Dr. Kalaga V. Madhav Profile

Dr. Kalaga V. Madhav

Section Head Astrophotonics (innoFSPEC) at Leibniz-Institut für Astrophysik Potsdam

SPIE Involvement:

Author

Area of Expertise:

Astrophotonics , Arrayed Waveguide Gratings , Photonic spectrographs , Frequency combs , Interferometry , Fiber Bragg Gratings

Websites:

Company Website | Personal Website

Publications (26)

Proceedings Article | 1 October 2024 Paper

Paper

Future space-based heterodyne interferometry: overcoming limitations in astronomical observations

William Karlsson, Someia Touil, Alan Günther, Aline Dinkelaker, Alyssa Mayer, Ahraar Muqsit, Paul Wilke, Thomas Mangoldt, Kalaga Madhav, Andreas Eckardt

Proceedings Volume 13130, 131300G (2024) https://doi.org/10.1117/12.3027463

KEYWORDS: Heterodyning, Stellar interferometry, Telescopes, Laser interferometry, Optical path differences, Radio interferometry, Interferometry, Visibility, Free space optics, Signal detection

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Proceedings Article | 28 August 2024 Poster + Paper

Poster + Paper

CHARA Array integrated optics testbench (CHARIOT) for on-sky experiments

Alyssa Mayer, Aline Dinkelaker, Kalaga Madhav, Lucas Labadie, Kévin Barjot, Nicholas Scott, Narsireddy Anugu, Aurélien Benoît, Robert Thomson, Robert Harris, Christopher Farrington, Rainer Koehler, Karolina Kubiak, Edgar Ligon, Gail Schaefer

Proceedings Volume 13095, 130951V (2024) https://doi.org/10.1117/12.3019140

KEYWORDS: Beam combiners, Mirrors, Integrated optics, K band, Optical path differences, Nulling interferometry, Telescopes, Equipment, Astrophotonics, Astronomical interferometry, Near infrared, Astronomical instrumentation engineering, Astronomical instrumentation, Femtosecond laser micromachining, Optical benches

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Proceedings Article | 26 August 2024 Poster + Paper

Poster + Paper

On the large quantity fabrication and reproducibility of all-fiber photonic lanterns

Julian Rypalla, Stella Vješnica, Kalaga Madhav, Adrian Lorenz, Tina Eschrich, Elmar Schmälzlin, Aline Dinkelaker, Martin Roth

Proceedings Volume 13100, 131006P (2024) https://doi.org/10.1117/12.3018846

KEYWORDS: Single mode fibers, Fabrication, Capillaries, Reproducibility, Telescopes, Astrophotonics, Cladding, Waveguide modes

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Proceedings Article | 26 August 2024 Poster + Paper

Poster + Paper

Novel phase masks with overlapping regions to fabricate fiber Bragg gratings for filtering sky emission lines

Xijie Luo, Aashia Rahman, Kalaga Madhav, Thomas Siefke, Ria Krämer, Daniel Richter, Uwe Zeitner, Stefan Nolte, Martin Roth

Proceedings Volume 13100, 1310068 (2024) https://doi.org/10.1117/12.3018363

KEYWORDS: Fiber Bragg gratings, Design, Fabrication, Optical filters, Astronomy

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Proceedings Article | 19 July 2024 Poster

Poster

Monolithic all-fiber Fabry-Perot comb for precision astronomy

Kalaga Madhav, Aashia Rahman

Proceedings Volume 13096, 13096A0 (2024) https://doi.org/10.1117/12.3020238

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Proceedings Article | 19 July 2024 Poster

Poster

Compact Arrayed Waveguide Stacked Multi-Object Spectrograph (CAWSMOS): design concept and preliminary results

Kalaga Madhav, Eloy Hernandez, Stella Vješnica, Alan Günther, Svend-Marian Bauer, Hakan Önel, Martin Roth

Proceedings Volume 13096, 13096A6 (2024) https://doi.org/10.1117/12.3020178

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Proceedings Article | 18 July 2024 Presentation + Paper

