About

Dr. Pradip Gatkine is a NASA Hubble Fellow currently based at Caltech, where he has been employed since September 2021. Prior to this, he held the David & Ellen Lee Prize Postdoctoral Fellowship at Caltech from September 2020 to September 2021. He earned his PhD in Astronomy from the University of Maryland in 2020, following a Master of Science in Astronomy from the same institution and a Bachelor of Technology with honors in Mechanical Engineering and a minor in Physics from the Indian Institute of Technology Bombay. Dr. Gatkine's research focuses on astrophysics, particularly the study of gamma-ray bursts (GRBs) and their host environments, as well as the circumgalactic medium around GRB hosts at high redshifts. His work involves multi-wavelength observations and the development of astrophotonic spectrographs, contributing to the understanding of star formation rates and feedback mechanisms in galaxies. Throughout his academic career, Dr. Gatkine has received numerous awards recognizing his research excellence, including the NASA Hubble Fellowship, the David & Ellen Lee Prize Postdoctoral Fellowship, and several honors from the University of Maryland and the Indian Institute of Technology Bombay. His research contributions span both observational astrophysics and instrumentation, with a strong emphasis on advancing spectroscopic techniques for astronomical applications.

Research topics

• Physics
• Astronomy
• Astrophysics
• Astrobiology

Selected publications

• Tri-coupler geometries for achromatic nulling interferometry in the near-infrared

  Open MIND · 2026-02-27

  preprint

  Astrophotonics is central to the next generation of astronomical instrumentation, enabling compact photonic integrated circuits for both ground-based observatories and future space missions. Beam combination for nulling interferometry suppresses starlight, revealing exoplanets and companions. Two-waveguide photonic combiners rely on symmetric evanescent, inherently chromatic, coupling to interfere light. A three-waveguide configuration, or tri-coupler, offers the potential for deeper, broader, and more stable achromatic nulls compared with two-waveguide approaches. This work compares the simulated performance of evanescent tri-couplers and a multimode interference coupler across the 1.5-1.8 micron band, evaluating exoplanet throughput, starlight attenuation, sensing characteristics, and estimations on fabrication tolerance. All three tri-couplers achieved >40dB attenuation over a 270nm bandwidth. Including component loss, the tapered tri-coupler has the highest total throughput, averaging 97%, whereas the standard tri-coupler began with an equivalent exoplanet throughput and fell to 50% at the band edges. The tapered tri-coupler was further redesigned to achieve a non-degenerate sensing state. The MMI, while limited to a starlight attenuation of 40dB by uncoupled light, showed the greatest tolerance to fabrication errors. Future designs aim to combine high exoplanet throughput, deep starlight attenuation, and non-degenerate sensing within a single integrated architecture. This work provides a simulation suite for three tri-couplers.

  DOI

• Tri-coupler geometries for achromatic nulling interferometry in the near-infrared

  ArXiv.org · 2026-02-27

  articleOpen access

  Astrophotonics is central to the next generation of astronomical instrumentation, enabling compact photonic integrated circuits for both ground-based observatories and future space missions. Beam combination for nulling interferometry suppresses starlight, revealing exoplanets and companions. Two-waveguide photonic combiners rely on symmetric evanescent, inherently chromatic, coupling to interfere light. A three-waveguide configuration, or tri-coupler, offers the potential for deeper, broader, and more stable achromatic nulls compared with two-waveguide approaches. This work compares the simulated performance of evanescent tri-couplers and a multimode interference coupler across the 1.5-1.8 micron band, evaluating exoplanet throughput, starlight attenuation, sensing characteristics, and estimations on fabrication tolerance. All three tri-couplers achieved >40dB attenuation over a 270nm bandwidth. Including component loss, the tapered tri-coupler has the highest total throughput, averaging 97%, whereas the standard tri-coupler began with an equivalent exoplanet throughput and fell to 50% at the band edges. The tapered tri-coupler was further redesigned to achieve a non-degenerate sensing state. The MMI, while limited to a starlight attenuation of 40dB by uncoupled light, showed the greatest tolerance to fabrication errors. Future designs aim to combine high exoplanet throughput, deep starlight attenuation, and non-degenerate sensing within a single integrated architecture. This work provides a simulation suite for three tri-couplers.

