Photonic Routing Research Articles

Nonreciprocal interference and coherent photon routing in a three-port optomechanical system.

We study the interference between different weak signals in a three-port optomechanical system, which is achieved by coupling three cavity modes to the same mechanical mode. If one cavity serves as a control port and is perturbed continuously by a control signal, nonreciprocal interference can be observed when another signal is injected upon different target ports. In particular, we exhibit frequency-independent perfect blockade induced by the completely destructive interference over the full frequency domain. Moreover, coherent photon routing can be realized by perturbing all ports simultaneously, with which the synthetic signal only outputs from the desired port. We also reveal that the routing scheme can be extended to more-port optomechanical systems. The results in this paper may have potential applications for controlling light transport and quantum information processing.

Silicon Photonic Switch Topologies and Routing Strategies for Disaggregated Data Centers

Disaggregation enabled by silicon photonic switch fabrics is a path to low-cost and energy-efficient data centers. The routing strategy, which can be seamlessly incorporated into the switch control plane, potentially provides an additional dimension for the physical-layer performance optimization, at no extra cost. In this paper, we analyze the role of optical routing strategies for silicon photonic switch fabrics. We define and quantify the number of global switching states in various switching topologies and discuss their relationship to the number of switch permutations. We propose a topology-agnostic approach that is shown to optimize fabric-wide switch path power penalties and consequently reduce the dynamic-range requirement on receivers. Additionally, it potentially compensates for device fabrication variations by taking advantage of the redundancy in switching states over switch permutations; thus, increasing fabrication tolerance. Significant power penalty improvements are demonstrated via both our simulation and test platforms, even for moderate-scale silicon switches.

Fully tunable and switchable coupler for photonic routing in quantum detection and modulation.

Photonic routing is a key building block of many optical applications challenging its development. We report a $2\times 2$2×2 photonic coupler with a splitting ratio switchable by a low-voltage electronic signal with 10 GHz bandwidth and tens of nanoseconds latency. The coupler can operate at any splitting ratio ranging from 0:100 to 100:0 with the extinction ratio of 26 dB in optical bandwidth of 1.3 THz. We show sub-nanosecond switching between arbitrary coupling regimes including a balanced 50:50 beam splitter, 0:100 switch, and a photonic tap. The core of the device is based on a Mach-Zehnder interferometer in a dual-wavelength configuration allowing real-time phase lock with long-term sub-degree stability at single-photon level. Using the reported coupler, we demonstrate for the first time, to the best of our knowledge, a perfectly balanced time-multiplexed device for photon-number-resolving detectors and also the active preparation of a photonic temporal qudit state up to four time bins. Verified long-term stable operation of the coupler at the single-photon level makes it suitable for a wide application range in quantum information processing and quantum optics in general.

Tuning silicon-rich nitride microring resonances with graphene capacitors for high-performance computing applications.

We demonstrate the potential of a graphene capacitor structure on silicon-rich nitride micro-ring resonators for multitasking operations within high performance computing. Capacitor structures formed by two graphene sheets separated by a 10 nm insulating silicon nitride layer are considered. Hybrid integrated photonic structures are then designed to exploit the electro-absorptive operation of the graphene capacitor to tuneably control the transmission and attenuation of different wavelengths of light. By tuning the capacitor length, a shift in the resonant wavelength is produced giving rise to a broadband multilevel photonic volatile memory. The advantages of using silicon-rich nitride as the waveguiding material in place of the more conventional silicon nitride (Si3N4) are shown, with a doubling of the device's operational bandwidth from 31.2 to 62.41 GHz achieved while also allowing a smaller device footprint. A systematic evaluation of the device's performance and energy consumption is presented. A difference in the extinction ratio between the ON and OFF states of 16.5 dB and energy consumptions of <0.3 pJ/bit are obtained. Finally, it has been demonstrated that increasing the permittivity of the insulator layer in the capacitor structure, the energy consumption per bit can be reduced even further. Overall, the resonance tuning enabled by the novel graphene capacitor makes it a key component for future multilevel photonic memories and optical routing in high performance computing.