Presentation + Paper

Preliminary results of the Potsdam Arrayed Waveguide Spectrograph

Eloy Hernandez, Alan Günther, Stella Vješnica, Svend-Marian Bauer, Andreas Stoll, Hakan Önel, Kalaga Madhav, Martin Roth

Proceedings Volume 13096, 130960L (2024) https://doi.org/10.1117/12.3018014

KEYWORDS: Arrayed waveguide gratings, Sensors, Waveguides, Spectrographs, Cryostats, Near infrared spectroscopy, Astrophotonics, Frequency combs

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Arrayed waveguide gratings (AWG) have gained attention as promising integrated spectrographs for ground-based telescopes, airborne applications, and spaceborne instrumentation due to their low mass, diffraction limit characteristics, thermal stability, and robustness against vibrations and misalignment. The Potsdam Arrayed Waveguide Spectrograph (PAWS) is a cross-dispersive instrument based on an integrated photonic spectrograph (IPS) that is optimized for the astronomical H-Band and was designed and developed by innoFSPEC at the Leibniz Institute for Astrophysics Potsdam (AIP). The main element is a second-generation AWG that is fibre coupled and works as a first dispersive element. To work as an IPS, the dispersed light of the AWG is sampled at the output facet and magnified by a microscope objective. The light is then fed into a free-space optical system housed in a cryostat working at 140 K. An afocal relay re-images the exit pupil of the microscope into the plane of a cross-dispersive element containing a diffractive grating. Subsequently, an objective focuses the resulting echellogram on a Teledyne 2k × 2k H2RG near-infrared array working at 80 K. To validate the functionality of the system, different light sources have been used. A tunable laser source generated an echellogram through frame stacking. Furthermore, the cross-dispersed output of a supercontinuum source and of an in-house developed frequency comb system were recorded under varying input conditions of the AWG, successfully achieving first light laboratory measurements. Throughout multiple cycles and measurements of the instrument, several parameters and characteristics were identified, providing opportunities for optimization to enhance the instrument’s performance and facilitate the miniaturization of future iterations. In this manuscript, we will provide a concise overview of the PAWS instrument, the preliminary results of laboratory measurements, and lessons learned to improve the future iterations of the next generation near-infrared cross-dispersed integrated photonic spectrograph. PAWS represents a pioneering demonstration of an astronomy optimized AWG chip, showcasing the advantageous capabilities of integrated photonic spectrograph.

Proceedings Article | 17 March 2023 Presentation + Paper

Presentation + Paper

Astrophotonics: photonic integrated circuits for astronomical instrumentation

Martin Roth, Kalaga Madhav, Andreas Stoll, Daniel Bodenmüller, Aline Dinkelaker, Aashia Rahman, Eloy Hernandez, Alan Günther, Stella Vjesnica

Proceedings Volume 12424, 124240B (2023) https://doi.org/10.1117/12.2655630

KEYWORDS: Arrayed waveguide gratings, Waveguides, Astronomy, Spectrographs, Photonic integrated circuits, Frequency combs, Telescopes, Spectral resolution, Design and modelling, Beam combiners

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Proceedings Article | 29 August 2022 Presentation + Paper

Presentation + Paper

MARCOT Pathfinder at Calar Alto progress report

Martin Roth, Jesús Aceituno, José Ortiz, Kalaga Madhav, Stefan Cikota, John Davenport, Thomas Fechner, Pedro Amado, Fran Pozuelos, Rafael Luque, Nicolas Morales

Proceedings Volume 12182, 121820M (2022) https://doi.org/10.1117/12.2629901

KEYWORDS: Telescopes, Cladding, Single mode fibers, Capillaries, Spectrographs, Mirrors, Exoplanets

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Proceedings Article | 29 August 2022 Poster + Paper

Poster + Paper

The BlueMUSE calibration unit: phase-A studies

Martin Roth, Peter Weilbacher, Andreas Kelz, Kalaga Madhav, Eloy Hernandez, Johan Richard, Rémy Giroud, Roland Bacon

Proceedings Volume 12184, 121845S (2022) https://doi.org/10.1117/12.2629630

KEYWORDS: Calibration, Lamps, Fabry–Perot interferometers, Spectrographs, Frequency combs, Velocity measurements, Telescopes

