UC Santa Barbara

Solid-state quantum emitters are an indispensable resource for quantum photonic technologies including optical quantum processors, transceivers for secure communications and networking, and random number generation. These technologies can be made into compact and efficient modules by leveraging the mature silicon photonics ecosystem; however, suitable quantum emitters have not yet been demonstrated in silicon-based photonics. The development of CMOS-compatible, high-quality quantum emitters capable of on-demand single-photon generation could revolutionize the field of quantum information in the same way the laser has transformed global communications and high-speed data networks.

Two key requirements are necessary to address this challenge: (1) identification of emitters capable of high purity, high indistinguishability, and bright single-photon generation, and (2) the deterministic integration and alignment of such emitters with silicon-based photonic microcavities to achieve efficient on-chip emission. Many platforms have been developed to address the first challenge, including quantum dots, diamond color centers, and defects in two-dimensional materials . The second challenge has been more difficult to overcome and calls for a hetero-integrated approach that integrates materials hosting high-quality emitters into the silicon-photonic fabrication flow.

In recent years, the discovery of defect-based single quantum emitters (SQEs) in 2D materials (2DMs), most notably WSe2 and h-BN, has given a boost to this effort. In this thesis, I present our experiments that shed light on the origins of SQEs in 2DMs and practical methods to site-specifically engineer SQEs in 2D materials with 50 nm spatial resolution, near unity yield, over 95% purity, and record-breaking working temperatures--an achievement exclusive to 2D material platforms. I will present several advances in photonic integration of these emitters that resulted in a development of a 2D-compatible photonic integration platform. The first is the growth of high-quality, non-stoichiometric silicon nitride, which eliminates the auto-fluorescence background in stoichiometric Si3N4 films. The second is the process to embed emitters within the photonic waveguiding layer, enabling efficient coupling to a single guided optical mode and the third is the alignment of the emitter position and optical dipole moment with the cavity mode, resulting in > 46% on-chip single-photon collection efficiency and > 95% single-photon purity at room temperature. This is the first demonstration of microcavity integration of quantum emitters in two-dimensional material emitters with silicon-based photonics, which improved the on-chip coupling efficiency by an order-of-magnitude over previous demonstrations.

Finally, I will present an outlook to the future of this platform and specifically our progress to integrate our cavity-coupled SQEs into diode structures enabling electrical triggering of single-photons and prototyping the first on-chip quantum light emitting device (qLED).