Pulse Compressor
Adds positive or negative group-delay dispersion to a pulse, shortening it when the correction cancels dispersion accumulated earlier in the setup.
Open in the canvas →In the real world
An ultrashort pulse is shortest when its frequency components arrive with the spectral phase required by its transform limit. Material dispersion makes those components acquire different delays, producing chirp and a longer temporal envelope. A pulse compressor introduces the opposite spectral-phase curvature so the accumulated group-delay dispersion (GDD) approaches zero and the pulse becomes shorter again.
Real compressors commonly use diffraction-grating pairs, prism pairs, chirped mirrors, or combinations of them. Their geometry determines not only second-order GDD but also third- and higher-order dispersion, throughput, spatial chirp, and alignment sensitivity. The useful setting therefore compensates the measured upstream dispersion rather than having a universally correct negative value.
In OpticalSetup
The Pulse Compressor is a straight-through, zero-thickness GDD element. Set Applied GDD positive or negative; the value is added to every pulsed ray crossing its clear aperture, while transmission efficiency applies the configured loss. A negative setting compresses only when it cancels positive GDD already on the path — placed before any glass, the same negative magnitude broadens a transform-limited pulse instead.
For Gaussian and sech² sources, the travelling packet overlay reads the local accumulated GDD along each traced segment. A chirped source also carries a signed input GDD inferred from its bandwidth and duration, so a compressor can shorten it to the transform limit and further GDD stretches it again. Flat-top supercontinua use the endpoint group-delay difference across their full band. The true duration, model name, GDD, and stretch or compression factor remain available numerically at a downstream detector.
This is a lumped second-order phase proxy, not a physical compressor prescription. It does not trace the compressor's internal grating, prism, or chirped-mirror geometry; it does not model carrier phase, third-order dispersion, spatial chirp, pulse-front tilt, nonlinear phase, or arbitrary spectral phase. Input chirp is limited to the positive/negative quadratic-phase estimate implied by the authored duration and bandwidth; a pulse whose phase is unknown or whose paths disagree reads unavailable at a detector, and its packet keeps its configured length on the canvas as a glyph, not a prediction. On-screen packet length is a qualitative glyph; detector numbers retain the unclamped second-order result.