Acoustic, Microwave and Optical Devices in Lithium Niobate and Diamond

Abstract

Microwave photons are dominating local information processing, while optical photons are essential for long-distance communications. Micro/nano-devices hybridizing microwave and optical signals can thus provide unique opportunities for classical and quantum computing, realization of chip scale and distributed networks, and so on. The interaction between microwave and optical signals relies on nonlinear processes, which occur in nonlinear crystals, atoms, and solid-state emitters. In this dissertation, I present hybrid platforms for microwave electronics, microwave acoustics, and integrated optics using a nonlinear crystal, lithium niobate, and a solid-state quantum emitter, nitrogen-vacancy centers in diamond. I investigate the developed platforms from theoretical considerations and system dynamics to numerical simulations and experimental realizations. First, I developed a design methodology for high-performance surface acoustic wave resonators using phononic band structure engineering. The experimentally-demonstrated frequency-quality-factor product, an important figure of merit for acoustic resonators, of $10^{13}$ compares favorably to state of the art (at room temperature). Next, non-Hermitian acoustic systems are experimentally demonstrated by engineering the material response to acoustic waves using external electronic circuits. The piezoelectricity of lithium niobate is leveraged to bridge the acoustic and electrical systems via interdigital transducers, which are interlocking metallic electrodes placed on piezoelectric materials. The electrical system can provide desired gain, loss, and nonlinearity for the acoustic system. We demonstrate nonreciprocal isolation of $10$ dB for microwave phonons in the parity-time-symmetric nonlinear acoustic resonators. I, further, demonstrate acoustically-mediated microwave-to-optical conversion in thin-film lithium niobate. Enhanced by the interdigital-transducer-coupled acoustic resonators, optical Mach-Zehnder interferometers and racetrack cavities exhibit improved optical modulations by the input microwaves. A microwave optical link with unitary link gain is also experimentally achieved. Finally, I explore a wide-filed microwave imaging technique using the unique spin-dependent fluorescence of nitrogen-vacancy color centers in diamond. These luminescent defects in diamond map the near-field magnetic fields at microwave frequency to fluorescence intensities. Using this technique, I demonstrate a potential application in a noninvasive monitoring of the activity of integrated circuits.