 nm. To extend t h i s r a n g e t o w a r d s s h o r t e r w a v e 280
lengths, we have u s e d a 100MW ruby l a s e r f o l lowed by an A D P - f r e q u e n c y - d o u b l e r and a liquid f i l t e r of cobalt c h l o r i d e in alcohol. The r e s u l t ing p u l s e s of 347 nm light of 200 ± 20 kW peak p o w e r w e r e u s e d to pump the dye solutions c o n t a i n e d in a 10 m m s q u a r e cuvette with all four s i d e s p o l s i h e d a s in r e f . 2. A v a r i e t y of dyes e x h i b i t ed l a s e r e m i s s i o n that could be o b s e r v e d a s a b r i l l i a n t l y c o l o r e d spot on a distant s c r e e n . B e a m d i v e r g e n c e a n g l e s w e r e about the s a m e as
Volume24A, number 5
PHYSICS LETTERS
,<" -
t
I
0
o
a
{',4
b
27 February 1967
l a s e r wavelength in n m ; solvent; c o n c e n t r a t i o n in m i l l i m o l e / l i t e r ) : 3 - e t h y l a m i n o p y r e n e - 5 , 8, 10t r i s u l f o n i c acid (Na-salt) (441; water; 2.5), 2,4,6t r i p h e n y l - p y r i l i u m f l u o r o b o r a t e (485; methanol; 1.7), f l u o r e s c e i n (539; water/NaOH; 10.0), r h o d a mine B (608; ethanol; 2.0). E s p e c i a l l y noteworthy is the fact, that these dyes a r e not only cyanine o r phthalocyanine dyes as in the case of the hitherto known dye l a s e r s but differ widely in c h e m i cal constitution. Some dyes that showed no l a s e r e m i s s i o n , when pumped at 347 nm, r e a d i l y l a s e d when pumped at 532 nm with 50 to 100 kW p u l s e s from a f r e q u e n c y - d o u b l e d n e o d y m i u m g l a s l a s e r b e c a u s e of the higher a b s o r p t i o n coefficient at this wavelength, as e.g. 3 , 3 ' - d i e t h y l o x a d i c a r b o cyanine iodide (658; methanol; 1.0). T h e r e is no doubt that with the a l m o s t u n l i m i t e d n u m b e r of dyes available s e v e r a l dye l a s e r s may be found for any wavelength within the v i s i b l e s p e c t r u m . We will use the pumping method r e p o r t e d in this l e t t e r to look for dye l a s e r s which can be pumped by m o r e conventional methods.
C Fig. 1. Oscillograms (retraced for the reproduction); sweep speed 5 nsee/cm. The power corresponding to two major scale divisions is annotated to the right of each oscillogram. (a) Exciting pulse at 347-nm. (b) Dye laser pulse from a cuvette with 2.5 × 10 -3 M solution of 3-ethylaminopyrene-5, 8, 10-trisulfonic acid, (Nasalt) pumped with the pulse of fig. la. (c) Same as in(b) but pumping pulse attenuated to 40 kW. those r e p o r t e d for the longer wavelength dye l a s e r s . The s p e c t r a were photographed with a Steinheil s p e c t r o g r a p h and the peak power and pulse f o r m of the dye l a s e r p u l s e s o b s e r v e d with a photocell and o s c i l l o s c o p e a s in ref. 2. O s c i l l o g r a m s of the u l t r a v i o l e t exciting p u l s e s and the r e s u l t i n g p u l s e s of blue dye l a s e r with full and a t t e n u a t e d excitation power a r e given in fig. 1. As in the c a s e of r e d and i n f r a r e d dye l a s e r s , the l a s e r wavelength was found to be a function of c o n c e n t r a t i o n , t e m p e r a t u r e and cavity, Q [2]. Among the dyes that showed l a s e r action a r e the following well-known s u b s t a n c e s (in p a r e n t h e s e s :
T h i s work was supported by the Deutsche F o r s c h u n g s g e m e i n s c h a f t . We thank the d i r e c t o r of this Institute, Prof. Dr. Hans Kuhn, for his i n t e r e s t and e n c o u r a g e m e n t . We also thank Prof. Dr. K. Dimroth, Dr. C. R e i c h a r d t and D. K. H. D r e x hage for gifts of dye s a m p l e s .
References 1. p.P.Sorokin and J.R. Lankard, IBM J. Res. Develop 10 (1966) 162. 2. F.P.Schlifer. W.Sehmidt and J. Volze. Appl. Phys. Letters 9 (1966) 306. 3. P.P.Sorokin, W.H. Culver, E.C.Hammond and J.R0 Lankard, IBM J. Res. Develop 10 (1966) 401. 4. M.L.Spaeth and D. P. Bortfeld, Appl. Phys. Letters 9 (1966) 179.
