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Living biological tissue is an example of dynamic scattering media with a millisecond-level speckle decorrelation time Thus far, owing to the limited speed of wavefront characterization in existing methods, spatiotemporal focusing beyond the optical diffusion limit has only been realized with static scattering media 43 , In contrast, T-CUP demonstrates single-shot femtosecond imaging of transient light patterns in a dynamic scattering medium Fig.
By integrating T-CUP with interferometry, it is possible to examine the scattered electric field of a broadband beam, which would assist in the design of phase conjugation of spatiotemporal focusing in living biological tissue. Therefore, our work, as an important step in imaging instrumentation, will open up new routes toward deep-tissue wide-field two-photon microscopy, photodynamic therapy, and optogenetics. By improving the frame rate by two orders of magnitude compared with the previous state-of-the-art 23 , T-CUP demonstrated that the ever-lasting pursuit of a higher frame rate is far from ending.
As the only detection solution thus far available for passively probing dynamic self-luminescent events at femtosecond timescales in real time, T-CUP was used to reveal spatiotemporal details of transient scattering events that were inaccessible using previous systems. The compressed-sensing-augmented projection extended the application of the Radon transformation to probing spatiotemporal datacubes. This general scheme can be potentially implemented in other imaging modalities, such as tomographic phase microscopy 45 and time-of-flight volumography With continuous improvement in streak camera technologies 48 , future development may enable a 1 quadrillion fps 10 15 fps frame rate with a wider imaging spectral range, allowing direct visualization and exploration of irreversible chemical reactions 49 and nanostructure dynamics We first derive the expression for the data acquisition of T-CUP in a continuous model.
For data acquisition, T-CUP records the intensity distribution of the dynamic scene, I x, y, t , in two projected views Supplementary Fig. The first view, termed the time-unsheared view, directly records the dynamic scene with an external CCD camera Fig. This recording process is expressed as. The second view, termed the time-sheared view, records the projected view of the spatiotemporal scene from an oblique angle Supplementary Fig.
Specifically, the dynamic scene is first spatially encoded by a pseudo-random binary mask, followed by femtosecond shearing along one spatial axis by a time-varying voltage applied to a pair of sweep electrodes before the scene is finally spatiotemporally integrated on an internal CCD camera in the streak camera. Mathematically, the optical energy measured by the internal CCD camera, E s , is related to I x, y, t by. For image reconstruction, we discretized Eqs. Given the known measurement matrix and leveraging the intrinsic sparsity in the dynamic scene, we estimate that the datacube for the transient scene by solving the inverse problem of Eq.
Following the intermediate image, a beam splitter sends the incident light in two directions. The transmitted beam is passed onto a DMD Texas Instruments, LightCrafter by a 4 f imaging system with a unit magnification ratio. A pseudo-random binary pattern is displayed on the DMD to encode the input image. After being reflected by the beam splitter, the spatially encoded dynamic scene is projected onto the entrance port of a femtosecond streak camera Hamamatsu, C Inside the streak camera, the spatially encoded dynamic scene is first relayed to a photocathode that generates a number of photoelectrons proportional to the light intensity distribution.
To temporally shear the spatially encoded dynamic scene, a sweep voltage deflects the photoelectrons to different vertical positions according to their time of flight. The deflected photoelectrons are multiplied by a micro-channel plate and then converted back into light by a phosphor screen. With two-view recording, the light throughput for the T-CUP system is Kolner, B. Space-time duality and the theory of temporal imaging.
IEEE J. Foster, M. Silicon-chip-based ultrafast optical oscilloscope. Nature , 81—84 Patera, G. Quantum temporal imaging: application of a time lens to quantum optics. Zhu, G. Simultaneous spatial and temporal focusing of femtosecond pulses. Express 13 , — Oron, D. Scanningless depth-resolved microscopy. Papagiakoumou, E. Functional patterned multiphoton excitation deep inside scattering tissue. Photonics 7 , — Salem, R. Application of space—time duality to ultrahigh-speed optical signal processing. Photonics 5 , — Goda, K. Dispersive Fourier transformation for fast continuous single-shot measurements.
Scanless two-photon excitation of channelrhodopsin Methods 7 , — Katz, O. Focusing and compression of ultrashort pulses through scattering media. Beresna, M. Ultrafast laser direct writing and nanostructuring in transparent materials. Photonics 6 , — Jing, C. Characteristics and applications of spatiotemporally focused femtosecond laser pulses. Stockbridge, C. Focusing through dynamic scattering media. Express 20 , — Kammel, R.
