Simulation of single transparent molecule interaction with an optical microcavity

Abstract

Finite-element simulations of nanoscale molecule interaction with the evanescent radiation field of an optical resonant microcavity are conducted to characterize the detection of single transparent molecules using the microcavity as an extremely sensitive micro/nano-sensor. The model sensor is an integrated device consisting of a dielectric microdisk and a waveguide that can be nanofabricated on Si-based dielectric thin film. When the microdisk is operated at a whispering-gallery mode, a strong evanescent field arises, surrounding the periphery of the cavity. Foreign target molecules such as proteins present in the near-field will interact with the electromagnetic resonant field and induce changes to the resonance. Such induced changes are investigated in this report and their significance in the detection of single molecules for nanotechnology development is discussed.

Biosensing in a microelectrofluidic system using optical whispering-gallery mode spectroscopy

“…13,14 To validate the current simulation, the adsorption of BSA at two different concentrations (20 pM and 500 pM) onto a silica micro resonator at pH 6.6 in the absence of external electrical field is simulated and compared with the experimental results by Yeung et al 28,31 The parameter values used in the simulation were given in Table I of Yeung et al through a simple Langmuir model. 28 The surface saturation concentration are calculated as 0.448 Â 10 À13 and 5.418 Â 10 À12 mol/m 2 for 20 pM and 500 pM, respectively.…”

“…Nowadays, research on whispering-gallery mode (WGM) based biosensing has attracted increasing attention, because of its extremely high sensitivity in the detection of molecules or nano-entities. [12][13][14][15] It is well known that WGM resonance frequencies depend on the effective size and refractive index of the resonator. [16][17][18] At a resonance, photons are trapped and internally reflected in an orbit within the resonator surface of circular shape.…”

“…As the photons guided by total internal reflection in the resonator circulate many times, they interact repeatedly with adsorbate on the surface of the resonator, leading to resonance frequency shifts. [12][13][14] On the other side, temperature variation due to absorption of laser energy during laser scanning or pumping 19 could change resonator conditions because of the thermal expansion and thermo-optic effects. 20 Ma et al 20,21 measured resonance wavelength shifts against temperature changes for different silica beads.…”

Whispering Gallery Mode Devices for Sensing and Biosensing

“…Of course, one can detect the change of the surrounding refractive index by immersing the microdisk in different analyte fluids [192][193][194][195][196][197][198][199]. Microdisks have also been tested as displacement sensors [200], gamma ray sensors [201], gas sensors [202], surface curvature sensors, [203] and of course as biosensors [194,197,[204][205][206][207][208][209][210]. Each of these applications will be briefly discussed.…”

“…Microdisks can also be used for bio-sensing applications [194,197,[204][205][206][207][208][209][210], much like the case for microspheres discussed earlier. The surface of the microdisks can be functionalized by methods listed in Sect.…”