281
PHYSICS LETTERS
Now we m a k e the u s u a l p l a s m a p h y s i c s a s s u m p tion that ~ << 1: the c h a r a c t e r of the e x a c t c o r r e l a tion function follows f r o m the p r o p e r t i e s of the B e s s e l function. F o r notational c o n v e n i e n c e we i n t r o d u c e the d i m e n s i o n l e s s v a r i a b l e z = x / 2 l . Then, j u s t a s f o r the t h r e e - d i m e n s i o n a l p r o b l e m , t h e r e a r e t h r e e d o m a i n s : Ca) z < exp(-1/E): g ( x ) ~ -1 + (eTz) 2~ (v is the E u l e r - M a s c h e r o n i c o n stant); (b) e x p ( - 1 / c ) < z < 1: g~x) ~ 2e In (e~z) + + O(E 2); (c) z > 1 : g(x) ~ -~ ~½z e - ~ e -2z. Region Ca) is w h e r e the r e p u l s i v e t w o - p a r t i c l e d y n a m i c s d o m i n a t e s the b e h a v i o r . Region (c) is the d is t a n t r e gion w h e r e the t w o - p a r t i c l e potential is s c r e e n e d out. The B a l e s c u - L e n a r d type of a p p r o x i m a t e s o l u tion is obtained by d i s c a r d i n g g(x) c o m p a r e d to unity on the l e f t - h a n d - s i d e in eq. (2). The c o n s e quent solution i s found d i r e c t l y f r o m (2): g ( x t a p p r o x i m a t e ) = -2E g o (x/l).
(6)
T h i s is what one could obtain f r o m the e x a c t s o lution (5) by taking the l i m i t E ~ 0. C l e a r l y such a l i m i t i n g p r o c e s s is not u n i f o r m l y valid, s i n c e it will m i s s the r e g i o n (a) that joins to the boundary condition g(0) = -1. The c o n s e q u e n t s i n g u l a r i t y at the o r i g i n (Ko(Y) ~ - l n y a s y --* 0) is a r e f l e c t i o n of this fact.
NEW
DYE
LASERS
COVERING
27 February 1967
F i n a l l y , f r o m eq. (5) we can by an i n t e g r a t i o n [3] get the equation of s t a t e f o r a t w o - d i m e n s i o n a l p l a s m a : P V = N k T {1 -½~). The s i m p l i c i t y of this r e s u l t is in c o n t r a s t to the t h r e e - d i m e n s i o n a l c a s e , which i n v o l v e s ~21n ~ and h i g h e r t e r m s in E. It is a p l e a s u r e to thank P r o f e s s o r Max K r o o k f o r s t i m u l a t i n g d i s c u s s i o n s . T h i s work was supp o r t e d in p a r t by the United States National S c i e n c e Foundation under Grant GK-65, and by the D i v i s i o n of E n g i n e e r i n g and Applied P h y s i c s , Harvard University.
References 1. R.Balescu, Phys. Fluids 3 {1960) 52; A. Lenard, Ann. Phys. (N.Y.) 3 (1960) 390. 2. R.L.Guernsey, Phys. Fluids 7 (1964) 792 and 1600. 3. E.A. Frieman and D.L.Book, Phys. Fluids 6 (1963) 1700. 4. G.L. Lamb and B. Burdick, Phys. Fluids 7 (1964) 1087. 5. G.N.Watson, Theory of Bessel functions, (Cambridge University Press, 1958). Note that as y ~ 0, yeKE(y) --* ½2£ F(e).
THE
VISIBLE
SPECTRUM
F. P. S C H A F E R , W. SCHMIDT and K. MARTH Physikalisch-Chernisches Institut der Universititt Marburg, Germany Received 31 January 1967
The operation of dye lasers in the wavelength range from 440 to 700 nm is reported. Dyes with widely differing chemical constitution were used.
