Astrophotonics

Objectives

Astrophotonics is a rapidly developing field that aims to develop photonic technologies that can enhance the sensitivity and functionality of the next generation of ground-based optical/infrared instrumentation for European and Worldwide astronomical facilities, including the European Extremely Large Telescope (E-ELT). The objective of the work-package is to develop revolutionary guided-wave photonic technologies that can efficiently couple seeing-limited (un-corrected) and partially AO-corrected PSFs into highly stable and precise optical/infrared spectrographs, with very little optical loss or degradation of the signal. The two technologies underpinning the development are (i) multicore fibre (MCF) photonic lanterns, which provide ultra-low loss connections between multimode and single-mode waveguides, and (ii) 3D waveguide structures fabricated by ultrafast laser inscription (ULI), which can arbitrarily reformat the light pattern by routing the single-mode waveguides. Together, these complementary technologies can increase the stability and sensitivity of precision spectrographs by rendering their design insensitive to the telescope's focal plane parameters, embedding complex narrow line filters for low-cost, compact, robust and efficient OH suppression in the near IR, and suppressing modal noise in multimode relay fibres. Individually or in combination, they can efficiently implement diffraction-limited functions and instrumentation to benefit science cases requiring high precision and high throughput visible/NIR spectroscopy from ground-based telescopes such as extra-solar planet detection, galactic archaeology, galactic evolution and real time cosmology. The proposed revolutionary technology developments are possible because of the leverage from the multi-billion-euro industrial investments in related infrastructure and development programmes.

Description of work

The work builds on the OPTICON FP7 Astrophotonic activities and regionally funded programmes of the partners. The proposed activities will both complement and collaborate with the Adaptive Optics and Interferometry packages within this proposal, also continued (unfunded) collaborations are planned with the AAO, USYD, WHT, INAF, ZAH, Optoscribe (Industry).

1. Systems engineering

Here we will develop the top-level requirements, specifications and device/system architectures (including packaging) for each of the targeted applications, verifying the devices on-sky where possible. The activities will include developing a brief science case, the device requirements and an implementation plan based on “use case scenarios” for European instrumentation projects, e.g. ELT-MOS, ELT-HIRES. The WP is led by AIP with contributions from HWU, UBATH, UDUR and UH.

2. Multicore optical fibre and optical fibre photonic lantern development

Photonic lanterns will be designed and fabricated from multicore optical fibres for both seeing-limited and AO-corrected applications, e.g. E-ELT and VLT. The activities will include the design and fabrication of multicore fibres, the design and fabrication of photonic lanterns, and the basic characterization and (where possible) on-sky testing of the packaged devices. Devices with up to 50,000 cores and operating in the wavelength range of 360-2200 nm are feasible. The WP is led by UBATH with contributions from AIP.

3. Photonic reformatters and 3D waveguide structures

3D waveguide structures will be designed and fabricated within glass blocks using ultrafast laser inscription (ULI). The targeted activities will be divided in four areas: 3D waveguide structure optimisation, photonic reformatters (both ULI-only and hybrid fibre/ULI devices), Bragg grating devices for narrow line filtering, and ULI structures such as mid-IR photonic lantern and beam combiners for interferometry. The aim is to test the devices on-sky. The WP is led by HWU in close collaboration with AIP, UBATH and the interferometry community.

4. Modelling and optimisation of AO coupling with photonic devices.

The baseline operating mode of the E-ELT provides an AO-corrected PSF. Initial on-sky results with photonic devices installed on the CANARY AO system showed using PSF optimisation routines could greatly improve AO to photonic device coupling. However with the ability to design and write complex 3D waveguides, we can also design a photonic device that could optimally couple the AO corrected PSF. The key to this optimisation is understanding how phase aberrations in the PSF impact guided modes within the device which will be modelled by combining custom AO simulation and commercial photonics propagation codes. The performance of a device with optimised internal structure will then be installed on the UDUR AO test-bed. This will lead to on-sky tests with the CANARY AO system at the WHT. Modelling, design and laboratory characterisation of a photonic device optimised for AO-coupling will not only greatly enhance understanding of the photonic devices, but also be applicable to all future AO-fed fibre-coupled instruments. The WP is led by UDUR in close collaboration with AIP and the adaptive optics community.

5. Optimisation of astrophotonic devices for precision spectroscopy.

A stable laboratory based precision spectroscopy test-bed for astrophotonic devices will be used. It is based around an 85k resolution spectrograph designed to work at both optical and near infrared wavelengths with access to a local on-sky feed. A key element of this system is an integrated precision radial-velocity pipeline. It will provide a flexible test facility for our photonic devices that mimics state of the art telescope facilities as closely as possible. The WP is led by UH in collaboration with AIP and the precision spectroscopy community.

6. Coordination, Outreach, innovation and dissemination

The aim is to efficiently and effectively coordinate and disseminate astrophotonic developments within astronomy and other disciplines. These activities will provide logistic support for: technology transfer; dissemination into the community via websites, public media, publication, conference, workshop, trade fairs, summer schools and industrial networking events; market and roadmap analysis; maintaining community interaction; and joint collaborative activities. This will build on the OPTICON astrophotonic activities in FP6 & FP7. The WP is led by AIP with contributions from HWU, UBATH, UDUR and UH.

Key Outcomes for Astronomy

1. Low mode noise multicore scrambling fibre and photonic reformatters for precision spectroscopy.

2. Photonic OH-suppression filters for near-IR spectroscopy

3. Enhanced understanding of telescope and AO coupling with photonic devices.

4. Transfer of astrophotonic technology and techniques to applications outside astronomy, such a telecommunications, medical, biophotonics and earth science.

Benefits for Society

Additionally the programme aims to: (i) help train a new generation of engineers with specific skills in astrophotonics; (ii) work effectively with established photonics experts in academia and industry; (iii) return the benefit of any new technologies developed to industry, for the economic benefit of the community; and (iv) transfer knowledge to critical research areas such as bio-medical science, energy generation and climate research. The benefits of knowledge transfer to non-astronomical applications from this programme in both academia and industry are expected to be high and the programme plans to continue its FP7 outreach activities that including organising regular summer schools.