THE INTEGRATED PHOTONIC SPECTROGRAPH MULTIPLE OFF-AXIS INPUTS AND TELESCOPE RESULTS

1. THE INTEGRATED PHOTONIC SPECTROGRAPH • MULTIPLE OFF-AXIS INPUTS AND TELESCOPE RESULTS • Nick Cvetojevic1,2, Nemanja Jovanovic1,2, Joss Bland-Hawthorn3, Roger Haynes4, Mick Withford5, and Jon Lawrence1,2 • 1. Department of Physics and Astronomy, Macquarie University, NSW, 2109, Australia • 2. Australian Astronomical Observatory, NSW, 2122, Australia • 3. Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW, 2006, Australia • innoFSPEC, Astrophysikalisches Institut Potsdam, Potsdam, 14482, Germany • CUDOS, Centre for Ultra-high Bandwidth Devices for Optical Systems, Australia

2. The Integrated Photonic Spectrograph • A complete “spectrograph on a chip” for astronomy • Fully integrated photonic platform with no moving parts, no alignment, high stability • Mass-producible and small

3. Current-Generation Spectrographs Existing spectrographs for astronomy are very large, full of custom built parts, and very expensive Component & Spectrograph Size increases with Telescope Diameter 2 Cost ~ Diameter ! Bland-Hawthorn & Horton (2006) http://www.astronomy.com/asy/default.aspx?c=a&id=2863

4. Non-Monolithic Designs Why not use a multitude of smaller, cheaper, replaceable spectrographs to do the same thing? Ideal for fiber-fed multi-object spectroscopy VIRUS Identical modules combine to form one large spectrograph 25% of the cost of the monolithic design Still very large! http://www.as.utexas.edu/hetdex/

5. The Spectrograph Chip • Silica chip with an lithographically written Arrayed Waveguide Grating structure • Typically used in Telecommunication Networks

6. Focal Surface The Spectrograph Chip Arrayed Waveguide Grating Array of Waveguides Output Free Propagation Zone Input Free Propagation Zone Input Fibre

7. The Photonic Lantern Converts a Multimode fibre into multiple Single Mode fibres for efficient interfacing with a telescope 1x MMF with N modes N x SMF Photonic Lantern

8. Arrayed Waveguide Grating Photonic Lantern Simultaneous Multi-Fibre Input By interfacing multiple SMFs to one chip we can increase its observational efficiency and reduce the total amount of chips used

9. Multiple Off-Axis Fibre Launch So what happens to the spectral output when inputting multiple fibres? Waveguide Array Free Prop. Zone 1550 nm

10. Blue Red We would assume that if the fibres are offset enough for the FSR not to overlap we could get separate spectra on the output Top View Front View Fibre #1 Fibre #2 Fibre #3 Unfortunately this is not the case!

11. Blue Red This causes the spectra to be superimposed regardless of the fibre input position Top View Front View However, if we use a cross-disperser we can uncouple the spectra from the different fibres Fibre #1 Fibre #2 Fibre #3

12. Blue Higher Orders Blue Cross Dispersed Red Red Red Blue If cross-dispersed, we can simultaneously record the spectra from multiple fibres. We can fit as many as the gap between the orders allows. Front View Fibre #2 Fibre #3 Fibre #1 Fibre #1 Fibre #2 Fibre #3 12-14 Fibres at 125 um spacing

13. The AAT

14. The Demonstrator Instrument Lenslet Array Multimode Fibres 12x SMF Photonic Lantern

15. The initial IPS setup • 3 different setups on one assembly. • Designed to be interchanged on the night

16. The initial IPS setup Laser @ 1550nm

17. The initial IPS setup • Setup #1 – Wide wavelength window, Medium resolution • R ~5000, full H-Band, 12 SMF, 1 MMF • Setup #2 – Highest resolution, Small wavelength coverage. • R ~7000, 50nm wide band, 14 SMF, 1 MMF • Setup #3 – 2 Chips on one detector, Anamorphic optics • R ~2000, full H-Band, 24 SMF, 2 MMF

18. The Boss supervising The IPS going on the AAT

19. The initial IPS setup Unfortunately, initial tests showed we were not getting enough light through and approaching the noise floor of our detector. Our detector was not sensitive enough We decided to use IRIS2, and MacGyvered together a new interface between the IPS and IRIS2

20. The Raw Results Antares Different Orders 1450 nm 1780 nm Spectra from individual Fibres

21. The Raw Results alf Ara (Be Star) V* Pi 01 Gru (Cold red giant)

22. Conclusion • We have demonstrated simultaneous input of multiple single mode fibres directly into an AWG chip is possible and practical for Astronomy • If used, cross dispersion is all but essential • We have successfully demonstrated the first IPS-like device on a telescope, with spectra taken from 3 different types of stars. • Currently, redesigning the AWG chips to improve FSR, R, Wavelength • Looking at using AO systems to directly couple into SMF

23. THANK YOU