arXiv subjects

Thomas Y. L. Ang

Publications and source records attributed to Thomas Y. L. Ang.

3 recordsLinked to original sources

arXiv2026

Free-Running Waveguide-Integrated Single-Photon Avalanche Detectors for Visible Light

Waveguide-integrated single-photon avalanche detectors (SPADs) are essential components of integrated photonics platforms for scalable extreme-low-light applications without the use of cryogenics. Here, we demonstrate an integrated SPAD for visible light operating at room temperature in a free-running mode without gating. The device is based on a doped silicon diode end-fire-coupled to a silicon nitride (SiN) photonic integrated circuit (PIC). We investigate a range of lateral and vertical doping profile designs, and operate the devices with a simple current-mode passive quenching circuit. The optimal device is a laterally-doped p-i-n+ SPAD with a maximum photon detection efficiency (PDE) of 1.95 +/- 0.32% for input light at 685 nm wavelength, when reverse-biased at an excess of 1.5 V beyond the breakdown voltage of 15.0 V. We identify promising avenues for improving device performance, which would enable such integrated SPADs to be an attractive choice for cutting-edge integrated photonics solutions in quantum technologies, low-light imaging, and high-speed communications at visible wavelengths.

physics.optics↗

arXiv2024

Responsivity evaluation of photonics integrated photodetectors via pairwise measurements with an attenuation circuit

Integrated photonics platforms offer a compact and scalable solution for developing next-generation optical technologies. For precision applications involving weak signals, the responsivity as well as the accurate calibration of the integrated photodetectors at low optical powers become increasingly important. It remains challenging to perform a calibration traceable to mW-level primary standards without relying on external attenuation setups. Here, we utilize an on-chip attenuation circuit, composed of a series of cascaded directional couplers (DCs), to evaluate the responsivity of integrated photodetectors (PDs) at uW optical power levels with mW inputs to the chip. Moreover, we show that a pairwise measurement method, involving the simultaneous measurement of the integrated PD photocurrent and an auxiliary optical output which is coupled off-chip, systematically improves the experimental uncertainties compared to a direct PD photocurrent measurement. For 3 cascaded DCs, the pairwise measurement improves the repeatability error from 1.21% to 0.22%, with an overall expanded calibration uncertainty (k=2) of 10.13%. The latter is dominated by the scattering noise floor and fiber-to-chip coupling errors, which can be significantly improved with better device fabrication control. Our method can be extended to a fully integrated calibration solution for waveguide-integrated single-photon detectors.

physics.optics↗

arXiv2020

Photonic convolutional neural networks using integrated diffractive optics

With recent rapid advances in photonic integrated circuits, it has been demonstrated that programmable photonic chips can be used to implement artificial neural networks. Convolutional neural networks (CNN) are a class of deep learning methods that have been highly successful in applications such as image classification and speech processing. We present an architecture to implement a photonic CNN using the Fourier transform property of integrated star couplers. We show, in computer simulation, high accuracy image classification using the MNIST dataset. We also model component imperfections in photonic CNN and show that the performance degradation can be recovered in a programmable chip. Our proposed architecture provides a large reduction in physical footprint compared to current implementations as it utilizes the natural advantages of optics and hence offers a scalable pathway towards integrated photonic deep learning processors.

eess.SP↗