Enhancing precision in fs-laser material processing by simultaneous spatial and temporal focusing. Light Sci. Mikami, H. Ultrafast optical imaging technology: principles and applications of emerging methods. Nanophotonics 5 , 98— Schaffer, C. Dynamics of femtosecond laser-induced breakdown in water from femtoseconds to microseconds. Express 10 , — Velten, A. Recovering three-dimensional shape around a corner using ultrafast time-of-flight imaging.
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Li, Z. Single-shot tomographic movies of evolving light-velocity objects. Serial time-encoded amplified imaging for real-time observation of fast dynamic phenomena. Nature , — Nakagawa, K. Photonics 8 , — Ehn, A. FRAME: femtosecond videography for atomic and molecular dynamics. Kubota, T. Moving picture recording and observation of three-dimensional image of femtosecond light pulse propagation.
Express 15 , — Gao, L. Single-shot compressed ultrafast photography at one hundred billion frames per second. Nature , 74—77 Liang, J. Single-shot real-time video recording of a photonic Mach cone induced by a scattered light pulse. Encrypted three-dimensional dynamic imaging using snapshot time-of-flight compressed ultrafast photography. The restricted isometry property and its implications for compressed sensing. Bor, Z. Femtosecond pulse front tilt caused by angular dispersion. Hebling, J.
Derivation of the pulse front tilt caused by angular dispersion. Mermillod-Blondin, A. Time-resolved imaging of laser-induced refractive index changes in transparent media. Sun, Q. Measurement of the collision time of dense electronic plasma induced by a femtosecond laser in fused silica.
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Lumpkin, A. First dual-sweep streak camera measurements of a photoelectric injector drive laser. Methods Phys. A , — Brady, D. Multiscale gigapixel photography. Vitek, D. Spatio-temporally focused femtosecond laser pulses for nonreciprocal writing in optically transparent materials. Express 18 , — Wang, Z. Time-resolved shadowgraphs of transient plasma induced by spatiotemporally focused femtosecond laser pulses in fused silica glass.
Wang, X. High-frame-rate observation of single femtosecond laser pulse propagation in fused silica using an echelon and optical polarigraphy technique. Li, G.
Second harmonic generation in centrosymmetric gas with spatiotemporally focused intense femtosecond laser pulses. Ultrafast waveform compression using a time-domain telescope. Photonics 3 , — Ultrafast optical signal processing based upon space-time dualities. Light Technol. Weiner, A. Durfee, C. Breakthroughs in photonics spatiotemporal focusing: advances and applications.
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Horng, J. Imaging electric field dynamics with graphene optoelectronics.
Single-shot real-time femtosecond imaging of temporal focusing | Light: Science & Applications
Single-shot terahertz-field-driven X-ray streak camera. Hockett, P. Time-resolved imaging of purely valence-electron dynamics during a chemical reaction. Gorkhover, T. Femtosecond and nanometre visualization of structural dynamics in superheated nanoparticles. Photonics 10 , 93—97 Download references. The authors thank Dr. Zhengyan Li from the University of Ottawa, Dr. The authors also acknowledge Yujia Chen and Chiye Li for experimental assistance and Professor James Ballard for close reading of the manuscript.
All authors were involved in revising the manuscript. Correspondence to Lihong V. Reprints and Permissions. Optics Communications Journal of Materiomics Physical Review Letters Optics Letters Optics and Lasers in Engineering Advanced search. Skip to main content. Subjects Imaging and sensing Optical physics. The pre-industrial night, however, was widely regarded with dread and fascination in equal measure: "I curse the night," confessed William Drummond in , "but doth from day me hide.
But those who had good reason, legitimate or illicit, to venture outdoors "during the night season" nonetheless developed a whole range of tricks to help them. In an age before widespread light pollution, the illumination of the moon and the stars was far more useful on a clear night, starlight alone cast shadows. People knew their neighbourhoods intimately: every tree, every hedge, every post. On the Downs, great piles of chalky soil, known as "down lanterns", served as beacons.
Bark would be cut from strategic trees to expose the lighter wood beneath. The senses of hearing barking dogs , smell a honeysuckle bush and touch a notch cut in a banister at a sharp turn in the stairs became all the more important. For before artificial lighting, indoors was just as treacherous as outdoors: in Sweden, it was common practice to push the furniture against the walls before retiring to bed, so you wouldn't bump into it if you rose in the middle of the night.
