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Giant optical pulse shortening through pulse-transmission mode operation of a ruby laser
Volume 22, number 2
i
'
PHYSICS LETTERS
-hw
1 August 1966
eV
h~p
At. 30keV
14 12 10
hto:
hw'B
o i
~
~ he,
o
THICKNESS
/ t - - -
0
I00
200
300
4~o
.D
~o~
Fig. 2. Experimental and theoretzcal values of the surface energy loss peaks versus foil thmkness.
o '^";
~
~ cau se of t h e i r halfwldths. The ~/w+ - l o s s shows a distract shift with chang, ng foil t h i c k n e s s zn d i s a g r e e m e n t with the r e s u l t s of S c h m l l s e r [9].
\,s
L
0
2
4
h~, 6
8 10 ~ E
--
12
lh
16
-
RefeTences
6oI
1. H. Boersch, J. Gelger and H. Hellwlg, Phymes Letters 3 (1962) 64. H.Boersch, J.Gelger and W.Stmkel, Z. Phys. 180 (1964) 415. 2. L.G.Schulz, J. Opt. Soc. Am. 44 (1954) 357. 3. L.G.Schulz and F.R.Tangherlm,, J. Opt. Soc. Am. 44 (1954) 362. 4. I.N.Shlyarevskli and R.G.Yarovaya, Optms and Spectrosc. 16 (1964) 45. 5. W.R.Hanter, J. Opt. Soc. Am. 54 (1964) 208. 6. R.H.Rltchm, Phys. Rev. 106 (1957) 874. 7. J.Gelger and K.Wlttmaack, Z. Phys. lm Druck. 8. Yu.A.Romanov, Radloflzzka, 7 (1964)828. 9. P.Schmtiser, Z. Phys. 180 (1964) 105.
18eV
Fig. 1. Dlstrzbutmn of the real part of the dmlectrm constant of aluminum versus energy, and energy loss spectra of aluminum fofid of varmus thmlmesses. f i l t e r t h i s angle i s a m a x i m u m v a l u e . T h e r e f o r e the m e a s u r e d v a l u e s should be l o c a t e d outside the t h e o r e t i c a l c u r v e s , which was found m m o s t c a s e s . F o r foil t h i c k n e s s e s m o r e than 300/~ the two s u r f a c e p eak s could not be s e p a r a t e d b e -
GIANT
OPTICAL
PULSE
SHORTENING OPERATION
THROUGH OF
A
RUBY
PULSE-TRANSMISSION
MODE
LASER
J . E R N E S T , M. MICHON and J . DEBRIE Centre R e c h e r c h e s de la Compagnze G~n~rale d Electrzczt~ D $ p a r t e m e n t R e c h e r c h e s Physzques de B a s e M a r c o u s s s s (Essonne) - F r a n c e
Recezved 15 June 1966
P u l s e - t r a n s m i s s i o n mode o p e r a t i o n , a s p r o p o s e d by V u y l s t e k e [1], and d i s c u s s e d by Kay and Waldman [2], has been o b s e r v e d using a ruby l a s e r Q - s w l t c h e d by m e a n s of a K e r r - c e l l . Output p u l s e s of t i m e - d u r a t i o n 3 n s e c and e n e r g y up to 100 m J have been obtained.
