AstroPhotonics Technology Lab

Astrophotonics is an exciting new field marking the synergy between the science of astronomy and photonics technology. The cost and size of conventional astronomical instruments scale as the volume of the telescope (i.e., cube of the telescope diameter). But the advent of astrophotonics has opened up avenues to massively miniaturize astronomical spectrographs and reverse the cost and size spiral. With collaborators across the world, this group is working on the development and on-sky demonstration of various innovative astrophotonic devices including on-chip photonic spectrographs, photonic beam combiners, Mach-Zehnder interferometers as well as fiber-based devices such as photonic lanterns. While the main application is for astronomy and exoplanet science, several broader applications (such as telecom, sensing, etc.) are possible. Gatkine led an Astrophotonics white paper for the Astro2020 Decadal Survey. He also co-led the Astrophtonics Roadmap (along with Jovanovic), a global comprehensive effort with 25 chapters showcasing the latest developments in Astrophotonics and the challenges to be resolved in this decade.

The wide gamut of various innovative astrophotonic technologies on the horizon (from Astrophotonics Roadmap 2023).

Relevant Publications:

  1. P. Gatkine et al. Astro2020: Astrophotonics White Paper, Submitted to the National Academy of Sciences for Astro 2020 Decadal Survey, Bulletin of American Astronomical Society, 51g.285G, 2019, p1-14
  2. N. Jovanovic, P. Gatkine et al. 2023 Astrophotonics Roadmap: pathways to realizing multi-functional integrated astrophotonic instruments, JPhys Photonics, 2023.

Development of on-chip Astrophotonic Spectrographs

We are developing a variety of on-chip spectrographs built entirely from small-scale integrated photonic devices, miniaturizing the spectrometer to the size of a shoe-box. At its heart is the concept of Arrayed waveguide gratings, which allows fine-tuning of path lengths of individual light channels to get constructive interference peaks at precise locations, within a few nanometers. All of this photonic action happens on a tiny chip (~ 2cm x 2cm) fabricated using various nanofabrication processes. We are working to mature this technology for the stringent requirements in astronomy such as high-resolultion, high efficiency, broadband, and polarization independent. We aim to prepare this technology for future investigations of exoplanet atmospheres and galaxies using ground-based extremely large telescopes (ELTs) and future space missions such as Habitable Worlds Observatory (HWO).


The concept of Arrayed Waveguide Gratings. Light is channeled into an array of waveguides to create path differences to achieve the desired spectral response.

Relevant Publications:

  1. P. Gatkine et al. Potential of commercial SiN MPW platforms for developing mid/high-resolution integrated photonic spectrographs for astronomy, 2021, Applied Optics, 60(19), D15-D32
  2. P. Gatkine, S. Veilleux, M. Dagenais, Astrophotonic Spectrographs, 2019, Applied Sciences
  3. P. Gatkine et al. Arrayed waveguide grating spectrometers for astronomical applications: new results, 2017, Optics Express 25 (15), 17918-17935
  4. P. Gatkine et al. An on-chip astrophotonic spectrograph with a resolving power of 12,000, 2021, Proceedings of SPIE Volume 11819, article ID 118190I
  5. P. Gatkine et al. Development of an integrated near-IR astrophotonic spectrograph, 2020, Proceedings of SPIE Volume 11451, article ID 114516L
  6. P. Gatkine et al. Towards a multi-input astrophotonic AWG spectrograph, 2018, Proceedings of SPIE Volume 10706
  7. P. Gatkine et al. Development of high-resolution arrayed waveguide grating spectrometers for astronomical applications: first results, 2016, Proceedings of SPIE Volume 9912, article ID 991271
  8. T. Zhu, Y. Hu, P. Gatkine, et al. Ultrabroadband High Coupling Efficiency Fiber-to-Waveguide Coupler Using Si3N4 / SiO2 Waveguides on Silicon, IEEE Photonics Journal, vol. 8, no. 5, 2016
Press release: Best student presentation award at SPIE Astronomical Instrumentation + Telescopes, Edinburgh, UK


Atmospheric OH-suppression using Photonic Bragg Gratings

For ground-based telescopes, atmospheric-OH emission lines lead to a bright background in near-infrared, thus greatly reducing signal-to-noise ratio (SNR) for faint objects such as distant GRB afterglows. The photonic technology of Fiber Bragg Gratings (FBGs) has been recently demonstrated to significantly reduce the NIR background by blocking the OH-emission lines without significantly affecting the interline continuum. We simulate and characterize the performance of fiber Bragg gratings (FBGs) and waveguide Bragg gratings (WBGs) in the near-IR using a detailed model of sky background, atmospheric background and emission as well as instrument pipeline. The preliminary results show an estimated ten-fold improvement in signal-to-noise ratio.


A schematic of the simulation pipeline for FBGs on RIMAS

Relevant Publication:

  1. T. Zhu, Y. Hu, P Gatkine, et al. Arbitrary On-chip Optical Filter Using Complex Waveguide Bragg Gratings, Applied Physics Letters 2016 108:10
  2. Y. Hu, Y. Zhang, P Gatkine, et al. Characterization of low-loss waveguides using Bragg gratings, IEEEJournal of Selected Topics in Quantum Electronics, 24(4):1-8 (2018)
  3. T. Zhu, Y. Hu, P Gatkine, et al. An efficient approach to characterize low-loss waveguides using Bragg gratings Conference on Lasers and Electro-Optics, OSA, paper JW2A.65 (2018)

Photonic Lanterns

Due to the large spot size in a ground-based seeing-limited observation, channeling this light requires the use of large multimode fibers (MMFs, ∼several tens of modes). However, the photonic manipulation is only possible for single-mode fibers/waveguides. A photonic lantern is an adiabatic taper enabling a low-loss transition from the MMF to a set of single-mode fibers/waveguides.3 Photonic lanterns also make it possible to reformat the beam by rearranging the output single-mode fibers, thus tremendously enhancing the flexibility.


The concept of photonic lanterns. A 1x7 photonic lantern is shown in the inset.

Relevant Publications:

  1. P. Gatkine et al. Astro2020: Astrophotonics White Paper, Submitted to the National Academy of Sciences for Astro 2020 Decadal Survey, Bulletin of American Astronomical Society, 51g.285G, 2019, p1-14

Gamma-Ray bursts as the probes of early universe

Gamma-ray bursts (GRBs) are bright flashes peaking in gamma-ray, releasing as much energy in a few seconds as the sun over a course of its 10-billion-year lifetime. GRB afterglows have been detected from low redshift ∼0.01 out to redshift of 8.2 (Tanvir et al. 2009), thus probing all the way back to the first billion years of the universe . The prompt gamma-ray emission is followed by a multiwavelength synchrotron afterglow lasting a few days. The prompt discovery and localization of GRBs, thanks to NASA's Swift mission, has allowed a rapid follow-up of the afterglows with ground-based telescopes. The afterglow spectra harbor absorption features produced by the material along the line-of-sight (host galaxy, circumgalactic medium and intergalactic medium), The ions (at low and high ionized state) provide an excellent opportunity to explore the GRB Host galaxy environment, the excitation mechanism of these lines, metallicity and dust content. I particularly study the circumgalactic medium, residing at the nexus of accretion flows, galactic winds and outflows. I use the high-resolution spectra of GRB afterglows to study the kinematics of these feedback mechanisms of GRB hosts and their evolution as a function redshift.

Left: GRBs as cosmological probes: Tracing the era of formation of first galaxies, Right: The galaxy ecosystem with accretion, outflows, clouds and the GRB sightline sampling various components of the ecosystem

Relevant Publications:

  1. P. Gatkine, et al. The CGM-GRB Study II: Outflow-Galaxy Connection at z ∼ 2−6 , 2020, The Astrophysical Journal (Submitted)
  2. P. Gatkine, S. Vogel, S. Veilleux New radio constraints on the obscured star formation rates of massive GRB hosts at redshifts 2-3.5 , 2019, The Astrophysical Journal, 897, 2020, p 1-9
  3. P. Gatkine, S. Veilleux, A. Cucchiara, The CGM-GRB Study. I. Uncovering The CircumGalactic Medium around GRB hosts at redshifts 2-6, 2019, The Astrophysical Journal, 884, 66