Silicon waveguide optical modulator driven by metal-insulator transition of vanadium dioxide cladding layer.

We have fabricated compact optical modulators consisting of a Si waveguide with a VO2 cladding layer. These devices showed a sharp decrease in transmittance at around 60 degrees C, which is attributable to the metal-insulator transition of the VO2 cladding layer. By systematically varying the length of the device, we evaluated the transmission losses per unit length of the device to be 1.27 dB/mu m, when the VO2 cladding layer was in the insulating (ON) state and 4.55 dB/mu m when it was in the metallic (OFF) state. Furthermore, we found that the device showed an additional loss in the OFF state, which is attributable to a structural effect. As a result, an 8-mu m-long device showed a large extinction ratio of more than 33 dB. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement