Silicon is the most widely used semiconductor material. It is cheap, abundant, and non-toxic – maybe most importantly: industry has spent a fortune developing it over the last half a century, and the complementary metal-oxide-semiconductor (CMOS) methods are undoubtedly the most mature nanofabrication technology, enabling a fast transition from research to commercialization. Foundries achieve unchallenged performance in terms of yield, resolution, and complexity – but often sacrifice the extreme performance needed to study novel physics in order to maintain a high throughput.
In this talk, I will present a silicon nanofabrication process tailored to the silicon-on-insulator platform, which is capable of manufacturing nanometer-scale features vertically and with low roughness. We combine this process with fabrication-constrained topology optimization to realize a dielectric cavity with a mode volume V = 3×10−4 𝜆^3, quality factor Q = 1100, and footprint 4𝜆^2 for telecom photons with a 𝜆 ∼ 1550 nm wavelength. The cavity confines light inside an 8-nm–bowtie etched with an ultra-high aspect ratio of 30, and the mode volume is an order of magnitude smaller compared to previous experiments in dielectrics. We measure the near-field of the cavity mode to corroborate the extreme dielectric confinement of light [Nat. Commun. 13, 6281 (2022)].
Additionally, we use the same process to fabricate reconfigurable silicon photonic circuits based on nano-electro-mechanical systems (NEMS). This offers efficient tunability by changing the effective refractive index of a suspended waveguide, enabling fast and compact phase-shifters and splitters for photonic integrated circuits such as switching-networks [arXiv:2204.14257 (2022)]. It further enables compact and low-cost telecom delay-lines and I will present the main application of my PhD developing a chip-scale NEMS spectrometer.
In the last part of my talk I will discuss additional applications of this high-resolution nanofabrication within phononics [Nat. Nanotechnol. 17, 947-951 (2022)], and photonic topological insulators [arXiv:2206.11741].
Marcus is a PhD student at the Technical University of Denmark and has a BSc in Physics from the University of Bath in England (2017) and an MSc from the University of Copenhagen (2019). He works on the design, fabrication, and characterization of nano-electro-mechancial silicon photonics, focusing on high-resolution silicon nanofabrication and the novel physics that can be explored when pushing the fabrication frontier. Marcus has worked with complex mask design and electron-beam lithography for more than 6 years since early in his BSc, both in academic projects and later as a software developer in the startup company Beamfox Proximity.