threshold pumping. At that, the slope of the wavelength function of the central mode
equaled “on the threshold” to 13,002 μm versus the DC pumping current of QWLD
is 0.086 μm/mA or 0.086 mm/mA, which corresponds to the function slope of the
QWLD versus the DC current of pumping S v ¼ 0.75 THz/(50 mA) ¼ 0.015 THz/
mA. The maximal relative deviations of the optical frequency in the current range
20–70 mA are 0.75 THz/229 THz ¼ 0.0032.
At calculation of AFC and PFC of the laser, we used the following values of
parameters in Eq. (7.41), which are the same as in [10, 12] for the mesa-strip QWLD
with the thickness of the dielectric film of d ¼ 1.2 μm and with the number of
quantum wells equaled to five: g 0 ¼ 10
3 , R d ¼ 5 Ω, С L ¼ 4 Â 10
À12 F, Г а ¼ 0.043,
r D ¼ 10.6; R τ ¼ 0.05, τ ph ¼ Т OF ¼ 1.2 Â 10
À12 s, τ D ¼ 7.2 Â 10
À12 s; I thr ¼ 12 mA,
ε sh ¼ 0, τ n1 ¼ Т 1 ¼ 0.5 Â 10
À9 s.
Figure 7.17c, d shows AFC and PFC of the mesa-strip QWLD calculated from
Eq. (7.37) for different pumping currents from 15 to 85 mA at the value of the
threshold pumping current of 12 mA and 13 mA, relatively. We see that at small
Fig. 7.17 The watt–ampere characteristic of QWLD (a). The function of the wavelength of QWLD
emission versus the pumping current (b). Calculated (solid curves) and experimental (dotted curves)
AFC (c) and PFC (d) of the mesa-strip QWLD for various bias (pumping) currents. The threshold
pumping current of QWLD is 12 mA
7.3 OEO DM Analysis on the Base of Abbreviated Differential Equations
399