Dynamics of a semiconductor laser with feedback and modulation: experiments and model comparison.

Area of Science:

• Semiconductor laser physics
• Nonlinear dynamics
• Optical engineering

Background:

• Semiconductor lasers near threshold exhibit low frequency fluctuations (LFF) with irregular intensity spikes.
• Sinusoidal current modulation can synchronize these spikes, but a detailed comparison with theoretical models is lacking.

Purpose of the Study:

• To compare experimental and numerical dynamics of semiconductor lasers under optical feedback and modulation.
• To assess the accuracy of the Lang-Kobayashi (LK) model in predicting modulated LFF dynamics.
• To quantify spike timing regularity using the Fano factor.

Main Methods:

• Experimental study of a semiconductor laser near threshold with optical feedback and sinusoidal current modulation.
• Numerical simulations using the Lang-Kobayashi (LK) model.
• Calculation of the Fano factor to quantify spike timing regularity from intensity time-series.

Main Results:

• Sinusoidal modulation can lock the timing of LFF spikes, leading to highly regular spike sequences.
• Good qualitative agreement was found between experimental results and LK model simulations.
• The Fano factor effectively quantifies spike timing regularity, showing significant reduction under optimal modulation conditions.

Conclusions:

• The Lang-Kobayashi model provides a good qualitative description of modulated LFF dynamics in semiconductor lasers.
• Sinusoidal current modulation is an effective method for controlling and regularizing semiconductor laser spike timing.
• The Fano factor is a valuable tool for analyzing temporal order in spike sequences.