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On-chip integrated lasers are key devices to deliver the high bandwidth expected from nanophotonic interconnects. However, lasers are highly sensitive to temperature variation, which influences the lasing efficiency and the wavelengths of emitted optical signals, both of which are key factors in interconnect power efficiency. It is, thus, necessary to develop techniques for efficient thermal-aware control of lasers. In this brief, we propose the grouping of lasers for efficient power control of their temperature. Laser grouping is carried out taking into account the layout symmetries, and a design method allows the definition of control laws. [ABSTRACT FROM AUTHOR]

Nanoscale semiconductor lasers have been developed recently using either metal, metallo-dielectric, or photonic crystal nanocavities. While the technology of nanolasers is steadily being deployed, their expected performance for on-chip optical interconnects is still largely unknown due to a limited understanding of some of their key features. Specifically, as the cavity size is reduced with respect to the emission wavelength, the stimulated and the spontaneous emission rates are modified, which is known as the Purcell effect in the context of cavity quantum electrodynamics. This effect is expected to have a major impact in the "threshold-less" behavior of nanolasers and in their modulation speed; but its role is poorly understood in practical laser structures, characterized by significant homogeneous and inhomogeneous broadening and by a complex spatial distribution of the active material and cavity field. In this paper, we investigate the role of the Purcell effect in the stimulated and spontaneous emission rates of semiconductor lasers taking into account the carriers' spatial distribution in the volume of the active region over a wide range of cavity dimensions and emitter/cavity linewidths, enabling the detailed modeling of the static and dynamic characteristics of either micro- or nano-scale lasers using single-mode rate-equations analysis. The ultimate limits of scaling down these nanoscale light sources in terms of Purcell enhancement and modulation speed are also discussed showing that the ultrafast modulation properties predicted in nanolasers are a direct consequence of the enhancement of the stimulated emission rate via reduction of the mode volume. [ABSTRACT FROM AUTHOR]

Nano-scale Multifunctional Logic Gates based on Si hybrid plasmonic waveguides (HPWGs) are designed by utilizing the multimode interference (MMI) effect. The proposed device is composed of three input waveguides, three output waveguides and an MMI waveguide. The functional size of the device is only 1000 nm × 3200 nm, which is much smaller than traditional Si-based all-optical logic gates. By setting different input signals and selecting suitable threshold value, OR, AND, XOR and NOT gates are achieved simultaneously or individually in a single device. This may provide a way for ultrahigh speed signal processing and future nanophotonic integrated circuits. [ABSTRACT FROM AUTHOR]

Ultracompact optical directional coupler is one of the key elements for nanoscale optical networks and highly integrated optical circuits. Although the transverse size has been reduced down to subwavelength by exploiting plasmonic waveguides, the longitudinal size has remained yet on the micrometer-scale, which seems to be a fundamental limitation by the conventional configuration based on cross-talk coupling between two neighboring waveguides. We have proposed a novel conception of optical directional coupler based on loss-overcompensated resonant coupling between two plasmonic waveguides via an in-between gain-assisted nanocavity. The loss-overcompensated state can be achieved by adjusting pumping rate in the nanocavity. The validity of the proposed conception is confirmed by numerical simulations of a physical model with the deep-subwavelength planar footprint of 300 nm × 300 nm, THz bandwidth, and an exceptionally low energy consumption on the order of 0.1 fJ per signal pulse. To our knowledge, it is the first proposed ultrafast nanoscale four-port directional coupler. [ABSTRACT FROM AUTHOR]

In this paper, a novel type of all-optical logic device based on graphene surface plasmon polaritons (GSP) is proposed. By utilizing linear interference between the GSP waves propagating in the different channels, this new structure can realize six different basic logic gates including OR, XOR, NOT, AND, NOR, and NAND. The state of “ON/OFF” of each input channel can be well controlled by tuning the optical conductivity of graphene sheets, which can be further controlled by changing the external gate voltage. This type of logic gate is compact in geometrical sizes and is a potential block in the integration of nanophotonic devices. [ABSTRACT FROM AUTHOR]

