Page 108 - Tunable Lasers Handbook

4 CO, Isotope Lasers and Their Applications 89

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10-10

- M = 50
h
d

:
g 10.11
2
u)
A HP 5061 CESIUM
P ATOMIC STANDARD
0
z
W
2
; 10-12
E
@ C02 SHORT-TERM STABILITY

0.01 0.1 1 .o 10 I00
SAMPLE TIME, T (s)
FIGURE 1s Time-domain frequency stability of the 2.6978618-GHz beat note of the 'jCl30,
laser i-Ri21) transition and the lTl6O0, reference laser I-P(?Oj transition in the two-channel hetero-
dyne calibration system (Fig. 13) with the 4.3-pm fluorescence stabilization technique For the sake
of comparison. the stabilities of a cesium clock and short-term stabilities of individuai CO, lasers are
also shown. Note that the frequencj stabilities of the CO, and the cesium-stabilized systems shown
are about the same and that the CO, radar has achieved short-term stabilities of at least tlbo to three
orders of magnitude better than those of microwave systems. (Reprinted with permission from
SooHoo eral. [76]. 0 1981 IEEE.)

4.3-ym fluorescence stabilization technique [56.76.77]. The solid and hollow
circles represent two separate measurement sequences of the Allan variance of
the frequency stability

Each measurement consisted of M = 50 consecutive samples for a sample time
duration (observation time) of T seconds. Figure 15 shows that we have achieved
OJT) <?x 10-12 for T-10 sec. Thus a frequency measurement precision of about
50 Hz may be readily achieved within a few minutes.