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(Color online) (a) Scanning electron micrograph of the L3-type cavity. (b) High- mode electric field amplitude distribution, as predicted by FDTD simulations. (c) FDTD simulations of frequency and changes as changes from to . A high- and low- cavity were tuned: for and , for and , for , for for both high and low modes, for , and for . The lines for and (black dotted lines) are also plotted and overlap exactly with the lines labeled and . As can be seen, the magnitude of the relative frequency change is independent of , but the higher cavity is degraded more strongly by the change in index. For an increase in , the increases due to stronger total internal reflection confinement in the slab, as expected.
(Color online) Numerical model of a free-carrier tuned cavity. In (a), the cavity is always illuminated by a light source. Panel (b) shows the cavity resonance at the peak of the free-carrier distribution and later, as indicated by the yellow arrows in (a). The time-integrated spectrum is shown as the asymmetric black line (labeled Sp) in (b), and corresponds to the signal seen on the spectrometer, which is the integral over the whole time window of the shifted cavity. The asymmetric spectrum indicates shifting. In (c) and (d) the same data are plotted, but now we consider the cavity illuminated only by QD emission with a turn-on delay of due to the carrier capture lifetime , and a QD lifetime of . In (d), the asymmetry of the line is even smaller in this case.
(Color online) Experimental result of FC cavity tuning for the L3 cavity. Panels (a) and (b) show wavelength vs time plots of the cavity, as it is pumped. Panels (c) and (d) show normalized spectra of the cavity taken at different time points from the data in (a) and (b). In (a), the cavity is always illuminated by a light source and pulsed with a Ti:sapphire pulse. Panel (b) shows the normalized cavity spectrum at the peak of the FC distribution and later, as indicated by the yellow arrows in (a). In order to verify that the cavity tunes at the arrival at the pulse, we combine the pulsed excitation with a weak cw above-band pump. The emission due to the cw source is always present, and this very weak emission is reproduced in panel (b) as the broad background with a peak at the cold cavity resonace in (b). The time-integrated spectrum is shown as the black line (spectrometer) in (b). In (c) and (d) the same data are plotted, but now we consider the cavity illuminated only by QD emission pulsed by and pulses from the Ti:sapphire source. In (d), suppression by about. 0.4–0.35 at the cold cavity resonance can be seen. The inset shows a strongly asymmetric spectrum of a dipole-type cavity under excitation of and the same cavity at low power after prolonged excitation. Such strong excitation degrades the .
(Color online) Thermal tuning of the L3 cavity under cw excitation. (a) Measured (left axis) and (right axis) as a function of pump power for the L3 cavity, obtained from the fits to the spectra shown in (b). The initially increases due to moderate gain and then degrades, while shifts linearly. The straight dashed line fits with 95% confidence and with root mean square deviation of . At very high power, the change in frequency does not follow the same trend. The inset in (b) shows a plot of , which is a measure of the number of lines that we shift the cavity by. A shift of three linewidths is obtained.
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