Silicon waveguide optical modulator driven by metal-insulator transition of vanadium dioxide cladding layer

Area of Science:

• Photonics
• Materials Science
• Nanotechnology

Background:

• Optical modulators are crucial components in photonic integrated circuits.
• Vanadium dioxide (VO₂) exhibits a metal-insulator transition (MIT) near room temperature, offering potential for tunable optical properties.
• Integrating VO₂ with silicon waveguides presents an opportunity for novel optical modulation.

Purpose of the Study:

• To fabricate and characterize compact optical modulators utilizing a silicon (Si) waveguide with a VO₂ cladding layer.
• To investigate the modulation performance and loss characteristics of these devices.
• To evaluate the extinction ratio achievable with varying device lengths.

Main Methods:

• Fabrication of Si waveguides integrated with VO₂ cladding.
• Characterization of optical transmittance as a function of temperature.
• Systematic variation of device length to determine transmission losses.
• Analysis of the impact of VO₂'s metal-insulator transition on device performance.

Main Results:

• A sharp decrease in transmittance was observed around 60 °C, attributed to the VO₂ metal-insulator transition.
• Transmission losses were measured at 1.27 dB/µm in the insulating (ON) state and 4.55 dB/µm in the metallic (OFF) state.
• An additional loss in the OFF state was identified, linked to a structural effect.
• An 8-µm-long device achieved a high extinction ratio exceeding 33 dB.

Conclusions:

• Compact optical modulators based on Si/VO₂ waveguides are feasible.
• The devices leverage the VO₂ metal-insulator transition for optical modulation.
• High extinction ratios are achievable, demonstrating potential for integrated photonic applications.