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A report on Additive Manufacturing Materials for EU funded OPTICON work package - Additive Astronomy Integrated-component Manufacturing(A2IM).

The project "Novel Astronomical Instrumentation through photonic Reformatting" is a DFG-funded collaboration to exploit the recognized potential of photonics solutions for a radically new approach to astronomical instrumentation for optical/infrared high precision spectroscopy and high angular resolution imaging. We present a project overview and initial development results from our Adaptive Optics-photonic test bed, Ultrafast Laser Inscribed waveguides for interferometric beam combination and 3D printing structures for astronomical instrumentation. The project is expected to lead to important technological breakthroughs facilitating uniquely functionality and technical solutions for the next generation of instrumentation., 15 pages, 11 figures, SPIE Astronomical Telescopes + Instrumentation

The 4MOST1 instrument is a multi-object-spectrograph for the ESO-VISTA telescope. The 4MOST long fiber feed links the AESOP2 fiber positioner to two low-resolution spectrographs (1624 fibers) and one high-resolution spectrograph (812 fibers). In addition to the 2436 science fibers, the system includes guide fiber bundles, metrology fiducial fibers and simultaneous calibration fibers for the spectrographs. To validate the design approaches, including fiber connectors and cable rotator, pre-production fiber cables have been built and evaluated. This paper presents the near final design of the fiber feed subsystem and its performance results pertaining to throughput homogeneity, focal ratio degradation, and connector loss of the pre-production cables.

4MOST is a fibre-fed, multi-object spectroscopic survey facility to be installed on the VISTA telescope at ESO's Paranal observatory. This paper presents the final mechanical design of the optical fibre route from the fibre positioner at the focal plane of VISTA to the fibre-slits within the high- and low-resolution spectrographs below the azimuth platform. The technical challenges are to provide a safe, durable and efficient fibre route for over 2400 fibres. To accommodate the movements of the telescope, a Cassegrain Cable Wrap and a novel elevation chain concept has been prototyped and extensively tested to validate the design solutions.

Modal noise has been shown to critically limit the signal-to-noise ratio achievable in fiber-coupled, high-resolution spectrographs. We are investigating new fiber technologies that can potentially solve the modal noise issues in the NIR region. The new technology that we present is a combination of a multicore fiber (MCF) and a photonic lantern (PL) specifically designed to provide highly efficient phase scrambling in the NIR with a low mode count. In this paper we give an overview of the specifications, design and manufacture of the multicore fiber and photonic lantern. We also present the initial modal noise test results for the MCF-PL and an octagonal multimode fiber for comparison.

The problem of atmospheric emission from OH molecules is a long standing problem for near-infrared astronomy. PRAXIS is a unique spectrograph which is fed by fibres that remove the OH background and is optimised specifically to benefit from OH-Suppression. The OH suppression is achieved with fibre Bragg gratings, which were tested successfully on the GNOSIS instrument. PRAXIS uses the same fibre Bragg gratings as GNOSIS in its first implementation, and will exploit new, cheaper and more efficient, multicore fibre Bragg gratings in the second implementation. The OH lines are suppressed by a factor of ∼ 1000, and the expected increase in the signal-to-noise in the interline regions compared to GNOSIS is a factor of ∼ 9 with the GNOSIS gratings and a factor of ∼ 17 with the new gratings. PRAXIS will enable the full exploitation of OH suppression for the first time, which was not achieved by GNOSIS (a retrofit to an existing instrument that was not OH-Suppression optimised) due to high thermal emission, low spectrograph transmission and detector noise. PRAXIS has extremely low thermal emission, through the cooling of all significantly emitting parts, including the fore-optics, the fibre Bragg gratings, a long length of fibre, and the fibre slit, and an optical design that minimises leaks of thermal emission from outside the spectrograph. PRAXIS has low detector noise through the use of a Hawaii-2RG detector, and a high throughput through a efficient VPH based spectrograph. PRAXIS will determine the absolute level of the interline continuum and enable observations of individual objects via an IFU. In this paper we give a status update and report on acceptance tests.

In recent decades, spectroscopic capabilities have been significantly enhanced by new technological developments, in particular spatial reformatting. Spatial reformatting allows multiple functionalities: the observation of a larger area of sky, obtaining the spectra of all spatial elements under the same atmospheric conditions; modification of the shape and size of the field of view; focal-ratio conversion for the optimized coupling between the telescope and the spectrograph; increase in the spatial and spectral resolving power; the observation of multiple objects; homogeneity in the illumination; scrambling of spatial and/or phase induced structure with the instrument, thus improving the system stability; relocation of the exit pupil, especially important for telecentric systems. The impact of reformatting and the breadth of science cases is so great that many alternative methods and technologies have been proposed: image slicers using refractive or reflective solutions; optical fibers with different core sizes and geometries; microlenses used in isolation or combined with fibers and more recently, photonic devices such as Photonic lanterns to produce modal decomposition. In this paper, a comparison between all currently available options is presented, with a detailed analysis of their advantages and limitations and a proposal for a new reformatter combining slicers and photonic devices. This proposal presents the advantages of the other alternatives and additionally offers: minimization of focal-ratio degradation; produces image and modal decomposition; improves the throughput along the spectral range, increases the spectral resolving power and adds the functionality of scrambling. All of these advantages are combined in a system where photonic and astronomical instrumentation capabilities are joined in an innovative solution with many applications, like for example, the Extremely Large Telescope.

