Data sharing practices and data availability upon request differ across scientific disciplines.

Data sharing is one of the cornerstones of modern science that enables large-scale analyses and reproducibility. We evaluated data availability in research articles across nine disciplines in Nature and Science magazines and recorded corresponding authors' concerns, requests and reasons for declining data sharing. Although data sharing has improved in the last decade and particularly in recent years, data availability and willingness to share data still differ greatly among disciplines. We observed that statements of data availability upon (reasonable) request are inefficient and should not be allowed by journals. To improve data sharing at the time of manuscript acceptance, researchers should be better motivated to release their data with real benefits such as recognition, or bonus points in grant and job applications. We recommend that data management costs should be covered by funding agencies; publicly available research data ought to be included in the evaluation of applications; and surveillance of data sharing should be enforced by both academic publishers and funders. These cross-discipline survey data are available from the plutoF repository.

Action Recognition Using Single-Pixel Time-of-Flight Detection.

Action recognition is a challenging task that plays an important role in many robotic systems, which highly depend on visual input feeds. However, due to privacy concerns, it is important to find a method which can recognise actions without using visual feed. In this paper, we propose a concept for detecting actions while preserving the test subject's privacy. Our proposed method relies only on recording the temporal evolution of light pulses scattered back from the scene. Such data trace to record one action contains a sequence of one-dimensional arrays of voltage values acquired by a single-pixel detector at 1 GHz repetition rate. Information about both the distance to the object and its shape are embedded in the traces. We apply machine learning in the form of recurrent neural networks for data analysis and demonstrate successful action recognition. The experimental results show that our proposed method could achieve on average 96.47 % accuracy on the actions walking forward, walking backwards, sitting down, standing up and waving hand, using recurrent neural network.

Characterization of few-fs deep-UV dispersive waves by ultra-broadband transient-grating XFROG.

A multi-shot transient-grating cross-correlation frequency-resolved optical gating (FROG) is implemented for the characterization of nanojoule-scale, few-femtosecond, deep-ultraviolet pulses. In theory, the system can characterize pulses with a bandwidth extending from below 200 nm to above 1.5 µm. It is experimentally shown that a 200 THz (50 nm) wide dispersive wave centered at 275 nm, generated in a gas-filled HC-PCF, has a temporal duration of 4 fs. The numerical simulations agree well with the experiment. The results confirm that dispersive wave emission in a gas-filled HC-PCF can be used as a novel source of ultrashort UV pulses in a range of applications, for example, ultrafast UV pump-probe spectroscopy.

Endlessly single-mode photonic crystal fiber as a high resolution probe.

We sample ultra-broadband light, focused onto a diffraction-limited spot, to an endlessly single-mode photonic crystal fiber (ESM) and detect both the field amplitude and phase using a SEA TADPOLE interferometer. We resolve spatial features up to 2.5 times finer than the fiber mode size while sampling the periodic features of the bipolar oscillating field in the transverse section. The resolution enhancement is expected also in other types of single-mode fibers in intensity measurements and leads to an inexpensive method for characterizing the point-spread function of such optical fields, e.g., diffraction-limited spots from microscope objectives. In addition, we demonstrate the guidance of a high-NA light field in the fine structure of an ESM fiber mode. The results are especially valuable for devices where a fiber tip acts as an input slit and defines the spatial resolution, e.g., fiber-based interferometers, spectrometers, and sensors.

Realization of laterally nondispersing ultrabroadband Airy pulses.

We present the measurements of the spatiotemporal impulse response of a system creating nondispersing Airy pulses, i.e., ultrabroadband Airy beams whose main lobe size remains constant over propagation. A custom refractive element with a continuous surface profile was used to impose the cubic phase on the input beam. The impulse response of the Airy pulse generator was spatiotemporally characterized by applying a white-light spatial-spectral interferometry setup based on the SEA TADPOLE technique. The results were compared with the theoretical model and previously spatiotemporally characterized Airy pulses generated by a spatial light modulator.

Spatiotemporal characterization of ultrabroadband Airy pulses.

We present experimental results of a full spatiotemporal characterization of an optical system for ultrabroadband Airy pulse generation with a liquid-crystal-on-silicon spatial light modulator. Measurements with a few micrometer spatial and almost one-wave-cycle temporal resolution were performed using a white light spatial spectral interferometry setup based on the SEA TADPOLE ultrashort pulse characterization technique. The results were compared with the theoretical model for Airy pulse propagation.

Basic diffraction phenomena in time domain.

Using a recently developed technique (SEA TADPOLE) for easily measuring the complete spatiotemporal electric field of light pulses with micrometer spatial and femtosecond temporal resolution, we directly demonstrate the formation of theo-called boundary diffraction wave and Arago's spot after an aperture, as well as the superluminal propagation of the spot. Our spatiotemporally resolved measurements beautifully confirm the time-domain treatment of diffraction. Also they prove very useful for modern physical optics, especially in micro- and meso-optics, and also significantly aid in the understanding of diffraction phenomena in general.

Direct spatiotemporal measurements of accelerating ultrashort Bessel-type light bullets.

We measure the spatiotemporal field of ultrashort pulses with complex spatiotemporal profiles using the linear-optical, interferometric pulse-measurement technique SEA TADPOLE. Accelerating and decelerating ultrashort, localized, nonspreading Bessel-X wavepackets were generated from a approximately 27 fs duration Ti:Sapphire oscillator pulse using a combination of an axicon and a convex or concave lens. The wavefields are measured with approximately 5 microm spatial and approximately 15 fs temporal resolutions. Our experimental results are in good agreement with theoretical calculations and numerical simulations.

Measuring the spatiotemporal field of ultrashort Bessel-X pulses.

We present direct measurements of the spatiotemporal electric field of an ultrashort Bessel-X pulse generated using a conical lens (axicon). These measurements were made using the linear-optical interferometric technique SEA TADPOLE, which has micrometer spatial resolution and femtosecond temporal resolution. From our measurements, both the superluminal velocity of the Bessel pulse and the propagation invariance of the central spot are apparent. We verified our measurements with simulations.