Advances in optoplasmonic sensors – combining optical nano/microcavities and photonic crystals with plasmonic nanostructures and nanoparticles

Abstract

Nanophotonic device building blocks, such as optical nano/microcavities and plasmonic nanostructures, lie at the forefront of sensing and spectrometry of trace biological and chemical substances. A new class of nanophotonic architecture has emerged by combining optically resonant dielectric nano/microcavities with plasmonically resonant metal nanostructures to enable detection at the nanoscale with extraordinary sensitivity. Initial demonstrations include single-molecule detection and even single-ion sensing. The coupled photonic-plasmonic resonator system promises a leap forward in the nanoscale analysis of physical, chemical, and biological entities. These optoplasmonic sensor structures could be the centrepiece of miniaturised analytical laboratories, on a chip, with detection capabilities that are beyond the current state of the art. In this paper, we review this burgeoning field of optoplasmonic biosensors. We first focus on the state of the art in nanoplasmonic sensor structures, high quality factor optical microcavities, and photonic crystals separately before proceeding to an outline of the most recent advances in hybrid sensor systems. We discuss the physics of this modality in brief and each of its underlying parts, then the prospects as well as challenges when integrating dielectric nano/microcavities with metal nanostructures. In Section 5, we hint to possible future applications of optoplasmonic sensing platforms which offer many degrees of freedom towards biomedical diagnostics at the level of single molecules.

Label‐Free Optical Single‐Molecule Micro‐ and Nanosensors

“…Although this may be a good idea, we hope that we have identified another route to break new grounds, by combining the field of plasmonics with the field of dielectric optical microcavities. In certain cases, this optoplasmonic approach can take advantage of the best of both fields, as demonstrated for single‐molecule sensors with unprecedented levels of detection sensitivity such as single ion sensing . Applying quantum optical measurement techniques to current sensing techniques might further enhance detection sensitivity as demonstrated by the evanescent sensing of single molecules using a tapered optical fiber .…”

“…This mechanism has been successfully exploited to achieve label‐free detection of single molecules. In this section, we highlight the plasmonic, microcavity, and optoplasmonic sensors (a combination of both plasmonic and microcavity sensors) that have very recently enabled the label‐free detection of single molecules.…”

“…Now micro‐ and nanosensors have reached a sensitivity level that allows for the detection of very small single molecules . These extreme advances in label‐free optical detection were first made possible by enhancing the interactions of light with molecules on metal nanostructures.…”

Experimental demonstration of dissipative sensing in a self-interference microring resonator

“…Optical sensing is one of the most important pillars of modern information technology. Various platforms have been utilized to perform optical sensing, such as Fabry-Perot cavities [1], optical fibers/waveguides [2,3], surface plasmonic nano-structures [4,5], and whispering gallery mode (WGM) resonators [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Thanks to the high optical quality factor (Q-factor) and the small mode volume, WGM resonators show excellent sensing performance with high sensitivity and low limit of detection among these platforms.…”

On‐Chip Spiral Waveguides for Ultrasensitive and Rapid Detection of Nanoscale Objects

“…In the past few years, the research focuses on exploring sensing mechanisms to enhance the sensitivity. For example, by microresonant system using the plasmonic enhancement and exceptional point, the sensitivity of optical sensors has been improved down to the single biomolecules and single atomic ions . Optical nanofibers, with the concept of elastic light scattering in dark field, can even reach the quantum‐noise limit .…”