Photonic lanterns typically allow for single-mode action in a multimode fibre. Since their invention over a decade ago for applications in astrophotonics, they have found important uses in diverse fields of applied science. To date, large aperture highly-mulitmoded to single-mode lanterns have been difficult as fabrication techniques are not practical for mass replication. Here as a proof of concept, we demonstrate three different devices based on multicore fibre photonic lanterns with: 100µm core diameters; NAs = 0.16 and 0.15; and requiring 259 single-mode core system, specifically 7 multicore fibres each with 37 cores, instead of 259 individual single-mode fibres. The average insertion loss excluding coupling efficiencies is only 0.4dB (>91% transmission). This concept has numerous advantages, in particular, (i) it is a direct scaleable solution, (ii) eases imprinting of photonic functions, e.g. fibre Bragg gratings; and (iii) new approach for large-area optical fibre slicers for future large-aperture telescopes.

We investigate the generation of optical frequency combs through a cascade of four-wave mixing processes in nonlinear fibres with optimised parameters. The initial optical field consists of two continuous-wave lasers with frequency separation larger than 40 GHz (312.7 pm at 1531 nm). It propagates through three nonlinear fibres. The first fibre serves to pulse shape the initial sinusoidal-square pulse, while a strong pulse compression down to sub-100 fs takes place in the second fibre which is an amplifying erbium-doped fibre. The last stage is a low-dispersion highly nonlinear fibre where the frequency comb bandwidth is increased and the line intensity is equalised. We model this system using the generalised nonlinear Schrödinger equation and investigate it in terms of fibre lengths, fibre dispersion, laser frequency separation and input powers with the aim to minimise the frequency comb noise. With the support of the numerical results, a frequency comb is experimentally generated, first in the near infra-red and then it is frequency-doubled into the visible spectral range. Using a MUSE-type spectrograph, we evaluate the comb performance for astronomical wavelength calibration in terms of equidistancy of the comb lines and their stability. Fil: Zajnulina, M.. Leibniz Institute for Astrophysics Potsdam; Alemania Fil: Chavez Boggio, J. M.. Leibniz Institute for Astrophysics Potsdam; Alemania Fil: Böhm, M.. Universitat Potsdam; Alemania Fil: Rieznik, Andrés Anibal. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Tecnológico de Buenos Aires; Argentina Fil: Fremberg, T.. Leibniz Institute for Astrophysics Potsdam; Alemania Fil: Haynes, R.. Leibniz Institute for Astrophysics Potsdam; Alemania Fil: Roth, M. M.. Leibniz Institute for Astrophysics Potsdam; Alemania

A comprehensive design of a folded-architecture arrayed-waveguide-grating (AWG)-device, targeted at applications as integrated photonic spectrographs (IPS) in near-infrared astronomy, is presented. The AWG structure is designed for the astronomical H-band (1500 nm–1800 nm) with a theoretical maximum resolving power R = 60,000 at 1630 nm. The geometry of the device is optimized for a compact structure with a footprint of 5.5 cm × 3.93 cm on SiO 2 platform. To evaluate the fabrication challenges of such high-resolution AWGs, effects of random perturbations of the effective refractive index (RI) distribution in the free propagation region (FPR), as well as small variations of the array waveguide optical lengths are numerically investigated. The results of the investigation show a dramatic degradation of the point spread function (PSF) for a random effective RI distribution with variance values above ∼ 10 - 4 for both the FPR and the waveguide array. Based on the results, requirements on the fabrication technology for high-resolution AWG-based spectrographs are given in the end.

To our knowledge, efficient generation of broadband four-wave mixing cascades centered at 1 μm and spanning 600 nm is experimentally demonstrated for the first time. This frequency comb is generated from a two-tone seed with a maximum peak power of 25 W in a low-dispersion photonic crystal fiber. It consists of up to 44 new idler waves generated symmetrically around the seed.

The 4MOST Facility is a high-multiplex, wide-field, brief-fed spectrograph system for the ESO VISTA telescope. It aims to create a world-class spectroscopic survey facility unique in its combination of wide-field multiplex, spectral resolution, spectral coverage, and sensitivity. At the end of 2014, after a successful concept optimization design phase, 4MOST entered into its Preliminary Design Phase. Here we present the process and tools adopted during the Preliminary Design Phase to define the subsystems specifications, coordinate the interface control documents and draft the system verification procedures.

