- Email: [email protected]
High peak power pulsed 10μ CO2 laser
Volume 20, n u m b e r 4
PHYSICS
less than the theoretically smallest possible (nonzero) constraint towards circularity (j = 2 ~ j 2). These comparisons indicate that the constraint o b s e r v e d on t h e 1.523 /~ l a s e r m i g h t b e a r e s i d u a l effect rather than evidence against theory; howe v e r , the o r i g i n of t h e e f f e c t i s n o t c l e a r . F i n a l l y , we m e n t i o n s o m e q u a l i t a t i v e o b s e r v a t i o n s m a d e on a 23 c m p l a n a r d. c . - e x c i t e d H e - N e laser operating simultaneously at several neon transitions. Among the laser lines observed were t h e 1.152 p l i n e (2s 2 --- 2P2 , j = 1 ~ j = 2), t h e 1 . 1 7 7 p l i n e (2s 2 ~ 2P2 , j = 1 ~ j = 1), t h e 1.198 l i n e (2s 3 ~ 2P2 , j = 0 ~ j = 1) a n d the 1.207 p l i n e (2s5 ~ 2p 6, j = 2 - - - j = 2 ) . A t 1.152 /x two s t r o n g m o d e s o c c u r r e d , l i n e a r ly p o l a r i z e d a t r i g h t a n g l e s . A t t h e o t h e r w a v e lengths weak single modes were observed. As a r u l e t h e m o d e s a t 1.177 / x a n d 1.198 ~ s h o w e d o r thogonal linear polarizations with azimuths coinc i d i n g w i t h t h o s e of t h e two 1.152 ~ m o d e s r e s p e c tively; under certain tuning conditions, however, t h e i r p o l a r i z a t i o n s a p p e a r e d to b e o p p o s i t e l y c i r cular. Presumably the observed general prefer-
HIGH
PEAK
POWER
C. F R A P A R D ,
LETTERS
1March1966
e n c e f o r l i n e a r p o l a r i z a t i o n of t h e s e two w e a k m o d e s i s d u e to the s a t u r a t i o n - i n d u c e d a n i s o t r o p i e s b u r n t b y the two s t r o n g 1.152 /x m o d e s , c i r c u l a r p o l a r i z a t i o n o c c u r r i n g o n l y w h e n t h e s e two a n i s o t r o p i e s ( w h i c h a r e o p p o s i t e in s i g n ) e x a c t l y c o m p e n s a t e e a c h o t h e r . T h e 1.207 p m o d e w a s i n v a r i a b l y o b s e r v e d to b e c i r c u l a r l y p o l a r i z e d ; u n der pulsed-operating conditions both left and rightcircular polarization randomly occurred.
References
1. H. De Lang, G. Bouwhuis and E. T. F e r g u s o n , P h y s i c s L e t t e r s 19 (1965) 482. 2. D. P o l d e r and W.Van Haeringen, P h y s i c s L e t t e r s 19 (1965) 380. 3. H.De Lang, Magnetic phenomena in gas l a s e r s , (Zeeman Centennial Conference, A m s t e r d a m , Sept e m b e r 1965) to be published in P h y s i c s . 4. C.V. Heer and R.D. Graft, Phys. Rev. 140A (1965) 1088. 5. H.G. Van Bueren, J . Haisma and H. De Lang, P h y s i c s L e t t e r s 2 (1962) 340.
PULSED
10t~ CO 2 LASER
*
M. R O U L O T a n d X . Z I E G L E R
Centre de R e e h e r c h e s de la Cornpagnie G~n$rale d ' E l e c t r i c i t ~ D$parternent R e c h e r c h e s P h y s i q u e s de B a s e M a r c o u s s i s (Essonne) - F r a n c e
Received 28 D e c e m b e r 1965
P e a k l a s e r p o w e r s of 220 W, 450 W and 825 W w e r e o b s e r v e d in p u r e CO2, CO 2 - N 2 - 0 2 and CO2 - N2 He p u l s e d d i s c h a r g e s . N o d e l a y b e t w e e n c u r r e n t and l a s e r p u l s e w a s o b s e r v e d , l a s e r p u l s e w i d t h s w e r e found to b e a f u n c t i o n of t h e g a s m i x t u r e , l a s t i n g 500 p s in p u r e CO 2 w h i l e it w a s r e d u c e d to 150 /is w h e n helium was added.
