LNOI photonic wire switch based on phase transition material

An on-chip switch based on lithium-niobate-on-insulator (LNOI) photonic wire (PW) is proposed. The switch consists of a pulley LNOI PW and a microring resonator (MRR) coupled with a 160° LNOI PW arc loaded with a temperature phase transition material (PTM). A pulley PW is adopted to promote coupling efficiency. The PTM is used to control the mode guided in the MRR and realize the switching function by utilizing its amorphous and crystalline states. As the PTM is in the amorphous state, the coupling between the PTM-loaded LNOI PW arc and the MRR occurs, resulting in that mode in the MRR is destructive and cannot keep resonant, the light power in the pulley LNOI PW has little loss, and hence the switching on is realized. As the PTM is crystalline, the coupling does not happen due to phase mismatch. The mode in the MRR keeps constructive and resonant. As a result, light power is highly lossy there and the switch is off. We have carried out design and optimization of the proposed device, and presented an optimal geometry. The study shows that the optimal device has a smaller size of 24 × 23 μm2 and excellent switching performances, including larger extinction ratio of 14.2 dB, lower insertion loss of 1.8 dB in the state of switching on, and smaller shift of resonance wavelength < 0.5 nm in the conversion procedure of the on/off state. The ultra-compact device may find its application in on-chip high-density photonic integrated circuits.