We review the potential of Astrophotonics, a relatively young field at the interface between photonics and astronomical instrumentation, for spectro-interferometry. We review some fundamental aspects of photonic science that drove the emer- gence of astrophotonics, and highlight the achievements in observational astrophysics. We analyze the prospects for further technological development also considering the potential synergies with other fields of physics (e.g. non-linear optics in condensed matter physics). We also stress the central role of fiber optics in routing and transporting light, delivering complex filters, or interfacing instruments and telescopes, more specifically in the context of a growing usage of adaptive optics., SPIE Astronomical Telescopes and Instrumentation conference, June 2016, 21 pages, 10 Figures

The 4MOST instrument is a multi-object-spectrograph for the ESO-VISTA telescope. The 4MOST fiber feed subsystem is composed of a fiber positioner (AESOP) holding 2436 science fibers based on the Echidna tilting spine concept, and the fiber cable, which feeds two low-resolution spectrographs (1624 fibers) and one high-resolution spectrograph (812 fibers). In order to optimize the fiber feed subsystem design and provide essential information required for the spectrograph design, prototyping and testing has been undertaken. In this paper we give an overview of the current fiber feed subsystem design and present the preliminary FRD, scrambling, throughput and system performance impact results for: maximum and minimum spine tilt, fiber connectors, cable de-rotator simulator for fiber cable lifetime tests.

After having demonstrated that an IFU, attached to a microscope rather than to a telescope, is capable of differentiating complex organic tissue with spatially resolved Raman spectroscopy, we have launched a clinical validation program that utilizes a novel optimized fiber-coupled multi-channel spectrograph whose layout is based on the modular MUSE spectrograph concept. The new design features a telecentric input and has an extended blue performance, but otherwise maintains the properties of high throughput and excellent image quality over an octave of wavelength coverage with modest spectral resolution. We present the opto-mechanical layout and details of its optical performance., Comment: 13 pages, 13 figures. Submitted in SPIE Astronomical Telescopes + Instrumentation, Paper No. 9912-72

In this paper, we study how the spectral information is transmitted through a 1:61 photonic lantern (PL) when illuminating the multimode (MM) end with a point source. We found that the spectrum undergoes two major effects between the MM input and the independent single-mode (SM) outputs of the PL. First, at resolution R = 775 (at 1550 nm), the overall output spectrum envelope strongly differs from SM to SM outputs. The spectra measured at the 61 SM outputs also vary when the small point object (10 μm in diameter, compared with the 100 μm diameter MM core) is moved across the MM fibre end-face of the PL. However, the sum of all the spectra measured at the SM outputs is very close to the spectrum of the point source, and is insensitive to the position of the point source. Secondly, at resolution R = 77 500 a fine 150 pm periodic structure was observed at the SM outputs. We found that a PL in the MM–SM configuration (i.e. MM input/SM outputs) is a very stable system regarding variations of the transmitted spectra when it is left mechanically non-perturbated and only submitted to environment-related changes, compared to a conventional step-index MM fibre of same core diameter. The latter clearly shows characteristic modal noise. Furthermore, we showed that at resolution R = 77 500 the sum of the spectra measured at 61 the SM outputs is very close to the spectrum of the point source, and does not present the 150 pm periodic oscillations. We also studied two PLs spliced together in the MM–SM–MM configuration and the results showed that the spliced PLs perform very well as mode scramblers, especially under conditions where conventional step-index MM fibres usually fail at performing effective scrambling.

The background noise between 1 and 1.8 microns in ground-based instruments is dominated by atmospheric emission from hydroxyl molecules. We have built and commissioned a new instrument, GNOSIS, which suppresses 103 OH doublets between 1.47 - 1.7 microns by a factor of ~1000 with a resolving power of ~10,000. We present the first results from the commissioning of GNOSIS using the IRIS2 spectrograph at the AAT. The combined throughput of the GNOSIS fore-optics, grating unit and relay optics is ~36 per cent, but this could be improved to ~46 per cent with a more optimal design. We measure strong suppression of the OH lines, confirming that OH suppression with fibre Bragg gratings will be a powerful technology for low resolution spectroscopy. The integrated OH suppressed background between 1.5 and 1.7 microns is reduced by a factor of 9 compared to a control spectrum using the same system without suppression. The potential of low resolution OH suppressed spectroscopy is illustrated with example observations. The GNOSIS background is dominated by detector dark current below 1.67 microns and by thermal emission above 1.67 microns. After subtracting these we detect an unidentified residual interline component of ~ 860 +/ 210 ph/s/m^2/micron/arcsec^2. This component is equally bright in the suppressed and control spectra. We have investigated the possible source of the interline component, but were unable to discriminate between a possible instrumental artifact and intrinsic atmospheric emission. Resolving the source of this emission is crucial for the design of fully optimised OH suppression spectrographs. The next generation OH suppression spectrograph will be focussed on resolving the source of the interline component, taking advantage of better optimisation for a FBG feed. We quantify the necessary improvements for an optimal OH suppressing fibre spectrograph design.

Dynamic spectral analysis of astronomical events has the potential to deliver the information needed to clarify or complete important theoretical descriptions of astronomical phenomena. There is currently a lack of detailed sub-minute observations due to limitations in instruments and detectors. Here, we present an investigation into the feasibility of using fibre Bragg gratings (FBGs) as single-line spectral filters specifically for temporal spectral astronomy, attaining both a high spectral and fast temporal resolution simultaneously. We present the device concept and discuss it in the context of two readily available FBG profiles. We demonstrate that this instrument concept could resolve spectral shifts down to 0.02 nm (3.9 km s −1 ) with sub-second temporal resolution on a 4-m class telescope, which is far superior to existing techniques that attain resolutions of 0.05 nm over several minutes.

