A microfabricated Fabry-Perot optical resonator has been used for atom detection and photon production with less than 1 atom on average in the cavity mode. Our cavity design combines the intrinsic scalability of microfabrication processes with direct coupling of the cavity field to single-mode optical waveguides or fibers. The presence of the atom is seen through changes in both the intensity and the noise characteristics of probe light reflected from the cavity input mirror. An excitation laser passing transversely through the cavity triggers photon emission into the cavity mode and hence into the single-mode fiber. These are first steps toward building an optical microcavity network on an atom chip for applications in quantum information processing.
We have fabricated curved optical micromirrors on silicon. We expect to be able to form open optical cavities between these mirrors and plane mirrors coated on the ends of optical fibres. The curved mirror templates have been prepared with less than 10 nm surface roughness by means of isotropic chemical etching. Two different methods are used for the fabrication of the mirrors: the first method uses a silicon oxide mask, while the second uses dry etching to form an indentation in the silicon surface that is opened out by wet isotropic etching. After coating the silicon substrate with gold, good quality mirrors are obtained with R ∼ 98% in the near infra-red. We find that a reflectivity of approximately 98% can be achieved by this method. Cavities formed from these mirrors will be useful for manipulating single atoms.
Neutral-atom array and cavity quantum electrodynamics offer complementary strengths for quantum science: scalable, reconfigurable qubit architectures and strong coherent light-matter coupling. Combining them in a single platform requires an optical cavity with simultaneously high cooperativity, sufficient mode volume to accommodate atom array, and ample side optical access for atom trapping, imaging, cooling, and rearrangement, a combination that is challenging to achieve. Here we realize an atomic array integrated with a millimeter-scale Fabry--Pérot cavity whose optically-characterized single-atom cooperativity reaches
ηcav=125±13. Atom-cavity transmission spectra of trapped atoms yield an effective spectroscopic cooperativity
ηspec=106±3, providing an in-situ verification of strong coupling in the integrated platform. In this integrated system, we achieve a state-measurement fidelity of
99.925−18+15% for a single atom with a 4-
μs readout time. We also demonstrate simultaneous coupling of up to 21 individually trapped atoms to the antinode of the cavity mode. The key technical advance is a two-step mirror-fabrication method combining precision mechanical shaping and carbon-dioxide laser polishing, which produces concave fused-silica mirrors with sub-millimeter radii of curvature and residual roughness below
2 A˚. Our results establish a regime of cavity-integrated atomic array that simultaneously provides high cooperativity, large mode volume, and flexible manipulation of individual atoms, opening opportunities for cavity-assisted quantum state readout and long-range entanglement-engineering in atom-array platforms.
We report a process for fabricating high quality, defect-free spherical mirror templates suitable for developing high finesse optical Fabry-Perot resonators. The process utilizes the controlled re-flow of borosilicate glass and differential pressure to produce mirrors with 0.3 nm surface roughness. The dimensions of the mirrors are in the 0.5–5 mm range making them suitable candidates for integration with on-chip neutral atom and ion experiments where enhanced interaction between atoms and photons is required. Cavities constructed with these mirror templates are well suited to quantum information applications such as single photon sources and atom-photon entanglement.
We report on the development of on-chip microcavities and show their potential as a platform for cavity quantum electrodynamics experiments. Microcavity arrays were formed by the controlled buckling of SiO2/Ta2O5 Bragg mirrors and exhibit a reflectance-limited finesse of 3500 and mode volumes as small as 35λ3. We show that the cavity resonance can be thermally tuned into alignment with the D2 transition of 87Rb and outline two methods for providing atom access to the cavity. Owing to their small mode volume and high finesse, these cavities exhibit single-atom cooperativities as high as C1=65. A unique feature of the buckled-dome architecture is that the strong-coupling parameter g0/κ is nearly independent of the cavity size. Furthermore, strong coupling should be achievable with only modest improvements in mirror reflectance, suggesting that these monolithic devices could provide a robust and scalable solution to the engineering of light-matter interfaces.
This thesis reports on the development of an array of plane-concave Fabry-Perot microcavities containing atoms (or other quantum emitters), interconnected by UV-written waveguides on a silica-on-silicon chip. The microcavities are formed by a mirror coated on the end facet of the chip and an array of spherical micromirrors etched on silicon. This is to our knowledge the first attempt at implementing the emerging coupled-cavities QED paradigm. The device we propose possesses a degree of control, flexibility and tuning unmatched in other suggested implementations: The atoms can be manipulated inside the cavity by auxiliary lasers and the cavity-cavity coupling rate as well as the atom-cavity coupling can be tuned. It is highly scalable. Calculation of the complete (classical) optical spectrum of the device is presented. The quantum dynamics that may eventually be observed has also been studied. Waveguide chips containing couplers and phase shifter have been fabricated. We have successfully demonstrated the operation of the elementary sub-systems: the strong optical coupling between a microcavity and a waveguide resonator, and the tunable strong coupling between two evanescently coupled waveguide resonators. No experiments with atoms or other quantum emitters were attempted, because the waveguide propagation loss is so large that no quantum physics can be observed. There is hope that this can be overcome in the future by using other waveguide technologies.