The l a s e r used in the e x p e r i m e n t s c o m p r z s e s , a s shown on fig. 1, a 9 0 ° - r u b y r o d , 10 m m in d i a m e t e r , 10 cm in length, a G l a n - t y p e p o l a r i z e r b e a m s p l i t t e r (G), a K e r r - c e l l (K), and two 98.5% r e f l e c t i n g m u l t l l a y e r m i r r o r s . The c a m t y length m ay be v a r i e d f r o m 40 to 90 cm . The p u l s e - t r a n s 147
Volume 22, number 2
PHYSICS LETTERS
m i s s i o n mode operation m a y be d e s c r i b e d a s follows: 1) D u r i n g p u m p i n g of the r u b y rod, a V h / 4 p u l s e i s applied to the K e r r - c e l l , thus blocking laser operation. 2) At peak f l u o r e s c e n c e , the voltage a c r o s s the K e r r - c e l l i s brought to z e r o . The l a s e r i s then n o r m a l l y switched into operation, winch s t a r t s with a b u i l d - u p p e r i o d which, depending on pumping, l o s s , and cavity l~ngth, m a y be of the o r d e r of 50 to 150 n s . 3) A c c o r d i n g to L e n g y e l ' s and W a g n e r ' s [3] model, the giant p u l s e of c o h e r e n t light r i s e s then within a few n a n o s e c o n d s , depending e s s e n t i a l l y on p u m p i n g level, i . e . , i n i t i a l population i n v e r s i o n . As the m i r r o r coupling of the l a s e r i s m i n i m u m (or the Q i s v e r y high), the population i n v e r s i o n i s in the i d e a l case r a p i d l y brought to z e r o , while the e l e c t r o m a g n e t i c e n e r gy, within the cavity, r e a c h e s i t s peak value. Without any f u r t h e r switching of the c a w t y - Q the light pulse would then decay c o m p a r a t i v e l y s l o w ly, due to the low r e s i d u a l c a w t y - l o s s . As m o n i t o r e d through one of the cavity m i r r o r s , the light p u l s e would then be a s y m m e t r i c a l (short r i s e - t i m e , long d e c a y - t i m e ) . T h i s we call the "primary pulse". 4) If now a Vh/4 step i s suddenly applied to the K e r r - c e l l , p r e c i s e l y when the light field i s m a x i m u m reside the cavity, then, due to rotaiaon of the p o l a r i z a t i o n , a l l the e l e c t r o m a g n e t i c e n e r gy can be m p r i n c i p l e e x t r a c t e d f r o m the cawty by r e f l e c t i o n off the b e a m - s p l i t t i n g p o l a r i z e r , witlun quite a s h o r t p e r i o d of t i m e . As c o n s i d e r e d m r e f s . 1 and 2, one e s s e n t i a l l i m i t a t i o n to this p u l s e - l e n g t h i s the r i s e - t i m e of the second optical switching p u l s e . However, even with i n finitely s h o r t r i s e - t i m e s , it i s obvious that the the "switched" pulse d u r a t i o n could not be l e s s than 2 / / c , l being the cavity optical length. In our e x p e r i m e n t s , a negative V h / 4 (i.e. 16 kV) voltage i s applied to the K e r r - c e l l while p u m p i n g the r u b y . At peak f l u o r e s c e n c e , a p o s i b y e V~t/4 step, g e n e r a t e d through a t h y r a l r o n t r i g g e r e d capacity d i s c h a r g e , and s h a r p e n e d by m e a n s of a coaxial s p a r k - g a p , i s applied to the K e r r - c e l l , thus b r i n g i n g the voltage a c r o s s it to p r a c t i c a l l y zero. T h i s s t e p - p u l s e then t r a v e l s through a s h o r t - c i r c u i t e d length of 5 0 ~ cable L, and r e s t o r e s a negative V h / 4 voltage a c r o s s the cell a f t e r a d e l a y - t i m e At = 2 / J r (v = p r o p a g a tion v e l o m t y along a 50~2 coaxial line). The o v e r all u s e - t i m e of the optical K e r r - s h u t t e r has been m e a s u r e d u s i n g a g a s - l a s e r , a fast p h o t o m u l t l p l i e r and a T e k t r o n i x 519 o s c i l l o s c o p e , and i s found to be about 2 n s . F o r a fixed cavity l o s s , 148
1 August 1966
K
r
~
.
u
16KVLi_..~-~,,I,/SSG
__
---2-
t, L_
L.
