| A novel all-optical switch of quantum dot photonic crystal (QD-PC) based on InAs/GaAs semiconductor heterostructure is proposed. The reasons lie in the fact that there are a large quantum-confined Stark shift (QCSS), good temperature behavior and a very large built-in strain in the dots leading to a very large change in the effective bandgap (～1.05eV) in the QDs on GaAs substrate, which can generate the excitonic radiation near the fiber zero dispersion window. Based on this structure, a great deal of work is done. All of first, the reflection and transmission spectra of QD-RPC are calculated based on pump-probe technique. The result shows that the spectra depend strongly on the temperature and uniformity of QDs. At low temperature, a good stop band requires uniformity of QDs is not in excess of0.002and temperature is not in excess of80K in a good uniformity of QDs. It is very obvious that the temperature behavior is more excellent than that in quantum well RPCs. Secondly, the switching contrasts are studied for this structure. In the reflection, the reflection light intensity is almost100%and the switching contrasts can arrive at30dB at both the uniform limit0.002and the temperature10K for the QD-PC all-optical switch and the switching contrasts can exceed50dB but transmission light intensity is weaker than that in reflection. In general, the maximum transmissivity is not in excess of50%. Finally, a series of return to zero codes (RZ) in the switch are simulated. The result shows the RZ with the pulse width as10ps can keep a good transmission. Moreover, the QD-RPCs as all-optical switch are applicable to all-optical web are analyzed and discussed as well... |
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