Query: ultrafast imaging

title: Single shot ultrafast imaging attaining 70 trillion frames per second
abstract: Real time imaging of countless femtosecond dynamics requires extreme speeds orders of magnitude beyond the limits of electronic sensors. Existing femtosecond imaging modalities either require event repetition or provide single shot acquisition with no more than 10 13 frames per second (fps) and 3 x 10 2 frames. Here, we report compressed ultrafast spectral photography (CUSP) which attains several new records in single shot multi dimensional imaging speeds. In active mode, CUSP achieves both 7 x 10 13 fps and 10 3 frames simultaneously by synergizing spectral encoding, pulse splitting, temporal shearing, and compressed sensing enabling unprecedented quantitative imaging of rapid nonlinear light matter interaction. In passive mode, CUSP provides four dimensional (4D) spectral imaging at 0.5 x 10 12 fps, allowing the first single shot spectrally resolved fluorescence lifetime imaging microscopy (SR FLIM) As a real time multi dimensional imaging technology with the highest speeds and most frames, CUSP is envisioned to play instrumental roles in numerous pivotal scientific studies without the need for event repetition. Ultrafast imaging has been limited by the speed of electronic sensors. Here, the authors demonstrate single shot compressed ultrafast spectral photography, which combines spectral encoding, pulse splitting, temporal shearing, and compressed sensing in order to achieve real time imaging at 70 trillion frames per second.

title: Ultrafast and broadband photodetectors based on a perovskite/organic bulk heterojunction for large dynamic range imaging
abstract: Organic inorganic hybrid perovskite (OIHP) photodetectors that simultaneously achieve an ultrafast response and high sensitivity in the near infrared (NIR) region are prerequisites for expanding current monitoring, imaging, and optical communication capbilities. Herein, we demonstrate photodetectors constructed by OIHP and an organic bulk heterojunction (BHJ) consisting of a low bandgap nonfullerene and polymer, which achieve broadband response spectra up to 1 mm with a highest external quantum efficiency of approximately 54% at 850 nm, an ultrafast response speed of 5.6 ns and a linear dynamic range (LDR) of 191 dB. High sensitivity, ultrafast speed and a large LDR are preeminent prerequisites for the practical application of photodetectors. Encouragingly, due to the high dynamic range imaging capacity, high quality visible NIR actual imaging is achieved by employing the OIHP photodetectors. We believe that state of the art OIHP photodetectors can accelerate the translation of solution processed photodetector applications from the laboratory to the imaging market. Novel photodetectors developed by researchers in China provide imaging in the near infrared (NIR) region with record breaking efficiency and speed. A new class of semiconducting materials called organic inorganic hybrid perovskites (OIHPs) display excellent optical and electrical properties for thin film solar cells, LEDs and light detectors. To expand their detection range to NIR, which is useful for biomedical applications, OIHPs can be combined with structures called organic bulk heterojunctions (BHJs) Now, Weida Hu, Liang Shen and co workers at Jilin University, Chinese Academy of Sciences and Peking University have designed new OIHP BHJ photodetectors that efficiently detect a wide range of both visible and NIR radiation. Their prototype sensors have ultra fast response times of just 5.6 nanoseconds and remain sensitive even in low brightness, suggesting that they could accelerate the movement of OIHP devices from lab tests to commercial imaging.

title: Ultrafast Imaging Techniques

title: Ultrafast Imaging at All Frequencies
abstract: A new algorithm could allow researchers to capture attosecond, multiwavelength images of an object.

title: Ultrafast imaging on the formation of periodic ripples on a Si surface with a prefabricated nanogroove induced by a single femtosecond laser pulse.
abstract: This paper reports the ultrafast imaging on the formation of periodic surface ripples induced by a single 800 nm, 50 fs laser pulse. The evolution process is observed on a Si surface with a prefabricated nanogroove. The ripples emerge very quickly, only 3 ps after the laser pulse with a fluence of 0.18 J/cm2 irradiating on the surface, and last for several hundreds of picoseconds. The ultrafast dynamics of laser matter interaction, such as free carrier excitation, carrier and lattice heating, surface plasmon polariton (SPP) excitation, etc, are studied theoretically. The theoretical and experimental results support that the periodic ripples are caused by the periodic energy deposition due to SPP excitation. The emerge time could identify the surface melting causing the formation of periodic ripples, and exclude the other thermal effects, for example, hydrodynamics.

