Abstract
We show, via simulations, that an optical fiber taper waveguide can be an efficient tool for photoluminescence and resonant, extinction spectroscopy of single emitters, such as molecules or colloidal quantum dots, deposited on the surface of a thin dielectric membrane. Placed over a high refractive index membrane, a tapered fiber waveguide induces the formation of hybrid mode waves, akin to dielectric slotted waveguide modes, that provide strong field confinement in the low index gap region. The availability of such gap-confined waves yields potentially high spontaneous emission enhancement factors (approximately 20), fluorescence collection efficiencies (approximately 23%), and transmission extinction (approximately 20%) levels. A factor of two improvement in fluorescence and extinction levels is predicted if the membrane is instead replaced with a suspended channel waveguide. Two configurations, for operation in the visible (approximately 600 nm) and near-infrared (approximately 1300 nm) spectral ranges are evaluated, presenting similar performances.
Highlights
In Ref. [1], a dielectric waveguide structure, consisting of two high refractive index regions separated by a narrow, low refractive index slot, was shown to support propagating modes with a very high field concentration in the slot region
We show, via simulations, that an optical fiber taper waveguide can be an efficient tool for photoluminescence and resonant, extinction spectroscopy of single emitters, such as molecules or colloidal quantum dots, deposited on the surface of a thin dielectric membrane
We use electromagnetic simulations to show that an optical fiber taper waveguide can be used as an efficient probe for resonant and non-resonant spectroscopy of individual emitters bound to the surface of thin dielectric membranes
Summary
In Ref. [1], a dielectric waveguide structure, consisting of two high refractive index regions separated by a narrow, low refractive index slot, was shown to support propagating modes with a very high field concentration in the slot region. While the existence of the aforementioned gap modes was mentioned in that article, their potential application in performing efficient spectroscopy of individual surface-bound dipoles was only briefly discussed, and not analyzed at any level of detail. A discussion of the results follows in Section 6, and Section 7 concludes the paper
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