Asymmetric comb waveguide for strong interactions between atoms and light

Abstract

Coupling quantum emitters and nanostructures, in particular cold atoms and optical waveguides, has recently raised a large interest due to unprecedented possibilities of engineering light-matter interactions. In this work, we propose a new type of periodic dielectric waveguide that provides strong interactions between atoms and guided photons with an unusual dispersion. We design an asymmetric comb waveguide that supports a slow mode with a quartic (instead of quadratic) dispersion and an electric field that extends far into the air cladding for an optimal interaction with atoms. We compute the optical trapping potential formed with two guided modes at frequencies detuned from the atomic transition. We show that cold Rubidium atoms can be trapped as close as 100 nm from the structure in a 1.3-mK-deep potential well. For atoms trapped at this position, the emission into guided photons is largely favored, with a beta factor as high as 0.88 and a radiative decay rate into the slow mode 10 times larger than the free-space decay rate. These figures of merit are obtained at a moderately low group velocity of c/50.

Systematic design of a robust half-W1 photonic crystal waveguide for interfacing slow light and trapped cold atoms

“…Because of the complex shape of the local density of states accessible to the atoms, the behavior of Γ ′ is hard to infer. We performed a numerical calculation of Γ ′ using the same method as in [27] and found that Γ ′ ≃ 0.8Γ 0 , at the position of the trap minimum, i.e. at 116 nm from the surface.…”

“…and first pioneering demonstrations obtained, albeit with a limited number of atoms and without stable trapping in the evanescent field. Some theoretical proposals on novel interesting structures supporting atom trapping in the evanescent field have emerged since, such as a slot [26] or a comb waveguide [27]. Structures must also provide a large optical access to bring atoms close to their surface.…”

Atom-light interactions using optical nanofibres—a perspective

“…Various waveguide designs have already been proposed to engineer guided modes for stronger interaction with quantum systems, specifically cold atoms [87][88][89]. In nanofibre-based waveguides, aside from the fundamental mode, HE 11 , three distinct types of guided modes are used for this purpose (see figure 2).…”

Systematic design of a robust half-W1 photonic crystal waveguide for interfacing slow light and trapped cold atoms

“…To quantify the coupling of the atoms to the guided mode we also define the β factor, β = Γ 1D /Γ tot with Γ tot = Γ 1D + Γ , and Γ the decay rate in all the other radiation modes than the guided slow mode. Because of the complex shape of the local density of states accessible to the atoms, the behaviour of Γ is hard to infer, but its modulation is expected to be minimal as seen in [25,26]. Hence we assume for the following Γ Γ 0 .…”

“…Up to now, only a corrugated slot waveguide (so-called alligator waveguide) [19][20][21][22][23] has been implemented and first pioneering demonstrations obtained, albeit with a limited number of atoms and without stable trapping in the evanescent field. Some theoretical proposals on novel interesting structures supporting atom trapping in the evanescent field have emerged since, such as a slot [24] or a comb waveguide [25]. Structures must also provide a large optical access to bring atoms close to their surface.…”