Time-delay signature suppression in a chaotic semiconductor laser by fiber random grating induced random distributed...

Area of Science:

• Optics and Photonics
• Nonlinear Dynamics
• Semiconductor Lasers

Background:

• Semiconductor lasers are crucial for various applications, but their chaotic dynamics are often characterized by a time-delay signature (TDS).
• The presence of TDS in chaotic semiconductor lasers can limit their use in secure communication and random number generation.
• Existing methods to suppress TDS often involve complex external cavity designs or specific feedback conditions.

Purpose of the Study:

• To demonstrate chaotic light emission from a semiconductor laser without a discernible time-delay signature (TDS).
• To investigate the effect of random distributed feedback from a fiber random grating on laser dynamics.
• To theoretically and numerically explore the suppression of TDS in semiconductor lasers.

Main Methods:

• Fabrication of a fiber random grating with random index modulation periods via point-by-point inscription.
• Perturbation of a semiconductor laser using distributed feedback from the fabricated fiber random grating.
• Development of a theoretical model based on the modified Lang-Kobayashi equations to simulate chaotic dynamics.
• Numerical exploration of laser diode behavior under random feedback conditions.

Main Results:

• The semiconductor laser exhibited chaotic light emission when subjected to random distributed feedback.
• The random feedback from the fiber random grating destroyed the phase-correlated mode condition, suppressing the TDS.
• The fabricated fiber random grating introduced a large number of phase-uncorrelated cavity modes, leading to high-dimensional chaos.
• Experimentally, a negligible TDS value (minimum of 0.0088) was obtained, representing the smallest reported to date.

Conclusions:

• Distributed feedback from a fiber random grating is an effective method for achieving chaotic emission from semiconductor lasers without TDS.
• The proposed method offers a novel approach to conceal the TDS, paving the way for advanced applications.
• The findings highlight the potential of engineered random feedback for controlling laser dynamics and generating high-dimensional chaos.