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Proceedings Article | 29 August 2022 Presentation + Paper

Presentation + Paper

System integration of the Potsdam Arrayed Waveguide Spectrograph (PAWS)

Eloy Hernandez, Alan Günther, Svend-Marian Bauer, Christian Dani Guzmán, Christer Sandin, Andreas Stoll, Stella Vjesnica, Kalaga Madhav, Martin M. Roth

Proceedings Volume 12184, 121841O (2022) https://doi.org/10.1117/12.2627318

KEYWORDS: Sensors, Temperature metrology, Cryocoolers, Cryogenics, Bridges, Computer aided design, Molybdenum, Spectrographs, Mirrors, Electronics

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Proceedings Article | 26 August 2022 Presentation + Paper

Presentation + Paper

Ultrafast laser inscription of integrated optics two-telescope beam combiners for K-band interferometry at the CHARA array

Jacopo Siliprandi, David MacLachlan, Calum Ross, Tarun Sharma, Lucas Labadie, Kalaga Madhav, Abani Nayak, Aline Dinkelaker, Martin Roth, Ettore Pedretti, Theo ten Brummelaar, Nicholas Scott, Vincent Coudé du Foresto, Robert Thomson, Aurélien Benoît

Proceedings Volume 12183, 1218314 (2022) https://doi.org/10.1117/12.2629899

KEYWORDS: Waveguides, K band, Directional couplers, Interferometry, Ultrafast lasers, Integrated optics, Beam splitters, Spatial light modulators

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Proceedings Article | 26 August 2022 Poster + Paper

Poster + Paper

On-sky experiment of the discrete beam combiner: lessons learned and strategies for improved calibration of the transfer function

Abani Shankar Nayak, Lucas Labadie, Tarun Sharma, Simone Piacentini, Giacomo Corrielli, Roberto Osellame, Ettore Pedretti, Aline Dinkelaker, Eloy Hernandez, Kalaga Madhav, Martin Roth

Proceedings Volume 12183, 121832H (2022) https://doi.org/10.1117/12.2629673

KEYWORDS: Visibility, Waveguides, Cameras, Sensors, Photometry, Calibration, Telescopes, Photodetectors, Interferometry, Integrated optics

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Proceedings Article | 13 December 2020 Poster + Paper

Poster + Paper

Testbed for coupling starlight into fibers and astrophotonic instruments

Momen Diab, Aline Dinkelaker, John Davenport, Kalaga Madhav, Martin Roth

Proceedings Volume 11451, 114516G (2020) https://doi.org/10.1117/12.2564720

KEYWORDS: Adaptive optics, Optical fibers, Waveguides, Telescopes, Turbulence, Optical calibration, Single mode fibers, Atmospheric optics, Wavefronts, Cameras

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Proceedings Article | 13 December 2020 Poster + Presentation + Paper

Poster + Presentation + Paper

Optomechanical design of PAWS, the Potsdam Arrayed Waveguide Spectrograph

Eloy Hernandez, Andreas Stoll, Svend-Marian Bauer, Amokrane Berdja, Rafael Bernardi, Dani Guzman, Alan Günther, Kalaga Madhav, Martin Roth, Christer Sandin, Constanza Villanueva

Proceedings Volume 11451, 114515O (2020) https://doi.org/10.1117/12.2562174

KEYWORDS: Waveguides, Spectrographs, Single mode fibers, Optical design, Telescopes, Calibration, Microscopes, Free space optics, Integrated photonics, Astronomy

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Proceedings Article | 13 December 2020 Presentation + Paper

Presentation + Paper

Optical fibre pseudo-slits for astronomy

John Davenport, Momen Diab, Aashana Tripathi, Kalaga Madhav, Martin Roth

Proceedings Volume 11451, 1145123 (2020) https://doi.org/10.1117/12.2562652

KEYWORDS: Optical fibers, Astronomy, Connectors, Shape memory alloys, Multimode fibers, Fiber optics, Single mode fibers, Astrophysics, Telescopes, Spectrographs

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Proceedings Article | 13 December 2020 Presentation + Paper

