Low-voltage quantum well microring-enhanced Mach-Zehnder modulator

Area of Science:

• Optoelectronics
• Semiconductor Devices
• Photonics

Background:

• Mach-Zehnder modulators (MZMs) are crucial for optical communication.
• Achieving low-voltage operation and high extinction ratios in MZMs remains a challenge.
• Quantum-confined Stark effect in multiple quantum wells (MQWs) offers potential for enhanced electro-optic modulation.

Purpose of the Study:

• To investigate the modulation characteristics of a novel InGaAs/InAlAs multiple quantum well (MQW) microring-enhanced Mach-Zehnder modulator (MRE-MZM).
• To demonstrate low-voltage operation with a high extinction ratio.
• To reduce the V(π) · L product compared to conventional MZMs.

Main Methods:

• Fabrication of high-mesa waveguide structures using solid-source molecular beam epitaxy and inductively coupled plasma etching.
• Integration of a single microring resonator in one arm of the MZM.
• Utilizing a five-layer asymmetric coupled quantum well (FACQW) for the MQW core.
• Employing a directional coupler with an asymmetric branching ratio as an input coupler.

Main Results:

• The fabricated MRE-MZM demonstrated a high extinction ratio of approximately 27 dB.
• The static modulation achieved a V(π) · L product of 1.7 Vmm.
• This V(π) · L product is one-quarter of that for a conventional MZM with a similar waveguide structure.

Conclusions:

• The novel MRE-MZM design enables significantly reduced driving voltage.
• The microring resonator enhances the phase shift, leading to improved modulator performance.
• This device represents a promising advancement for efficient and low-power optical modulation.