Collaborative Research: A reliable electro-optic astrocomb with 350-1000 nm coverage enabled by nonlinear nanophotonics

California Institute Of Technology, Pasadena CA

Investigators

Abstract

While the discovery of exoplanets was one of humanity's longest-awaited scientific achievements, there remain outstanding goals: (1) the advancement of our knowledge of the formation and evolution of planetary systems, and (2) the discovery and characterization of habitable planets. This technology program directly addresses these important goals by providing new astronomical instrumentation lay the groundwork for the detection of Earth-like planets. A key missing technology is a wavelength calibration light source in the blue-visible region of the spectrum. This project will provide this technology by designing a new mechanism to produce a visible and near-ultraviolet calibration system called a laser frequency comb. The investigators will evaluate the reliability of this calibration system over extended timescales, which will be critical to the improved robustness, cost and efficiency. This system will be used with the Keck Planet Finder instrument. Exciting updates from this work will be used for public outreach, education and inclusivity activities. A laser frequency comb (LFC) has intrinsic properties that make it an ideal calibration source for radial velocity spectroscopy with precision better than 10 cm/s. The full potential of the LFC has not been realized for astronomical applications because of its limited spectral extent into the visible and near ultraviolet, generally poor reliability that requires regular maintenance, and high cost. This research will address these challenges by developing a new nonlinear nanophotonic waveguide technology based on poled thin-film lithium niobate. The lithium niobate platform provides the advantage of chi-squared nonlinear interactions in domain-engineered waveguides that enable the generation of light in the critical 350-500 nm spectral band with 10-100 times the efficiency over existing silica fibers. Indeed, starting with a narrowband comb at 1550 nm, the full wavelength coverage will extend from 350 nm to beyond 2000 nm. In addition to the long-term goal of detecting Earth-analogs, LFC-quality calibration in the blue (<500 nm) will help deliver the masses of Earth-size planets from Kepler (whose radii are known), yielding valuable bulk density measurements, expand our ability to understand internal structures of cool stars via precision Doppler asteroseismic measurements, and help shed light on the enigmatic population of super-Earths and sub-Neptune-size planets that require precise masses to constrain compositions. Moreover, this cross-disciplinary work will provide training the next generation of instrumentation scientists and engineers. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.