THE INTEGRATED PHOTONIC SPECTROGRAPH MULTIPLE OFF-AXIS INPUTS AND TELESCOPE RESULTS Nick Cvetojevic 1,2, Nemanja Jovanovic 1,2, Joss Bland-Hawthorn 3, Roger Haynes 4, Mick Withford 5, and Jon Lawrence 1,2 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 4.innoFSPEC, Astrophysikalisches Institut Potsdam, Potsdam, 14482, Germany 5.CUDOS, Centre for Ultra-high Bandwidth Devices for Optical Systems, Australia

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

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 Cost ~ Diameter ! 2 Bland-Hawthorn & Horton (2006)

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

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

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

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

Photonic Lantern Arrayed Waveguide Grating 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

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

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

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

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

The AAT

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

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

The initial IPS setup 1550nm

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

The Boss supervising The IPS going on the AAT

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

The Raw Results Antares 1450 nm1780 nm Different Orders Spectra from individual Fibres

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

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

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