  PublisherOA PDF

• Developing photonic components for nulling applications

  2025-09-18

  article
  PublisherDOI

• Implicit Electric Field Conjugation with the Photonic Lantern Nuller

  ArXiv.org · 2025-03-31

  preprintOpen access

  The Photonic Lantern Nuller (PLN) is an instrument concept designed to characterize exoplanets within a single beam-width from its host star. The PLN leverages the spatial symmetry of a mode-selective photonic lantern (MSPL) to create nulled ports, which cancel out on-axis starlight but allow off-axis exoplanet light to couple. The null-depths are limited by wavefront aberrations in the system as well as by imperfections in the lantern. We show that the implicit electric field conjugation algorithm can be used to reduce the stellar coupling through the PLN by orders of magnitude while maintaining the majority of the off-axis light, leading to deeper null depths (~10^{-4}) and thus higher sensitivity to potential planet signals. We discuss a theory for the tradeoff we observed between the different ports, where iEFC improves the nulls of some ports at the expense of others, and show that targeting one port alone can lead to deeper starlight rejection through that port than when targeting all ports at once. We also observe different levels of stability depending on the port and discuss the implications for practically implementing this technique for science observations.

  PublisherOA PDFDOI

• Open-source Python library for customizable AWG design and simulation in astronomy

  2025-08-01

  article

  Arrayed Waveguide Gratings (AWGs) are a powerful emerging technology useful for high-resolution spectroscopy. They offer spatially efficient solutions for wavelength multiplexing and demultiplexing, the latter of which is specifically useful for spectral analysis. The growing demand for precise and customizable AWG designs in astronomy highlights the need for more specialized simulation tools. This paper aims to showcase the development of an open-source Python library for simulating and designing these AWG devices, with a focus on applications in astronomy. The library simulates electric-field propagation through all the elements of a conventional AWG device and produces a theoretical spectral response for a given, user-defined, input wavelength range. Other design inputs include resolving power and free spectral range. The Python framework allows the user to customize all parts of the device to quickly optimize the design for desired specifications. The library also enables the conversion of specifications to an AWG CAD design using existing open-source CAD tools, such as Nazca; an open-source, Python-based photonics design tool. Initial simulations demonstrate the library’s ability to replicate spectral responses from known AWG device designs with high accuracy. The tool has successfully provided feedback on changing design choices, indicating the validity of the approach. This Python library is a highly customizable simulation tool for AWG device design and optimization, enabling researchers in the field of astronomical instrumentation to streamline the design process. It has significant potential to accelerate the development of astrophotonic spectrographs for astronomy.

  PublisherDOI

• Implicit electric field conjugation with a photonic lantern nuller

  Journal of Astronomical Telescopes Instruments and Systems · 2025-05-11

  articleOpen access

  The photonic lantern nuller (PLN) is an instrument concept designed to characterize exoplanets within a single beam width from its host star. The PLN leverages the spatial symmetry of a mode-selective photonic lantern to create nulled ports, which cancel out on-axis starlight but allow off-axis exoplanet light to couple. The null depths are limited by wavefront aberrations in the system as well as by imperfections in the lantern. We show that the implicit electric field conjugation (iEFC) algorithm can be used to reduce the stellar coupling through the PLN by orders of magnitude while maintaining the majority of the off-axis light, leading to deeper null depths (∼10−4) and thus higher sensitivity to potential planet signals. We discuss a theory for the tradeoff we observed among the different ports, where iEFC improves the nulls of some ports at the expense of others, and show that targeting one port alone can lead to deeper starlight rejection through that port than when targeting all ports at once. We also observe different levels of stability depending on the port and discuss the implications of practically implementing this technique for scientific observations.

  PublisherDOI

• Development of an on-chip double Bracewell nulling interferometer in the near-infrared for the CHARA array

