We propose an all-photonic, non-volatile memory and processing element based on phase-change thin-films deposited onto nanophotonic waveguides. Using photonic microring resonators partially covered with Ge 2 Sb 2 Te 5 (GST) multi-level memory operation in integrated photonic circuits can be achieved. GST provides a dramatic change in refractive index upon transition from the amorphous to crystalline state, which is exploited to reversibly control both the extinction ratio and resonance wavelength of the microcavity with an additional gating port in analogy to optical transistors. Our analysis shows excellent sensitivity to the degree of crystallization inside the GST, thus providing the basis for non-von Neuman neuromorphic computing.The ability to write, store and retrieve data is at the very heart of information processing. Various techniques are employed to efficiently cope with the vast spread of speed and long term storage needs. In particular Phase Change Memories (PCMs), promise to revolutionize the field of information processing by bridging the gap between the short-term, but very quick operation of on-chip memories and the long-term, but relatively slow storage systems such as solid-state devices and hard-drives [1][2][3]. Not only can phase change materials switch in a matter of picoseconds [4-6], they are also able to retain information for very long periods of time [2,7]. In addition, they scale extremely well to the nanoscale, with present-day demonstrations of 6nm cells employing electrical switching [7,8]. Specifically Ge 2 Sb 2 Te 5 (GST) is the most commonly used alloy for such applications. By reversibly transforming the crystalline structure between amorphous and crystalline states using electrical pulses, the resistive properties of the thin film can be varied by several orders of magnitude [9]. PCMs also demonstrate a large difference in reflectivity upon phase-transition, an effect that has led to their commercial use in optical storage discs, such as DVDs and Blue-Ray discs [10].Herein, we propose a chalcogenide-based integrated photonic memory element, with the ability for sub-nanosecond reading and writing, while still retaining data for several years. We analyze the photonic architecture as illustrated in Fig.1(a), which comprises a microring resonator coupled to nanophotonic waveguides. In contrast to photonic memories and mechanical resonators [11], the photonic circuit allows for static tunability which is maintained when the control light has been switched off. We base our analysis on silicon nitride-on-insulator substrates for broadband optical applications. Silicon nitride can be used to fabricate high-quality nanophotonic components for both telecoms and visible applications [12,13]. The feeding waveguide is optimized for single mode operation at 1550nm input wavelength. Inside the ring resonator a small region of the waveguide is suspended similar to waveguides used for nanomechanical sensing [14] and opto-mechanical operation [15]. A thin film of phase change material (GST) is...
Diamond offers unique material advantages for the realization of micro-and nanomechanical resonators because of its high Young's modulus, compatibility with harsh environments and superior thermal properties. At the same time, the wide electronic bandgap of 5.45 eV makes diamond a suitable material for integrated optics because of broadband transparency and the absence of free-carrier absorption commonly encountered in silicon photonics. Here we take advantage of both to engineer full-scale optomechanical circuits in diamond thin films. We show that polycrystalline diamond films fabricated by chemical vapour deposition provide a convenient wafer-scale substrate for the realization of high-quality nanophotonic devices. Using free-standing nanomechanical resonators embedded in on-chip Mach-Zehnder interferometers, we demonstrate efficient optomechanical transduction via gradient optical forces. Fabricated diamond resonators reproducibly show high mechanical quality factors up to 11,200. Our low cost, wideband, carrier-free photonic circuits hold promise for all-optical sensing and optomechanical signal processing at ultra-high frequencies.
We demonstrate niobium titanium nitride superconducting nanowires patterned on stoichiometric silicon nitride waveguides for detecting visible and infrared photons. The use of silicon nitride on insulator on silicon substrates allows us to simultaneously realize photonic circuits for visible and infrared light and integrate them with nanowire detectors directly on-chip. By implementing a traveling wave detector geometry in this material platform, we achieve efficient single photon detection for both wavelength regimes. Our detectors are an ideal match for integrated quantum optics as they provide crucial functionality on a wideband transparent waveguide material.Interfacing optical circuitry and high-efficiency single photon detectors with low loss is one of the key challenges of quantum photonic technologies [1,2]. Ideally, these components are integrated with non-classical light sources on a scalable monolithic platform [3]. To satisfy the source and circuit demands makes it highly desirable to work with a material system which allows for simultaneous operation at visible and infrared wavelengths. This is achievable by using silicon nitride (SiN) waveguides with low optical absorption allowing for low-loss wave-guiding both in the infrared [4] and visible [5] wavelength regime. The recent discovery of a surface (2) effect in silicon nitride [6] also brings the possibility of creating non-classical on-chip photon sources into reach. On the other hand, superconducting nanowire single-photon detectors (SSPD) are well suited for the integration with nanophotonic circuitry and offer superior performance compared to more traditional detector technologies [7,8]. The detection mechanism is based on the superconducting to normal state transition of a nanowire segment, induced by the absorption of a single photon creating a localized hot-spot [9]. Most state-of-the-art SSPDs are implemented as niobium nitride (NbN) meander wires designed as stand-alone units coupled to optical fibers and achieve high speed operation with high timing accuracy and sensitivity over a broad spectral range [9,10,11]. These detectors are optimized for high system efficiency as desired for free-space or optical fiber environments, e.g. in quantum key distribution [12] or high-data-rate optical (space) communication [13,14]. The waveguide coupled SSPDs presented here is a development primarily addressing the needs of integrated photonics and quantum information processing [7,15].
We demonstrate how light from an electrically driven carbon nanotube can be coupled directly into a photonic waveguide architecture. Waferscale, broadband sources are realized integrated with nanophotonic circuits allowing for propagation of light over centimeter distances. Moreover, we show that the spectral properties of the emitter can be controlled directly on chip with passive devices using Mach-Zehnder interfero-meters and grating structures.
We demonstrate high optical quality factors in aluminum nitride (AlN) photonic crystal nanobeam cavities. Suspended AlN photonic crystal nanobeams are fabricated in sputter-deposited AlN-on-insulator substrates using a self-protecting release process. Employing one-dimensional photonic crystal cavities coupled to integrated optical circuits we measure quality factors up to 146,000. By varying the waveguide-cavity coupling gap, extinction ratios in excess of 15 dB are obtained. Our results open the door for integrated photonic bandgap structures made from a low loss, wide-transparency, nonlinear optical material system
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