Controllable Delay and Polarization Routing of Single Photons

AbstractFull control of single photons is important in quantum information and quantum networking. In particular, controlling the photon–atom interaction can be an appealing means to realize more complex quantum experiments. As a matter of example, the storage of photons into atomic media represents one key approach to memory‐assisted quantum communication and computing. Here it is shown that the propagation of single photons from a semiconductor quantum dot can be deliberately controlled by an atomic vapor under the application of an external magnetic field. The present results enable the use of an atomic vapor as a precise and reliable wavelength selective delay and allows for routing the single photons according to their polarization and the external magnetic field. With an overall delay of 25 ns, it is possible to fine‐tune the arrival time of the photons by more than 600 ps which matches the scale of the quantum dot's lifetime. The experimental data are fully reproduced by a theoretical model.

A single plasmon router based on the V-type three-level quantum dot sandwiched between two plasmonic waveguides

A single photon router with a desired high routing rate is of great importance for quantum networks. Recently, coupling between channeled plasmons and quantum emitters have been widely used to explore the routing feasibility in hybrid systems. As a capable alternative, we suggested a scheme of a single plasmon router using a V-type three-level quantum dot (QD) sandwiched between two plasmonic waveguides. We theoretically investigated the transmission and transfer rates of single plasmons in the complex system via the real-space approach. Our calculations show that the single plasmons from the incident route could be redirected by controlling such parameters as the intensity of the classical field, the detunings and the couplings between the QD and the plasmonic waveguides. Our proposed scheme could be used not only for the design of a single plasmon router but also for the design of quantum switches and quantum couplers in quantum photonic integrated circuits.

Hyperparallel transistor, router and dynamic random access memory with unity fidelities.

We theoretically implement some hyperparallel optical elements, including quantum single photon transistor, router, and dynamic random access memory (DRAM). The inevitable side leakage and the imperfect birefringence of the quantum dot (QD)-cavity mediates are taken into account, and unity fidelities of our optical elements can be achieved. The hyperparallel constructions are based on polarization and spatial degrees of freedom (DOFs) of the photon to increase the parallel efficiency, improve the capacity of channel, save the quantum resources, reduce the operation time, and decrease the environment noises. Moreover, the practical schemes are robust against the side leakage and the coupling strength limitation in the microcavities.

Waveguide-type optical circuits for the recognition of optical 8PSK-coded labels

This paper discusses optical label recognition for photonic label routing. The label recognition is one of the key functions in photonic label routing related functions including optical label extraction, recognition of the label and label rewriting. In a previous study, we have proposed a basic waveguide-type circuit for the recognition of an optical label encoded in quadri-phase-shift-keying (QPSK) format, which consists of a 3-dB directional coupler, two Y-branches and an asymmetric X junction coupler. In order to increase the number of labels represented by the same symbol number, we propose 8PSK recognition circuits based on the QPSK recognition circuit. The input-output relation of the proposed circuits is theoretically discussed and the noise tolerance is also investigated. From the theoretical analysis, the proposed optical-waveguide circuits recognize the 8PSK labels by detecting the position of the output port having either the maximum or minimum intensity. The bit-error performance of the proposed circuits is clarified by computer simulation. It is found that the minimum-output detection scheme for a one-symbol 8PSK label is superior from the viewpoint of noise tolerance. The proposed method also addresses the scalability of two-symbol 8PSK coded labels. The maximum-output detection scheme demonstrates improved scalability performance.

Silicon photonic add-drop filter for quantum emitters.

Integration of single-photon sources and detectors to silicon-based photonics opens the possibility of complex circuits for quantum information processing. In this work, we demonstrate integration of quantum dots with a silicon photonic add-drop filter for on-chip filtering and routing of telecom photons. A silicon microdisk resonator acts as a narrow filter that transfers the quantum dot emission and filters the background over a wide wavelength range. Moreover, by tuning the quantum dot emission wavelength over the resonance of the microdisk, we can control the transmission of the quantum dot emission to the drop and through channels of the add-drop filter. This result is a step toward the on-chip control of single photons using silicon photonics for applications in quantum information processing, such as linear optical quantum computation and boson sampling.

