n I, F, z 1 2 N1 N2 ( ). 1 N2W21=N2s21F 2 1 N1W12=N1s12F 1 2. dF dz (.1.7) , , : (1.50)
, s12=s21=s.
, I=Fhn, (1.50) I:
(1.51)
(1.51) , N2>N1, dI/dz>0, . N2<N1, dI/dz<0, .. .
, , , .. . , n, .
, N2>N1, . , . , , .
.1.7 . | 1.8. I(z) . |
(1.51) , I0=I(z=0) (1.52)
(1.52a)
, (1.52) : I=I0eGz (1.53)
(1.52) , , (1.54)
a - , : = . (1.55)
(1.55 )
I(z) (N2>N1) (N2 < N1) .1.8.
, (, ), b :
. (1.56)
a, .
a=s(N1-N2)=sDN, W12=sF, F=I/hn, I=ρυ : (1.57)
Wn=W12g(n)=B12 rn g(n), - Wn - n, g(n) . : . (1.58)
, rn .
(1.58)
δ . , ..
.
n=n0, g(n0)=2/(p D n). (1.58) :
(1.59)
(1.59) (1.57) :
, (1.60)
σ 2→1:
|
|
(1.61)