Date of Award
Spring 2023
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Electrical Engineering (ENAS)
First Advisor
Han, Jung
Abstract
Thin-film lithium niobate (TFLN) is currently one of the most exciting integrated photonic material platforms because of its extra-ordinary non-linear optical properties, low-loss propagation, strong Pockels, piezo and optomechanical response, and so on. Integrated photonics based on TFLN has far-reaching impacts on both classical and quantum technologies and is commercially important for current telecommunication and quantum communication technologies. This thesis will outline the development of some key ingredients for integrated photonic circuits on TFLN that are important for both classical and quantum applications and may play a vital role in both scientific research and commercial technologies based on TFLN-integrated photonics. In this thesis, we will demonstrate the first experimental realization of waveguide integrated superconducting nanowire single photon detector on a nanophotonic χ2 (TFLN) material platform, a key ingredient for integrated quantum photonics. Then, we will highlight our work on developing first-order periodically poled TFLN waveguides for efficient non-linear optical processes on TFLN. We will describe the successful poling of Z-cut TFLN with a poling period as low as 2?m and with a duty cycle close to 50% required for maximum non-linear conversion efficiency covering the transparency window of lithium niobate (LN). Using such PPLN waveguides, we will show our experimental realization of blue light generation in a nanophotonic platform. For practical classical and quantum photonics applications on the TFLN platform, we will then propose a novel fiber-to-chip coupling scheme for the efficient coupling of light to an integrated nanophotonic chip. We will experimentally show that light can be efficiently coupled to an integrated photonic chip from the backside of the chip through the thick substrate by using an apodized grating coupler and a top metal mirror with a clad oxide layer in between with proper thickness. Using this novel coupling scheme, we demonstrate coupling efficiency as high as -1dB for both TE and TM modes on TFLN. Next, we will present our development of hybrid superconducting-photonic circuits on lithium niobate on sapphire (LNoS) platform. Along with the design principle, we will describe the full fabrication process flow for high-Q photonic and microwave circuits on the LNoS platform. Next, based on the developed hybrid superconducting-photonic circuits on the LNoS platform, we show efficient bidirectional microwave-to-optics conversion with an on-chip efficiency of 1.02% along with stable operation at cryogenic temperature. Finally, to improve the system efficiency of the microwave-to-optics converters, we will propose and experimentally demonstrate a double inverse taper design on the LNoS platform and improve the fiber-to-chip coupling efficiency to -2.2dB per facet. The developed waveguide integrated single photon detector, periodically poled nanophotonic waveguides, and high-efficiency fiber-to-chip couplers in this thesis may play a significant role in both scientific and commercial research for both classical and quantum photonic applications. And the developed hybrid photonic-superconducting circuits on TFLN can play a critical role in developing an efficient interconnect between superconducting qubit-based quantum computers.
Recommended Citation
Sayem, Ayed Al, "Integrated Nano-Photonic Circuits on thin-film Lithium Niobate" (2023). Yale Graduate School of Arts and Sciences Dissertations. 1043.
https://elischolar.library.yale.edu/gsas_dissertations/1043