Man had advanced, by the late 18th century, from the first flaming torches through primitive lights made, as long as 15, years ago, by placing moss or some other fibre in a shell or hollow stone, and filling it with animal fat to, on the continent at least, handsome pottery and metal oil lamps sporting sophisticated wicks and artfully sealed reservoirs filled with olive, sesame, fish, nut or plant oil.
In Britain, for some reason, we favoured candles.
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As a rough estimate, one watt electric bulb generates the light of approximately candles. By the late s, most of our aristocratic homes would have been lit by a selection of candles made of expensive beeswax, or perhaps from even more expensive spermaceti, the wax extracted from the head cavities of sperm whales. The poor, overwhelmingly, made do with humble rush lights: reeds dipped in some form of animal fat. These burned even more unevenly than tallow candles and smelled worse, but did the job, more or less, for an hour or so.
What job were they required to do? What did decent folk do after dark? The upper-class young blades drank the night away. Men in towns and cities took themselves to an alehouse. Others had chores after the evening meal: furniture to build, tools to repair, beer to brew. Women carded and spun wool, and wove it. There were parlour games to play, folk tales to tell, gossip to swap, friends and family to entertain. The literate few read, or wrote. And then, by 9pm or at the latest 10, to bed.
Once there, Ekirch relates in perhaps his most fascinating revelation, pre-industrial man slept a segmented sleep. He has found more than references, from Homer onwards, to a "first sleep" that lasted until maybe midnight, and was followed by "second sleep". In between the two, people routinely got up, peed, smoked, read, chatted, had friends round, or simply reflected on the events of the previous day — and on their dreams. Plenty also had sex, by all accounts far more satisfactorily than at the end of a hard day's labouring. Couples who copulated "after the first sleep", wrote a 16th-century French doctor, "have more enjoyment, and do it better".
Experiments by Dr Thomas Wehr at America's National Institute of Mental Health appear to bear out the theory that this two-part slumber is man's natural sleeping pattern: a group of young male volunteers deprived of light at night for weeks at a time rapidly fell into the segmented sleep routine described in so many of Ekirch's documentary sources. It could even be, Wehr has theorised, that many of today's common sleeping disorders are essentially the result of our older, primal habits "breaking through into today's artificial world".
Of all this have we been robbed by the onward march of industrial lighting. By we, of course, I mean most people in the developed world. It's worth remembering that there are still large parts of the globe where it's still up at sunrise, and to bed pretty soon after sundown. But in some ways, argues Ekirch, rather than making night-time more accessible, we are actually risking its gradual extinction. City-dwellers, and many others, have now all but lost their view of the heavens, a source of awe and wonder since the beginning of time.
And since affordable artificial lighting now allows all of us to go to bed so much later, consolidating our sleep into one more or less continuous spell, our dreamlife has been disrupted and our understanding of ourselves impaired.
So thanks, William Murdoch. That's it, then: winter's on the way — and not because the leaves are off the trees, or the mercury's dipping at night. No, what's clinched it is the end of British summer time, and the way the sun suddenly seems to be abandoning us an hour earlier. Always a bit hard to get the old head around, British summer time. The point is that while we can't shift the times of sunrise and sunset, we can, if those times don't particularly suit, shift our clocks, so that the hours of daylight better match our living patterns.
That's the idea, anyway. The problem is that British summer time, known internationally as daylight saving time, or DST, was, as the name implies, invented for summer: we shift the clocks forward an hour at the end of March, so instead of getting light at, say, 4am in summer, which is no use to anyone because we're all safely tucked up in bed, it actually gets light at 5am. Consequently, instead of getting dark again at 8pm, it gets dark at 9pm, allowing us all to be out and about making the most of all those balmy summer evenings or something.
Unfortunately, during the shorter winter day we shift the clocks back to Greenwich mean time again, so while the mornings are marginally lighter, it gets dark soon after lunch. He resented having to cut his golf round short at dusk, so in proposed changing the summer clock by 80 minutes: 20 minutes forward on successive Sundays in April, and back by the same amount on September Sundays. But the prime minister, and several other leading figures, didn't, and in the end it was Germany, eager to save coal in wartime, that first adopted DST, a month before Britain came round in May And the debate has raged ever since.
Broadly speaking, retailers love DST because it gives people more daylight to shop in, and governments argue that the greater leisure and sports opportunities contribute to the health and happiness of the nation. There is an alternative. The theory is that lighter evenings would not only boost the leisure and tourism industries, but reduce accidents as they did during a brief trial in the s.