Supercontinuum Mach–Zehnder
Two arms, complementary spectra, and a path-dependent average power.
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This interferometer splits a flat 400–700 nm supercontinuum and recombines the two copies at an ideal beamsplitter. Each output has a spectrometer. Different wavelengths acquire different relative phases, so changing the delay changes the output spectrum as well as the total power.
Try the delay control
The source has Interference enabled, and the delay line sweeps one arm from 0 to 0.002 mm and back at 0.1 Hz. As it moves, the fringes run across the two spectrometer screens (400 to 700 nm) and the spectra of the two ports stay complementary. The two output powers always sum to the input in this lossless example.
To hold one point, select the delay line and set Motion to Static. At 0 mm the arms are matched: one port receives all the light and the other is dark. At 0.0005 mm the ports read 0.769 and 0.231; at 0.002 mm, 0.553 and 0.447.
Select the laser and open its Interference panel: the coherence length of this band is about 0.58 µm, so the 2 µm sweep runs from full contrast to well past it, where the total power at each port settles towards one half while the spectrum is still deeply modulated.
Turn Interference off on the source to compare with power addition: each port receives half the input and the spectra retain the source shape.
This is same-source, time-integrated interference through ideal phase-known optics. It does not reconstruct the combined temporal field: pulse duration, autocorrelation and oscilloscope traces after recombination are unavailable. Pulse animation stops at recombination. Unknown coating/material phase or an exceeded spectral/path budget is reported rather than assigned a phase. Older saved sources keep their previous power-only behavior until Interference is enabled.