Absorption detection using optical waveguide cavities

Loock, Hans‐Peter; Barnes, Jack A.; Gagliardi, G.; Li, Runkai LiR.; Oleschuk, Richard D.; Wächter, Helen

doi:10.1139/v10-006

Cited by 11 publications

(6 citation statements)

References 60 publications

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“…In this Letter, we demonstrate that SPR sensing can also be performed in the time domain by combining an SPR sensor with the so-called cavity ring-down spectroscopy (CRDS) technique [6,7], without any direct optical intensity measurements, spectroscopic analysis, or complicated postprocessing. In this configuration, an SPR 'chip' is integrated into a mirror-based optical cavity where the sensor acts as an additional intracavity optical loss.…”

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confidence: 99%

Surface plasmon resonance optical cavity enhanced refractive index sensing

et al. 2013

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We report on a method for surface plasmon resonance (SPR) refractive index sensing based on direct time-domain measurements. An optical resonator is built around an SPR sensor, and its photon lifetime is measured as a function of loss induced by refractive index variations. The method does not rely on any spectroscopic analysis or direct intensity measurement. Time-domain measurements are practically immune to light intensity fluctuations and thus lead to high resolution. A proof of concept experiment is carried out in which a sensor response to liquid samples of different refractive indices is measured. A refractive index resolution of the current system, extrapolated from the reproducibility of cavity-decay time determinations over 133 s, is found to be about 10(-5) RIU. The possibility of long-term averaging suggests that measurements with a resolution better than 10(-7) RIU/√Hz are within reach.

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confidence: 99%

Surface plasmon resonance optical cavity enhanced refractive index sensing

et al. 2013

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“…A cavity of microliter dimensions may be made by reducing the distance between the mirrors to millimeters. − Alternatively, one can insert either a cuvette or flow cell − or a liquid film , into a larger two-mirror cavity. Another possibility is to use total internal reflection as a third cavity mirror and probe the sample with the evanescent wave. − Even smaller volumes of much less than 1 μL can be interrogated by using a fiber optic waveguide as the cavity medium. ,, We have demonstrated such measurements in several versions at various wavelengths and with different fluid delivery designs. ,− …”

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confidence: 99%

Simultaneous and Continuous Multiple Wavelength Absorption Spectroscopy on Nanoliter Volumes Based on Frequency-Division Multiplexing Fiber-Loop Cavity Ring-Down Spectroscopy

Waechter

Munzke²,

Jang³

et al. 2011

Anal. Chem.

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We demonstrate a method for measuring optical loss simultaneously at multiple wavelengths with cavity ring-down spectroscopy (CRD). Phase-shift CRD spectroscopy is used to obtain the absorption of a sample from the phase lag of intensity modulated light that is entering and exiting an optical cavity. We performed dual-wavelength detection by using two different laser light sources and frequency-division multiplexing. Each wavelength is modulated at a separate frequency, and a broadband detector records the total signal. This signal is then demodulated by lock-in amplifiers at the corresponding two frequencies allowing us to obtain the phase-shift and therefore the optical loss at several wavelengths simultaneously without the use of a dispersive element. In applying this method to fiber-loop cavity ring-down spectroscopy, we achieve detection at low micromolar concentrations in a 100 nL liquid volume. Measurements at two wavelengths (405 and 810 nm) were performed simultaneously on two dyes each absorbing at mainly one of the wavelengths. The respective concentrations could be quantified independently in pure samples as well as in mixtures. No crosstalk between the two channels was observed, and a minimal detectable absorbance of 0.02 cm(-1) was achieved at 405 nm.

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“…Several innovations have further enhanced the utility of optical detection in microchannels, including device-integrated reflectors [4,6], filters [7], attenuators [8], waveguides [9,10] and microlenses [11,12]. The integration of optofluidic technologies with microchannels has paved the way for the development of a variety of optical lab-on-a-chip systems, such as cell sorting [13], microscopy [14], particle analysis [15], surface-enhanced Raman spectroscopy [16] and cavity ring-down spectroscopy [17].…”

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confidence: 99%

A guiding light: spectroscopy on digital microfluidic devices using in-plane optical fibre waveguides

2015

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We present a novel method for in-plane digital microfluidic spectroscopy. In this technique, a custom manifold (.stl file available online as ESM) aligns optical fibres with a digital microfluidic device, allowing optical measurements to be made in the plane of the device. Because of the greater width vs thickness of a droplet on-device, the in-plane alignment of this technique allows it to outperform the sensitivity of vertical absorbance measurements on digital microfluidic (DMF) devices by ∼14×. The new system also has greater calibration sensitivity for thymol blue measurements than the popular NanoDrop system by ∼2.5×. The improvements in absorbance sensitivity result from increased path length, as well as from additional effects likely caused by liquid lensing, in which the presence of a water droplet between optical fibres increases fibre-to-fibre transmission of light by ∼2× through refraction and internal reflection. For interrogation of dilute samples, stretching of droplets using digital microfluidic electrodes and adjustment of fibre-to-fibre gap width allows absorbance path length to be changed on-demand. We anticipate this new digital microfluidic optical fibre absorbance and fluorescence measurement system will be useful for a wide variety of analytical applications involving microvolume samples with digital microfluidics.

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Absorption detection using optical waveguide cavities

Cited by 11 publications

References 60 publications

Surface plasmon resonance optical cavity enhanced refractive index sensing

Surface plasmon resonance optical cavity enhanced refractive index sensing

Simultaneous and Continuous Multiple Wavelength Absorption Spectroscopy on Nanoliter Volumes Based on Frequency-Division Multiplexing Fiber-Loop Cavity Ring-Down Spectroscopy

A guiding light: spectroscopy on digital microfluidic devices using in-plane optical fibre waveguides

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