We conducted a comprehensive characterization of key phenomena in digital micromirror devices (DMD) using an ultrashort pulse beam of 98.8 fs @800nm. Firstly, we determined the fluence threshold, which was found to be 0.19 J/cm^2. Secondly, we quantified the nonlinear dispersion introduced by the DMD in the pulse beam using the SPIDER method. Our measurements revealed a second order GDD value of 473 fs^2, a third-order dispersion (TOD) of 3700 fs^3, and a fourth-order dispersion (FOD) of -2027000 fs^4. Our research significantly advances our understanding of DMD behavior and its interaction with ultrashort pulses, thereby optimizing their use in optical applications.
We propose a novel approach employing structured sampling and a single-pixel detector to measure, simultaneously, the spatial profile and the spatially resolved temporal profile of a femtosecond laser beam with an autocorrelation method. The experimental system integrates a Digital Mirror Device (DMD) into a conventional autocorrelation setup. An experimental comparison with a raster scanning method illustrates the advantages of this setup, achieving comparable accuracy with reduced energy levels. This study introduces a promising technique for the precise characterization of ultrafast laser pulses, with potential applications in various fields that demand accurate spatial and temporal measurements as material processing or imaging applications.
This work presents a commercial webcam CMOS (Complemented-Metal-Oxide-Semiconductor) implemented as a spectrometer for femtosecond pulses characterization at the Near-Infrared region (NIR, 1.1 - 1.6 μm), applying spectral interferometry. The spectral interferometry setup consists of a collinear Michelson interferometer in which two femtosecond pulses replicas, generated from a home-made Optical Parametric Oscillator (fs-OPO), are relatively delayed with respect to each other. A reflecting grating disperses the pulse replicas and then, the modulated spectrum is generated in a 2-Fourier setup, using a single lens, with the CMOS sensor located at the Fourier plane. The NIR CMOS response is produced through the Two-Photon Absorption (TPA) effect, capable of generating the nonlinear spectral intensity and the corresponding modulated spectrum (spectral interferometry signal). The cost-effective TPAspectrometer is capable of measuring the interferogram, with a high resolution of 0.72nm and very high sensitivity of few 𝜇W average power or few fJ per pulse. Finally, we calculate the spectral phase difference using a phase retrieval algorithm from the nonlinear spectral interferometry signal.
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