Hybrid Si$_3$N$_4$/VO$_2$ Modulator Thermally Triggered by a Graphene Microheater

Si
₃
N
₄
has emerged as a prominent material for expanding the capability of silicon photonics to wavelengths below <; 1 μm. However, realizing an efficient optical modulator, a key building block for any integrated optics platform, remains a major challenge in Si
₃
N
₄
mainly because this material has a vanishing Pockels coefficient. Here, we propose a compact Si
₃
N
₄
based optical modulator by using a thin VO
₂
layer on top of a Si
₃
N
₄
strip waveguide where amplitude modulation is achieved via phase transition of the VO
₂
layer. To reduce the actuation time of the temperature induced VO
₂
phase transition, a mono-layer graphene microheater is designed for the active Si
₃
N
₄
VO
₂
waveguide. Our simulations indicate a high extinction ratio of ~8.28 dB/μm with an insertion loss of ~2.8 dB/μm at the design wavelength of 850 nm for the proposed modulator and wideband operation in the wavelength range of 800-900 nm. It is shown that employing the electrical and thermal properties of graphene not only leads to a significant reduction of the power consumption of the device but also, decreases the actuation time compared to previous modulators based on the thermal phase transition of the VO
₂
.