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We report on the analysis of electroabsorption in thin GaAs/Al0.3Ga0.7As nanophotonic waveguides with an embedded p–i–n junction. By measuring the transmission through waveguides of different lengths, we derive the propagation loss as a function of electric field, wavelength, and temperature. The results are in good agreement with the Franz–Keldysh model of electroabsorption extending over 200 meV below the GaAs bandgap, i.e., in the wavelength range of 910–970 nm. We find a pronounced residual absorption in forward bias, which we attribute to Fermi-level pinning at the waveguide surface, producing over 20 dB/mm loss at room temperature. These results are essential for understanding the origin of loss in nanophotonic devices operating in the emission range of self-assembled InAs semiconductor quantum dots toward the realization of scalable quantum photonic integrated circuits. [ABSTRACT FROM AUTHOR]

Semiconductor quantum dots in photonic integrated circuits enable scaling quantum‐information processing to many single photons and quantum‐optical gates. Obtaining high‐purity and coherent single photons from quantum dots requires spectral filtering to select individual excitonic transitions. Here, an on‐chip wavelength‐tunable filter integrated with a single‐photon source, which preserves the optical properties of the emitter, is demonstrated. Nanomechanical motion is used for tuning the resonant wavelength over 10 nm, enabling operation at cryogenic temperatures, and single‐photon emission from a quantum dot under non‐resonant excitation is demonstrated without resorting to free‐space optical filters. These results are key for the development of fully integrated de‐multiplexing, multi‐path photon encoding schemes, and multi‐emitter circuits. [ABSTRACT FROM AUTHOR]

We have designed and fabricated a shallow-etched grating on gallium arsenide nanomembranes for efficient chip-to-fiber coupling in quantum photonic integrated circuits. Experimental results show that the grating provides a fiber-coupling efficiency of >60%, a greatly suppressed back reflection of <1% for the designed wavelength of 930 nm, and a 3-dB bandwidth of >43 nm. Highly efficient single-photon collection from embedded indium arsenide quantum dots to an optical fiber was realized with the designed grating, showing an average six-fold increase in the photon count compared to commonly used circular gratings, offering an efficient interface for on-chip quantum information processing. [ABSTRACT FROM AUTHOR]

We discuss relevant design considerations for the fabrication of electromechanically tunable photonic crystal cavities based on double semiconductor slabs. A simple optical and electromechanical model of the device based on coupled-mode theory and electrostatics is discussed and used jointly with 3-D finite-element calculations of optical cavity modes to extract the tuning-range dependence on geometrical parameters. A design rule, which avoids the sticking of membranes due to capillary forces and keeps a large tunability, is defined. The details of the fabrication process and a summary of the experimental results on GaAs and InGaAsP/InP material systems are given. We also address the problem of nonsymmetric devices, where the thicknesses of the membranes are not exactly the same, resulting in an imbalanced power emission of coupled modes. [ABSTRACT FROM AUTHOR]