Abstract:

Shortwave-infrared (SWIR) light underpins optical and quantum communications, night vision and biomedical imaging, yet planar InGaAs and Ge detectors struggle to reach single-photon sensitivity without cryogenic cooling because of their dark current and thermal noise. In this talk, I will demonstrate a highly sensitive self-powered InGaAs nanowire photodetector with single-photon-level sensitivity at 1310 nm. The device utilizes a p+ InGaAs/Indium Tin Oxide (ITO) radial heterojunction nanowire structure, enabling strong optical confinement, efficient carrier extraction, and significant reduction of dark current. The resulting self-powered photodiode detects SWIR pulses containing only a few photons at room temperature and enables single-pixel imaging under extremely low illumination.

Because the optical response of these nanowires is set by their geometry, the same platform can do more than detect light efficiently. I will then present ongoing work in which an elliptical, tapered nanowire splits the fundamental guided mode into two orthogonally polarized resonances. The optically isotropic InGaAs absorber then shows orthogonal dual-band linear dichroism: its preferred polarization axis switches by 90° between two SWIR bands. Because this anisotropy is defined lithographically, pixels with rotated nanowire arrays can be fabricated simultaneously on one chip, opening a new route toward compact detectors with enhanced functions that resolve both the polarization and the spectral information of the incident light.

Bio:

I received my B. Sc. (Hons) degree in Physics from the University of Peradeniya Sri Lanka in 2018. From 2018 to 2021, I worked as a teaching assistant and later as a probationary lecturer at the University of Peradeniya before I joined as a PhD student at the TMOS Centre at the Australian National University under the supervision of Prof Lan Fu. My current research project focuses on the design, fabrication, and characterization of III/V nanowire-based, 1. Single photon detectors 2. IR photodetectors and 3. Polarization-sensitive photodetectors.