The traditional ways of tuning a Silicon photonic network are mainly based on the thermal-optic effect or the free carriereffect of silicon. The drawbacks of these methods are the volatile nature and the extremely small change in the complexrefractive index (Δn<0.01). In order to achieve low energy consumption and smaller footprint for applications such asphotonic memories or computing, it is essential that the two optical states of the system exhibit high optical contrast andremain non-volatile. Phase change materials such as GST provide a solution in that it exhibits drastic contrast in refractiveindex between the two non-volatile crystallographic states which can be switched reversibly. Here, we first show that GSTcan be integrated with a Si ring resonator to demonstrate a quasi-continuous optical switch with extinction ratio as high as33dB. Secondly, we demonstrated GST-integrated 1×2 and 2×2 Si photonic switches using a three-waveguide couplerdesign which exhibits a low insertion loss of ～1dB and a compact coupling length of ～30μm. The crosstalk is as small as-10dB over a bandwidth of 30nm.
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