Intensity noise reduction in quantum dot comb laser by lower external carrier fluctuations.

Area of Science:

• Optoelectronics
• Semiconductor Lasers
• Photonics

Background:

• Carrier noise significantly impacts laser performance, affecting linewidth enhancement factor (LEF) and relative intensity noise (RIN).
• Quantum dot lasers are promising for high-speed optical communication due to their unique properties.

Purpose of the Study:

• To investigate the effect of different carrier noise distributions on the LEF and RIN of a 100 GHz quantum dot mode-locked laser (MLL).
• To explore methods for optimizing laser performance for dense wavelength division multiplexing (DWDM) applications.

Main Methods:

• Utilized a 100 GHz quantum dot fourth-order colliding-pulse mode-locked laser (MLL).
• Compared laser performance under a normal pump (Gaussian carrier sequences) and a quiet pump (sub-Poissonian carrier sequences).
• Analyzed LEF and RIN across various reverse saturable absorber (SA) bias voltages.

Main Results:

• Under normal pumping, LEF was near zero (0-2.5 V SA bias), achieving RIN as low as -156 dB/Hz.
• Quiet pumping reduced both LEF (by up to 0.58 at 0 V) and RIN (by >3 dB at 0 V) across all SA bias conditions.
• The most significant noise reduction was observed at low reverse SA bias voltages with quiet pumping.

Conclusions:

• Quiet pumping offers a straightforward approach to minimize optical noise in quantum dot lasers.
• This method is effective for optimizing multi-channel light sources for DWDM systems.
• Achieving low LEF and RIN is critical for advanced optical communication technologies.