We have observed high intensity laser radiation a t 10.6 p f r o m p u r e C O 2 s e a l e d i n a t u b e a n d e x cited by high voltage pulses. Similar results have b e e n o b t a i n e d u s i n g a m i x t u r e of C O 2 - N 2 - He. Under quite different conditions, Patel had previously obtained stimulated emission from pure C O 2 b u t w i t h r e l a t i v e l y low p e a k p o w e r [1]. S e v e r a l * Work supported by D. R. M. E. 384
e x p e r i m e n t s d e s i g n e d to o b t a i n h i g h p o w e r C . W . l a s e r s u s i n g p u r e C O 2 a n d m i x t u r e of C O 2 - N 2 [2, 3, 4] h a v e b e e n d o n e s i n c e t h e o r i g i n a l w o r k of P a t e l [1, 5] a n d L e g a y - S o m m a i r e e t a l . [6]. T h e t u b e u s e d in o u r e x p e r i m e n t s h a d a n 18 m m i n t e r i o r d i a m e t e r a n d 1.80 m d i s c h a r g e - l e n g t h . T h e two m i r r o r s w e r e c o a t e d w i t h g o l d a n d p l a c e d i n a n a l m o s t c o n f o c a l c o n f i g u r a t i o n . One of t h e m i r r o r s h a d a 4 m m h o l e f o r d i f f r a c t i o n c o u p l i n g of t h e o u t put power.
Volume 20, number4
PHYSICS LETTERS
1-d 500
Pw
I
o
500. Pwl 0 200 W, J
1-b
'
Pw' V
1-a
10 kV
:
I
0.5
1 ms
1March1966
peak p o w e r of 220 W (fig. lb) f o r a gas p r e s s u r e of 1.5 m m Hg. No d el ay b et w een the c u r r e n t pulse and the l a s e r pulse was found. The high r e p e t i t i o n r a t e s u s e d allowed us to m e a s u r e a m e a n p o w e r of 4 W with a t h e r m o p i l e . With a m i x t u r e of CO 2 - N 2 - 0 2 we found peak p o w e r s of about 450 W (fig. l c) and an a v e r a g e p o w e r of 7 W. The p u l se length was a p p r o x i m a t e ly the s a m e as obtained with p u r e CO 2. When the oxygen was r e p l a c e d by h e l i u m we obtained c o n s i d e r a b l y s h o r t e r p u l se lengths, of the o r d e r of 150 Vs. F o r this c a s e the p a r t i a l p r e s s u r e s w e r e CO 2 - 1.5 m m Hg, N 2 - 1.0 m m Hg, He - 2 m m Hg. The a v e r a g e p o w er was n e a r l y the s a m e as f o r the m i x t u r e containing the oxygen (7.5 W), but peak p o w e r s of 825 W w e r e obtained f o r c h a r g i n g v o l t a g e s of the o r d e r of 10 000 V (fig. ld). T h e s e e x p e r i m e n t s , p a r t i c u l a r l y with h el i u m , indicated l a s e r p o w e r s well below s a t u r a t i o n . Much h i g h e r outputs a r e to be e x p e c t e d with m o r e adapted p u l se g e n e r a t o r s . T h e s e r e s u l t s d e m o n s t r a t e the i n t e r e s t of h e l i u m in this type of l a s e r [3] and lead us to e x p e c t C . W . l a s e r s with p o w e r l e v e l s s u p e r i o r to one kilowatt in the n e a r future. We g r a t e f u l l y acknowledge helpful d i s c u s s i o n s with L. Henry and F. Legay.
Fig. 1 L a s e r r a d i a t i o n was d e t e c t e d by a g o l d - g e r m a nium p h o t o c e l l at 77 ° K. C a l i b r a t e d g e r m a n i u m a t t e n u a t o r s w e r e i n s e r t e d so that the peak p o w e r incident on the p h o t o c e l l did not e x c e e d 20 W. The p u l s e s w e r e p r o d u c e d by a t r i g g e r e d c a p a c i t o r d i s c h a r g e . This s y s t e m p e r m i t t e d us to obtain 100 lzs p u l s e s (fig. l a ) . The peak v o lt a g e could be r e g u l a t e d b et ween 0 and 10000 V, with the c u r r e n t v a r y i n g f r o m 0 to 1.0 A. F o r the c a s e of p u r e CO 2 at p r e s s u r e s of 0.5 2.5 m m Hg we obtained the following r e s u l t s : The l a s e r p u l s e s w e r e 500 p s (height ~ width) with a
References 1. C.K.N.Patel, Phys.Rev. 136 (1964) Al187. 2. C.K.N.Patel, Appl. Phys. Letters 7 (1965} 10. 3. Moeller and J.Dane Rigden, Appl. Phys. Letters 7 (1965) 10. 4. C.Frapard, P.Laur~s, M.Roulot, Comptes Rend., to be published. 5. C.K.N.Patel, Phys.Rev. Letters 13 (1964} 21. 6. N. Legay--Sommaire, L.Henry, F.Legay, Comptes Rend. 260 (1965) 260.