  2025-09-18

  articleSenior author

  Astrophotonics is advancing long-baseline nulling interferometry by enabling direct imaging and spectroscopy of faint astronomical objects including exoplanets and faint binary star systems. On-chip instruments, with footprints of only a few centimeters, maximize stability, feedback control, and design flexibility, while minimizing thermo-mechanical disturbances and cost. These advancements are poised to provide extremely high angular resolution with minimal noise, particularly in the near-infrared. The successful deployment of the on-chip Keck Interferometer Nuller (KIN), GLINT nuller on the Subaru telescope, and the recently commissioned VLTI’s Nulling Observations of exoplaneTs and dusT (NOTT) demonstrate the potential of such astrophotonic technologies. In the northern hemisphere, the Center for High Angular Resolution Astronomy (CHARA) Array, located at Mt. Wilson, is equipped with the world’s longest baseline in the near-infrared. CHARA provides an ideal platform for nulling interferometry at sub-milliarcsecond angular resolution by leveraging its existing adaptive optics and fringe tracking facilities. In addition, self-calibration techniques such as the double Bracewell architecture proposed by Angel and Woolf can enable starlight suppression in the range of 10⁻⁴ to 10⁻⁶ in broadband. In this poster, we present our simulations of various science cases motivating the development of an astrophotonic near-infrared H-band nulling beam combiner for the CHARA array. We will present a quantification of the achievable observations in the limiting magnitude, contrast, and angular separation parameter space.

  PublisherDOI

• SNR estimation for studying exoplanet transits with astrophotonic spectrographs

  2025-08-01

  article
  PublisherDOI

• Towards space-qualification of astrophotonic devices in the optical/IR

  2025-08-01 · 1 citations

  article

  Astrophotonics, a specialized branch of integrated optics, is transforming observational astronomy by providing compact and efficient photonic solutions to replace traditional bulky optical systems. Originally stemming from the telecommunication industry, astrophotonics has matured into a distinct field tailored to the demanding requirements of astronomical applications. The state-of-the-art has indicated that optical properties such as throughput, polarization, and birefringence are heavily influenced by the choice of material and the fabrication process, for example, lithography and ultrafast laser inscription. Emerging space-based projects, i.e., NASA’s flagship program - Habitable World Observatory (HWO), are driving the demand for sophisticated photonic devices that can operate across visible to infrared wavelengths. Such space missions require the development and testing of astrophotonic technologies in simulated space environments that meet the stringent requirements of astronomy, including optical performance, mechanical robustness, thermal stability, durability against high-energy particles, and reliability, as specified in the General Environmental Verification Standard (GEVS) GSFC-STD7000 guideline. In this report, we outline the experimental and statistical approaches employed to evaluate the space qualification of both passive and active waveguide-based astrophotonic devices. In these initial efforts, we describe the testing of SiO₂-based near-infrared components, for instance, Photonic Lanterns, Arrayed Waveguide Gratings (AWGs), Directional Couplers, Mach–Zehnder interferometers (MZIs), and their interfaces with fibers under low-earth orbit simulated space conditions, including thermal cycling, vacuum, and acceleration testing. We measure the degradation of on-chip throughput, coupling efficiency, spectral response, and birefringence of the devices, and identify their mechanical failure points. These tests will aid in developing strategies for robust design, fabrication, and packaging of astrophotonic devices in space environments.

  PublisherDOI

• Cross-dispersion setup for an integrated near IR astrophotonic spectrograph

  2025-01-23

  article

  Here we present an optical cross-dispersion setup for an astrophotonic spectrograph in the near-IR H-band (1460 to 1630nm). In this spectrograph, the arrayed waveguide grating (AWG) chip acts as the main dispersing element. An AWG produces a 1D spectrum with overlapping spectral orders, and we designed a cross-dispersion setup that can cross-disperse these overlapping spectral orders perpendicular to the 1D spectral output. This setup consists of a collimating lens, a grating, and a focusing lens. The cross-dispersed 2D spectrum is then imaged onto a near-IR detector array. The AWG we used for this project has a spectral resolution of (λ/δλ) of ∼1000 and a free spectral range of 10nm. An on-sky solar test was performed and analyzed, demonstrating the potential of this setup.

  PublisherDOI

Frequent coauthors

• Sylvain Veilleux

  73 shared

• S. B. Cenko

  Joint Space Science Institute

  72 shared

• Dimitri Mawet

  39 shared

• Nemanja Jovanović

  California Institute of Technology

  38 shared

• E. Troja

  University of Rome Tor Vergata

  36 shared

• Barnaby Norris

  30 shared

• S. Dichiara

  28 shared

• Sergio G. Leon-Saval

  University of Sydney

  27 shared

Education

• PhD, Astronomy

  University of Maryland, College Park

  2020

• B Tech, Mechanical Engineering

  Indian Institute of Technology Bombay

  2014