A complete ultrashort pulse diagnostic requires a linear spectrum associated with a nonlinear autocorrelation or interferometric measurement. A new method is presented requiring only a grating spectrometer and two second harmonic crystals. Spectra of fundamental, second harmonic, and two cascaded spectra are used to reconstruct the spectral phase. A few proof-of-concept examples with simple phases are demonstrated using Nelder-Mead algorithm. A differential evolution genetic algorithm is introduced when the pulse has a more complicated shape or phase.
Ning Hsu, Luke Horstman, and Jean-Claude Diels, "Pulse characterization by cascading nonlinearity inside a spectrometer (CaNIS)," Proc. SPIE 10517, Real-time Measurements, Rogue Phenomena, and Single-Shot Applications III, 105170M (Presented at SPIE LASE: January 30, 2018; Published: 23 February 2018); https://doi.org/10.1117/12.2290848.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon