Optical sensing with Anderson localized light

Abstract

Optical sensing is of importance in a variety of applications [1]: it can permit the detection of hazardous/desired contaminants, monitor chemical reactions and provide quantitative analysis of processes [1] To this end, a range of devices have been developed, based on the confinement of light via plasmonic resonances and photonic crystal cavities. The former suffer from relatively broad resonances, the latter, while providing higher sensitivities thanks to the sharper resonances, are not scalable.
In order to circumvent the problem of scalability we realize photonic crystal sensors that use fabrication imperfections as a resource to provide highly efficient light confinement [2].
Photonic crystal waveguides confining light in the visible are characterized by means of confocal micro-photoluminescence spectroscopy. Isopropyl alcohol (IPA) is deposited onto the surface of a device: the local refractive index change (of 0.38) spectrally shifts the cavity resonances of as much as 15.2nm, for a resonance linewidth of 0.15nm. The shift is of more than 100 times the linewidth of the cavity and is fully reversible once the IPA evaporates [3].
By studying the temperature dependence of the optical resonances, we show temperature sensing, improved light confinement at cryogenic temperatures and the potential of temperature tuning the spectral resonances for quantum optics experiments.
Our results prove that Anderson localization of light can be used as a novel platform for high-quality optical sensing, benefitting from the sharp resonances proper to photonic crystal devices and the scalability provided by the use of fabrication imperfections as a resource to confine light. Each device also provides tens of optical resonances which could allow multiple sensor readings from a single device.
[1] J. Hodgkinson et al., Meas. Sci. Technol. 24, 012004 (2013)
[2] T. Crane et al., ACS Photonics 4, 2274 (2017)
[3] O. Trojak et al., Appl. Phys. Lett. 111, 141103 (2017)

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ORCID for Oliver, Joe Trojak: orcid.org/0000-0003-2296-6036

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