Presentation + Paper

NAIR: Novel Astronomical Instrumentation through photonic Reformatting

Robert Harris, Tarun Kumar Sharma, John Davenport, Philipp Hottinger, Theodoros Anagnos, Abani Shankar Nayak, Andreas Quirrenbach, Lucas Labadie, Kalaga Madhav, Martin Roth

Proceedings Volume 11451, 1145108 (2020) https://doi.org/10.1117/12.2562493

KEYWORDS: Imaging spectroscopy, Astronomical instrumentation, Photonic devices, Spectroscopes, Astrophotonics, Telescopes, Interferometry, Waveguides, 3D printing, Astronomical imaging

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Proceedings Article | 13 December 2020 Presentation + Paper

Presentation + Paper

First on-sky results with an interferometric discrete beam combiner (DBC) at the William Herschel Telescope

Abani Shankar Nayak, Tarun Kumar Sharma, Lucas Labadie, Simone Piacentini, Giacomo Corrielli, Roberto Osellame, Éric Gendron, Jean-Tristan Buey, Fanny Chemla, Mathieu Cohen, Nazim Bharmal, Lisa Bardou, Lazar Staykov, James Osborn, Timothy Morris, Ettore Pedretti, Aline Dinkelaker, Kalaga Madhav, Martin Roth

Proceedings Volume 11446, 114461D (2020) https://doi.org/10.1117/12.2562563

KEYWORDS: Interferometry, Telescopes, Integrated optics, Waveguides, Spatial filters, Infrared radiation, Laser development, Channel waveguides, Ultrafast lasers, Borosilicate glass

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Proceedings Article | 13 December 2020 Presentation + Paper

Presentation + Paper

K-band integrated optics beam combiners for CHARA fabricated by ultrafast laser inscription

Fraser Pike, Tarun Sharma, Aurélien Benoît, David MacLachlan, Aline Dinkelaker, Abani Nayak, Kalaga Madhav, Martin Roth, Lucas Labadie, Ettore Pedretti, Theo ten Brummelaar, Nicholas Scott, Vincent Coudé du Foresto, Robert Thomson

Proceedings Volume 11446, 114460K (2020) https://doi.org/10.1117/12.2561663

KEYWORDS: Integrated optics, K band, Ultrafast lasers, Astronomy, Astrophotonics, Waveguides, Information operations, Glasses, Optical filters, Atmospheric optics

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Proceedings Article | 9 March 2020 Presentation

Presentation

Integrated discrete beam combiner with a pupil remapper for stellar interferometry (Conference Presentation)

Simone Piacentini, Giacomo Corrielli, Abani Shankar Nayak, Tarun Kumar Sharma, Kalaga Madhav, Ettore Pedretti, Stefano Minardi, Lucas Labadie, Roberto Osellame

Proceedings Volume 11287, 112870B (2020) https://doi.org/10.1117/12.2545027

KEYWORDS: Stellar interferometry, Telescopes, Interferometry, Astronomy, Waveguides, Spatial resolution, Astronomical telescopes, Wavefronts, Interferometers, Photonic integrated circuits

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Proceedings Article | 9 March 2020 Presentation

Presentation

Femtosecond laser writing of 3D polarization insensitive integrated devices for astrophotonics (Conference Presentation)

Simone Piacentini, Giacomo Corrielli, Abani Shankar Nayak, Tarun Kumar Sharma, Kalaga Madhav, Andrea Adami, Ettore Pedretti, Stefano Minardi, Lucas Labadie, Roberto Osellame

Proceedings Volume 11270, 112700S (2020) https://doi.org/10.1117/12.2544978

KEYWORDS: Polarization, Femtosecond phenomena, Astrophotonics, Telescopes, Waveguides, Stellar interferometry, Birefringence, Annealing, Interferometry, Integrated photonics

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Proceedings Article | 3 January 2020 Paper

Paper

Integrated optics-interferometry using pupil remapping and beam combination at astronomical H-band

Abani Shankar Nayak, Simone Piacentini, Tarun Kumar Sharma, Giacomo Corrielli, Roberto Osellame, Lucas Labadie, Stefano Minardi, Ettore Pedretti, Kalaga Madhav, Martin Roth

