Design and Analysis of a Polarization-Insensitive VO₂/Graphene Optical Modulator Using a 3D Heat Transfer Method

Abstract

Phase change materials like vanadium dioxide (VO 2 ) have recently gained particular attention to realize effective optical modulators. In this paper, we propose a high-performance optical modulator based on VO 2 . The structure is constructed by a stack of two graphene sheets spaced by a VO 2 layer that are all grown over a silicon waveguide. The input light propagating along the modulating region of the waveguide can interact with the VO 2 at the top and side of the structure. When an external voltage is applied across the graphene sheets, the VO 2 changes to the metallic phase and the modulator is set at the off state. Most of the previously reported VO 2 -based modulators are polarization sensitive and suffer from high polarization diversity. When such modulators are integrated into a fiber-based optical system containing light with random polarization, the modulation efficiency is profoundly degraded. In our proposed modulator, the structure is optimized to achieve a polarization-insensitive response with an off-state propagation loss of ∼14 dB/μm. The TE (TM) insertion loss is also calculated to be as low as 2.25 dB/μm (3.22 dB/μm), so that an extinction ratio of as high as ∼11.5 dB/μm is obtained. In addition, the required low modulating voltage of 1.12 V and reasonable modulation speed of 390 MHz together with the low energy consumption of 2.1 fJ/bit could make our proposed modulator a good candidate for photonic integrated systems.

Design of Antireflection and Enhanced Thermochromic Properties of TiO2/VO2 Thin Films

“…The phase transition in VO 2 can also be triggered by force, light and electricity. [ 4–6 ] The phase transition endows VO 2 with potential applications in spacecraft thermal radiation device, [ 7 ] supercapacitor, [ 8 ] electrode material, [ 9,10 ] optical modulator, [ 11 ] optical switch, [ 12 ] microwave passive electronic device, [ 13 ] phase change memory, [ 14 ] field effect transistor, [ 15 ] micro and nano oscillator, [ 16 ] sensor, [ 17 ] THz device, [ 18 ] and smart glass. [ 19–21 ] VO 2 thin films on glass can sense the environmental temperature, and switch the transmittance of sunlight in the infrared wavelength range at high and room temperatures, and adjust the input of solar radiation energy and indoor temperature spontaneously.…”

“…The phase transition in VO 2 can also be triggered by force, light and electricity. [4][5][6] The phase transition endows VO 2 with potential applications in spacecraft thermal radiation device, [7] supercapacitor, [8] electrode material, [9,10] optical modulator, [11] optical switch, [12] microwave passive electronic device, [13] phase change memory, [14] field reaction magnetron sputtering. 200 nm TiO 2 / 100 nm VO 2 thin films show excellent overall thermochromic properties with the T lum value of 46.29% and the ΔT sol value of 16.03%, which is consistent with the simulation results.…”