David O. Bracher

Deterministic coupling of delta-doped nitrogen vacancy centers to a nanobeam photonic crystal cavity

The negatively-charged nitrogen vacancy center (NV) in diamond has generated significant interest as a platform for quantum information processing and sensing in the solid state. For most applications, high quality optical cavities are required to enhance the NV zero-phonon line (ZPL) emission. An outstanding challenge in maximizing the degree of NV-cavity coupling is the deterministic placement of NVs within the cavity. Here, we report photonic crystal nanobeam cavities coupled to NVs incorporated by a delta-doping technique that allows nanometer-scale vertical positioning of the emitters. We demonstrate cavities with Q up to ~24,000 and mode volume V ~

High quality SiC microdisk resonators fabricated from monolithic epilayer wafers

0.47({\lambda}/n)^{3}

Selective Purcell enhancement of two closely linked zero-phonon transitions of a silicon carbide color center.

as well as resonant enhancement of the ZPL of an NV ensemble with Purcell factor of ~20. Our fabrication technique provides a first step towards deterministic NV-cavity coupling using spatial control of the emitters.

Fabrication of High-Q Nanobeam Photonic Crystals in Epitaxially Grown 4H-SiC

The exquisite mechanical properties of SiC have made it an important industrial material with applications in microelectromechanical devices and high power electronics. Recently, the optical properties of SiC have garnered attention for applications in photonics, quantum information, and spintronics. This work demonstrates the fabrication of microdisks formed from a p-N SiC epilayer material. The microdisk cavities fabricated from the SiC epilayer material exhibit quality factors of as high as 9200 and the approach is easily adaptable to the fabrication of SiC-based photonic crystals and other photonic and optomechanical devices.

Bottom-up engineering of diamond micro- and nano-structures

Significance Semiconductor point defects have shown great promise in their application to quantum information and sensing in the solid state. However, it is an ongoing challenge to efficiently access the light emitted by these spin-active defects and, furthermore, to enhance the emission at wavelengths that can be used to create indistinguishable photons. Such emission enhancement can be achieved by placing the defects within optical microcavities. Here, using 1D photonic crystal cavities, we report the significant enhancement of point-defect emission in silicon carbide, which hosts a suite of intriguing spin-active defects. In addition to measuring large enhancements, we also demonstrate how the cavity coupling can potentially allow access to a variety of information about the defects and their environment. Point defects in silicon carbide are rapidly becoming a platform of great interest for single-photon generation, quantum sensing, and quantum information science. Photonic crystal cavities (PCCs) can serve as an efficient light–matter interface both to augment the defect emission and to aid in studying the defects’ properties. In this work, we fabricate 1D nanobeam PCCs in 4H-silicon carbide with embedded silicon vacancy centers. These cavities are used to achieve Purcell enhancement of two closely spaced defect zero-phonon lines (ZPL). Enhancements of >80-fold are measured using multiple techniques. Additionally, the nature of the cavity coupling to the different ZPLs is examined.

Fabrication of high-quality nanobeam photonic crystal cavities in 4H silicon carbide with embedded color centers

Silicon carbide (SiC) is an intriguing material due to the presence of spin-active point defects in several polytypes, including 4H-SiC. For many quantum information and sensing applications involving such point defects, it is important to couple their emission to high quality optical cavities. Here we present the fabrication of 1D nanobeam photonic crystal cavities (PCC) in 4H-SiC using a dopant-selective etch to undercut a homoepitaxially grown epilayer of p-type 4H-SiC. These are the first PCCs demonstrated in 4H-SiC and show high quality factors (Q) of up to ∼7000 as well as low modal volumes of <0.5 (λ/n)(3). We take advantage of the high device yield of this fabrication method to characterize hundreds of devices and determine which PCC geometries are optimal. Additionally, we demonstrate two methods to tune the resonant wavelengths of the PCCs over 5 nm without significant degradation of the Q. Lastly, we characterize nanobeam PCCs coupled to luminescence from silicon vacancy point defects (V1, V2) in 4H-SiC. The fundamental modes of two such PCCs are tuned into spectral overlap with the zero phonon line (ZPL) of the V2 center, resulting in an intensity increase of up to 3-fold. These results are important steps on the path to developing 4H-SiC as a platform for quantum information and sensing.

Bottom-up Engineering of Diamond Nanostructures

Engineering nanostructures from the bottom up enables the creation of carefully engineered complex structures that are not accessible via top down fabrication techniques, in particular, complex periodic structures for applications in photonics and sensing. In this work, we propose and demonstrate a bottom up approach that can be adopted and utilized to controllably build diamond nanostructures. A realization of periodic structures and optical wave-guiding is achieved by growing nanoscale single crystal diamond through a defined pattern.

Bottom-up engineering of diamond micro- and nano-structures: Bottom-up engineering of diamond nanostructures

A wide band-gap semiconductor with a long history of growth and device fabrication, silicon carbide (SiC) has attracted recent attention for hosting several defects with properties similar to the nitrogen vacancy center in diamond. In the 4H polytype, these include the silicon vacancy center and the neutral divacancy, which have zero phonon lines (ZPL) in the near-IR and may be useful for quantum information and nanoscale sensing. For many such applications, it is critical to increase the defect emission into the ZPL by coupling the emission to an optical cavity. Accordingly, we have pursued the fabrication of high quality 1D nanobeam photonic crystal cavities (PCCs) in 4H-SiC, using homoepitaxially grown material and a photoelectrochemical etch to provide optical isolation. These PCCs are distinctive in their high theoretical quality factors (Q > 106) and low modal volumes (V < 0.5 (λ/n)3). Here, we present arrays of nanobeam PCCs with varied lattice constant containing embedded silicon vacancy defects generated by electron irradiation, to assess its viability as a method for defect creation. The lattice constant variation allows us to create devices with modes spanning the entire range of the silicon vacancy emission. We accordingly demonstrate nanobeam PCCs with resonant modes near both ZPLs of the silicon vacancy defect. Moreover, we measure devices with the highest Q cavity modes coupled to point defect emission in SiC yet reported, providing evidence that electron irradiation can be used to generate point defects while maintaining high quality optical devices.

Fabrication of thin diamond membranes for photonic applications

Engineering nanostructures from the bottom up enables the creation of carefully engineered complex structures that are not accessible via top down fabrication techniques, in particular, complex periodic structures for applications in photonics and sensing. In this work, we propose and demonstrate a bottom up approach that can be adopted and utilized to controllably build diamond nanostructures. A realization of periodic structures and optical wave-guiding is achieved by growing nanoscale single crystal diamond through a defined pattern.

Hybrid Plasmonic Photonic Crystal Cavity for Enhancing Emission from near-Surface Nitrogen Vacancy Centers in Diamond

Engineering nanostructures from the bottom up enables the creation of carefully engineered complex structures that are not accessible via top down fabrication techniques, in particular, complex periodic structures for applications in photonics and sensing. In this work, we propose and demonstrate a bottom up approach that can be adopted and utilized to controllably build diamond nanostructures. A realization of periodic structures and optical wave-guiding is achieved by growing nanoscale single crystal diamond through a defined pattern.