--- sd_hide_title: true --- # croak ```{rubric} Complete Retrieval by Optimisation and Adjoint Kernels ``` **croak** reconstructs the spectral amplitude and phase of an ultrashort laser pulse from a frequency-resolved optical gating (FROG) trace. Use the graphical interface or a Python script to prepare data, retrieve a pulse, interpret the result, and estimate uncertainty. (highlights)= ## What croak can do Beyond the standard thin-medium FROG model, croak's measurement model can include propagation through a dispersive nonlinear medium, the different arrival times of crossing beams, and chromatic focusing and collection of the generated signal. For few-femtosecond pulses these effects change the trace enough that a thin-medium fit reproduces it closely yet returns the wrong pulse. The [capabilities overview](reference/features.md) lists the supported models, interactions and solvers. ```{image} _static/hero.png :alt: A retrieval summary showing the data and model traces, residual, and temporal and spectral pulse profiles. :align: center :width: 90% ``` ::::{grid} 1 1 2 2 :gutter: 3 :::{grid-item-card} Introduction :link: introduction/index :link-type: doc Install croak, choose an interface, and follow three guided retrieval tutorials. ::: :::{grid-item-card} User guide :link: user_guide/index :link-type: doc Work through a measurement, from data preparation to interpretation. Find the physics, equations, and numerical methods alongside each topic. ::: :::{grid-item-card} Examples :link: examples/index :link-type: doc Explore runnable examples of data cleaning, retrieval, instrument effects, dispersion tuning, and uncertainty. ::: :::{grid-item-card} Developer's guide :link: developer_guide/index :link-type: doc Set up a development environment, understand the package, and contribute code or documentation. ::: :::{grid-item-card} API :link: reference/api/index :link-type: doc Look up Python functions, classes, parameters, return values, and conventions. ::: :::: New to pulse retrieval? Begin with the [introduction](introduction/index.md). If you already have a trace, follow [preparing and checking data](user_guide/data.md). To understand a result, see [interpreting results](user_guide/results.md) and [uncertainty](user_guide/uncertainty.md). Terms are defined in the [glossary](reference/glossary.md); the papers and methods behind croak are in the [references](reference/bibliography.md). ```{toctree} :hidden: :maxdepth: 3 Introduction User guide Examples Developer's guide API ```