385
PHYSICS
less than the theoretically smallest possible (nonzero) constraint towards circularity (j = 2 ~ j 2). These comparisons indicate that the constraint o b s e r v e d on t h e 1.523 /~ l a s e r m i g h t b e a r e s i d u a l effect rather than evidence against theory; howe v e r , the o r i g i n of t h e e f f e c t i s n o t c l e a r . F i n a l l y , we m e n t i o n s o m e q u a l i t a t i v e o b s e r v a t i o n s m a d e on a 23 c m p l a n a r d. c . - e x c i t e d H e - N e laser operating simultaneously at several neon transitions. Among the laser lines observed were t h e 1.152 p l i n e (2s 2 --- 2P2 , j = 1 ~ j = 2), t h e 1 . 1 7 7 p l i n e (2s 2 ~ 2P2 , j = 1 ~ j = 1), t h e 1.198 l i n e (2s 3 ~ 2P2 , j = 0 ~ j = 1) a n d the 1.207 p l i n e (2s5 ~ 2p 6, j = 2 - - - j = 2 ) . A t 1.152 /x two s t r o n g m o d e s o c c u r r e d , l i n e a r ly p o l a r i z e d a t r i g h t a n g l e s . A t t h e o t h e r w a v e lengths weak single modes were observed. As a r u l e t h e m o d e s a t 1.177 / x a n d 1.198 ~ s h o w e d o r thogonal linear polarizations with azimuths coinc i d i n g w i t h t h o s e of t h e two 1.152 ~ m o d e s r e s p e c tively; under certain tuning conditions, however, t h e i r p o l a r i z a t i o n s a p p e a r e d to b e o p p o s i t e l y c i r cular. Presumably the observed general prefer-
HIGH
PEAK
POWER
C. F R A P A R D ,
LETTERS
1March1966
e n c e f o r l i n e a r p o l a r i z a t i o n of t h e s e two w e a k m o d e s i s d u e to the s a t u r a t i o n - i n d u c e d a n i s o t r o p i e s b u r n t b y the two s t r o n g 1.152 /x m o d e s , c i r c u l a r p o l a r i z a t i o n o c c u r r i n g o n l y w h e n t h e s e two a n i s o t r o p i e s ( w h i c h a r e o p p o s i t e in s i g n ) e x a c t l y c o m p e n s a t e e a c h o t h e r . T h e 1.207 p m o d e w a s i n v a r i a b l y o b s e r v e d to b e c i r c u l a r l y p o l a r i z e d ; u n der pulsed-operating conditions both left and rightcircular polarization randomly occurred.
References
1. H. De Lang, G. Bouwhuis and E. T. F e r g u s o n , P h y s i c s L e t t e r s 19 (1965) 482. 2. D. P o l d e r and W.Van Haeringen, P h y s i c s L e t t e r s 19 (1965) 380. 3. H.De Lang, Magnetic phenomena in gas l a s e r s , (Zeeman Centennial Conference, A m s t e r d a m , Sept e m b e r 1965) to be published in P h y s i c s . 4. C.V. Heer and R.D. Graft, Phys. Rev. 140A (1965) 1088. 5. H.G. Van Bueren, J . Haisma and H. De Lang, P h y s i c s L e t t e r s 2 (1962) 340.
PULSED
10t~ CO 2 LASER
*
M. R O U L O T a n d X . Z I E G L E R
Centre de R e e h e r c h e s de la Cornpagnie G~n$rale d ' E l e c t r i c i t ~ D$parternent R e c h e r c h e s P h y s i q u e s de B a s e M a r c o u s s i s (Essonne) - F r a n c e
Received 28 D e c e m b e r 1965
P e a k l a s e r p o w e r s of 220 W, 450 W and 825 W w e r e o b s e r v e d in p u r e CO2, CO 2 - N 2 - 0 2 and CO2 - N2 He p u l s e d d i s c h a r g e s . N o d e l a y b e t w e e n c u r r e n t and l a s e r p u l s e w a s o b s e r v e d , l a s e r p u l s e w i d t h s w e r e found to b e a f u n c t i o n of t h e g a s m i x t u r e , l a s t i n g 500 p s in p u r e CO 2 w h i l e it w a s r e d u c e d to 150 /is w h e n helium was added.
