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.
With increasing demands in all-optical signal processing functions such as switching and modulating in integrated photonic-electronic circuits, plasmonic modulators are getting lots of attentions. In this paper, we present a novel design of hybrid plasmonic modulator based on insulator-metal phase transition in vanadium dioxide (VO2). The device consists of two silicon tapers and a metal-VO2-insulator-silicon hybrid plasmonic structure that are inserted into a strip silicon waveguide, with 120 nm x 800 nm modulating section within 450 nm x 2 μm device footprint. By taking advantages of the large refractive index contrast between the metal and semiconductor phase of VO2, the proposed modulator achieves a high modulation depth of 14.852 dB with a low insertion loss of 1.804 dB. Moreover, we have systematically analyzed the geometry dependence of the device and the influence of broadband light on modulation performances. Considering the effects of seed layer in VO2 deposition process, we have also studied the modulating performances using different dielectric layers. Our design can be practically fabricated, and a complete process flow is provided. We believe this work has great values in promoting the industrial process of silicon photonics in the fields of optical communication and data storage.
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