Frequency tunable optoelectronic oscillator based on a directly modulated DFB semiconductor laser under optical...

Area of Science:

• Photonics and Optics
• Semiconductor Lasers
• Microwave Engineering

Background:

• Optoelectronic oscillators (OEOs) are crucial for generating microwave signals.
• Distributed-feedback (DFB) semiconductor lasers offer tunable frequency but have packaging limitations.
• Optical injection can enhance laser performance and overcome limitations.

Purpose of the Study:

• To propose and demonstrate a frequency tunable OEO.
• To utilize optical injection to enhance a DFB laser for OEO applications.
• To achieve a simple, low-cost, and wide-tuning range microwave signal generation system.

Main Methods:

• A directly modulated DFB semiconductor laser was subjected to optical injection.
• The injection ratio and frequency detuning between master and slave lasers were adjusted.
• The performance of the OEO, including frequency tunability and phase noise, was experimentally evaluated.

Main Results:

• The optical injection enhanced the relaxation oscillation frequency of the DFB laser.
• The OEO achieved a radio frequency (RF) threshold gain below 20 dB.
• A wide frequency tuning range from 5.98 to 15.22 GHz was demonstrated.
• Phase noise of -104.8 dBc/Hz at 10 kHz offset was measured for a 9.75 GHz signal.

Conclusions:

• The proposed OEO successfully overcomes DFB laser packaging limitations via optical injection.
• The system offers a simple, cost-effective solution for tunable microwave signal generation.
• The demonstrated wide frequency tunability and low phase noise are promising for various applications.