<p>We present a comprehensive computational analysis of visible light interference patterns from three input beams. High-contrast interference fields, like hexagonal intensity lobe lattices, are produced by carefully examining a variety of input beam characteristics, angular orientations, and polarization. The simulations are based on scalar wave theory under the paraxial approximation and are performed on a subwavelength-resolution spatial grid to resolve fine-scale intensity characteristics. Optimized patterns induce photorefractive effects in LiNbO₃, permanently imprinting crystals via exposure. Defect sensitivity is evaluated in another investigation by introducing nanoscale anomalies (~ 10&#xa0;nm), which result in observable disruptions in high-intensity regions of the interference pattern. Our approach makes it easier to design defect-sensitive photonic structures and offers a practical path to real-time monitoring and precise manufacturing of nonlinear optical devices.&#xa0; </p>