L6 - gain and threshold

Question 1

Rate of eE. Energy propagation through plane area A

Answer 1

I(z) A

Question 2

Poynting thheorem for PW propgation option for in vac innvacuum

Answer 2

1/c (dI/dt) + dI/dz = Sig I (N2-N1)
in vac RHS = 0 since I = 0
unit [1/m^3]

Question 3

gain factor

Answer 3

Dig (N2-(g2/g1)N1)

Question 4

If g indep of I and z ow intensity change with z inside gain material

Answer 4

I(z) = I(0) e^(gz)
Exp incr until sat

Question 5

g dep on

Answer 5

g prop A (via sig)
g prop population inversion (N2-N1)
unit: per distance

Question 5

g dep on

Answer 5

g prop A (via sig)
g prop population inversion (N2-N1)
unit: per distance

Question 6

3 sources of loss in laser

Answer 6

Mirror:
output coupling (t), absorb, scat

Question 7

Conservation of energy at a mirror

Answer 7

r+t+s = 1

Question 8

Gt

Answer 8

GAIN FOR WHICH INTENSITY FOES NOT INCR OR DECR
minimum I for laser action

Question 9

Shape of sig

Answer 9

Lorentzian around nu = nu21

Question 10

Assumption of var in I inside cavity

Answer 10

Assume negligable change in intensity with distance in the oscillatior
I+ - i- APPROX 0

Question 11

roundtrip time in cavity

Answer 11

time = speed/dist
Tau = c/2L