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Fzg. 1. Experimental set-up.
the pumping level of the ruby m u s t be adjusted so that t i m e At 3ust equals the l a s e r b u i l d - u p t i m e plus the time for the giant p r i m a r y p u l s e to reach its maximum intensity. Fig. 2 shows a typical t r a n s m i s s i o n mode pulse, as m o m t o r e d by a Korad KD-1 photocell and a T e k t r o n i x 519 oscilloscope. The output e n e r g y i s about 50 mJ, and the pulse half-width about 3.5 n s e c for a 1000 J pump energy, and a cavity length of 40 cm. In that case, p u l s e - t r a n s m i s s i o n mode delay time i s about 100 n s e c , and the p u l s e - t r a n s m i s s i o n mode switching o c c u r s at p r e c i s e l y the peak i n t e n s i t y of the p r i m a r y pulse. When i n c r e a s i n g the pump e n e r g y to about 1800 J and consequently r e d u c i n g the delay t i m e to m a t c h the b u i l d - u p t i m e to about 70 n s e c , one gets t r a n s m i s m o n mode p u l s e s of e n e r g y up to 100 m J and a p p r o x i m a t e l y s a m e durataon. However, a s p u r i o u s signal a p p e a r s together with the t r a n s m i s s i o n mode pulse p r o p e r , which IS p r a c t i c a l l y coincident with the p r i m a r y pulse although somewhat n a r r o w e r . Also, this s p u r i o u s - p u i s e I n t e n s i t y i n c r e a s e s as a non l i n e a r function of pump e n e r g y . This i n d i c a t e s tbat this s p u r i o u s signal is m o s t probably due to self d e p o l a r i z a t i o n of the p r i m a r y p u l s e b e a m produced by the optical K e r r - e f f e c t [4], within the n l t r o b e n z e n e . F u r t h e r evidence is given by p r e l i m i n a r y e x p e r i m e n t s on p u l s e - t r a n s m i s s i o n mode-sw~tclnng of a n e o d y m i u m - g l a s s l a s e r , whereby this signal i s negligible, up to 180 m J of t r a n s m i s s i o n m o d e - p u l s e e n e r g y F o r a given p u l s e e n e r g y , the optical e l e c t r i c field i n t e n s i t i e s a r e much weaker for a Nd3+: g l a s s l a s e r than for a ruby l a s e r , due to b r o a d e r o v e r a l l l a s e r e m i s s i o n h n e w i d t h s [5] (20 .~ as a g a i n s t 0.1~), so that opt i c a l K e r r - e f f e c t s should be much l e s s i m p o r t a n t . The r a t i o of the t r a n s m i s s i o n m o d e - p u l s e e n e r g y to the s u m - e n e r g y of both p r i m a r y p u l s e s , n o r m a l l y coupled out of the l a s e r through both high r e f l e c t i n g m i r r o r s without p u l s e - t r a n s m i s s i o n m o d e - s w i t c h i n g , IS about 3 to 4 in our
Volume 22, number 2
PHYSICS LETTERS
1 August 1966
I
/\
(a)