As massive microprocessors with thousands of cores are on the horizon, using Radio Frequency (RF) or state-of-the-art nanophotonic on-chip interconnects appears as a solution to cope with current latency constraints. Due to their reliance on numerous static circuitry to generate communication channels, proposed architectures cannot rearbitrate the available bandwidth to on-chip nodes according to instantaneous traffic demands. In this paper, we present an Orthogonal Frequency Division Multiple Access (OFDMA) based wired on-chip RF interconnect as an effective reconfigurable and broadcast capable modulation. A hierarchical 2048-core CMP architecture is explained along with its hybrid cache coherency mechanism. Based on this novel architecture, we introduce an innovative bandwidth arbitration mechanism which allocates more bandwidth to cache-line carrying long packets without requiring extra signaling overhead. Exploiting broadcast capability and effective reconfigurability, we show that this bimodal packet aware communication infrastructure can provide up to 10 × less average latency compared to a static counterpart under certain circumstances. [ABSTRACT FROM AUTHOR]

Electrospinning is a nanotechnology process whereby an external electric field is used to accelerate and stretch a charged polymer jet, so as to produce fibers with nanoscale diameters. In quest of a further reduction in the cross section of electrified jets hence of a better control on the morphology of the resulting electrospun fibers, we explore the effects of an external rotating electric field orthogonal to the jet direction. Through intensive particle simulations, it is shown that by a proper tuning of the electric field amplitude and frequency, a reduction of up to a 30% in the aforementioned radius can be obtained, thereby opening new perspectives in the design of future ultra-thin electrospun fibers. Applications can be envisaged in the fields of nanophotonic components as well as for designing new and improved filtration materials. [ABSTRACT FROM AUTHOR]

On-chip nanophotonics offer high throughput, yet energy-efficient communication, traits that can prove critical to the continuance of multicore chip scalability. In this paper, we investigate and propose silicon nanophotonic components that are embedded entirely in the silica (SiO2) substrate, i.e., reside subsurface, as opposed to die on-surface silicon nanophotonics of prior-art. Among several offered advantages, such silicon-in-silica (SiS) nanophotonic structures empower the implementation of nonobstructive interconnect geometries that deliver an improved power-performance balance, as demonstrated experimentally. First, using exhaustive simulations based on commercial-grade optical software-based tools, we show that such SiS structures are feasible, and derive their geometry characteristics and design parameters. As a second step, utilizing SiS optical channels and filters, we then design two distinct SiS-based nanophotonic network-on-chip (PNoC) mesh-diagonal links topologies as a means of demonstrating our proof of concept. In further pushing the performance envelope, we next develop: 1) an associated contention-aware adaptive routing function and 2) a parallelized photonic channel allocation scheme, with both coupled to SiS-based PNoCs as elements, to respectively replace under-performing routing and flow-control photonic protocols currently utilized. An extensive experimental evaluation, including utilizing traffic benchmarks gathered from full-system chip multiprocessor simulations, shows that our methodology boosts network throughput by up to 59.7%, reduces communication latency by up to 78.7%, while improving the throughput-to-power ratio by up to 31.6% when compared to the state-of-the-art. [ABSTRACT FROM PUBLISHER]

Fiber-based devices for operation in fully optical networks are relatively large in size and can not be used in photonic integrated circuits (PICs). We have developed an efficient graphene-based nanophotonic switching nanocell, working in linear regime (cross state) and in non-linear regime (bar state) with relatively low optical power, so that they can be cascaded and integrated in PICs. Indeed, that device is a fully optical switch, which can work in dense wavelength division multiplexing systems. [ABSTRACT FROM AUTHOR]

In this paper, a type of compact nanosensor based on a metal-insulator-metal structure is proposed and investigated through cascading double asymmetric cavities, in which their metal cores shift along different axis directions. The cascaded asymmetric structure exhibits high transmission and sharp Fano resonance peaks via strengthening the mutual coupling of the cavities. The research results show that with the increase of the symmetry breaking in the structure, the number of Fano resonances increase accordingly. Furthermore, by modulating the geometrical parameters appropriately, Fano resonances with high sensitivities to the changes in refractive index can be realized. A maximum figure of merit (FoM) value of 74.3 is obtained. Considerable applications for this work can be found in bio/chemical sensors with excellent performance and other nanophotonic integrated circuit devices such as optical filters, switches and modulators. [ABSTRACT FROM AUTHOR]

