InGaAs/InAlAs multiple-quantum-well optical modulator integrated with a planar antenna for a millimeter-wave...

Area of Science:

• Optoelectronics
• Semiconductor Devices
• Optical Communications

Background:

• Radio-over-fiber (RoF) systems require efficient modulation of optical signals with millimeter-wave (MMW) frequencies.
• Traditional modulators face challenges in achieving high-speed modulation at MMW frequencies.
• Integrating antennas directly with optical modulators offers a potential solution for compact and high-performance RoF systems.

Purpose of the Study:

• To fabricate and experimentally demonstrate a novel InGaAs/InAlAs multiple-quantum-well (MQW) optical phase modulator integrated with a planar antenna.
• To investigate the high-speed modulation performance of this integrated device under MMW signal irradiation.
• To explore the underlying physical mechanism responsible for the modulation operation.

Main Methods:

• Fabrication of an InGaAs/InAlAs MQW optical phase modulator integrated with a planar antenna.
• Experimental demonstration of high-speed modulation under MMW signal irradiation at 57.5 GHz.
• Characterization of modulation performance using carrier-to-sideband ratio (CSR) and phase shift (Δϕ).

Main Results:

• The fabricated modulator achieved a CSR of 62.7 dB and a phase shift of 1.46 mrad under MMW irradiation (∼77 W/m²).
• The device operated effectively over the C band for optical communications.
• The modulation was attributed to the significant refractive index change induced by the quantum-confined Stark effect in the MQW.

Conclusions:

• This work presents the first demonstration of a semiconductor refractive index change used as an antenna-coupled optical modulator.
• The integrated MQW optical phase modulator shows promising performance for MMW RoF systems.
• The device leverages the quantum-confined Stark effect for efficient high-frequency modulation.