A silicon-on-insulator slab for topological valley transport

Backscattering suppression in silicon-on-insulator (SOI) is one of the central issues to reduce energy loss and signal distortion, enabling for capability improvement of modern information processing systems. Valley physics provides an intriguing way for robust information transfer and unidirectional coupling in topological nanophotonics. Here we realize topological transport in a SOI valley photonic crystal slab. Localized Berry curvature near zone corners guarantees the existence of valley-dependent edge states below light cone, maintaining in-plane robustness and light confinement simultaneously. Topologically robust transport at telecommunication is observed along two sharp-bend interfaces in subwavelength scale, showing flat-top high transmission of ~10% bandwidth. Topological photonic routing is achieved in a bearded-stack interface, due to unidirectional excitation of valley-chirality-locked edge state from the phase vortex of a nanoscale microdisk. These findings show the prototype of robustly integrated devices, and open a new door towards the observation of non-trivial states even in non-Hermitian systems.

Tunable quantum routing via asymmetric intercavity couplings

Routing efficiently the photon signals between different channels is essential in an optical quantum network. Recent chiral waveguide–emitter coupling techniques are widely applied to improve the routing capabilities in waveguide systems. As a possible alternative, we put forward a proposal to control the quantum routing of photons by adjusting asymmetric intercavity couplings on both sides of a cross-cavity in an X-shaped coupled-resonator waveguide. With the robust and tunable intercavity couplings, high transfer rate between quantum channels and expected probability distributions of two ports in the same output channel can be easily implemented. The asymmetric intercavity coupling may be utilized as a new handle to efficiently control the single-photon routing.

Error-detected single-photon quantum routing using a quantum dot and a double-sided microcavity system**Project supported by the Scientific Research Foundation of Shanxi Institute of Technology (Grant No. 201706001), the Fund for Shanxi “1331 Project” Key Subjects Construction, the China Postdoctoral Science Foundation (Grant No. 2017M612411), the Education Department Foundation of Henan Province, China (Grant No. 18A140009), and the National Natural Science

Based on a hybrid system consisting of a quantum dot coupled with a double-sided micropillar cavity, we investigate the implementation of an error-detected photonic quantum routing controlled by the other photon. The computational errors from unexpected experimental imperfections are heralded by single photon detections, resulting in a unit fidelity for the present scheme, so that this scheme is intrinsically robust. We discuss the performance of the scheme with currently achievable experimental parameters. Our results show that the present scheme is efficient. Furthermore, our scheme could provide a promising building block for quantum networks and distributed quantum information processing in the future.

Single-photon routing in a multi-T-shaped waveguide

We investigate quantum routing in a multi-T-shaped waveguide coupled to driven cyclic three-level systems. Exact expressions of the scattering coefficients for the double-T and triple-T waveguides are obtained by employing the discrete-coordinate scattering and the transfer matrix approach, respectively. Our results show that high transfer-rate routing of single photons from the input infinite channel to the other channels can be effectively implemented in the extended multi-T configuration, in contrast with the single-T waveguide with the transfer of no more than 0.5. The proposed router may be utilized as a scalable quantum device to control single-photon routing.

Design, fabrication, and metrology of 10 × 100 multi-planar integrated photonic routing manifolds for neural networks

We design, fabricate, and characterize integrated photonic routing manifolds with 10 inputs and 100 outputs using two vertically integrated planes of silicon nitride waveguides. We analyze manifolds via top-view camera imaging. This measurement technique allows the rapid acquisition of hundreds of precise transmission measurements. We demonstrate manifolds with uniform and Gaussian power distribution patterns with mean power output errors (averaged over 10 sets of 10 inputs) of 0.7 and 0.9 dB, respectively, establishing this as a viable architecture for precision light distribution on-chip. We also assess the performance of the passive photonic elements comprising the system via self-referenced test structures, including high-dynamic-range beam taps, waveguide cutback structures, and waveguide crossing arrays.

Integrated waveguides and deterministically positioned nitrogen vacancy centers in diamond created by femtosecond laser writing.

