What causes differences when calculating the theoretical wave equation using Maxwell's equations versus the paraxial approximation in optics?

💡 Explanation

The paraxial approximation simplifies Maxwell's equations by assuming that the beam's propagation direction is primarily along one axis; this mechanism, known as the slowly varying envelope approximation, neglects rapidly oscillating field components. Therefore, the results differ from full solutions because it ignores off-axis propagation, rather than including all terms.

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