We have observed high intensity laser radiation a t 10.6 p f r o m p u r e C O 2 s e a l e d i n a t u b e a n d e x cited by high voltage pulses. Similar results have b e e n o b t a i n e d u s i n g a m i x t u r e of C O 2 - N 2 - He. Under quite different conditions, Patel had previously obtained stimulated emission from pure C O 2 b u t w i t h r e l a t i v e l y low p e a k p o w e r [1]. S e v e r a l * Work supported by D. R. M. E. 384
e x p e r i m e n t s d e s i g n e d to o b t a i n h i g h p o w e r C . W . l a s e r s u s i n g p u r e C O 2 a n d m i x t u r e of C O 2 - N 2 [2, 3, 4] h a v e b e e n d o n e s i n c e t h e o r i g i n a l w o r k of P a t e l [1, 5] a n d L e g a y - S o m m a i r e e t a l . [6]. T h e t u b e u s e d in o u r e x p e r i m e n t s h a d a n 18 m m i n t e r i o r d i a m e t e r a n d 1.80 m d i s c h a r g e - l e n g t h . T h e two m i r r o r s w e r e c o a t e d w i t h g o l d a n d p l a c e d i n a n a l m o s t c o n f o c a l c o n f i g u r a t i o n . One of t h e m i r r o r s h a d a 4 m m h o l e f o r d i f f r a c t i o n c o u p l i n g of t h e o u t put power.
Volume 20, number4
PHYSICS LETTERS
1-d 500
Pw
I
o
500. Pwl 0 200 W, J
1-b
'
Pw' V
1-a
10 kV
:
I
0.5
1 ms
1March1966
peak p o w e r of 220 W (fig. lb) f o r a gas p r e s s u r e of 1.5 m m Hg. No d el ay b et w een the c u r r e n t pulse and the l a s e r pulse was found. The high r e p e t i t i o n r a t e s u s e d allowed us to m e a s u r e a m e a n p o w e r of 4 W with a t h e r m o p i l e . With a m i x t u r e of CO 2 - N 2 - 0 2 we found peak p o w e r s of about 450 W (fig. l c) and an a v e r a g e p o w e r of 7 W. The p u l se length was a p p r o x i m a t e ly the s a m e as obtained with p u r e CO 2. When the oxygen was r e p l a c e d by h e l i u m we obtained c o n s i d e r a b l y s h o r t e r p u l se lengths, of the o r d e r of 150 Vs. F o r this c a s e the p a r t i a l p r e s s u r e s w e r e CO 2 - 1.5 m m Hg, N 2 - 1.0 m m Hg, He - 2 m m Hg. The a v e r a g e p o w er was n e a r l y the s a m e as f o r the m i x t u r e containing the oxygen (7.5 W), but peak p o w e r s of 825 W w e r e obtained f o r c h a r g i n g v o l t a g e s of the o r d e r of 10 000 V (fig. ld). T h e s e e x p e r i m e n t s , p a r t i c u l a r l y with h el i u m , indicated l a s e r p o w e r s well below s a t u r a t i o n . Much h i g h e r outputs a r e to be e x p e c t e d with m o r e adapted p u l se g e n e r a t o r s . T h e s e r e s u l t s d e m o n s t r a t e the i n t e r e s t of h e l i u m in this type of l a s e r [3] and lead us to e x p e c t C . W . l a s e r s with p o w e r l e v e l s s u p e r i o r to one kilowatt in the n e a r future. We g r a t e f u l l y acknowledge helpful d i s c u s s i o n s with L. Henry and F. Legay.
Fig. 1 L a s e r r a d i a t i o n was d e t e c t e d by a g o l d - g e r m a nium p h o t o c e l l at 77 ° K. C a l i b r a t e d g e r m a n i u m a t t e n u a t o r s w e r e i n s e r t e d so that the peak p o w e r incident on the p h o t o c e l l did not e x c e e d 20 W. The p u l s e s w e r e p r o d u c e d by a t r i g g e r e d c a p a c i t o r d i s c h a r g e . This s y s t e m p e r m i t t e d us to obtain 100 lzs p u l s e s (fig. l a ) . The peak v o lt a g e could be r e g u l a t e d b et ween 0 and 10000 V, with the c u r r e n t v a r y i n g f r o m 0 to 1.0 A. F o r the c a s e of p u r e CO 2 at p r e s s u r e s of 0.5 2.5 m m Hg we obtained the following r e s u l t s : The l a s e r p u l s e s w e r e 500 p s (height ~ width) with a
References 1. C.K.N.Patel, Phys.Rev. 136 (1964) Al187. 2. C.K.N.Patel, Appl. Phys. Letters 7 (1965} 10. 3. Moeller and J.Dane Rigden, Appl. Phys. Letters 7 (1965) 10. 4. C.Frapard, P.Laur~s, M.Roulot, Comptes Rend., to be published. 5. C.K.N.Patel, Phys.Rev. Letters 13 (1964} 21. 6. N. Legay--Sommaire, L.Henry, F.Legay, Comptes Rend. 260 (1965) 260.
385