Fig. 2. Typical 3 nsec-pulse. Energy: 50 mJ 5 nsec/square. e x p e r i m e n t s . T i n s i s due to the fact that, in the o r d i n a r y type of Q-svatching, a l a r g e p a r t of the l a s e r e n e r g y i s d e g r a d e d through i n s e r t i o n loss (absorption and s c a t t e r i n g ) in the l a s e r cavity, w h e r e a s in the p u l s e - t r a n s m i s s i o n m o d e switcinng, the l a s e r e n e r g y i s coupled out of the cavity l u s t before t i n s a b s o r p t i o n decay p r o c e s s c a n take place. The e s t i m a t e d r a t i o of t r a n s m i s s i o n mode p u l s e peak power to p r i m a r y p u l s e peak power i n s i d e the l a s e r cavity i s of the o r d e r 0.8 i n our e x p e r i m e n t s . Fig. 3 shows p r i m a r y p u l s e s m o n i t o r e d off one of the h i g h - r e f l e c t i n g m i r r o r s , with p u l s e t r a n s m i s s i o n m o d e - o p e r a t i o n p r e s e n t , for a fixed d e l a y - t i m e A t (70 nsec), a fixed cavity length of 41 cm and pumping e n e r g i e s v a r y i n g f r o m 1800 to 2240 J, i.e. l a s e r b m l d - u p t i m e s v a r y i n g f r o m about 80 to 30 n s e c . Most of these o s c i l l o g r a m s show the typical a s y m m e t r i c a l shape of the p r i m a r y pulse, with r i s e - t i m e s of 1 0 n s e c , and d e c a y - t i m e s of about 40 to 50 n s e c . The fast d e c a y - t i m e of those p r i m a r y p u l s e s , due to p u l s e - t r a n s m i s s i o n m o d e - o p e r a t i o n (~ 3 n s e c ) i s m good a g r e e m e n t with the obs e r v e d t r a n s m i s s i o n mode p u l s e lengths. F i n a l l y the m e a s u r e d t r a n s m i s s i o n m o d e p u l s e length v a r i e s f r o m 3.5 nsec to 7 nsec with cavity lengths v a r y i n g f r o m 40 cm to 90 cm, when switching at peak p r i m a r y pulse power, and i s a h n e a r function of cavity length above 55 era. F u r t h e r work i s continuing on g l a s s - l a s e r pulse-transmission mode-switching. Frmtful d i s c u s s i o n s with J. Hanus a r e fully acknowledged.
(b)
r~
f
(d)
/
\
l
Fig.3. Typical primary pulses with pulse-transmission mode operation. Fixed delay hme At. Pumpmg energies v a n e s from 1800 to 2020 J - 10 nsec/ square. (~[)'1800 J, 06) 1880 J, (c) 1950 J, (d) 2020J.
References 1. A.A.Vuylsteke, J. Appl. P]~ys. 34, 1615. 2. R.B.Kay and G.S.Waldman, J. Appl. Phys. 36 1319. 3. B.A.Lengyel and W.G.Wagner, Proc. third Intern. Congr. on Quantum electromcs (Columbia Umverslty Press, 1964) p. 1427. 4. M.Padlette, C.R.Acad. Sc. Paris 262 S~rle B, p.264. 5. M.Mlchon et al., Physics Letters 19 (1965) 217.
* * * * *
149
i
'
PHYSICS LETTERS
-hw
1 August 1966
eV
h~p
At. 30keV
14 12 10
hto:
hw'B
o i
~
~ he,
o
THICKNESS
/ t - - -
0
I00
200
300
4~o
.D
~o~
Fig. 2. Experimental and theoretzcal values of the surface energy loss peaks versus foil thmkness.
o '^";
~
~ cau se of t h e i r halfwldths. The ~/w+ - l o s s shows a distract shift with chang, ng foil t h i c k n e s s zn d i s a g r e e m e n t with the r e s u l t s of S c h m l l s e r [9].
\,s
L
0
2
4
h~, 6
8 10 ~ E
--
12
lh
16
-
RefeTences
6oI
1. H. Boersch, J. Gelger and H. Hellwlg, Phymes Letters 3 (1962) 64. H.Boersch, J.Gelger and W.Stmkel, Z. Phys. 180 (1964) 415. 2. L.G.Schulz, J. Opt. Soc. Am. 44 (1954) 357. 3. L.G.Schulz and F.R.Tangherlm,, J. Opt. Soc. Am. 44 (1954) 362. 4. I.N.Shlyarevskli and R.G.Yarovaya, Optms and Spectrosc. 16 (1964) 45. 5. W.R.Hanter, J. Opt. Soc. Am. 54 (1964) 208. 6. R.H.Rltchm, Phys. Rev. 106 (1957) 874. 7. J.Gelger and K.Wlttmaack, Z. Phys. lm Druck. 8. Yu.A.Romanov, Radloflzzka, 7 (1964)828. 9. P.Schmtiser, Z. Phys. 180 (1964) 105.
