Shift of whispering-gallery modes in microspheres by protein adsorption

Arnold, Stephen; Khoshsima, M.; Teraoka, Iwao; Holler, Stephen; Vollmer, Frank

doi:10.1364/ol.28.000272

Cited by 685 publications

(563 citation statements)

References 9 publications

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“…Ganesan et al 45 measured the bound mass on a scanning probe cantilever due to the self-assembly of PEI and PAA monolayers. They reported measuring 24 pg of bound mass for a 5 layer polyelectrolyte stack over a surface area of 0.9 Â 10 À4 cm 2 which corresponded to a bound surface mass density of 2.67 Â 10 À7 g/cm 2 . The functionalized surface area of a single 1-D photonic crystal resonant sensor including the internal surface area of the holes is 8.36 mm 2 .…”

Section: Discussionmentioning

confidence: 99%

A multiplexed optofluidic biomolecular sensor for low mass detection

2009

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Optical techniques have proven to be well suited for in situ biomolecular sensing because they enable high fidelity measurements in aqueous environments, are minimally affected by background solution pH or ionic strength, and facilitate label-free detection. Recently, there has been significant interest in developing new classes of optically resonant biosensors possessing very high quality-factors. This high quality-factor enables them to resolve the presence of very small amounts of bound mass and leads to very low limits of detection. A drawback of these devices is that the majority of the resonant electromagnetic energy is confined within the solid light-guiding structure thus limiting the degree to which it overlaps with the bound matter. This in turn lowers the ultimate device sensitivity, or the change in output signal in response to changes in bound mass. Here we present a novel optofluidic biosensor platform that incorporates a unique one-dimensional photonic crystal resonator array which enables significantly stronger light-matter interaction. We show here how this, coupled with the ability of planar photonic crystals to spatially localize the optical field to mode volumes on the order of a wavelength cubed, enables a limit of detection on the order of 63 ag total bound mass (estimated using a polyelectrolyte growth model) and a device sensitivity an order of magnitude better than similar devices. The multiplexing capabilities of our sensor are demonstrated by the individual and concurrent detection of interleukins 4, 6 and 8 using a sandwich assay.

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Section: Discussionmentioning

confidence: 99%

A multiplexed optofluidic biomolecular sensor for low mass detection

2009

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“…The highest Q previously reported in water was only 10 6 in a large diameter silica microsphere. 3 Accurate measurements of Q-factors beyond 5 ϫ 10 8 were not possible in this experiment owing to laser linewidth stability. In principle, however, larger toroid diameters should exhibit quality factors as high as 1 ϫ 10 9 , in water, and 1 ϫ 10 10 in D 2 O.…”

Section: Figmentioning

confidence: 95%

Ultra-high-Q microcavity operation in H2O and D2O

Armani

Min

et al. 2005

Applied Physics Letters

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Optical microcavities provide a possible method for boosting the detection sensitivity of biomolecules. Silica-based microcavities are important because they are readily functionalized, which enables unlabeled detection. While silica resonators have been characterized in air, nearly all molecular detections are performed in solution. Therefore, it is important to determine their performance limits in an aqueous environment. In this letter, planar microtoroid resonators are used to measure the relationship between quality factor and toroid diameter at wavelengths ranging from visible to near-IR in both H 2 O and D 2 O, and results are then compared to predictions of a numerical model. Quality factors ͑Q͒ in excess of 10 8 , a factor of 100 higher than previous measurements in an aqueous environment, are observed in both High-Q and ultra-high-Q ͑UHQ͒ silica optical microcavities can perform as highly sensitive detectors; 1-3 they derive their excellent transduction abilities from long photon lifetimes within the whispering gallery of the microcavity. Unlike their optical waveguide counterparts, wherein the photon interacts with a functionalized surface only once, 4,5 recirculation within the microcavity allows photons to interact with the surface many times. Additionally, the surface of silica-based microcavities is easily sensitized using silanization agents, 6 amines, carbohydrates, the biotin-streptavidin system, 7 or antibodies. 8 For example, silica microsphere resonators, with a properly sensitized surface, were recently used to distinguish between two strands of DNA. 9 However, while detailed studies have been performed to determine the limits of a resonator's quality factor in air, 10-12 no comparable studies have been performed in water. Because most detection experiments are performed in a water-based solution, it is important to thoroughly understand the impact of this environment on the relationship between the diameter of the microtoroid resonator and the operational wavelengths of interest.To this end, UHQ silica microtoroid resonators were fabricated over a wide range ͑50-250 m͒ of major toroid diameters as shown in Fig. 1. 13 Experiments were performed in both water ͑H 2 O͒ and deuterium oxide ͑D 2 O͒. The D 2 O was purchased from Aldrich. D 2 O was chosen as the second liquid because it has the same refractive index and, in turn, the same radiation loss as H 2 O. However, its absorption at all wavelengths tested is significantly less. 14 This allowed for selective probing of the absorption-loss mechanism and verification of the model developed to describe this system.The model used finite element analysis to predict the Q-factor of microtoroid resonators immersed in water or D 2 S and accounted for two loss mechanisms: radiation loss and absorption loss. The absorption loss was numerically calculated at ͑680, 1300, 1570͒ nm using published values of H 2 O ͑0.0045, 1.12, 8.79͒ cm −1 and D 2 O ͑2.46 ϫ 10 −4 , 0.105, 0.327͒ cm −1 . 14 The modeling of radiation loss uses a fully vectorial two-dimensio...

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“…Cavity quality factors (Q factors) as high as 8 ϫ 10 9 [1,2], along with small mode volumes, have been essential driving forces for fundamental research areas such as cavity quantum electrodynamics, nonlinear optics, biosensing, and microscale lasers [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. The first studied ultrahigh-Q optical microcavities were liquid microdroplets.…”

Section: Introductionmentioning

confidence: 99%

Erbium-implanted high-Qsilica toroidal microcavity laser on a silicon chip

et al. 2004

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Lasing from an erbium-doped high-Q silica toroidal microcavity coupled to a tapered optical fiber is demonstrated and analyzed. Average erbium ion concentrations were in the range 0.009-0.09 at. %, and a threshold power as low as 4.5 W and an output lasing power as high as 39.4 W are obtained from toroidal cavities with major diameters in the range 25-80 m. Controlling lasing wavelength in a discrete way at each whispering-gallery mode was possible by changing the cavity loading, i.e., the distance between the tapered optical fiber and the microcavity. Analytic formulas predicting threshold power and differential slope efficiency are derived and their dependence on cavity loading, erbium ion concentration, and Q factor is analyzed. It is shown that the experimental results are in good agreement with the derived formulas.

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Shift of whispering-gallery modes in microspheres by protein adsorption

Cited by 685 publications

References 9 publications

A multiplexed optofluidic biomolecular sensor for low mass detection

A multiplexed optofluidic biomolecular sensor for low mass detection

Ultra-high-Q microcavity operation in H2O and D2O

Erbium-implanted high-Qsilica toroidal microcavity laser on a silicon chip

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