(In Reverse Order of publication, most recent first)
Title: Three-photon light-sheet fluorescence microscopy
Authors: A. Escobet-Montalbán, F. M. Gasparoli, J. Nylk, P. Liu, Z. Yang, and K. Dholakia
Abstract: We present the first demonstration of three-photon excitation light-sheet fluorescence microscopy. Light-sheet fluorescence microscopy in single- and two-photon modes has emerged as a powerful wide-field, low-photodamage technique for fast volumetric imaging of biological samples. We extend this imaging modality to the three-photon regime, enhancing its penetration depth. Our present study uses a conventional femtosecond pulsed laser at 1000 nm wavelength for the imaging of 450 μm diameter cellular spheroids. In addition, we show, experimentally and through numerical simulations, the potential advantages in three-photon light-sheet microscopy of using propagation-invariant Bessel beams in preference to Gaussian beams.
Title: Wide-field multiphoton imaging through scattering media without correction.
Authors: A. Escobet-Montalbán, R. Spesyvtsev, M. Chen, W. Afshar Saber, M. Andrews, C. Simon Herrington, M. Mazilu and K. Dholakia
Abstract: Optical approaches to fluorescent, spectroscopic, and morphological imaging have made exceptional advances in the last decade. Super-resolution imaging and wide-field multiphoton imaging are now underpinning major advances across the biomedical sciences. While the advances have been startling, the key unmet challenge to date in all forms of optical imaging is to penetrate deeper. A number of schemes implement aberration correction or the use of complex photonics to address this need. In contrast, we approach this challenge by implementing a scheme that requires no a priori information about the medium nor its properties. Exploiting temporal focusing and single-pixel detection in our innovative scheme, we obtain wide-field two-photon images through various turbid media including a scattering phantom and tissue reaching a depth of up to seven scattering mean free path lengths. Our results show that it competes favorably with standard point-scanning two-photon imaging, with up to a fivefold improvement in signal-to-background ratio while showing significantly lower photobleaching.