Diamond's nitrogen vacancy (NV) center is an optically active defect with long spin coherence times, showing great potential for both efficient nanoscale magnetometry and quantum information processing schemes. Recently, both the formation of buried 3D optical waveguides and high-quality single NVs in diamond were demonstrated using the versatile femtosecond laser-writing technique. However, until now, combining these technologies has been an outstanding challenge. In this Letter, we fabricate laser-written photonic waveguides in quantum grade diamond which are aligned to within micron resolution to single laser-written NVs, enabling an integrated platform providing deterministically positioned waveguide-coupled NVs. This fabrication technology opens the way toward on-chip optical routing of single photons between NVs and optically integrated spin-based sensing.

Reconfigurable Topological Phases in Next-Nearest-Neighbor Coupled Resonator Lattices.

We present a reconfigurable topological photonic system consisting of a 2D lattice of coupled ring resonators, with two sublattices of site rings coupled by link rings, which can be accurately described by a tight-binding model. Unlike previous coupled-ring topological models, the design is translationally invariant, similar to the Haldane model, and the nontrivial topology is a result of next-nearest couplings with nonzero staggered phases. The system exhibits a topological phase transition between trivial and spin Chern insulator phases when the sublattices are frequency detuned. Such topological phase transitions can be easily induced by thermal or electro-optic modulators, or nonlinear cross phase modulation. We use this lattice to design reconfigurable topological waveguides, with potential applications in on-chip photon routing and switching.

Quantum routing of single optical photons with a superconducting flux qubit

Controlling and swapping quantum information in a quantum coherent way between the microwave and optical regimes is essential for building long-range superconducting quantum networks but extremely challenging. We propose a hybrid quantum interface between the microwave and optical domains where the propagation of a single-photon pulse along a nanowaveguide is controlled in a coherent way by tuning electromagnetically induced transparency window with the quantum state of a flux qubit. The qubit can route a single-photon pulse with a single spin in nanodiamond into a quantum superposition of paths without the aid of an optical cavity - simplifying the setup. By preparing the flux qubit in a superposition state our cavity-less scheme creates a hybrid state-path entanglement between a flying single optical photon and a static superconducting qubit, and can conduct heralded quantum state transfer via measurement.

Ideal photonic absorption, emission, and routings in chiral waveguides

Chiral waveguides have recently being become the robust tools to manipulate the transports of photons along the selected directions. By designing the suitable atom–photon chiral couplings we show that the ideal absorption (i.e., approaching the 100% absorption), unidirectional emission (i.e., along only one of the selected directions), and the routing (i.e., without any reflected loss) of single waveguide photon can be implemented conveniently. The dissipative influences on these chiral quantum functions demonstrated here are discussed.

All-optical photon switching, router and amplifier using a passive-active optomechanical system

We propose a feasible and flexible scheme to realize all-optical photon switching, router and amplifier by using a passive-active optomechanical system consisting of a passive cavity, an active cavity and a common movable membrane oscillator. Due to the cooperation between the gain effect of the active cavity and the interference effect between the probe fields, some novel phenomena arise, such as the frequency-independent perfect reflection first proposed in this paper, controllable photon routing, tunable fast and slow lights and so on. Based on the results, a photon switching of absorption-amplification and fast-slow-light transitions, and a photon router with controllable direction and intensity can be realized by adjusting relevant parameters such as the strengths of control fields and the relative phase between probe fields. Such a scheme may provide a promising platform for controllable photon transport and photonic device fabrication.

Single-photon routing with whispering-gallery resonators

Quantum routing of single photons in a system with two waveguides coupled to two whispering-gallery resonators (WGRs) are investigated theoretically. Using a real-space full quantum theory, photonic scattering amplitudes along four ports of the waveguide network are analytically obtained. It is shown that, by adjusting the geometric and physical parameters of the two-WGR configuration, the quantum routing properties of single photons along the present waveguide network can be controlled effectively. The routing capability from input waveguide to another one can significantly exceed 0.5 near the resonance point of scattering spectra, which can be achieved with only one resonator. By properly designing the distance between two WGRs and the waveguide-WGR coupling strengths, the transfer rate between the waveguides can also reach certain sufficiently high values even in the non-resonance regime. Moreover, Fano-like resonances in the scattering spectra are designable. The proposed system may provide a potential application in controlling single-photon quantum routing.