Stochastic logic gate that exploits noise and polarization bistability in an optically injected VCSEL

Area of Science:

• Optics and Photonics
• Semiconductor Lasers
• Optical Computing

Background:

• Vertical-cavity surface-emitting lasers (VCSELs) exhibit polarization bistability.
• Optical injection can influence VCSEL dynamics and polarization states.
• Noise is often considered detrimental in laser-based computations.

Purpose of the Study:

• To investigate the use of VCSEL polarization dynamics and noise for all-optical logic operations.
• To demonstrate a reliable stochastic logic gate based on VCSELs.
• To determine the operational parameters for such a logic gate.

Main Methods:

• Numerical simulations of VCSEL dynamics under optical injection.
• Encoding logic inputs via orthogonal injection into the suppressed polarization mode.
• Decoding logic outputs from the emitted light's polarization state.

Main Results:

• An all-optical stochastic logic gate was successfully demonstrated.
• Reliable logic outputs were achieved by exploiting the interplay of polarization bistability and noise.
• The gate operates with bit times as short as 5 ns for specific spontaneous emission coefficients (β(sp) = 10⁻⁴–10⁻¹).

Conclusions:

• VCSELs can function as all-optical stochastic logic gates.
• This technology is implementable with commercially available VCSELs.
• The gate leverages intrinsic or external noise sources for reliable optical signal processing.