Noise reduction in a mode-locked semiconductor laser by coherent photon seeding

Area of Science:

• Optics and Photonics
• Laser Physics
• Semiconductor Devices

Background:

• Actively mode-locked extended-cavity semiconductor lasers are crucial for various applications.
• Laser noise, particularly low-frequency fluctuations, can degrade performance.
• Existing noise reduction techniques may compromise laser parameters.

Purpose of the Study:

• To investigate the efficacy of coherent photon seeding for noise reduction in semiconductor lasers.
• To evaluate the impact of different feedback mechanisms (wedge plate vs. phase-conjugate mirror) on laser noise.
• To assess noise reduction performance across a broad frequency spectrum without affecting pulse characteristics.

Main Methods:

• Utilized coherent photon seeding in an actively mode-locked extended-cavity semiconductor laser setup.
• Employed an auxiliary cavity with either a wedge plate or a phase-conjugate mirror for feedback.
• Measured noise reduction across low-frequency (0-5 MHz) and high-frequency (0.01-3.0 GHz) ranges.

Main Results:

• Achieved up to 36 dB noise reduction in the 0-5 MHz range, significantly decreasing pulse fluctuations.
• Observed noise reduction of up to 18 dB in the 0.01-3.0 GHz frequency range.
• Preserved the pulse duration at 26 ps and improved the time-bandwidth product.

Conclusions:

• Coherent photon seeding is an effective technique for substantial noise reduction in semiconductor lasers.
• Both conventional and phase-conjugate feedback methods demonstrate significant noise suppression capabilities.
• The method successfully reduces laser noise while maintaining critical pulse parameters and enhancing time-bandwidth product.