Single-Particle Dichroism Using Orbital Angular Momentum in a Microwave Plasmonic Resonator

Abstract

Dichroism measurement is mostly restricted to extensive numbers of molecules due to weak response from a single deep-subwavelength particle, and hence single-molecule dichroism is of essential importance for the in-depth study of enantiomers. This paper reports the dichroism capability of a single chiral particle within the diameter of 1/150 wavelengths and smaller, using sharp resonance dips of confined orbital angular momentum (OAM) modes, which are ultrasensitive to disturbance from chiral particles. The OAM modes are realized in a microwave plasmonic resonator via chiral symmetry breaking in the structure. Full-wave simulations and OAM density analysis of the resonant modes confirm the single-particle dichroism principle. Experimental results agree well with the simulations. The principle is demonstrated in the microwave frequency for convenient manipulations and intensive investigations, while it envisions ground-breaking applications of the confined OAM modes in on-chip single-molecule dichroism in the optical frequency range.

Optical vortex dichroism in chiral particles

“…Whilst previous chiroptical absorption mechanisms have been discovered for vortex light in oriented media, the importance of the result here is that it persists in fluids consisting of chiral particles, which has an acute importance in the field of optical activity and spectroscopies utilized in chemical and biochemical systems which are invariably in the liquid phase. There have been both a number of circular-vortex differential [19,47,48] and vortex differential [40,[49][50][51][52] effects reported, though no vortex dichroism (absorption) effects in isotropic chiral molecular matter of the nature here has been reported thus far to the best of our knowledge. The underlying principles of this work can easily be extended to other types of optical activity, such as optical rotation or Rayleigh and Raman optical activity (scattering effects).…”

Contactless Glucose Sensing at Sub‐Micromole Level Using a Deep‐Subwavelength Decimeter‐Wave Plasmonic Resonator

“…[32,33] In 2021, Zhang and Cui demonstrated a toroidal SLSP resonator with a diameter of 1/20 wavelength and an intrinsic Q-factor higher than 100, which envisions the SLSPs' potentials in traceamount biomedical sensing. [17,34] In this work, we propose an SLSP resonator in the microwave frequency, which is composed of two Archimedean spirals in a single-layer pattern. The fundamental resonance experimentally presents the deep-subwavelength confinement within a diameter of 𝜆 0 /41 (𝜆 0 is the free-space wavelength), and a measured Q-factor of 187.…”

Mixed-Resolution High-Q Sensor Based on Hybridized Spoof Localized Surface Plasmons

“…Following that, many different structures of spoof LSPs such as ultrathin corrugated metal-insulator-metal ring resonator [4], compact spoof LSPs [5], spoof LSP hybridization [6], spiral spoof LSPs [7], and meander line structure [8] were investigated and proposed. Spoof LSPs have been proven to be valuable in the design of resonators [9][10][11], filters [12,13], sensors [14], biomedical applications [15], etc. Due to the strong confinement of the electromagnetic field [16], the spoof LSP resonance has a high-Q-factor [17] and is sensitive to the surrounding environment.…”