High-Q and high finesse silicon microring resonator

We demonstrate the design, fabrication, and experimental characterization of a single transverse mode adiabatic microring resonator (MRR) implemented using the silicon-on- insulator (SOI) platform using local oxidation of silicon (LOCOS) approach. Following its fabrication, the device was characterized experimentally and an ultrahigh intrinsic Q-factor of ∼2 million with a free spectral range (FSR) of 2 nm was achieved, giving rise to a finesse of ∼1100, the highest demonstrated so far in SOI platform at the telecom band. We have further studied our device to analyze the source of losses that occur in the MRR and to understand the limits of the achievable Q-factor. The surface roughness was quantified using AFM scans and the root mean square roughness was found to be ∼ 0.32±0.03 nm. The nonlinear losses were further examined by coupling different optical power levels into the MRR. Indeed, we could observe that the nonlinear losses become more pronounced at power levels in the range of hundreds of microwatts. The demonstrated approach for constructing high-Q and high finesse MRRs can play a major role in the implementation of devices such as modulators, sensors, filters, frequency combs and devices that are used for quantum applications, e.g., photon pair generation.

CMOS-compatible electro-optical SRAM cavity device based on negative differential resistance

The impending collapse of Moore-like growth of computational power has spurred the development of alternative computing architectures, such as optical or electro-optical computing. However, many of the current demonstrations in literature are not compatible with the dominant complementary metal-oxide semiconductor (CMOS) technology used in large-scale manufacturing today. Here, inspired by the famous Esaki diode demonstrating negative differential resistance (NDR), we show a fully CMOS-compatible electro-optical memory device, based on a new type of NDR diode. This new diode is based on a horizontal PN junction in silicon with a unique layout providing the NDR feature, and we show how it can easily be implemented into a photonic micro-ring resonator to enable a bistable device with a fully optical readout in the telecom regime. Our result is an important stepping stone on the way to new nonlinear electro-optic and neuromorphic computing structures based on this new NDR diode.

MoSe2/WS2 heterojunction photodiode integrated with a silicon nitride waveguide for near infrared light detection with high responsivity

We demonstrate experimentally the realization and the characterization of a chip-scale integrated photodetector for the near-infrared spectral regime based on the integration of a MoSe₂/WS₂ heterojunction on top of a silicon nitride waveguide. This configuration achieves high responsivity of ~1 A W^-1 at the wavelength of 780 nm (indicating an internal gain mechanism) while suppressing the dark current to the level of ~50 pA, much lower as compared to a reference sample of just MoSe₂ without WS₂. We have measured the power spectral density of the dark current to be as low as ~1 × 10^-12 A Hz^-0.5, from which we extract the noise equivalent power (NEP) to be ~1 × 10^-12 W Hz^-0.5. To demonstrate the usefulness of the device, we use it for the characterization of the transfer function of a microring resonator that is integrated on the same chip as the photodetector. The ability to integrate local photodetectors on a chip and to operate such devices with high performance at the near-infrared regime is expected to play a critical role in future integrated devices in the field of optical communications, quantum photonics, biochemical sensing, and more.

Spectrally Gated Microscopy (SGM) with Meta Optics for Parallel Three-Dimensional Imaging

Volumetric imaging with high spatiotemporal resolution is of utmost importance for various applications ranging from aerospace and defense to real-time imaging of dynamic biological processes. To facilitate three-dimensional sectioning, current technology relies on mechanisms to reject light from adjacent out-of-focus planes either spatially or by other means. Yet, the combination of rapid acquisition time and high axial resolution is still elusive, motivating a persistent pursuit for emerging imaging approaches. Here we introduce and experimentally demonstrate a concept named spectrally gated microscopy (SGM), which enables a single-shot interrogation over the full axial dimension while maintaining a submicron sectioning resolution. SGM utilizes two important features enabled by flat optics (i.e., metalenses or diffractive lenses), namely, a short focal length and strong chromatic aberrations. Using SGM we demonstrate three-dimensional imaging of millimeter-scale samples while scanning only the lateral dimension, presenting a significant advantage over state-of-the-art technology.

Experimental demonstration of CMOS-compatible long-range dielectric-loaded surface plasmon-polariton waveguides (LR-DLSPPWs)

We demonstrate the design, fabrication and experimental characterization of long-range dielectric-loaded surface plasmon-polariton waveguides (LR-DLSPPWs) that are compatible with complementary metal-oxide semiconductor (CMOS) technology. The demonstrated waveguide configuration represents a silicon nitride ridge atop a thin strip of metal, which is positioned on a partially oxidized layer of silicon supported by a silicon oxide layer. The demonstrated waveguides feature reasonable mode confinement (~0.5μm2) and show rather long propagation (~700 μm) at telecom wavelengths. Owing to the existence of a metal strip within the structure, one can envision the co-propagation of electrical and photonic signals within the structure, enabling thereby seamless integration of photonic and electronic circuits. Electrical signals in metal strips supporting plasmonic modes can be used for variety of applications, e.g. to control the propagation of radiation via the thermo-optic effect.