Alternation of maxima and minima (Fig. 7.9) at the longitudinal offset on x in the
far zone from the emission source emphasizes the fact of adding of optical oscillations with different phase shifts. This result of the spatial interference field pattern is
true for the source, which has the finite dimensions of the emitting area. The special
attention we would like to attract to the dependence of the phase upon the longitudinal offset.
7.2.4 Plots of the Symmetric Distribution of the Field
in the Far Zone
Let us examine the plots in Figs. 7.10 and 7.11 of the symmetric distribution at
a 0 ¼ 0 of the module |E YL0 (x)|
2 and the argument Arg[E YL0 (0.2x)] of the function
(Eq. 7.36) in the far zone.
The region of values S 01 , S 02 , when practically all laser emission in the far zone is
concentrated in the single of double lobes of the directional pattern, has a special
interest in Fig. 7.10. The lobe position varies with S 02 variation. The plots of the
phase variations Φ YL0 ( y) of the optical emission are presented with the special
practical interest for OEO. Phase deviations from the “central value” are at
S 01 ¼ À 0.8, S 02 ¼ 0.4 about 10
, while in the case of double-lobe mode at
S 01 ¼ 0.2, S 02 ¼ À 1, the phase deviation is more than 150
. At values S 01 ¼ 0,
-15
|E
YL0 (x)| 2
-10
-5
-15
-10
-5
5
200
100
-100
-200
longitudinal offset x
Φ(x), deg
longitudinal offset x
a)
b)
5
100
200
Fig. 7.9 Dependences upon
the longitudinal offset x for
the symmetric case (a 0 ¼ 0)
in the far zone of the module
|E YL0 (x)|
2 and the argument
Arg[E YL0 (0.2x)] of the
function (Eq. 7.32) at
sinθ ¼ 0, a 0 ¼ 0, S 01 ¼ 0.4,
S 02 ¼ 0.4
384
7 Optoelectronic oscillator (OEO) as the Time and Spatial Correlator of Random. . .