Opto-electro modulators with nanometer-scale footprint are indispensable in integrated photonic electronic circuits. Due to weak light–matter interactions and limits of micro–nano fabrication technology, it is challenging to shrink a modulator to subwavelength size. In recent years, hybrid modulators based on surface plasmons have been proposed to solve this problem. Although the introduced high lossy surface plasmons provide large modulation depth, the polarization selectivity limits its application. Toward this end, in this paper, we present a design of an ultra-compact vanadium oxide ( V O 2 )-based plasmonic waveguide modulator for both transverse electric (TE) and transverse magnetic (TM) modes. The device consists of two silicon tapers and a silicon waveguide embedded with a V O 2 wedge. When electrical signals put on the device change the phase of  V O 2 from a metal to an insulator, the output optical signals along the waveguide are significantly modulated. For a 1.5 µm length modulator operating at 1.55 µm wavelength, the extinction ratio is 11.62 dB for the TE mode and 8.86 dB for the TM mode, while the insertion loss is 4.31 dB for the TE mode and 4.12 dB for the TM mode. Furthermore, the proposed design has excellent tolerance for fabrication process error, which greatly increases the yield rate of products and indicates a promotable application prospect.

Optical modulators with high modulating efficiency and nanoscale size are essential components of photonic communication networks. In recent years, optical modulators based on phase-change materials have considerable application prospects. However, it is still challenging to solve the problem that the footprint and modulation performance of modulators cannot be taken into account at the same time. To this end, we propose an ultra-compact right-angle curved waveguide optical modulator design based on vanadium dioxide (VO2), which consists of a high-loss right-angle curved waveguide and a rectangular VO2 embedded in its bend. Since VO2 has two stable phases of metal phase and semiconductor phase, there is a difference in its optical performance: when VO2 is in the semiconductor phase, its light transmission is low due to the high bending loss of the right-angle bending waveguide; When VO2 is in the metal phase, a mirror-like structure is formed at the bending of the right-angle waveguide, which significantly increases the output of the right-angle curved waveguide. The optical modulator with a footprint of 0.6μm×0.6μm has an extinction ratio of 8.6 dB operating at a wavelength of 1550 nm in transverse electric (TE) mode. Our design can achieve a high extinction ratio with high efficiency in an extremely small footprint, with great potential in constructing on-chip fast all-optical communication networks.