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Direct and Sensitive Phase Readout for Integrated Waveguide Sensors

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5 Author(s)
Halir, R. ; Dept. Ing. de Comun., Univ. de Malaga, Malaga, Spain ; Vivien, L. ; Le Roux, X. ; Xu, D.-X.
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Integrated optical affinity sensors based on Mach-Zehnder interferometers (MZIs) enable sensitive and label-free detection of chemical and biological molecules. However, since MZIs transduce optical phase changes into sinusoidal intensity variations, they exhibit a variable sensitivity that vanishes at the extrema of the transmittance function. Moreover, the direction of phase change cannot be unambiguously determined with these sensors. Here, we present a coherent detection scheme based on integrated optics that enables unambiguous readout of the optical phase with a constant sensitivity. Our approach furthermore cancels the effect of imperfections in the sensor hardware using a blind calibration scheme. We experimentally show completely linear readout of the optical phase, with a fourfold enhancement of average sensitivity compared to conventional detection.

(1) In our readout scheme the signals in the refernce arm and the sensing arm are combined in a 120^{circ} hybrid and are then processed to retrieve the full sensor amplitud and phase response, which is calibrated to cancel hardware imperfections. (2) The sensor is realized in silicon-on-insulator with a single etch step. (3) Experiments show that our detection approach is more accurate than the conventional approach, and that using calibration a completely linear read-out of optical phase is achieved. (1) In our readout scheme the signals in the refernce arm and the sensing arm are combined in a 120^{circ} hybrid and are then processed to retrieve the full sensor amplitud and phase response, which is calibrated to cancel hardware imperfections. (2) The sensor is realized in silicon-on-insulator with a single etch step. (3) Experiments show that our detection approach is more accurate than the conventional approach, and that using calibration a completely linear read-out of optical phase is achieved.

Published in:

Photonics Journal, IEEE  (Volume:5 ,  Issue: 4 )