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 87 Rb, 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.The implementation of a distributed quantum network could enable a global quantum communication system, [1,2] operations, [7,28] and to implement an elementary quantum network.[29] These works place single-atom quantum systems as a leading candidate for use in large-scale quantum networks. As a result, there is a strong interest in the integration of alkali atoms into robust, scalable, packaged optical cavities. [30,31] Furthermore, it is desirable for these optical cavities to have small mode volumes and be tunable to atomic transitions. [32][33][34] Here we report the development of 'buckled-dome' Fabry-Pérot microcavities designed for cQED applications, specifically on-chip coupling between single photons and single rubidium atoms. These cavities produce high single-atom cooperativities, can be easily tuned to atomic transitions, and can facilitate open-access for incorporation of atoms.The buckled-dome microcavities were fabricated via a monolithic self-assembly procedure. [35,36] First, a distributed Bragg reflector (10.5 periods SiO 2 /Ta 2 O 5 , starting and ending with Ta 2 O 5 ) was deposited on a fused silica substrate by reactive magnetron sputtering. Microcavities were defined by the lithographic patterning of a thin (∼15 nm) low-adhesion fluorocarbon layer, followed by the deposition of a second Bragg reflector identical to the initial reflector. Films with low loss and high compressive stress (∼200 MPa) were realized by using high target power (200 W), elevated substrate temperature (150• C), and low chamber pressure (4 mTorr).[37] Optical constants for single films were measured usarXiv:1601.03344v1 [cond-mat.mes-hall]

We describe the monolithic integration of microfluidic channels, optical waveguides, a collimating lens and a curved focusing transmission grating in a single PDMS-based microsystem. All optical and fluidic components of the device were simultaneously formed in a single layer of high refractive index (n~1.43) PDMS by soft lithography. Outer layers of lower-index (n~1.41) PDMS were subsequently added to provide optical and fluidic confinement. Here, we focus on the design and characterization of the microspectrometer part, which employs a novel self-focusing strategy based on cylindrical facets, and exhibits resolution <10 nm in the visible wavelength range. The dispersive behavior of the grating was analyzed both experimentally and using numerical simulations, and the results are in good agreement with simplified analytical predictions.

We describe an integrated system for wavelength interrogation, which uses tapered hollow Bragg waveguides coupled to an image sensor. Spectral shifts are extracted from the wavelength dependence of the light radiated at mode cutoff. Wavelength shifts as small as ~10  pm were resolved by employing a simple peak detection algorithm. Si/SiO₂-based cladding mirrors enable a potential operational range of several hundred nanometers in the 1550 nm wavelength region for a taper length of ~1  mm. Interrogation of a strain-tuned grating was accomplished using a broadband amplified spontaneous emission (ASE) source, and potential for single-chip interrogation of multiplexed sensor arrays is demonstrated.

We propose a strategy for real time multicolour detection of light emitting particles under flow conditions, using the diffracted orders of a grating. The method relies on the fact that the spatial (angular/linear) separation between the orders of a diffraction grating is a wavelength dependent quantity. Thus, the difference in arrival times at a fixed detector for neighbouring orders produced by a moving, light-emitting particle can be used as a wavelength sensing mechanism. We demonstrate this functionality using a prototype PDMS microfluidic device that incorporates a focusing transmission grating. A key attribute of this approach is that it requires only a single sensitive detector, such as a photomultiplier tube, in contrast to many conventional approaches which require multiple sensitive detectors or a detector array.

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