Fibre Multi-Object Spectrograph (FMOS) is the first near-infrared instrument with a wide field of view capable of acquiring spectra simultaneously from up to 400 objects. It has been developed as a common-use instrument for the F=2 prime-focus of the Subaru Telescope. The field coverage of 300 diameter is achieved using a new 3-element corrector optimized in the near-infrared (0.9-1.8μm) wavelength range. Due to limited space at the prime-focus, we have had to develop a novel fibre positioner, called " Echidna" , together with two OH-airglow suppressed spectrographs. FMOS consists of three subsystems: the prime focus unit for IR, the fibre positioning system/connector units, and the two spectrographs. After full systems integration, FMOS was installed on the telescope in late 2007. Many aspects of the performance were checked through various test and engineering observations. In this paper, we present the optical and mechanical components of FMOS, and show the results of our on-sky engineering observations to date. © 2010. Astronomical Society of Japan.

The Phase A design study of PILOT–the Pathfinder for an International Large Optical Telescope–has demonstrated that a wide-field 2.5 m optical/IR telescope can be constructed at Concordia for a reasonable cost. There are no technical “show stoppers”, and the cost of logistics is also quantifiable and reasonable. A strong science case has been developed and published as three separate papers. In order to proceed further, the next step is to undertake a detailed design study and identify potential manufacturers.

Background and Method: This study surveyed need in a group of psychiatric patients in Gloucester, using a new instrument, the CUES. Keyworkers gave out questionnaires to all patients with psychosis in contact with specialist services. A total of 148 forms were anonymously completed, with a response rate of 37% of the mental health services caseload. Results: 53.5 to 83.2% of patients were satisfied and 61.5 to 89.6% expressed their experiences ‘as good as’ a normative statement across the 16 domains. There was mostly ‘moderate’ agreement between satisfaction and normative questions by Kappa correlations, although responses to normative questions tended to be about 10% higher. Extensive free text responses were subject to content analysis, demonstrating needs across a wide range of health, social and leisure areas, many of which were not directly linked to the adequacy or otherwise of psychiatric treatment. Conclusions: The results imply that the CUES may be of value at an individual level to aid in care planning, and also have some value in aggregated form to benchmark user experiences of services.

We present a new accurate measurement of the HI mass function of galaxies from the HIPASS Bright Galaxy Catalog, a sample of 1000 galaxies with the highest HI peak flux densities in the southern hemisphere (Koribalski et al. 2003). This sample spans nearly four orders of magnitude in HI mass (from log M_HI/M_sun=6.8 to 10.6, H0=75) and is the largest sample of HI selected galaxies to date. We develop a bivariate maximum likelihood technique to measure the space density of galaxies, and show that this is a robust method, insensitive to the effects of large scale structure. The resulting HI mass function can be fitted satisfactorily with a Schechter function with faint-end slope alpha=-1.30. This slope is found to be dependent on morphological type, with later type galaxies giving steeper slopes. We extensively test various effects that potentially bias the determination of the HI mass function, including peculiar motions of galaxies, large scale structure, selection bias, and inclination effects, and quantify these biases. The large sample of galaxies enables an accurate measurement of the cosmological mass density of neutral gas: Omega_HI=(3.8 +/- 0.6) x 10^{-4}. Low surface brightness galaxies contribute only 15% to this value, consistent with previous findings.

Background: Service planning based on aggregated needs assessment is rarely practised. There is a lack of research into how population-based needs assessment approaches can be translated into routine clinical settings. Aims: This study aimed to ascertain the 2-month period prevalence of psychosis in Gloucester City, to investigate the level of need among those in contact with mental health services, and to identify the compromises which are involved in routine collection of data to inform services, compared with specifically funded research studies. Method People with ICD-10 diagnosis of functional psychosis were identified by searching General Practice and mental health service records in Gloucester City. The needs of the sub-sample in touch with mental health services were assessed using the Camberwell Assessment of Need Short Appraisal Schedule (CANSAS). Results: Four hundred and seventy-four cases were identified, including 403 in contact with mental health services. Staff CANSAS data were collected for 225 patients, with a mean rating of 7.0 met and 3.6 unmet needs per patient. Unmet need was higher in the non-Caucasian group. Conclusions: In this locality, patients with functional psychosis were largely in contact with mental health services, were in employment, were disproportionately looked after by a few City centre General Practitioners, and high levels were in supported accommodation. Higher levels of need were found than previously demonstrated. Systematic assessment of needs with research instruments to contribute to locality service planning is possible without a major research grant, but involves compromises on established research designs.

