Ultra-Compact Efficient Thermally Actuated Mach-Zehnder Modulator Based on VO₂

Abstract

Vanadium dioxide (VO2) has emerged as a prominent optical phase change material (O-PCM) for creating high performance devices based on hybrid silicon platforms. However, realizing an efficient and compact optical modulator required for Mach-Zehnder interferometer (MZI) structures, still remains a major challenge in active Si-platforms enabled by VO2. This is mainly due to the simultaneous variation of both real and imaginary parts of the refractive index during the phase transition process, which is a significant issue. A modified MZI structure is proposed in this paper while the refractive index variation issue is overcome by operating in the wavelength range between 1.5 to $1.6~\mu \text{m}$ including the optical C-band. An indium tin oxide (ITO) layer is considered as the microheater for the thermal excitation. An optimized triggering signal with an amplitude of 12.5 V along with an arm length of $2.35~\mu \text{m}$ of the MZI device ( $V_{\pi }L_{\pi }= 30 \,\,\text {V}\cdot \mu \text{m}$ ) established a $\pi $ -shift at the output of the device. The proposed device has ER >35 dB at the entire optical C-band and consumes $\sim 26$ pJ for modulating a single bit with a delay of 3.5 ns.

Keywords

• Mach-Zehnder interferometer
• optical modulation
• phase change material
• thermo-optical modulator
• vanadium dioxide