Laser Physics Imirov/Lecture 5 ch3 fall 2017.pdf · Laser Physics I PH481/581-VTA (Mirov)...
Transcript of Laser Physics Imirov/Lecture 5 ch3 fall 2017.pdf · Laser Physics I PH481/581-VTA (Mirov)...
1
Laser Physics I PH481/581-VTA (Mirov)
Introduction to Two Practical Laser Systems. The Ruby Laser. The Helium-Neon Laser
Lecture 5 chapter 3
Fall 2017C. Davis, “Lasers and Electro-optics”
2
Schematic Energy level Diagram of Three and Four Level Lasers
3
Threshold inversion in three and four-level lasers
3 2 1 0
If th e to ta l n u m b er o f p a rtic le s p e r u n it vo lu m e p a rtic ip a tin g in th e p u m p in g an d la s in gp ro cess is w e can w rite
, (3 .1 )In a th ree -leve l la se r, leve l 1 is e ssen tia lly th e g ro u n d
NN N N N N
3 2 1
2 1
s ta te , so, (3 .2 )
In a g o o d th ree -leve l la se r, leve l 3 sh o u ld tran sfe r its ex c ita tio n ve ry rap id ly to leve l 2 , so. (3 .3 )
T h e th resh o ld in vers io
N N N N
N N N
22 1
1
2
12 3
2
1
2 1 2
n is
. (3 .4 )
F ro m E q s . (3 .3 ) an d (3 .4 ),
( ) , (3 .5 )1
w h ich , if , g ives .2F o r a g o o d fo u r-leve l la se r in w h ich th e lo w er la se r leve l r
t
t
leve l
gN N Ng
g N NgN g
gNg g N
2 4
2
2 13
22 41
em ain s re la tive ly d ep o p u la ted .
, th e ra ltive ra te a t w h ich leve l 2 m u s t b e ex c ited to p ro d u ce an in vers io n is
. (3 .6 )1
U su a lly , , an d fo r
tleve l
tleve l
leve l t
t
N N
g N NN ggN Ng
N N
2 1
4
th e s im p le case th e ra tio o f p u m p in g ra te s b eco m es
. T h is n u m b er can eas ily b e 1 0 o r m o re .2 t
g gN
N
4
Introduction to Two Practical Laser Systems
The Ruby Laser
5
6
7
Simple Electrical Circuit for Driving a Flashlamp
8
9
Schematic Arrangement of Maiman’s Original Ruby Laser
Elliptical reflector for optical pumping of a laser crystal by a linear flashlamp
10
The Helium-Neon Laser
11
Energy level Diagram for the Helium-Neon Laser
12
Schematic Arrangement of the First Gas Laser
13
Typical Schematic Design of a Modern Gas Laser