The r e c e n t l y d e v e l o p e d dye l a s e r s [1-4] u s e the s t i m u l a t e d f l u o r e s c e n c e of o r g a n i c dye s o l u t i ons which a r e pumped by a giant p u l s e ruby l a s e r . Thus the w a v e l e n g t h r a n g e of dye l a s e r s is bounded t o w a r d s s h o r t e r w a v e l e n g t h s by the e x citation at 694 nm and t o w a r d s l o n g e r w a v e l e n g t h s by the a v a i l a b i l i t y of f l u o r e s c i n g dyes. Actually we h a v e o b s e r v e d dye l a s e r e m i s s i o n f r o m 720 to 1100 nm. To extend t h i s r a n g e t o w a r d s s h o r t e r w a v e 280
lengths, we have u s e d a 100MW ruby l a s e r f o l lowed by an A D P - f r e q u e n c y - d o u b l e r and a liquid f i l t e r of cobalt c h l o r i d e in alcohol. The r e s u l t ing p u l s e s of 347 nm light of 200 ± 20 kW peak p o w e r w e r e u s e d to pump the dye solutions c o n t a i n e d in a 10 m m s q u a r e cuvette with all four s i d e s p o l s i h e d a s in r e f . 2. A v a r i e t y of dyes e x h i b i t ed l a s e r e m i s s i o n that could be o b s e r v e d a s a b r i l l i a n t l y c o l o r e d spot on a distant s c r e e n . B e a m d i v e r g e n c e a n g l e s w e r e about the s a m e as
Volume24A, number 5
PHYSICS LETTERS
,<" -
t
I
0
o
a
{',4
b
27 February 1967
l a s e r wavelength in n m ; solvent; c o n c e n t r a t i o n in m i l l i m o l e / l i t e r ) : 3 - e t h y l a m i n o p y r e n e - 5 , 8, 10t r i s u l f o n i c acid (Na-salt) (441; water; 2.5), 2,4,6t r i p h e n y l - p y r i l i u m f l u o r o b o r a t e (485; methanol; 1.7), f l u o r e s c e i n (539; water/NaOH; 10.0), r h o d a mine B (608; ethanol; 2.0). E s p e c i a l l y noteworthy is the fact, that these dyes a r e not only cyanine o r phthalocyanine dyes as in the case of the hitherto known dye l a s e r s but differ widely in c h e m i cal constitution. Some dyes that showed no l a s e r e m i s s i o n , when pumped at 347 nm, r e a d i l y l a s e d when pumped at 532 nm with 50 to 100 kW p u l s e s from a f r e q u e n c y - d o u b l e d n e o d y m i u m g l a s l a s e r b e c a u s e of the higher a b s o r p t i o n coefficient at this wavelength, as e.g. 3 , 3 ' - d i e t h y l o x a d i c a r b o cyanine iodide (658; methanol; 1.0). T h e r e is no doubt that with the a l m o s t u n l i m i t e d n u m b e r of dyes available s e v e r a l dye l a s e r s may be found for any wavelength within the v i s i b l e s p e c t r u m . We will use the pumping method r e p o r t e d in this l e t t e r to look for dye l a s e r s which can be pumped by m o r e conventional methods.
C Fig. 1. Oscillograms (retraced for the reproduction); sweep speed 5 nsee/cm. The power corresponding to two major scale divisions is annotated to the right of each oscillogram. (a) Exciting pulse at 347-nm. (b) Dye laser pulse from a cuvette with 2.5 × 10 -3 M solution of 3-ethylaminopyrene-5, 8, 10-trisulfonic acid, (Nasalt) pumped with the pulse of fig. la. (c) Same as in(b) but pumping pulse attenuated to 40 kW. those r e p o r t e d for the longer wavelength dye l a s e r s . The s p e c t r a were photographed with a Steinheil s p e c t r o g r a p h and the peak power and pulse f o r m of the dye l a s e r p u l s e s o b s e r v e d with a photocell and o s c i l l o s c o p e a s in ref. 2. O s c i l l o g r a m s of the u l t r a v i o l e t exciting p u l s e s and the r e s u l t i n g p u l s e s of blue dye l a s e r with full and a t t e n u a t e d excitation power a r e given in fig. 1. As in the c a s e of r e d and i n f r a r e d dye l a s e r s , the l a s e r wavelength was found to be a function of c o n c e n t r a t i o n , t e m p e r a t u r e and cavity, Q [2]. Among the dyes that showed l a s e r action a r e the following well-known s u b s t a n c e s (in p a r e n t h e s e s :
T h i s work was supported by the Deutsche F o r s c h u n g s g e m e i n s c h a f t . We thank the d i r e c t o r of this Institute, Prof. Dr. Hans Kuhn, for his i n t e r e s t and e n c o u r a g e m e n t . We also thank Prof. Dr. K. Dimroth, Dr. C. R e i c h a r d t and D. K. H. D r e x hage for gifts of dye s a m p l e s .
References 1. p.P.Sorokin and J.R. Lankard, IBM J. Res. Develop 10 (1966) 162. 2. F.P.Schlifer. W.Sehmidt and J. Volze. Appl. Phys. Letters 9 (1966) 306. 3. P.P.Sorokin, W.H. Culver, E.C.Hammond and J.R0 Lankard, IBM J. Res. Develop 10 (1966) 401. 4. M.L.Spaeth and D. P. Bortfeld, Appl. Phys. Letters 9 (1966) 179.
281