18eV
Fig. 1. Dlstrzbutmn of the real part of the dmlectrm constant of aluminum versus energy, and energy loss spectra of aluminum fofid of varmus thmlmesses. f i l t e r t h i s angle i s a m a x i m u m v a l u e . T h e r e f o r e the m e a s u r e d v a l u e s should be l o c a t e d outside the t h e o r e t i c a l c u r v e s , which was found m m o s t c a s e s . F o r foil t h i c k n e s s e s m o r e than 300/~ the two s u r f a c e p eak s could not be s e p a r a t e d b e -
GIANT
OPTICAL
PULSE
SHORTENING OPERATION
THROUGH OF
A
RUBY
PULSE-TRANSMISSION
MODE
LASER
J . E R N E S T , M. MICHON and J . DEBRIE Centre R e c h e r c h e s de la Compagnze G~n~rale d Electrzczt~ D $ p a r t e m e n t R e c h e r c h e s Physzques de B a s e M a r c o u s s s s (Essonne) - F r a n c e
Recezved 15 June 1966
P u l s e - t r a n s m i s s i o n mode o p e r a t i o n , a s p r o p o s e d by V u y l s t e k e [1], and d i s c u s s e d by Kay and Waldman [2], has been o b s e r v e d using a ruby l a s e r Q - s w l t c h e d by m e a n s of a K e r r - c e l l . Output p u l s e s of t i m e - d u r a t i o n 3 n s e c and e n e r g y up to 100 m J have been obtained.
The l a s e r used in the e x p e r i m e n t s c o m p r z s e s , a s shown on fig. 1, a 9 0 ° - r u b y r o d , 10 m m in d i a m e t e r , 10 cm in length, a G l a n - t y p e p o l a r i z e r b e a m s p l i t t e r (G), a K e r r - c e l l (K), and two 98.5% r e f l e c t i n g m u l t l l a y e r m i r r o r s . The c a m t y length m ay be v a r i e d f r o m 40 to 90 cm . The p u l s e - t r a n s 147
Volume 22, number 2
PHYSICS LETTERS
m i s s i o n mode operation m a y be d e s c r i b e d a s follows: 1) D u r i n g p u m p i n g of the r u b y rod, a V h / 4 p u l s e i s applied to the K e r r - c e l l , thus blocking laser operation. 2) At peak f l u o r e s c e n c e , the voltage a c r o s s the K e r r - c e l l i s brought to z e r o . The l a s e r i s then n o r m a l l y switched into operation, winch s t a r t s with a b u i l d - u p p e r i o d which, depending on pumping, l o s s , and cavity l~ngth, m a y be of the o r d e r of 50 to 150 n s . 3) A c c o r d i n g to L e n g y e l ' s and W a g n e r ' s [3] model, the giant p u l s e of c o h e r e n t light r i s e s then within a few n a n o s e c o n d s , depending e s s e n t i a l l y on p u m p i n g level, i . e . , i n i t i a l population i n v e r s i o n . As the m i r r o r coupling of the l a s e r i s m i n i m u m (or the Q i s v e r y high), the population i n v e r s i o n i s in the i d e a l case r a p i d l y brought to z e r o , while the e l e c t r o m a g n e t i c e n e r gy, within the cavity, r e a c h e s i t s peak value. Without any f u r t h e r switching of the c a w t y - Q the light pulse would then decay c o m p a r a t i v e l y s l o w ly, due to the low r e s i d u a l c a w t y - l o s s . As m o n i t o r e d through one of the cavity m i r r o r s , the light p u l s e would then be a s y m m e t r i c a l (short r i s e - t i m e , long d e c a y - t i m e ) . T h i s we call the "primary pulse". 4) If now a Vh/4 step i s suddenly applied to the K e r r - c e l l , p r e c i s e l y when the light field i s m a x i m u m reside the cavity, then, due to rotaiaon of the p o l a r i z a t i o n , a l l the e l e c t r o m a g n e t i c e n e r gy can be m p r i n c i p l e e x t r a c t e d f r o m the cawty by r e f l e c t i o n off the b e a m - s p l i t t i n g p o l a r i z e r , witlun quite a s h o r t p e r i o d of t i m e . As c o n s i d e r e d m r e f s . 