Edwin Jan Klein - Universiteit Twente

Chapter 4
complex than the interaction at a wavelength of 3965 nm, as can be concluded from
the many oscillations in this figure.
Power/P In (dB)
0
-5
-10
-15
Reflected
Transmitted
-20
0 2 4 6 8
Time (ps)
Figure 4.41. Step responses of the transmitted and reflected light outside the bandgap at
3965 nm.
Power/P In (dB)
0
-20
-40
-60
Power/P In (dB)
2
0
-2
-4
-6
-8
-10
1.4 1.6 1.8
Time (ps)
2.0 2.2
0 2 4 6 8 10
Time (ps)
Figure 4.42. Step responses of the transmitted and reflected light in the middle of the
bandgap at 4455 nm. Inset: a close-up of the reflected step response showing a slight signal
overshoot.
108
Reflected
Reflected
Transmitted
Interestingly the reflected light reflects more power than is put into the grating for a
short duration, as is shown in the inset. This might be an actual physical effect as it
was for instance also seen in a different simulation that used grating indices of 1.5 and
4. However, none of the results of the time-domain simulations have currently been
compared with the results of other simulation methods. The effect might therefore
also be caused by unpredictable behavior of the simulation method used by Aurora,
although this is not very likely.
For reasons of simplicity only the time domain responses at the in- and output of the
grating have been recorded using the two probes placed in these locations. However,
the probes are just as easily inserted at different locations in the grating. This could be
used for instance, to analyze slow light or other phenomena within the grating. As
such Aurora might prove to be a valuable tool in examining this particular class of
complex optical devices.