Squeezing and guiding light into semiconductor nanostructures delivers revolutionary concepts of photonic devices, which may offer a practical pathway towards power-efficient optical networks. In this review, we consider photonic switches using semiconductor quantum dots (QDs) and photonic cavities. By intuitively introducing in a field enhancement factor, the optical nonlinearity of nano-photonic switches can be understood and this has shown their unique features to dramatically improve the power-density/speed limitation that has lain in conventional photonic switches for decades. In addition, the power consumption has been reduced due to the atom-like characterization of QDs as well as the nano-size footprint of photonic cavities. Based on this theoretical perspective, the current progress of QD/cavity switches is reviewed in terms of various optical nonlinearities which have been employed to demonstrate photonic switching at the nanoscale. Emerging functionalities enabled by cavity nonlinear effects such as the wavelength tuning and Purcell-factor tuning have been further introduced.
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