We present a Parkes multibeam H i survey of the Large Magellanic Cloud (LMC). This survey, which is sensitive to spatial structure in the range 200 pc ∼ 10 kpc, complements the Australia Telescope Compact survey, which is sensitive to structure in the range 15 pc ∼ 500 pc. With an rms column density sensitivity of 8 ×10 16 cm −2 for narrow lines and 4×10 17 cm −2 for typical linewidths of 40 km s −1 , emission is found to be extensive well beyond the main body of the LMC. Arm-like features extend from the LMC to join the Magellanic Bridge and the Leading Arm, a forward counterpart to the Magellanic Stream. These features, whilst not as dramatic as those in the SMC, appear to have a common origin in the Galactic tidal field, in agreement with recent 2MASS and DENIS results for the stellar population. The diffuse gas which surrounds the LMC, particularly at pa’s 90 ◦ to 330 ◦ , appears to be loosely associated with tidal features, but loosening by the ram pressure of tenuous Galactic halo gas against the outer parts of the LMC cannot be discounted. High-velocity clouds, which lie between the Galaxy and the LMC in velocity and which appear in the UV spectra of some LMC stars, are found to be associated with the LMC if their heliocentric velocity exceeds about +100 km s −1 . They are possibly the product of energetic outflows from the LMC disk. The H i mass of the LMC is found to be (4.8 ± 0.2) × 10 8 M⊙ (for an assumed distance of 50 kpc), substantially more than previous recent measurements.

Multi-core fiber Bragg gratings (MCFBGs) will be a valuable tool not only in communications but also various astronomical, sensing and industry applications. In this paper we address some of the technical challenges of fabricating effective multi-core gratings by simulating improvements to the writing method. These methods allow a system designed for inscribing single-core fibers to cope with MCFBG fabrication with only minor, passive changes to the writing process. Using a capillary tube that was polished on one side, the field entering the fiber was flattened which improved the coverage and uniformity of all cores.

The 4MOST Facility is a very high-multiplex, wide-field, fibre-fed spectrograph system for the VISTA telescope. Its aim is to create a world-class spectroscopic survey facility that is unique in its combination of wide-field multiplex, spectral resolution and coverage, and sensitivity. In such a complex instrumentation project, in which design and development activities are geographically distributed, a formal system engineering approach is essential for the success of the project. We present an overview of the systems engineering principles, and associated tools, implemented during the conceptual design phase, as well as the systems engineering activities planned for the preliminary design phase.

TOAD, the “Top Of the Atmosphere to Detector” simulator, is a primary engineering tool that accompanies the development of the 4MOST instrument. The ultimate goal is to provide a detailed, end-to-end performance model of 4MOST by providing the detector image for an artificial target field with less then 5% error. TOAD will be able to create a realistic output for any reasonable input. The input can be anything, from point sources through extended sources, calibration lamps or stray-light, entering the system at virtually any point in a optical path. During the development of the 4MOST facility, the TOAD simulator will give invaluable insight into the interaction of various parts of the instrument and the impact of engineering design decisions on the system performance.

4MOST,1 the 4m Multi-Object spectrographic Survey Telescope, is an upcoming optical, fiber-fed, MOS facility for the VISTA telescope at ESO's Cero Paranal Observatory (Chile). The preliminary design of 4MOST features 2,400 fibers split into a low-resolution (1,600 fibers, 390-900 nm, R > 5; 000) and a high-resolution channel (800 fibers, three arms, ~20-25 nm coverage each, R > 18; 000) with an Echidna-style positioner, and covering a hexagonal field of view of ~4.1 sqdeg. 4MOST's main science goals encompass massive (tens of millions of spectra), all-Southern sky (> 18; 000 sqdeg) surveys following up both the Gaia (optical) and eROSITA (X-ray) space missions, plus cosmological science that complements missions such as e.g. Euclid. In a novel approach, observations of these science cases, which are very different from another, are to be carried out in parallel (i.e., simultaneously); thus, from the very different science requirements, key user requirements have to be identified, stringently formulated, and condensed into a coherent set of system specifications. Clearly, identifying common grounds and thereby significantly reducing complexity in both the formulated requirements and the final 4MOST facility, is a very challenging task. In this paper, we will present science and user requirements, and how the latter flow down from the former, and eventually further down to the system-specification level. Special emphasis will be put on the identification of key requirements and their validation and verification protocols, so that significant trade-offs can be done as early on in the design phase as possible, with as little impact as possible on the science capabilities upstream.

We here report on recent progress on astronomical optical frequency comb generation at innoFSPEC-Potsdam and present preliminary test results using the fiber-fed Multi Unit Spectroscopic Explorer (MUSE) spectrograph. The frequency comb is generated by propagating two free-running lasers at 1554.3 and 1558.9 nm through two dispersionoptimized nonlinear fibers. The generated comb is centered at 1590 nm and comprises more than one hundred lines with an optical-signal-to-noise ratio larger than 30 dB. A nonlinear crystal is used to frequency double the whole comb spectrum, which is efficiently converted into the 800 nm spectral band. We evaluate first the wavelength stability using an optical spectrum analyzer with 0.02 nm resolution and wavelength grid of 0.01 nm. After confirming the stability within 0.01 nm, we compare the spectra of the astro-comb and the Ne and Hg calibration lamps: the astro-comb exhibits a much larger number of lines than lamp calibration sources. A series of preliminary tests using a fiber-fed MUSE spectrograph are subsequently carried out with the main goal of assessing the equidistancy of the comb lines. Using a P3d data reduction software we determine the centroid and the width of each comb line (for each of the 400 fibers feeding the spectrograph): equidistancy is confirmed with an absolute accuracy of 0.4 pm.