title: Ultrafast imaging in biomedical ultrasound
abstract: Although the use of ultrasonic plane wave transmissions rather than line per line focused beam transmissions has been long studied in research, clinical application of this technology was only recently made possible through developments in graphical processing unit (GPU) based platforms. Far beyond a technological breakthrough, the use of plane or diverging wave transmissions enables attainment of ultrafast frame rates (typically faster than 1000 frames per second) over a large field of view. This concept has also inspired the emergence of completely novel imaging modes which are valuable for ultrasound based screening, diagnosis, and therapeutic monitoring. In this review article, we present the basic principles and implementation of ultrafast imaging. In particular, present and future applications of ultrafast imaging in biomedical ultrasound are illustrated and discussed.

title: Ultrafast imaging of cell elasticity with optical microelastography
abstract: In wave physics, and especially seismology, uncorrelated vibrations could be exploited using "noise correlation" tools to reconstruct images of a medium. By using a high frequency vibration, a high speed tracking device, and a reconstruction technique based on temporal correlations of travelling waves we conceptualized an optical microelastography technique to map elasticity of internal cellular structures. This technique, unlike other methods, can provide an elasticity image in less than a millisecond, thus opening the possibility of studying dynamic cellular processes and elucidating new mechanocellular properties. We call this proposed technique "cell quake elastography." Elasticity is a fundamental cellular property that is related to the anatomy, functionality, and pathological state of cells and tissues. However, current techniques based on cell deformation, atomic force microscopy, or Brillouin scattering are rather slow and do not always accurately represent cell elasticity. Here, we have developed an alternative technique by applying shear wave elastography to the micrometer scale. Elastic waves were mechanically induced in live mammalian oocytes using a vibrating micropipette. These audible frequency waves were observed optically at 200,000 frames per second and tracked with an optical flow algorithm. Whole cell elasticity was then mapped using an elastography method inspired by the seismology field. Using this approach we show that the elasticity of mouse oocytes is decreased when the oocyte cytoskeleton is disrupted with cytochalasin B. The technique is fast (less than 1 ms for data acquisition) precise (spatial resolution of a few micrometers) able to map internal cell structures, and robust and thus represents a tractable option for interrogating biomechanical properties of diverse cell types.

title: Ultrafast Two Photon Imaging of a High Gain Voltage Indicator in Awake Behaving Mice
abstract: Optical interrogation of voltage in deep brain locations with cellular resolution would be immensely useful for understanding how neuronal circuits process information. Here, we report ASAP3, a genetically encoded voltage indicator with 51% fluorescence modulation by physiological voltages, submillisecond activation kinetics, and full responsivity under two photon excitation. We also introduce an ultrafast local volume excitation (ULoVE) method for kilohertz rate two photon sampling in vivo with increased stability and sensitivity. Combining a soma targeted ASAP3 variant and ULoVE, we show single trial tracking of spikes and subthreshold events for minutes in deep locations, with subcellular resolution and with repeated sampling over days. In the visual cortex, we use soma targeted ASAP3 to illustrate cell type dependent subthreshold modulation by locomotion. Thus, ASAP3 and ULoVE enable high speed optical recording of electrical activity in genetically defined neurons at deep locations during awake behavior.

title: Spatio temporally wideband ultrafast imaging
abstract: We present a 10's MHz imaging system through a simple spatio temporally sweeping unit which is constructed with incremental optical fibers. It is demonstrated that this imaging modality can be performed over an ultrawide wavelength range, i.e. 500 2000 nm.

title: Ultrafast dynamics of laser metal interactions in additive manufacturing alloys captured by in situ X ray imaging
abstract: Advanced in situ characterization is essential for determining the underlying dynamics of laser material interactions central to both laser welding and the rapidly expanding field of additive manufacturing. Traditional characterization techniques leave a critical experimental gap in understanding the complex subsurface fluid flow and metal evaporation dynamics inherent in laser induced heating of the metal. Herein, in situ ultra high speed transmission X ray imaging is revealed to be essential for bridging this information gap, particularly via comparison with and validation of advanced multiphysics simulations. Imaging on submicrosecond timescales enables correlation between dynamics of the laser generated vapor liquid interface and melt pool surface instabilities in industrially relevant alloys. X ray imaging and complimentary simulations reveal vapor depression oscillations and rapid expansion due to reflection of the processing laser from the front surface of the vapor depression. Pore formation studies at steady state and during prompt removal of laser heating at the end of track reveal that the rapidly solidifying melt pool traps pores near the base of the vapor filled depression. Moreover, pores within the melt pool are entrained by Marangoni convection which overcomes the force of buoyancy and forces the pores downward from the surface immediately before solidification. Observed solidification kinetics, consistent with previous results, give insight into surface morphology and porosity in the processed material. The information presented here is key for defining the physical models that describe laser material interaction and ultimately increases our understanding of the emerging field of laser based metal additive manufacturing.