Semipolar InGaN quantum-well laser diode with integrated amplifier for visible light communications

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• III-nitride photonic integrated circuits (PICs) are crucial for visible light applications.
• Integrating semiconductor optical amplifiers (SOAs) with laser diodes (LDs) on a single chip is a key challenge for visible wavelength PICs.

Purpose of the Study:

• To demonstrate a monolithically integrated dual-section InGaN/GaN quantum well (QW) laser diode with an amplifier region.
• To investigate the performance of this integrated device on a semipolar GaN substrate.

Main Methods:

• Fabrication of a dual-section LD with integrated amplifier on a semipolar GaN substrate.
• Characterization of threshold current reduction and optical gain under varying SOA driving voltages.
• Evaluation of amplification effects on optical output power.

Main Results:

• Threshold current in the laser gain region reduced from 229mA to 135mA with SOA activation.
• A significant optical gain of 5.7 dB was achieved at V_SOA = 6.25V.
• Optical output power increased from 8.2 mW to 30.5 mW, demonstrating effective amplification.

Conclusions:

• The integrated amplifier-LD successfully reduces threshold current and provides substantial optical gain.
• This device is suitable for Gbps data communication via on-off keying.
• This monolithic integration offers a compact, cost-effective solution for III-nitride on-chip photonic systems, enabling applications in smart lighting and visible light communications.