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We report a time-resolved single photon counting (TCSPC) imaging system based on a line-scanning architecture. The system benefits from the high fill-factor, active area, and large dimension of an advanced CMOS single photon avalanche diode (SPAD) array line-sensor. A two-dimensional image is constructed using a moving mirror to scan the line-sensor field-of-view (FOV) across the target, to enable the efficient acquisition of a two-dimensional 0.26 Mpixel TCSPC image. We demonstrate the capabilities of the system for TCSPC imaging and locating objects obscured in scattering media - specifically to locate a series of discrete point sources of light along an optical fibre submerged in a highly scattering solution. We demonstrate that by selectively imaging using early arriving photons which have undergone less scattering than later arriving photons, our TCSPC imaging system is able to locate the position of discrete point sources of light than a non-time-resolved imaging system., Comment: 12 pages, 5 figures submitted to Optica: Optics Express

Image slicing is a powerful technique in astronomy. It allows the instrument designer to reduce the slit width of the spectrograph, increasing spectral resolving power whilst retaining throughput. Conventionally this is done using bulk optics, such as mirrors and prisms, however more recently astrophotonic components known as photonic lanterns (PLs) and photonic reformatters have also been used. These devices reformat the multi-mode (MM) input light from a telescope into single-mode (SM) outputs, which can then be re-arranged to suit the spectrograph. The photonic dicer (PD) is one such device, designed to reduce the dependence of spectrograph size on telescope aperture and eliminate modal noise. We simulate the PD, by optimising the throughput and geometrical design using Soapy and BeamProp. The simulated device shows a transmission between 8 and 20 %, depending upon the type of adaptive optics (AO) correction applied, matching the experimental results well. We also investigate our idealised model of the PD and show that the barycentre of the slit varies only slightly with time, meaning that the modal noise contribution is very low when compared to conventional fibre systems. We further optimise our model device for both higher throughput and reduced modal noise. This device improves throughput by 6.4 % and reduces the movement of the slit output by 50%, further improving stability. This shows the importance of properly simulating such devices, including atmospheric effects. Our work complements recent work in the field and is essential for optimising future photonic reformatters.

We demonstrate determination of the location of the distal-end of a fibre-optic device deep in tissue through the imaging of ballistic and snake photons using a time resolved single-photon detector array. The fibre was imaged with centimetre resolution, within clinically relevant settings and models. This technique can overcome the limitations imposed by tissue scattering in optically determining the in vivo location of fibre-optic medical instruments.

Pan-STARRS1 has carried out a set of distinct synoptic imaging sky surveys including the $3\pi$ Steradian Survey and the Medium Deep Survey in 5 bands ($grizy_{P1}$). The mean 5$\sigma$ point source limiting sensitivities in the stacked 3$\pi$ Steradian Survey in $grizy_{P1}$ are (23.3, 23.2, 23.1, 22.3, 21.4) respectively. The upper bound on the systematic uncertainty in the photometric calibration across the sky is 7-12 millimag depending on the bandpass. The systematic uncertainty of the astrometric calibration using the Gaia frame comes from a comparison of the results with Gaia: the standard deviation of the mean and median residuals ($ \Delta ra, \Delta dec $) are (2.3, 1.7) milliarcsec, and (3.1, 4.8) milliarcsec respectively. The Pan-STARRS system and the design of the PS1 surveys are described and an overview of the resulting image and catalog data products and their basic characteristics are described together with a summary of important results. The images, reduced data products, and derived data products from the Pan-STARRS1 surveys are available to the community from the Mikulski Archive for Space Telescopes (MAST) at STScI., Comment: 38 pages, 29 figures, 12 tables

We present the results of our work on developing fully integrated devices (photonic dicers) for reformatting multimode light to a diffraction limited pseudo-slit. These devices can be used to couple a seeing-limited telescope point-spread-function to a spectrograph operating at the diffraction limit, thus enabling compact, high-resolution spectrographs that are free of modal-noise.

Photonic lanterns are made by adiabatically merging several single-mode cores into one multimode core. They provide low-loss interfaces between single-mode and multimode systems where the precise optical mapping between cores and individual modes is unimportant., Comment: 45 pages; article unchanged, accepted for publication in Advances in Optics and Photonics

Using ultrafast laser inscription, we report the fabrication of a prototype three-dimensional 121-waveguide fan-out device capable of reformatting the output of a 120 core multicore fiber (MCF) into a one-dimensional linear array. When used in conjunction with an actual MCF, we demonstrate that the reformatting function using this prototype would result in an overall throughput loss of approximately 7.0 dB. However, if perfect coupling from the MCF into the fan-out could be achieved, the reformatting function would result in an overall loss of only approximately 1.7 dB. With adequate development, similar devices could efficiently reformat the output of so-called "photonic lanterns" fabricated using highly multicore fibers.

We present the first high resolution polarization map of the ultraviolet emission from the outer jet in M87. The data were obtained by the Faint Object Camera (FOC) on the Hubble Space Telescope. The polarization map has a resolution of 0.2 arcsec and was derived using data from three linearly polarized images combined with the best available calibration data. The ultraviolet emission is highly polarized (~40\%) with the magnetic vector aligned roughly with the jet axis, except in the region of the brightest knot (Knot A) where the position angle changes abruptly and the magnetic vector becomes perpendicular to the jet axis. A similar behaviour is seen in the 2cm VLA radio polarization map. By aligning the FOC and VLA data, we present ultraviolet--2cm spectral index, depolarization and rotation measure maps. We identify a region of high depolarization adjacent to Knot A. This is the first direct observational evidence that indicates the presence of a cloud or filament of dense thermal material which is mixed with the synchrotron emitting plasma of the jet. The interaction of the jet with this cloud is likely to be responsible for the sudden increase in the brightness of the jet at Knot A due to an induced shock. We suggest that the dark line seen in the 2cm radio data between Knot A and Knot C could be the shadow or magnetotail of the depolarizing cloud in the jet., Comment: uuencoded compressed postscript. The preprint is also available at http://www.ast.cam.ac.uk/preprint/PrePrint.html

HST images of the western hot spot of the nearby FRII radio galaxy Pictor A resolve the hot spot into an amorphous region of highly polarized wisps. The high polarization (>~ 50%) indicates that the optical emission is synchrotron radiation and that the magnetic field structure has been well resolved. The magnetic field is oriented nearly perpendicular to the jet axis and apparently very uniform. We interpret these observations in terms of a compressed magnetic field at the working surface where the jet impinges on the intergalactic medium some 100 kpc from the nucleus of the host galaxy. Keywords: Polarization --- radiation mechanisms: nonthermal --- galaxies: active --- galaxies: individual: Pictor A --- galaxies: jets., Comment: uuencoded compressed postscript. The preprint is also available at http://www.ast.cam.ac.uk/preprint/PrePrint.html