Random polarization switching in gain-switched VCSELs for quantum random number generation.

Area of Science:

• Optics and Photonics
• Semiconductor Lasers
• Nonlinear Dynamics

Background:

• Vertical-cavity surface-emitting lasers (VCSELs) exhibit complex polarization dynamics.
• Polarization switching in VCSELs is a key phenomenon for optical device applications.
• Understanding random excitation is crucial for advanced laser functionalities.

Purpose of the Study:

• To experimentally and theoretically investigate the random excitation of linearly polarized modes in a gain-switched VCSEL.
• To determine the conditions for achieving equal probability of excitation for both polarized modes.
• To explore the potential for random number generation using this phenomenon.

Main Methods:

• Utilized a gain-switched VCSEL with polarization switching under continuous wave operation.
• Adjusted modulation conditions and sampling times to control polarization mode excitation.
• Analyzed probability of excitation, autocorrelation, and histograms of polarized signals.
• Performed experimental and theoretical studies.

Main Results:

• Achieved equal probability of excitation for both linearly polarized modes by tuning modulation and sampling parameters.
• Demonstrated that random polarization switching is independent of narrow bistable regions.
• Characterized the random polarization switching behavior through statistical analysis.

Conclusions:

• The random excitation of polarized modes in gain-switched VCSELs can be controlled.
• This controlled randomness opens possibilities for applications like random number generation.
• The findings contribute to a deeper understanding of VCSEL polarization dynamics.