Towards a multi-input astrophotonic AWG spectrograph. (arXiv:1905.13241v1 [astro-ph.IM])
<a href="http://arxiv.org/find/astro-ph/1/au:+Gatkine_P/0/1/0/all/0/1">Pradip Gatkine</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Veilleux_S/0/1/0/all/0/1">Sylvain Veilleux</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hu_Y/0/1/0/all/0/1">Yiwen Hu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bland_Hawthorn_J/0/1/0/all/0/1">Joss Bland-Hawthorn</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dagenais_M/0/1/0/all/0/1">Mario Dagenais</a>
Astrophotonics is the new frontier technology to develop diffraction-limited,
miniaturized, and cost-effective instruments for the next generation of large
telescopes. For various astronomical studies such as probing the early
universe, observing in near infrared (NIR) is crucial. To address this, we are
developing moderate resolution (R = 1500) on-chip astrophotonic spectrographs
in the NIR bands (J Band: 1.1-1.4 $mu m$; H band: 1.45-1.7 $mu m$) using the
concept of arrayed waveguide gratings (AWGs). We fabricate the AWGs using a
silica-on-silicon substrate. The waveguides on these AWGs are 2 $mu m$ wide
and 0.1 $mu m$ high Si3N4 core buried inside a 15 $mu m$ thick SiO2 cladding.
To make the maximal use of astrophotonic integration such as coupling the AWGs
with multiple single-mode fibers coming from photonic lanterns or fiber Bragg
gratings (FBGs), we require a multi-input AWG design. In a multi-input AWG, the
output spectrum due to each individual input channel overlaps to produce a
combined spectrum from all inputs. This on-chip combination of light
effectively improves the signal-to-noise ratio as compared to spreading the
photons to several AWGs with single inputs. In this paper, we present the
design and simulation results of an AWG in the H band with 3 input waveguides
(channels). The resolving power of individual input channels is 1500, while the
overall resolving power with three inputs together is 500, 600, 750 in three
different configurations simulated here. The free spectral range of the device
is 9.5 nm around a central wavelength of 1600 nm. For the standard multi-input
AWG, the relative shift between the output spectra due to adjacent input
channels is about 1.6 nm, which roughly equals one spectral channel spacing. In
this paper, we discuss ways to increase the resolving power and the number of
inputs without compromising the free spectral range or throughput.
Astrophotonics is the new frontier technology to develop diffraction-limited,
miniaturized, and cost-effective instruments for the next generation of large
telescopes. For various astronomical studies such as probing the early
universe, observing in near infrared (NIR) is crucial. To address this, we are
developing moderate resolution (R = 1500) on-chip astrophotonic spectrographs
in the NIR bands (J Band: 1.1-1.4 $mu m$; H band: 1.45-1.7 $mu m$) using the
concept of arrayed waveguide gratings (AWGs). We fabricate the AWGs using a
silica-on-silicon substrate. The waveguides on these AWGs are 2 $mu m$ wide
and 0.1 $mu m$ high Si3N4 core buried inside a 15 $mu m$ thick SiO2 cladding.
To make the maximal use of astrophotonic integration such as coupling the AWGs
with multiple single-mode fibers coming from photonic lanterns or fiber Bragg
gratings (FBGs), we require a multi-input AWG design. In a multi-input AWG, the
output spectrum due to each individual input channel overlaps to produce a
combined spectrum from all inputs. This on-chip combination of light
effectively improves the signal-to-noise ratio as compared to spreading the
photons to several AWGs with single inputs. In this paper, we present the
design and simulation results of an AWG in the H band with 3 input waveguides
(channels). The resolving power of individual input channels is 1500, while the
overall resolving power with three inputs together is 500, 600, 750 in three
different configurations simulated here. The free spectral range of the device
is 9.5 nm around a central wavelength of 1600 nm. For the standard multi-input
AWG, the relative shift between the output spectra due to adjacent input
channels is about 1.6 nm, which roughly equals one spectral channel spacing. In
this paper, we discuss ways to increase the resolving power and the number of
inputs without compromising the free spectral range or throughput.
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