We present results of comprehensive re-design of an arrayed waveguide grating (AWG)-based integrated photonic spectrograph (IPS), using Silica-on-Silicon (SOS) technology, to tailor specific performance parameters of interest to high-resolution (resolving power, R = lambda/Delta.lambda = 60,000) exoplanet astronomy and stellar seismology. The compactness, modularity, stability, replicability and small-lightweight-payload of the IPS are a few promising and innovative features in the design of high-resolution spectrographs for astronomy or other areas of sciences. The IPS is designed to resolve up to 646 spectral lines per spectral order, with a wavelength spacing of 25 pm, at a central wavelength of 1630 nm (Hband). The fabricated test waveguides have been stress engineered in order to compensate the inherent birefringence of SOS waveguides. The birefringence values of fabricated test structures were quantified, to be on the order 10-6 (theoretical value required to avoid the formation of ghost-images), through inscription of Bragg-gratings on straight waveguides and subsequent measurement of Bragg-reflection spectra. An interferometer system has been integrated with the SOS-IPS (in the same chip) for the characterization of phase errors of the waveguide array. Moreover, promising results of first fabricated key photonics components to form other complex integrated photonic circuits (IPCs), such as astro-interferometers, using silicon nitride-on-insulator (SNOI) technology are also presented. The fabricated IPCs include multimode interference based devices (power splitter/combiners, optical cross/bar-switches), directional-couplers with varying power ratios, Mach-Zehnder interferometers and an AWG. The first results of annealed, low-hydrogen SNOI based devices are promising and comparable to SOI and commercial devices, with device excess-loss less than 2 dB and under 1 dB/cm waveguide-loss in the IR-wavelength.

We present a new type of R-θ fiber actuator named PotsPos for multi-object astronomical spectroscopy. It was initially intended to use as an alternative positioner design for the 4-meter Multi-Object Spectroscopic Telescope (4MOST). Although another tilting spine technology developed by the Australian Astronomical Observatory (AAO) is currently chosen for the 4MOST, PotsPos design has some technical advantages over other positioning technologies and might therefore be an attractive choice for future spectrographs. The design would be similar in positioning capabilities to the tilting spine design but would not suffer from telecentricity and defocus errors. The mechanical design, suitable motors, computational results from dynamic simulations and finite element analyses are presented.

PRAXIS is a second generation instrument that follows on from GNOSIS, which was the first instrument using fibre Bragg gratings for OH background suppression. The Bragg gratings reflect the NIR OH lines while being transparent to light between the lines. This gives a much higher signal-noise ratio at low resolution but also at higher resolutions by removing the scattered wings of the OH lines. The specifications call for high throughput and very low thermal and detector noise so that PRAXIS will remain sky noise limited. The optical train is made of fore-optics, an IFU, a fibre bundle, the Bragg grating unit, a second fibre bundle and a spectrograph. GNOSIS used the pre-existing IRIS2 spectrograph while PRAXIS will use a new spectrograph specifically designed for the fibre Bragg grating OH suppression and optimised for 1470 nm to 1700 nm (it can also be used in the 1090 nm to 1260 nm band by changing the grating and refocussing). This results in a significantly higher transmission due to high efficiency coatings, a VPH grating at low incident angle and low absorption glasses. The detector noise will also be lower. Throughout the PRAXIS design special care was taken at every step along the optical path to reduce thermal emission or stop it leaking into the system. This made the spectrograph design challenging because practical constraints required that the detector and the spectrograph enclosures be physically separate by air at ambient temperature. At present, the instrument uses the GNOSIS fibre Bragg grating OH suppression unit. We intend to soon use a new OH suppression unit based on multicore fibre Bragg gratings which will allow increased field of view per fibre. Theoretical calculations show that the gain in interline sky background signal-noise ratio over GNOSIS may very well be as high as 9 with the GNOSIS OH suppression unit and 17 with the multicore fibre OH suppression unit., SPIE conference proceedings 9151

We present a new type of multicore fiber (MCF) and photonic lantern that consists of 511 individual cores designed to operate over a broadband visible wavelength range (380-860nm). It combines the coupling efficiency of a multimode fiber with modal stability intrinsic to a single mode fibre. It is designed to provide phase and amplitude scrambling to achieve a stable near field and far field illumination pattern during input coupling variations; it also has low modal noise for increased photometric stability. Preliminary results are presented for the new MCF as well as current state of the art octagonal fiber for comparison.