1 and 2, one e s s e n t i a l l i m i t a t i o n to this p u l s e - l e n g t h i s the r i s e - t i m e of the second optical switching p u l s e . However, even with i n finitely s h o r t r i s e - t i m e s , it i s obvious that the the "switched" pulse d u r a t i o n could not be l e s s than 2 / / c , l being the cavity optical length. In our e x p e r i m e n t s , a negative V h / 4 (i.e. 16 kV) voltage i s applied to the K e r r - c e l l while p u m p i n g the r u b y . At peak f l u o r e s c e n c e , a p o s i b y e V~t/4 step, g e n e r a t e d through a t h y r a l r o n t r i g g e r e d capacity d i s c h a r g e , and s h a r p e n e d by m e a n s of a coaxial s p a r k - g a p , i s applied to the K e r r - c e l l , thus b r i n g i n g the voltage a c r o s s it to p r a c t i c a l l y zero. T h i s s t e p - p u l s e then t r a v e l s through a s h o r t - c i r c u i t e d length of 5 0 ~ cable L, and r e s t o r e s a negative V h / 4 voltage a c r o s s the cell a f t e r a d e l a y - t i m e At = 2 / J r (v = p r o p a g a tion v e l o m t y along a 50~2 coaxial line). The o v e r all u s e - t i m e of the optical K e r r - s h u t t e r has been m e a s u r e d u s i n g a g a s - l a s e r , a fast p h o t o m u l t l p l i e r and a T e k t r o n i x 519 o s c i l l o s c o p e , and i s found to be about 2 n s . F o r a fixed cavity l o s s , 148
1 August 1966
K
r
~
.
u
16KVLi_..~-~,,I,/SSG
__
---2-
t, L_
L.
I __j
Fzg. 1. Experimental set-up.
the pumping level of the ruby m u s t be adjusted so that t i m e At 3ust equals the l a s e r b u i l d - u p t i m e plus the time for the giant p r i m a r y p u l s e to reach its maximum intensity. Fig. 2 shows a typical t r a n s m i s s i o n mode pulse, as m o m t o r e d by a Korad KD-1 photocell and a T e k t r o n i x 519 oscilloscope. The output e n e r g y i s about 50 mJ, and the pulse half-width about 3.5 n s e c for a 1000 J pump energy, and a cavity length of 40 cm. In that case, p u l s e - t r a n s m i s s i o n mode delay time i s about 100 n s e c , and the p u l s e - t r a n s m i s s i o n mode switching o c c u r s at p r e c i s e l y the peak i n t e n s i t y of the p r i m a r y pulse. When i n c r e a s i n g the pump e n e r g y to about 1800 J and consequently r e d u c i n g the delay t i m e to m a t c h the b u i l d - u p t i m e to about 70 n s e c , one gets t r a n s m i s m o n mode p u l s e s of e n e r g y up to 100 m J and a p p r o x i m a t e l y s a m e durataon. However, a s p u r i o u s signal a p p e a r s together with the t r a n s m i s s i o n mode pulse p r o p e r , which IS p r a c t i c a l l y coincident with the p r i m a r y pulse although somewhat n a r r o w e r . Also, this s p u r i o u s - p u i s e I n t e n s i t y i n c r e a s e s as a non l i n e a r function of pump e n e r g y . This i n d i c a t e s tbat this s p u r i o u s signal is m o s t probably due to self d e p o l a r i z a t i o n of the p r i m a r y p u l s e b e a m produced by the optical K e r r - e f f e c t [4], within the n l t r o b e n z e n e . F u r t h e r evidence is given by p r e l i m i n a r y e x p e r i m e n t s on p u l s e - t r a n s m i s s i o n mode-sw~tclnng of a n e o d y m i u m - g l a s s l a s e r , whereby this signal i s negligible, up to 180 m J of t r a n s m i s s i o n m o d e - p u l s e e n e r g y F o r a given p u l s e e n e r g y , the optical e l e c t r i c field i n t e n s i t i e s a r e much weaker for a Nd3+: g l a s s l a s e r than for a ruby l a s e r , due to b r o a d e r o v e r a l l l a s e r e m i s s i o n h n e w i d t h s [5] (20 .