Strategies for improved temporal response of glass-based optical switches

We present an optimization of the dynamics of integrated optical switches based on thermal phase shifters. These devices have been fabricated in the volume of glass substrates by femtosecond laser micromachining and are constituted by an integrated Mach–Zehnder interferometer and a superficial heater. Simulations, surface micromachining and innovative layouts allowed us to improve the temporal response of the optical switches down to a few milliseconds. In addition, taking advantage of an electrical pulse shaping approach where an optimized voltage signal is applied to the heater, we proved a switching time as low as 78 µs, about two orders of magnitude shorter with respect to the current state of the art of thermally-actuated optical switches in glass.

Anomalous behavior induced by water insertion in Molybdenum disulfide nanoflowers

The coexistence of negative photoconductivity and metallic-like behavior in conventional semiconductors is very uncommon. In this work, we report the existence of such unconventional physical properties in Molybdenum disulfide nanoflowers (MoS2-NF). This is achieved by making the surface of MoS2 hygroscopic by alcohol treatment and creating a transport channel that favors protonic over electronic conduction. On cooling the MoS2-NF in a heat sink, the excess water that condenses on the surface forms a proton (H3O+) wire which exhibits pinched hysteresis characteristics. The conductivity of MoS2 increased by two orders of magnitude in the proton-dominated conduction regime with an exceptionally high positive temperature coefficient of 1.3×104 Ω/K. Interestingly, MoS2-NF also exhibits strong negative photoresponse (NPC) at room temperature when illuminated with UV and infra-red radiation. This interesting behavior observed in MoS2 NF can be useful for energy harvesting applications and the realization of fast thermal memories and optical switches.

Self-controlling photonic-on-chip networks with deep reinforcement learning

We present a novel photonic chip design for high bandwidth four-degree optical switches that support high-dimensional switching mechanisms with low insertion loss and low crosstalk in a low power consumption level and a short switching time. Such four-degree photonic chips can be used to build an integrated full-grid Photonic-on-Chip Network (PCN). With four distinct input/output directions, the proposed photonic chips are superior compared to the current bidirectional photonic switches, where a conventionally sizable PCN can only be constructed as a linear chain of bidirectional chips. Our four-directional photonic chips are more flexible and scalable for the design of modern optical switches, enabling the construction of multi-dimensional photonic chip networks that are widely applied for intra-chip communication networks and photonic data centers. More noticeably, our photonic networks can be self-controlling with our proposed Multi-Sample Discovery model, a deep reinforcement learning model based on Proximal Policy Optimization. On a PCN, we can optimize many criteria such as transmission loss, power consumption, and routing time, while preserving performance and scaling up the network with dynamic changes. Experiments on simulated data demonstrate the effectiveness and scalability of the proposed architectural design and optimization algorithm. Perceivable insights make the constructed architecture become the self-controlling photonic-on-chip networks.

A tailored ultra-broadband electromagnetically induced transparency metamaterial based on graphene

Based on graphene, an ultra-broadband electromagnetically induced transparency (EIT) window with dynamic tunability is realized in theory. Through altering the Fermi level of graphene that can be regulated by the external voltage, the EIT window and the EIT effect, especially the slow-wave effect, can be easily adjusted. Moreover, the bandwidth of the EIT window can be changed by the incidence angle, achieving the transformation from broadband to narrowband. At the same time, by discussing the polarization state and loss index, the characteristics of polarization insensitivity and low loss are proved. Additionally, the influences of other parameters are discussed, such as the relaxation time of graphene and coupling distance. These unique features enable the designed EIT metamaterial to be masterly applied to optical switches, optical modulators, and slow-light devices.

Investigating the reliability of all-optical switches in transient mode

In this paper the scheme of 8×8 all-optical switch with two duplicating switching elements and the algorithm of its functioning are presented. For calculating the reliability of all-optical switches, the analytical method based on the Markov process theory is presented. This method allows us to calculate reliability indicators of the all-optical switches as downtime coefficient and availability factor in stationary and transient modes and time of transient mode. The results of numerical calculations show that an increase in the number of duplicating elements by one gives decrease in the downtime coefficient by 6 percent, and the time of the transient process is halved in this case.

High-capacity strictly non-blocking optical switches based on new dual principle

In this paper the new dual principle of designing high-capacity strictly non-blocking optical switches is presented for the first time. The new type of switches with decentralized control based on the dual principle has been developed for the first time too. In accordance with the scheme topology this type of switching system was called as the quasi-complete dual switch. It also is analysed the optical signals minimal transmission time that provide the non-blocking property of the new schemes. For the circuit and link complexity calculations the accurate analytical expressions are obtained for the first time. The numerical investigation shows that the proposed schemes significantly benefit in comparison with the well-known switches, for example, the crossbar and Clos schemes. The results of comparing of the dual switch and other types of self-routing switches throughput show an obvious advantage of the proposed scheme. It also is shown that the offered switch type can be considered as a perspective for high-capacity strictly non-blocking optical systems. Indeed, the strictly non-blocking property, the scalability, high throughput, and the decentralized control are the main advantages of offered switches.

Graphene-based dual-band near-perfect absorption in Rabi splitting between topological edge and Fabry-Perot cavity modes

We propose a graphene embedded one-dimensional (1D) topological photonic crystal heterostructure, where the strong coupling occurs between the topological edge mode (TEM) and the Fabry-Perot cavity mode (CM). It is shown that the strong coupling leads to the hybridization between TEM and CM, with a Rabi splitting. Based on finite element method (FEM), a dual-band near-perfect absorption, which can be actively tuned by the Fermi energy of the graphene and incident angle, is found in the Rabi splitting region. Theoretically, the TEM-CM coupling can be analyzed by the classic oscillator model. In particular, when the Fermi energy of graphene slightly increases around 0.4 eV, the dual-band near-perfect absorption shows a rapid decrease from one to zero, which offers a possible way for absorption optical switches.