Optical Sensors Based on Whispering Gallery Modes in Fluorescent Microbeads: Response to Specific Interactions

Himmelhaus, Michael; Krishnamoorthy, Sivashankar; François, Alexandre

doi:10.3390/s100606257

Cited by 51 publications

(55 citation statements)

References 18 publications

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“…Although these resonators exhibit useful properties, and have been widely used for refractive index sensing applications, substantial effort has been made in recent years to improve their sensing performance. Researchers have moved towards using smaller resonators, with early work considering submillimeter [3,12] silica spheres, and more recent developments enabling resonators as small as 10 to 50 μm in diameter [7,8,13,14]. Note that the refractive index sensitivity (S = δλ/δn) is known to be inversely proportional to the resonator radius (Δλ/λ = ΔR/R) [3,15].…”

Section: Introductionmentioning

confidence: 99%

“…refractive index) in the vicinity of the resonator [4,5]. While resonators with different geometry and optical properties have been investigated [6], spheres [3,5,7,8], toroids [1,9] or capillaries [2,10,11] have been the most widely studied. Although these resonators exhibit useful properties, and have been widely used for refractive index sensing applications, substantial effort has been made in recent years to improve their sensing performance.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Enhancing the radiation efficiency of dye doped whispering gallery mode microresonators

François¹,

Rowland²,

Afshar³

et al. 2013

Opt. Express

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Enhancing the radiation efficiency of dye doped whispering gallery mode microresonators

François¹,

Rowland²,

Afshar³

et al. 2013

Opt. Express

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“…The polymers used are poly(allylamine hydrochloride) (PAH) and poly(sodium 4 styrenesulfonate) (PSS), which are positively (PAH) and negatively (PSS) charged, respectively, in aqueous solutions. This system has been extensively studied by a plurality of analytical methods and is well understood [5]. The increase in thickness per PSS / PAH double layer amounts to 3 nm with a relative contribution of 2:1 (PSS : PAH).…”

Section: Adsorption Studiesmentioning

confidence: 99%

“…With proper surface functionalization, this property can be exploited for bacterial sensing, immuno-sensing, and the detection of DNA hybridization. While there exists a variety of other methods for the measurement of adsorbates, such as quartz microbalance, reflectometry, ellipsometry, and surface plasmon resonance, to name just the most common techniques, it should be noted that in the case of WGM microresonators, the adsorbing surface is truly microscopic (about 200 µm 2 ) [5], the particle can be easily directed to a wanted site, e.g. by means of optical tweezers, and further readily disposed after measurement without the need for exchanging the entire environment.…”

Section: Adsorption Studiesmentioning

confidence: 99%

Microsensors on the Fly

Himmelhaus¹

2016

Optik & Photonik

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Optically driven microresonators freely floating in liquids, embedded into transparent solid media, or even taken up by life cells, can be exploited as optical microsensors, which yield precise information on the immediate local condition of their respective environment. Besides plain physical information, such as on local refractive indices, mechanical stress, and mixture ratios in composite materials, the sensors may be applied as chemical and even bio-sensors for the specific targeting of biochemical binding reactions if accordingly functionalized. Sensitivity can be further improved by driving the sensors above the lasing threshold, thereby increasing signal intensity and optical resolution at the same time. In this article, we introduce the optical principles, present useful implementations, and illustrate feasibility of this still novel approach to optical sensing by a number of diverse examples.With the advent of the laser diode, microresonators capable of confining light to microscopic volumes have entered everyday's life with applications as laser pointers, light sources in CD, DVD and Blu-ray disk drives, and do-it-yourself metrology tools, to name just the most common examples. Intrinsically shaped into their gain medium, these semiconductor devices can achieve extremely small sizes in the micrometer regime, however, since they are electrically powered, they require a fixed connection to the macroscopic world in the form of some electrical driver, which still renders the entire device macroscopic.Here, we report about optically driven microresonators that overcome the need for fixation to a macroscopic power supply and thus turn into microsensors of 3D quantum system characterized by quantum numbers q, n, m for radial, azimuthal, and polar quantization and polarizations TE, TM (transverse electric / transverse magnetic modes, respectively). Fig. 1 (a) Illustration of a whispering gallery mode with quantum numbers q = 3 (three radial maxima), n = 44 (no. of wavelengths along circumference), and m = n (1 polar maximum); (b) Cross section in radial direction showing the field distribution of the WGM of (a); please note the exponential decay outside of the microresonator, which is a peculiarity of WGM resonators; (c) Fluorescence emission spectra of 10 µm coumarin 6G doped polystyrene microbeads as recorded with a set up as sketched in Fig. 2c; the spectrum plotted in blue origi nates from a spherical bead and exhibits several WGMs with q = 1 and several quantum numbers n (distinguished by a different number of wavelengths fitting into the circumference of the bead). For each quantum number n, there is a pair of modes with differing polariza tion (TE, TM) as indicated in the spectrum. The spectrum plotted in red stems from a particle stained with the same fluorophore, but with an odd shape, so that WGMs are not supported. By subtraction of the two spectra, the non resonant fluorescence background can be removed and the pure WGM spectrum is obtained (spectrum in green, Data of (c) taken from [6]).

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“…Therefore, the existance of the immobilized antibody leads to wavelength shifts. 6,37,38 Moreover, as shown in Fig. 3(d), in order to explore the effect of an antibody thin layer on the resonance, we calculated the theoretical scattering cross-section spectra of a PS microsphere using Mie scattering theory.…”

Section: Wgm Spectra Evaluation Of the Antibody Immobilization Ps Micmentioning

confidence: 99%

Optical Characterization of the Antigen-Antibody Thin Layer Using the Whispering Gallery Mode

et al. 2014

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We immobilized an antibody (anti-β-Galactosidase) on a polystyrene microsphere by using a covalent bond, and observed the resonance peaks in the scattered light intensity spectra related to the whispering gallery mode (WGM) excitation of the microsphere. The amount and the optical parameters, i.e., thickness and refractive index, of anti-β-Galactosidase on the sphere surface were evaluated based on an absorbance measurement and a resonance peak shift measurement, respectively. Moreover, we measured the variation of the WGM spectra depending on the concentration of the enzyme solution (β-Galactosidase), which allowed us to optically evaluate the thickness and the refractive index of the antigen-antibody layer from the shift of the WGM spectra peak.

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Optical Sensors Based on Whispering Gallery Modes in Fluorescent Microbeads: Response to Specific Interactions

Cited by 51 publications

References 18 publications

Enhancing the radiation efficiency of dye doped whispering gallery mode microresonators

Enhancing the radiation efficiency of dye doped whispering gallery mode microresonators

Microsensors on the Fly

Optical Characterization of the Antigen-Antibody Thin Layer Using the Whispering Gallery Mode

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