Simultaneous spatial and temporal focusing of femtosecond pulses

Appl. & Eng. Phys., Cornell Univ., Ithaca, NY, USA
Optics Express (Impact Factor: 3.49). 04/2005; 13(6):2153-9. DOI: 10.1109/CLEO.2005.202174
Source: PubMed

ABSTRACT We study and demonstrate the technique of simultaneous spatial and temporal focusing of femtosecond pulses, with the aim to improve the signal-to-background ratio in multiphoton imaging. This concept is realized by spatially separating spectral components of pulses into a "rainbow beam" and recombining these components only at the spatial focus of the objective lens. Thus, temporal pulse width becomes a function of distance, with the shortest pulse width confined to the spatial focus. We developed analytical expressions to describe this method and experimentally demonstrated the feasibility. The concept of simultaneous spatial and temporal focusing of femtosecond pulses has the great potential to significantly reduce the background excitation in multiphoton microscopy, which fundamentally limits the imaging depth in highly scattering biological specimens.

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Available from: James van Howe, Sep 27, 2015
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    • "This makes possible depth sectioning in widefield nonlinear microscopy. Simultaneous spatial and temporal focusing (SSTF) [2] occurs when the frequency components are also focused at the crossing plane. The increased intensity localization has advantages for micromachining and materials processing. "
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    ABSTRACT: Exploiting the characteristics of spatially chirped ultrafast pulses has been an increasingly active area of research. In this paper, we review the developments in the past year of the microscopy, materials processing, and micromachining fields, where the spatiotemporal structure of these beams is important. We also summarize progress in theoretical and experimental work to better control and characterize spatially chirped beams.
    IEEE Photonics Journal 06/2015; 7(3):1-6. DOI:10.1109/JPHOT.2015.2412454 · 2.21 Impact Factor
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    • "The principle of spatiotemporal focusing involves directing the laser pulse through an optical dispersive element (e.g., prisms, gratings) to produce an angularly dispersive beam [20] [21]. In this situation, the spectral components that comprise the ultrashot pulse are not spatially overlapped, and thereby, cannot add together to produce a transformlimited pulse in time. "
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    ABSTRACT: According to specific configurations, three-dimensional (3D) patterning involves both 3D bioimaging and laser micromachining. Recent advances in bioimaging have witnessed strong interests in the exploration of novel microscopy methods capable of dynamic imaging of living organisms with high resolution, and large field of view (FOV). For most, applications of bioimaging should be limited by the tradeoff between the speed, resolution, and FOV in common techniques, e.g., confocal laser scanning microscopy and two-photon microscopy. However, a recently proposed temporal focusing (TF) technique, based on spatio/temporal shaping of femtosecond laser pulses, enables depth-resolved bioimaging in a wide-field illumination. This lecture firstly provides a glimpse into the state-of-the-art progress of temporal focusing for bioimaging applications. Then we reveal a bizarre point spread function (PSF) of the temporal focusing system, both experimentally and theoretically. It can be expected that this newly emerged technique will exhibited new advances in not only 3D nonlinear bioimaging but also femtosecond laser micromachining in the future.
    2014 Photonics Asia; 10/2014
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    • "Temporally focused wide-field two-photon microscopy (TFM) of ultrafast optical pulses is an imaging technique by which depth-resolved wide-field two-photon images can be acquired without the need for raster scanning of the focal spot [1,2]. Because of its simplicity and high-speed image acquisition capability, TFM has been adapted to various biological imaging applications such as 3D super-resolution imaging [3], cellular dynamics imaging [4] and the depth-resolved fluorescence and phosphorescence lifetime imaging [5]. "
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    ABSTRACT: Although temporally focused wide-field two-photon microscopy (TFM) can perform depth resolved wide field imaging, it cannot avoid the image degradation due to scattering of excitation and emission photons when imaging in a turbid medium. Further, its axial resolution is inferior to standard point-scanning two-photon microscopy. We implemented a structured light illumination for TFM and have shown that it can effectively reject the out-of-focus scattered emission photons improving image contrast. Further, the depth resolution of the improved system is dictated by the spatial frequency of the structure light with the potential of attaining depth resolution better than point-scanning two-photon microscopy.
    Biomedical Optics Express 07/2013; 4(7):995-1005. DOI:10.1364/BOE.4.000995 · 3.65 Impact Factor
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