UCLA

Though almost 6,000 confirmed exoplanets discovered to date, only $\sim$ 200 have measured atmospheric spectra, none of which resemble the Earth. Even though such planets, and by extension solar-system-like exoplanetary systems may be rare, at least given current planet formation theories, the sheer number of exoplanetary systems suggests that our non-detection is mostly technological in nature. In particular, indirect detection methods such as the radial velocity and transit methods are biased towards higher masses, larger sizes, and/or smaller orbits, often yielding close-in gas giants or barren terrestrial planets scorched by stellar radiation. On the other hand, direct imaging techniques are biased towards larger orbits and larger planets, yielding cold gas giants often several times the mass of Jupiter. Planet formation remains similarly uncertain due to a lack of observables, with confirmed protoplanetary systems numbering only in the low single digits.

Nevertheless, the search for an Earth analog will be a priority for astronomy in the next decades. These efforts will be supported by the upcoming 30-m-class ground-based telescopes such as ESO's Extremely Large Telescope, as well as NASA's planned spaceborne flagship, the 6--8 m Habitable Worlds Observatory. These observatories will rely on new instruments which must overcome a suite of technical limits holding back the current state-of-the-art. At the highest level, our primary limit is one of contrast: an Earth-mass exoplanet orbiting a sun-like star will be outshone by 10 orders of magnitude in visible wavelengths, so that any exoplanetary light is obscured by a stellar glare too intense for current instruments to adequately block. The solution to this challenge will in turn require developments in the suppression of starlight, as well as wavefront control, while the subsequent characterization of the faint exoplanetary signal will require improvements to astronomical spectrometers and ultra-low-noise detectors. Of course, this list is non-exhaustive.

My dissertation considers how photonic devices -- primarily the photonic lantern -- can be applied to meet these technical challenges, and how such devices fit in the wider contexts of spectroscopy, wavefront sensing, and imaging. In the following chapters, I quantify the improvements in high-spectral-resolution diffraction-limited spectroscopy afforded by photonic lanterns, and then develop the photonic lantern as a focal-plane wavefront sensor. Taken together, these developments yield a combined spectrometer and wavefront sensor which achieves greater light efficiency and stability than conventional spectrometers, and which can simultaneously assist in coronagraphic wavefront control. Such a device would be well-suited for the future search of an exo-Earth, and more generally, the study of faint circumstellar environments. In tandem, my dissertation considers the tools and methods which enable the development of new photonic technologies for astronomy.