arXiv subjects

Neil Na

Publications and source records attributed to Neil Na.

7 recordsLinked to original sources

arXiv2026

Review of germanium-silicon single-photon avalanche diodes

While it took about a decade for a germanium (Ge) thin film grown on a silicon (Si) substrate to be successfully applied as a detector material for high-speed optical fiber communication application, it took about another decade to further expand its usage as a sensor material for active optical sensing and imaging applications. In this paper, we shall review the progress of a shortwave infrared (SWIR) single-photon detection (SPD) with germanium-silicon (GeSi) single-photon avalanche diode (SPAD), ranging from the first demonstration at cryogenic temperature (Z. Lu et al., 2011) to the recent demonstration at room temperature (N. Na et al, 2024). Potential new applications will also be discussed.

physics.ins-det↗

arXiv2025

Implementation of transformer-based LLMs with large-scale optoelectronic neurons on a CMOS compatible platform

The recent rapid deployment of datacenter infrastructures for performing large language models (LLMs) and related artificial intelligence (AI) applications in the clouds is predicted to incur an exponentially growing energy consumption in the near-term future. In this paper, we propose and analyze the implementation of the transformer model, which is the cornerstone of the modern LLMs, with novel large-scale optoelectronic neurons (OENs) constructed over a complementary metal-oxide-semiconductor (CMOS) compatible platform. With all of the required optoelectronic devices and electronic circuits integrated in a chiplet only about 2 cm by 3 cm in size, 175 billon parameters in the case of GPT-3 are shown to perform inference at an unprecedented speed of 12.6 POPS using only 40 nm CMOS process node, orchestrated by an optoelectronic version of systolic array with no data skew and negligible propagation delay, along with a high power efficiency of 74 TOPS/W and a high area efficiency of 19 TOPS/mm2. The influence of the quantization formats and the hardware induced errors are numerically investigated, and are shown to have a minimal impact. Our study presents a new yet practical path toward analog neural processing units (NPUs) to complement existing digital processing units.

cs.ET↗

arXiv2024

Room temperature operation of germanium-silicon single-photon avalanche diode

The ability to detect single photons has led to the advancement of numerous research fields. Although various types of single-photon detector have been developed, because of two main factors - that is, (1) the need for operating at cryogenic temperature and (2) the incompatibility with complementary metal-oxide-semiconductor (CMOS) fabrication processes - so far, to our knowledge, only Si-based single-photon avalanche diode (SPAD) has gained mainstream success and has been used in consumer electronics. With the growing demand to shift the operation wavelength from near-infrared to short-wavelength infrared (SWIR) for better safety and performance, an alternative solution is required because Si has negligible optical absorption for wavelengths beyond 1 {\mu}m. Here we report a CMOS-compatible, high-performing germanium-silicon SPAD operated at room temperature, featuring a noise-equivalent power improvement over the previous Ge-based SPADs by 2-3.5 orders of magnitude. Key parameters such as dark count rate, single-photon detection probability at 1,310 nm, timing jitter, after-pulsing characteristic time and after-pulsing probability are, respectively, measured as 19 kHz {\mu}m^2, 12%, 188 ps, ~90 ns and <1%, with a low breakdown voltage of 10.26 V and a small excess bias of 0.75 V. Three-dimensional point-cloud images are captured with direct time-of-flight technique as proof of concept. This work paves the way towards using single-photon-sensitive SWIR sensors, imagers and photonic integrated circuits in everyday life.

physics.ins-det↗

arXiv2024

Room-temperature photonic quantum computing in integrated silicon photonics with germanium-silicon single-photon avalanche diodes

Most, if not all, photonic quantum computing (PQC) relies upon superconducting nanowire single-photon detectors (SNSPDs) based on niobium (Nb) operated at a temperature < 4 K. This paper proposes and analyzes 300 K waveguide-integrated germanium-silicon (GeSi) single-photon avalanche diodes (SPADs) based on the recently demonstrated normal-incidence GeSi SPADs operated at room temperature, and shows that their performance is competitive against that of SNSPDs in a series of metrics for PQC with a reasonable time-gating window to resolve the issue of dark-count rate (DCR). These GeSi SPADs become photon-number-resolving avalanche diodes (PNRADs) by deploying a spatially-multiplexed M-fold-waveguide array of M GeSi SPADs. Using on-chip waveguided spontaneous four-wave mixing (SFWM) sources and waveguided field-programmable interferometer mesh (FPIM) circuits, together with the high-metric SPADs and PNRADs, high-performance quantum computing at room temperature is predicted for this PQC architecture.

quant-ph↗

arXiv2022

Van der Waals heterostructure mid-infrared emitters with electrically controllable polarization states and spectral characteristics

Modern infrared (IR) microscopy, communication, and sensing systems demand control of the spectral characteristics and polarization states of light. Typically, these systems require the cascading of multiple filters, polarization optics and rotating components to manipulate light, inevitably increasing their sizes and complexities. Here, we report two-terminal mid-infrared (mid-IR) emitters with electrically controllable spectral and polarization properties. Our devices are composed of two back-to-back p-n junctions formed by stacking anisotropic light-emitting materials, black phosphorus and black arsenic-phosphorus with MoS2. By controlling the crystallographic orientations and engineering the band profile of heterostructures, the emissions of two junctions exhibit distinct spectral ranges and polarization directions; more importantly, these two electroluminescence (EL) units can be independently activated, depending on the polarity of the applied bias. Furthermore, we show that when operating our emitter under the polarity-switched pulse mode, its EL exhibits the characteristics of broad spectral coverage, encompassing the entire first mid-IR atmospheric window, and electrically tunable spectral shapes. Our results provide the basis for developing groundbreaking technology in the field of light emitters.

physics.optics↗

arXiv2017

Quantum state transfer between valley and photon qubits

The electron-photon interaction in 2D materials obeys the rule of electron valley-photon polarization correspondence. At the quantum level, such correspondence can be utilized to entangle valleys and polarizations and attain the transfer of quantum states (or information) between valley and photon qubits. Our work presents a theoretical study of the interaction between the two types of qubits and the resultant quantum state transfer. A generic setup is introduced, which involves optical cavities enhancing the electron-photon interaction as well as facilitating both the entanglement and un-entanglement between valleys and polarizations required by the transfer. The quantum system considered consists of electrons, optically excited trions, and cavity photons, with photons moving in and out of the system. A wave equation based analysis is performed, and analytical expressions are derived for the two important figures of merits that characterize the transfer, namely, yield and fidelity, allowing for the investigation of their dependences on various qubit and cavity parameters. A numerical study of the yield and fidelity has also been carried out. Overall, this work shows promising characteristics in the valley-photon state transfer, with the conclusion that the valley-polarization correspondence can be exploited to achieve the transfer with good yield and high fidelity.

quant-ph↗

arXiv2010

Massive parallel generation of indistinguishable single photons via polaritonic superfluid to Mott-insulator quantum phase transition

We propose the superfluid to Mott-insulator quantum phase transition in an array of exciton-polariton traps can be utilized for massive parallel generation of indistinguishable single photons. By means of analytical and numerical methods, the device operations and system properties are studied using realistic experimental parameters. Such a deterministic, fault-tolerant, massive parallel generation may open up a new perspective in photonic quantum information processing.

quant-ph↗