~ as a g a i n s t 0.1~), so that opt i c a l K e r r - e f f e c t s should be much l e s s i m p o r t a n t . The r a t i o of the t r a n s m i s s i o n m o d e - p u l s e e n e r g y to the s u m - e n e r g y of both p r i m a r y p u l s e s , n o r m a l l y coupled out of the l a s e r through both high r e f l e c t i n g m i r r o r s without p u l s e - t r a n s m i s s i o n m o d e - s w i t c h i n g , IS about 3 to 4 in our
Volume 22, number 2
PHYSICS LETTERS
1 August 1966
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Fig. 2. Typical 3 nsec-pulse. Energy: 50 mJ 5 nsec/square. e x p e r i m e n t s . T i n s i s due to the fact that, in the o r d i n a r y type of Q-svatching, a l a r g e p a r t of the l a s e r e n e r g y i s d e g r a d e d through i n s e r t i o n loss (absorption and s c a t t e r i n g ) in the l a s e r cavity, w h e r e a s in the p u l s e - t r a n s m i s s i o n m o d e switcinng, the l a s e r e n e r g y i s coupled out of the cavity l u s t before t i n s a b s o r p t i o n decay p r o c e s s c a n take place. The e s t i m a t e d r a t i o of t r a n s m i s s i o n mode p u l s e peak power to p r i m a r y p u l s e peak power i n s i d e the l a s e r cavity i s of the o r d e r 0.8 i n our e x p e r i m e n t s . Fig. 3 shows p r i m a r y p u l s e s m o n i t o r e d off one of the h i g h - r e f l e c t i n g m i r r o r s , with p u l s e t r a n s m i s s i o n m o d e - o p e r a t i o n p r e s e n t , for a fixed d e l a y - t i m e A t (70 nsec), a fixed cavity length of 41 cm and pumping e n e r g i e s v a r y i n g f r o m 1800 to 2240 J, i.e. l a s e r b m l d - u p t i m e s v a r y i n g f r o m about 80 to 30 n s e c . Most of these o s c i l l o g r a m s show the typical a s y m m e t r i c a l shape of the p r i m a r y pulse, with r i s e - t i m e s of 1 0 n s e c , and d e c a y - t i m e s of about 40 to 50 n s e c . The fast d e c a y - t i m e of those p r i m a r y p u l s e s , due to p u l s e - t r a n s m i s s i o n m o d e - o p e r a t i o n (~ 3 n s e c ) i s m good a g r e e m e n t with the obs e r v e d t r a n s m i s s i o n mode p u l s e lengths. F i n a l l y the m e a s u r e d t r a n s m i s s i o n m o d e p u l s e length v a r i e s f r o m 3.5 nsec to 7 nsec with cavity lengths v a r y i n g f r o m 40 cm to 90 cm, when switching at peak p r i m a r y pulse power, and i s a h n e a r function of cavity length above 55 era. F u r t h e r work i s continuing on g l a s s - l a s e r pulse-transmission mode-switching. Frmtful d i s c u s s i o n s with J. Hanus a r e fully acknowledged.
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Fig.3. Typical primary pulses with pulse-transmission mode operation. Fixed delay hme At. Pumpmg energies v a n e s from 1800 to 2020 J - 10 nsec/ square. (~[)'1800 J, 06) 1880 J, (c) 1950 J, (d) 2020J.
References 1. A.A.Vuylsteke, J. Appl. P]~ys. 34, 1615. 2. R.B.Kay and G.S.Waldman, J. Appl. Phys. 36 1319. 3. B.A.Lengyel and W.G.Wagner, Proc. third Intern. Congr. on Quantum electromcs (Columbia Umverslty Press, 1964) p. 1427. 4. M.Padlette, C.R.Acad. Sc. Paris 262 S~rle B, p.264. 5. M.Mlchon et al., Physics Letters 19 (1965) 217.
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