The "Crooked Light" Experiment: A Pump-Probe Methodology for Detecting Engineered Vacuum Birefringence

This paper establishes a formal, computationally validated experimental protocol for the detection and measurement of engineered vacuum birefringence, a core prediction of non-linear Quantum Electrodynamics (QED). While standard attempts to measure the Heisenberg-Euler vacuum response rely on planar or Gaussian wave intersections, the "Crooked Light" protocol proposes the utilization of counter-propagating, counter-twisting Laguerre-Gaussian (LG0,1) optical vortices (the "Optical Tornado"). 3D Finite-Difference Time-Domain (FDTD) simulations demonstrate that the extreme ∇2S2 field gradients within this specific geometry create a stable, localized 3D potential well that stresses the local quantum vacuum. When a perfectly polarized, low-power probe laser is passed through this engineered metric, the simulation predicts a definitive, falsifiable signature: an induced orthogonal polarization leakage (Ex). Based on standard vacuum susceptibility parameters, the protocol predicts a specific rotation of +3.05 degrees. The detection of this shift offers a near-term, highly specific empirical signature for macroscopic spacetime metric engineering.