From Event: SPIE Commercial + Scientific Sensing and Imaging, 2018
Diffractive spreading is a fundamental property of light and inversely proportional to the beam waist of a propagating beam. For instance, a Gaussian beam at a wavelength of 800 nm focused into 7 micrometers full-width at half maximum (FWHM) at its beam waist would only have 137 micrometers Rayleigh range—the propagation distance from the waist for a beam to double its cross section. Here, we demonstrate a diffraction-free space-time light sheet (one-dimensional pulsed beam) with 7 micrometers FWHM propagating in free space for 25 mm while preserving its spatial features. By introducing a highly correlated spatio-temporal spectrum via a two-dimensional pulse shaper (consisting of a phase-only reflective spatial light modulator, a grating and a few cylindrical lenses), we generate various light sheets with arbitrary beam profiles at the pulse center and diffraction-free propagation distance of approximately 200 Rayleigh range that corresponds to its beam waist size at the pulse center. Arbitrary light-sheet profiles also include hollow sheets (bottle beams) and even Airy light sheets that are only transversely accelerating in the local time frame of the pulse and acceleration-free as a function of propagation distance. Moreover, we obtain the spatio-temporal beam profiles of the light sheets by experimentally measuring the complex spectra and performing computational two-dimensional Fourier transformations. Light sheets with arbitrary beam profiles and controllable spectrum properties may be instrumental in super-resolution light-sheet microscopy for 3D bio-imaging, nonlinear and multimodality spectroscopy, standoff detection of chemicals, and one-dimensional plasma and filamentation generation.
Hasan E. Kondakci and Ayman F. Abouraddy, "Diffraction-free light sheets with arbitrary beam profiles (Conference Presentation)," Proc. SPIE 10666, Three-Dimensional Imaging, Visualization, and Display 2018, 106660X (Presented at SPIE Commercial + Scientific Sensing and Imaging: April 17, 2018; Published: 15 May 2018); https://doi.org/10.1117/12.2305788.5783315126001.
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