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🌊 3D Slit Simulation

This simulator models wave propagation through single and double slits using a 2D FDTD (Finite-Difference Time-Domain) solver. The wave field is rendered as a 3D height-mapped surface with amplitude-based coloring — warm tones for peaks, cool tones for troughs.

A planar wave source on the left emits coherent waves toward a barrier with configurable slit openings. As waves pass through the slits, they diffract and interfere, producing characteristic patterns on the 3D surface and the 2D intensity panel.

⬤ ⬤ Polarization (Light mode): In double-slit mode with Light selected, you can choose between Same (∥) and Orthogonal (⊥) polarization. With same polarization, waves from both slits interfere normally, producing bright fringes. With orthogonal polarization, each slit emits a different polarization component — these cannot interfere, so the fringe pattern disappears and you see only two overlapping diffraction envelopes.

⬤ 45° Polarizer: When orthogonal polarization is active, enabling the 45° polarizer places a diagonal filter between the slits and the detector. This filter projects both orthogonal components onto the same axis: E_out = (E₁ + E₂)/√2. Since both components now share the same polarization direction, they can interfere again — and the fringe pattern reappears, just like same-polarization mode. This demonstrates a key principle of quantum optics: erasing "which-path" information restores interference.

The green detector screen samples the wave amplitude along a vertical line. The 2D panel shows the live waveform (green) and the sliding-window averaged intensity (red).

Created by Andy Kong