The innovation of optical frequency combs (OFCs) generated in passive mode-locked lasers has provided astronomy with unprecedented accuracy for wavelength calibration in high-resolution spectroscopy in research areas such as the discovery of exoplanets or the measurement of fundamental constants. The unique properties of OCFs, namely a highly dense spectrum of uniformly spaced emission lines of nearly equal intensity over the nominal wavelength range, is not only beneficial for high-resolution spectroscopy. Also in the low- to medium-resolution domain, the OFCs hold the promise to revolutionise the calibration techniques. Here, we present a novel method for generation of OFCs. As opposed to the mode-locked laser-based approach that can be complex, costly, and difficult to stabilise, we propose an all optical fibre-based system that is simple, compact, stable, and low-cost. Our system consists of three optical fibres where the first one is a conventional single-mode fibre, the second one is an erbium-doped fibre and the third one is a highly nonlinear low-dispersion fibre. The system is pumped by two equally intense continuous-wave (CW) lasers. To be able to control the quality and the bandwidth of the OFCs, it is crucial to understand how optical solitons arise out of the initial modulated CW field in the first fibre. Here, we numerically investigate the pulse evolution in the first fibre using the technique of the solitons radiation beat analysis. Having applied this technique, we realised that formation of higherorder solitons is supported in the low-energy region, whereas, in the high-energy region, Kuznetsov-Ma solitons appear.

4MOST, the 4m Multi-Object Spectroscopic Telescope, features a 2.5 degree diameter field-of-view with ~2400 fibers in the focal plane that are configured by a fiber positioner based on the tilting spine principle (Echidna/FMOS) arranged in a hexagonal pattern. The fibers feed two types of spectrographs; ~1600 fibers go to two spectrographs with resolution R>5000 and ~800 fibers to a spectrograph with R>18,000. Part of the ongoing optimization of the fiber feed subsystem design includes early prototyping and testing of key components such as fiber connectors and fiber cable management. Performance data from this testing will be used in the 4MOST instrument simulator (TOAD) and 4MOST system design optimization. In this paper we give an overview of the current fiber feed subsystem design, simulations and prototyping plans.

The 4MOST([1]) instrument is a concept for a wide-field, fibre-fed high multiplex spectroscopic instrument facility on the ESO VISTA telescope designed to perform a massive (initially >25x10(6) spectra in 5 years) combined all-sky public survey. The main science drivers are: Gaia follow up of chemo-dynamical structure of the Milky Way, stellar radial velocities, parameters and abundances, chemical tagging; eROSITA follow up of cosmology with x-ray clusters of galaxies, X-ray AGN/galaxy evolution to z similar to 5, Galactic X-ray sources and resolving the Galactic edge; Euclid/LSST/SKA and other survey follow up of Dark Energy, Galaxy evolution and transients. The surveys will be undertaken simultaneously requiring: highly advanced targeting and scheduling software, also comprehensive data reduction and analysis tools to produce high-level data products. The instrument will allow simultaneous observations of similar to 1600 targets at R similar to 5,000 from 390-900nm and similar to 800 targets at R>18,000 in three channels between similar to 395-675nm (channel bandwidth: 45nm blue, 57nm green and 69nm red) over a hexagonal field of view of similar to 4.1 degrees2. The initial 5-year 4MOST survey is currently expect to start in 2020. We provide and overview of the 4MOST systems: opto-mechanical, control, data management and operations concepts; and initial performance estimates.

4MOST is a wide-field, high-multiplex spectroscopic survey facility under development for the VISTA telescope of the European Southern Observatory (ESO). Its main science drivers are in the fields of galactic archeology, high-energy physics, galaxy evolution and cosmology. 4MOST will in particular provide the spectroscopic complements to the large area surveys coming from space missions like Gaia, eROSITA, Euclid, and PLATO and from ground-based facilities like VISTA, VST, DES, LSST and SKA. The 4MOST baseline concept features a 2.5 degree diameter field-of-view with similar to 2400 fibres in the focal surface that are configured by a fibre positioner based on the tilting spine principle. The fibres feed two types of spectrographs; similar to 1600 fibres go to two spectrographs with resolution R> 5000 (lambda similar to 390-930 nm) and similar to 800 fibres to a spectrograph with R> 18,000 (lambda similar to 392-437 nm & 515-572 nm & 605-675 nm). Both types of spectrographs are fixed-configuration, three-channel spectrographs. 4MOST will have an unique operations concept in which 5 year public surveys from both the consortium and the ESO community will be combined and observed in parallel during each exposure, resulting in more than 25 million spectra of targets spread over a large fraction of the southern sky. The 4MOST Facility Simulator (4FS) was developed to demonstrate the feasibility of this observing concept. 4MOST has been accepted for implementation by ESO with operations expected to start by the end of 2020. This paper provides a top-level overview of the 4MOST facility, while other papers in these proceedings provide more detailed descriptions of the instrument concept[1], the instrument requirements development[2], the systems engineering implementation[3], the instrument model[4], the fibre positioner concepts[5], the fibre feed[6], and the spectrographs[7].

Long period grating was UV inscribed into a multicore fiber consisting of 120 single mode cores. The multicore fiber that hosts the grating was fusion spliced into a single mode fiber at both ends. The splice creates a taper transition between the two types of fiber that produces a nonadiabatic mode evolution; this results in the illumination of all the modes in the multicore fiber. The spectral characteristics of this fiber device as a function of curvature were investigated. The device yielded a significant spectral sensitivity as high as 1.23 nm/m(-1) and 3.57 dB/m(-1) to the ultra-low curvature values from 0 to 1 m(-1). This fiber device can also distinguish the orientation of curvature experienced by the fiber as the long period grating attenuation bands producing either a blue or red wavelength shift. The finite element method (FEM) model was used to investigate the modal behavior in multicore fiber and to predict the phase-matching curves of the long period grating inscribed into multicore fiber.

