Ultraviolet Astronomical Spectrograph Calibration With Laser Frequency Combs From Nanophotonic Waveguides

By Keith Cowing
Status Report
June 26, 2023
Filed under , , , , ,
Ultraviolet Astronomical Spectrograph Calibration With Laser Frequency Combs From Nanophotonic Waveguides
Nanophotonic lithium niobate waveguides. a, Geometry of a nanophotonic lithium niobate (LiNbO3) waveguide, showing the optical mode profile for the fundamental transverse electric field (TE) mode and a possible poling pattern with spatially variable poling period Λ. The extraordinary crystal axis is oriented along the x-direction to access the highest electro-optic tensor element of LiNbO3. b, Poling periods Λ required for quasi-phase matching of various nonlinear optical processes for waveguides of different (top) width as a function of the fundamental comb’s wavelength. SHG: second harmonic generation; SHG + F: sum-frequency generation of second harmonic and fundamental comb; THG + F: sum-frequency generation of third harmonic and fundamental comb; SHG + SHG: sum-frequency generation of the second harmonic. Higher-order phase matching with three-fold period Λ is indicated (the current fabrication limit only allows for Λ > 2 µm). c, Photograph of a waveguide in operation and scanning electron microscope image of the LiNbO3 on silica (SiO2). d,e,f,g, Examples of waveguide designs showing poling pattern (top), experimentally generated spectra for different input pulse energies provided by a 100 MHz, 80 fs mode-locked laser with central wavelength of 1560 nm (waveguide cross-section and on chip-pulse energy as indicated) and pyChi [57] simulation results (bottom) for a pulse energy of 50 pJ. — astro-ph.IM

Astronomical precision spectroscopy underpins searches for life beyond Earth, direct observation of the expanding Universe and constraining the potential variability of physical constants across cosmological scales.

Laser frequency combs can provide the critically required accurate and precise calibration to the astronomical spectrographs. For cosmological studies, extending the calibration with such astrocombs to the ultraviolet spectral range is highly desirable, however, strong material dispersion and large spectral separation from the established infrared laser oscillators have made this exceedingly challenging.

Here, we demonstrate for the first time astronomical spectrograph calibrations with an astrocomb in the ultraviolet spectral range below 400 nm. This is accomplished via chip-integrated highly nonlinear photonics in periodically-poled, nano-fabricated lithium niobate waveguides in conjunction with a robust infrared electro-optic comb generator, as well as a chip-integrated microresonator comb.

These results demonstrate a viable route towards astronomical precision spectroscopy in the ultraviolet and may contribute to unlocking the full potential of next generation ground- and future space-based astronomical instruments.

Markus Ludwig, Furkan Ayhan, Tobias M. Schmidt, Thibault Wildi, Thibault Voumard, Roman Blum, Zhichao Ye, Fuchuan Lei, François Wildi, Francesco Pepe, Mahmoud A. Gaafar, Ewelina Obrzud, Davide Grassani, François Moreau, Bruno Chazelas, Rico Sottile, Victor Torres-Company, Victor Brasch, Luis G.Villanueva, François Bouchy, Tobias Herr

Subjects: Optics (physics.optics); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2306.13609 [physics.optics] (or arXiv:2306.13609v1 [physics.optics] for this version)
Submission history
From: Tobias Herr
[v1] Fri, 23 Jun 2023 16:51:12 UTC (4,178 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