Exploration of rare-earth ion transitions and host materials for spectral hole burning applications and quantum information science
Marsh, Aaron Daniel
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Due to their capacity for generating and manipulating light, the rare-earths are a foundational part of many cutting-edge technologies, ranging from lighting to quantum communications. Optical applications based on rare-earth doped materials are restricted to their transition energies. There are large bands, including the telecom window, where available rare-earth transitions typically have poor properties at liquid helium temperatures. The limitations are determined by the fundamental interactions between rare-earth ions and their host materials; comprehension of the interactions can be leveraged to significantly improve the properties of rare-earth quantum states. Three unexplored rare-earth optical transitions are investigated in this thesis: the Tm 3+ 3 H6<-->3 F3 at ~690 nm, the Pr 3+ 3 H 4<-->3 F 3 at ~1584 nm, and the Tm 3+ 3 F4<-->3 H 4 at ~1451 nm. The first transition suppresses non-radiative relaxation through engineering of the host material phonon spectrum. The 3 F 3 lifetime is extended to ~100 microsecond in Tm 3+ :KPb 2Br 5. The material Tm 3+:LaF 3 is also prepared for high-contrast spectral filtering in ultrasound-optical medical imaging sensitive to blood oxygenation at ~690 nm. Narrow 380 kHz holes are burned; simulations of hole burning indicate that ~60 dB of filtering contrast at ~3MHz is possible. Likewise, non-radiative relaxation is suppressed on the Pr 3+ transition at ~1584 nm in the low-phonon energy host RbPb 2Br 5. Four sites are revealed, with ~2-5 GHz spectrally resolved inhomogeneous broadenings, ~0.5-1 ms T 1 lifetimes, pseudoquadrupole level storage, and ~750 ns coherence times. This material is discussed for use as an L-band quantum memory. The excited state transition of Tm 3+ at ~1451 nm is then explored for quantum memories. High-resolution spectroscopy finds ~1 GHz inhomogeneous broadenings, ~6 ms lifetimes, and laser-limited ~30 MHz holes are burned. Techniques for measuring the properties of excited state transitions are described. Throughout, experimental methods and applications demonstrate the close relationship between lanthanide research and devices. Rare-earth doped crystals are used as an all-optical, high-resolution sensor package for characterizing cryostats in situ, and spectral hole burning characterizes laser performance as a real-time, ~1 MHz resolution spectrum analyzer. The exploration of rare-earth transitions is found to enable new research and new applications, with many other transitions yet to be explored.