Dispersion engineering in silicon nitride (SiX NY ) waveguides is investigated through the optimization of the waveguide transversal dimensions and refractive indices in a multi-cladding arrangement. Ultra-flat dispersion of -84.0 +/- 0.5 ps/nm/km between 1700 and 2440 nm and 1.5 +/- 3 ps/nm/km between 1670 and 2500 nm is numerically demonstrated. It is shown that typical refractive index fluctuations as well as dimension fluctuations during the fabrication of the SiX NY waveguides are a limitation for obtaining ultra-flat dispersion profiles. Single- and multi-cladding waveguides are fabricated and their dispersion profiles measured (over nearly 1000 nm) using a low-coherence frequency domain interferometric technique. By appropriate thickness optimization, the zero-dispersion wavelength is tuned over a large spectral range in both single-cladding waveguides and multi-cladding waveguides with small refractive index contrast (3 %). A flat dispersion profile with 3.2 ps/nm/km variation over 500 nm is obtained in a multi-cladding waveguide fabricated with a refractive index contrast of 37 %. Finally, we generate a nearly three-octave supercontinuum in this dispersion flattened multi-cladding SiX NY waveguide.

Dispersion-flattening in silicon-nitride waveguides (dispersion variation of 2ps/nm/km over 500nm) is demonstrated by optimizing the parameters of three cladding layers. SC generation spanning three octaves is shown in those waveguides.

As part of ongoing efforts towards development of integrated optoelectronic platforms on a single chip, specifically integrated photonic spectrographs for Astronomy, we report numerical and experimental results from dispersion engineering in integrated silicon nitride waveguides.

Microlens arrays are now widely used in a variety of astronomical instruments that require high performance. This paper describes the applications of microlenses in astronomical spectroscopy and discusses the necessary performance requirements. A variety of optical tests, including high dynamic range point-spread function measurements and determination of encircled energy, were developed to characterize the performance of a variety of lenslet arrays. Results are presented that indicate the best types of lenslet array for use for astronomical spectroscopy.

A blind survey for HI bright galaxies in the southern Zone of Avoidance, (212 deg < l < 36 deg; |b| < 5 deg), has been made with the 21 cm multibeam receiver on the Parkes 64 m radiotelescope. The survey, sensitive to normal spiral galaxies to a distance of about 40 Mpc and more nearby dwarfs, detected 110 galaxies. Of these, 67 have no counterparts in the NASA/IPAC Extragalactic Database. In general, the uncataloged galaxies lie behind thicker obscuration than do the cataloged objects. All of the newly-discovered galaxies have HI flux integrals more than an order of magnitude lower than the Circinus galaxy. The survey recovers the Puppis cluster and foreground group (Kraan-Korteweg & Huchtmeier 1992), and the Local Void remains empty. The HI mass function derived for the sample is satisfactorily fit by a Schechter function with parameters alpha = 1.51 +- 0.12, Phi* = 0.006 +- 0.003, and log M* = 9.7 +- 0.10.

Starbug is a new concept for a robotic positioning system able to deploy many payloads, such as pickoff optics, optical fibres, integral field units over the focal surface of a telescope. Aimed at addressing some of the weakness of current positioning systems, Starbug employs micro-robotic actuators to independently and simultaneously position multiple small payloads accurately on an arbitrarily large field plate. Targeted at offering a cost-effective positioning system for both optical and infrared instrumentation it is being developed to; operate in cryogenic environments, position to micron level resolution, simultaneous move arbitrary numbers of payloads and included micro-tracking for minor positional adjustments that could compensate for differential atmospheric refraction effects and instrument flexure.

MMI-based sub-micron planar waveguide architectures, with 15μm access waveguide separation to enable highintegration density, show higher tolerance to fabrication artifacts. The first results show 3-4 dB device insertion loss and around 1dB/cm waveguide loss.

Dispersion engineering in integrated silicon nitride waveguides is numerically and experimentally investigated. We show that by modifying the transversal dimensions of the silicon nitride core, it is possible to have a good control of the chromatic dispersion. The inaccuracies due to typical fabrication process in PECD-Si X N Y films shows that the dispersion uncertainty is in the order of 20 ps/nm-km at 1550 nm. Silicon nitride waveguides were then fabricated using the same PECVD process and the chromatic dispersion was measured using a low-coherence frequency domain interferometry technique. A comparison between measurements and simulations shows good agreement.

Silicon nitride ring resonators with diameter of 250 and 500 μm are fabricated and their spectral characteristics investigated with the ultimate goal of optical frequency comb generation for astronomical spectrograph calibration. A continuously tunable laser was used to evaluate the spectral characteristics (propagation losses and transmission properties) of PECVD silicon nitride waveguides and ring-resonators. Losses were measured to be smaller than 0.75 dB/cm over the range between 1500 nm and 1620 nm. The transmission properties of the fabricated ring resonators were assessed for the TE and TM modes, showing promise for the ultimate goal of astronomical optical frequency comb generation.