Visible Photonics in Thin-Film Lithium Niobate and Transition Metal Dichalcogenides for Classical and Quantum Information Applications

Abstract

Visible to near infrared (VNIR) light is used in domains ranging from short reach interconnects to interstellar spectroscopy. Despite the widespread use of these wavelengths, integrated photonic components operating in this regime have found significantly less utility. This is in part because the material systems commonly used to realize these components are themselves limited. In this thesis, I address this challenge by developing VNIR photonics in two emerging material platforms offering unique properties: thin film lithium niobate and two-dimensional transition metal dichalcogenides. In particular, I demonstrate low-loss and high performance electro-optic circuits operating at VNIR wavelengths in thin film lithium niobate. I begin by demonstrating sub-1 V drive voltage modula- tors (as low as 0.42 V·cm), and use these to demonstrate the first reported integrated electro optic frequency combs operating at various VNIR wavelengths. I then report on processes to ensure these components have both 1) low optical loss and 2) electro-optic stability by exploring the impact of standard nanofabrication processes on device performance. This study allows me to demonstrate VNIR circuits with propagation losses as low as 0.15 dB/cm, and stable electro-optic response down to sub-Hz drive frequencies. Using these improvements, I design and fabricate VNIR components useful for quantum information applications, including low insertion loss couplers ( 1 dB/facet), high bandwidth (> 40 GHz) amplitude and phase modulators, and on-chip switches. Additionally, I use these components to build circuits such as multi-modulator units that enable input VNIR laser light to be carved in the time domain and subsequently shifted in the frequency domain - all on a single chip. Finally, I turn to another emerging material platform, two-dimensional tungsten diselenide (WSe2), and explore the impact of strain on its VNIR optical response. This study reveals that localized (∼ 100 nm) strain can drastically tune the VNIR emission of WSe2 and helps provide insight into the origin of bright single photon emitters in this system.