Proceedings Volume 11203, 112030V (2020) https://doi.org/10.1117/12.2541608

KEYWORDS: Visibility, Integrated optics, Astronomy, Telescopes, Physics, Interferometry, Ultrafast lasers, Waveguides, Deformable mirrors, Astrophysics

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Proceedings Article | 3 January 2020 Paper

Paper

Integrated echélle gratings for astrophotonics

Andreas Stoll, Yu Wang, Kalaga Madhav, Martin Roth

Proceedings Volume 11203, 112030Z (2020) https://doi.org/10.1117/12.2541554

KEYWORDS: Spectral resolution, Astrophotonics, Waveguides, Diffraction gratings, Diffraction, Spectrographs, Optical design, Near infrared, Imaging spectroscopy, Spectroscopes

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Proceedings Article | 10 July 2018 Paper

Paper

High-performance integrated photonic spectrometers based on arrayed waveguide gratings in silica

Ziyang Zhang, Andreas Stoll, Kalaga Madhav, Julia Fiebrandt, Vadim Makan, Kirill Makan, Kai Sun, Dele Zhu, Martin Roth

Proceedings Volume 10706, 107063C (2018) https://doi.org/10.1117/12.2311856

KEYWORDS: Waveguides, Spectrometers, Astronomy, Silica, Integrated photonics, Spectral resolution, Spectrographs, Polarization, Wave propagation, Wavefronts

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Proceedings Article | 10 July 2018 Presentation

Presentation

FBG development for OH suppression at innoFSPEC Potsdam (Conference Presentation)

Martin Roth, Ziyang Zhang, Kalaga Madhav, Julia Fiebrandt

Proceedings Volume 10706, 1070605 (2018) https://doi.org/10.1117/12.2311787

KEYWORDS: Fiber Bragg gratings, Near infrared, Diffraction, Optical alignment, Control systems, Modulation, Algorithm development, Process control, Space telescopes, Telescopes

Read Abstract +

The power of the next generation of telescopes that will rely largely on the combination of light-collecting area with excellent (ideally: diffraction limited) image quality. Therefore, the focus will heavily lean on adaptive optics and the near infrared wavelength regime. A severe limiting factor is the presence and strength of atmospheric OH emission lines in the NIR. OH suppression techniques involving fiber Bragg gratings (FBG) have been proposed, however as yet not fully demonstrated on sky. We are involved in the first generation FBG prototype development with partners in Australia, including the GNOSIS and PRAXIS on-sky experiments. Since the supply of suitable multi-notch filters is no longer available from industry, we have made an effort at innoFSPEC Potsdam to build a specialized laboratory for the development and manufacture of 2nd generation FBGs for OH suppression. Suppression of the strong NIR OH emission lines requires a single grating that reflects multiple wavelengths, spaced at non-periodic intervals, with flat-top profile and high suppression ratio. It has been shown that aperiodic fiber Bragg gratings (AFBGs) can provide such functions. However, the fabrication technology requires accurate optical alignment of several degrees of freedom as well as complex control of modulated beams to form a varying interference pattern. In our work, an algorithm is developed from the index profile of a multi-notch AFBG to the design of a complex phase-mask that can generate a matching UV diffraction pattern, which will in turn inscribe an single-mode fiber into the chosen AFBG. With such a phase mask, the fabrication of the AFBGs will be reduced to a simple UV-exposure process, i.e., the complex alignment and control processes of the interference pattern from modulated beams are avoided altogether. The resulting reliable and reproducible fabrication process will dramatically reduce of the cost of such filters. Packaging aspects for a complete sky emission filter system will also be discussed.

Proceedings Article | 14 May 2010 Paper

Paper

Macro-bend optical fiber linear displacement sensor

Kalaga Madhav, Yuliya Semenova, Gerald Farrell

Proceedings Volume 7726, 772608 (2010) https://doi.org/10.1117/12.854631

KEYWORDS: Sensors, Lead, Optical fibers, Model-based design, Cladding, Picosecond phenomena, Fiber optics sensors, Coating, Absorption, Reflection

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Showing 5 of 26 publications

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