Surface plasmons provide a pathway to efficiently absorb and confine light in metallic nanostructures, thereby bridging photonics to the nano scale. The decay of surface plasmons generates energetic 'hot' carriers, which can drive chemical reactions or be injected into semiconductors for nano-scale photochemical or photovoltaic energy conversion. Novel plasmonic hot carrier devices and architectures continue to be demonstrated, but the complexity of the underlying processes make a complete microscopic understanding of all the mechanisms and design considerations for such devices extremely challenging.Here,we review the theoretical and computational efforts to understand and model plasmonic hot carrier devices.We split the problem into three steps: hot carrier generation, transport and collection, and review theoretical approaches with the appropriate level of detail for each step along with their predictions.We identify the key advances necessary to complete the microscopic mechanistic picture and facilitate the design of the next generation of devices and materials for plasmonic energy conversion. [ABSTRACT FROM AUTHOR]

From the photoinduced transport of energy that accompanies photosynthesis to the transcontinental transmission of optical data that enable the Internet, our world relies and thrives on optical signals. To highlight the importance of optics to society, the United Nations designated 2015 as "The International Year of Light and Light-based Technologies." Although conventional optical technologies are limited by diffraction, plasmons—collective oscillations of free electrons in a conductor—allow optical signals to be tailored with nanoscale precision. Following decades of fundamental research, several plasmonic technologies have now emerged on the market, and numerous industrial breakthroughs are imminent. This article highlights recent industrially relevant advances in plasmonics, including plasmonic materials and devices for energy; for medical sensing, imaging, and therapeutics; and for information technology. Some of the most exciting industrial applications include solar-driven water purifiers, cell phone Raman spectrometers, high-density holographic displays, photothermal cancer therapeutics, and nanophotonic integrated circuits. We describe the fundamental scientific concepts behind these and related technologies, as well as the successes and challenges associated with technology transfer. [ABSTRACT FROM AUTHOR]

Surface plasmons, collective oscillations of conduction electrons, hold great promise for the nanoscale integration of photonics and electronics. However, nanophotonic circuits based on plasmons have been significantly hampered by the difficulty in achieving broadband plasmonic waveguides that simultaneously exhibit strong spatial confinement, a high quality factor and low dispersion. Quantum plasmons, where the quantum mechanical effects of electrons play a dominant role, such as plasmons in very small metal nanoparticles and plasmons affected by tunnelling effects, can lead to novel plasmonic phenomena in nanostructures. Here, we show that a Luttinger liquid of one-dimensional Dirac electrons in carbon nanotubes exhibits quantum plasmons that behave qualitatively differently from classical plasmon excitations. The Luttinger-liquid plasmons propagate at 'quantized' velocities that are independent of carrier concentration or excitation wavelength, and simultaneously exhibit extraordinary spatial confinement and high quality factor. Such Luttinger-liquid plasmons could enable novel low-loss plasmonic circuits for the subwavelength manipulation of light. [ABSTRACT FROM AUTHOR]

We report on monolithic integration of active quantum cascade laser (QCL) materials with passive waveguides formed by using proton implantation. Proton implantation reduces the electron concentration in the QCL layers by creating deep levels that trap carriers. This strongly reduces the intersubband absorption and the free-carrier absorption in the gain region and surrounding layers, thus significantly reducing optical loss. We have measured loss as low as α = 0.33 cm-1 in λ = 9.6 μm wavelength proton-implanted QCL material. We have also demonstrated lasing in active-passive integrated waveguides. This simple integration technique is anticipated to enable low-cost fabrication in infrared photonic integrated circuits in the mid-infrared (λ ~ 3-16 μm). [ABSTRACT FROM AUTHOR]

Graphene, a well-known two-dimensional sheet, has attracted strong interest for both fundamental studies and applications. Due to its high intrinsic thermal conductivity, graphene has many potential applications in thermal management, such as in heat spreaders and flexible heaters. In this paper, a graphene-based transparent flexible heat conductor for nanophotonic integrated devices is demonstrated. The graphene heat conductor is designed to deliver heat from a non-local traditional metal heater to nanophotonic integrated devices for realizing efficient thermal tuning. With the present graphene heat conductor, a thermally tuning silicon Mach-Zehnder interferometer and micro-disk have been realized with good performance in terms of heating efficiency and temporal response. This indicates that the present graphene-based transparent flexible heat conductor provides an efficient and beneficial heating method for thermally tuning nanophotonic integrated devices. [ABSTRACT FROM AUTHOR]

Diamond integrated photonic devices are promising candidates for emerging applications in nanophotonics and quantum optics. Here, we demonstrate active modulation of diamond nanophotonic circuits by exploiting mechanical degrees of freedom in free-standing diamond electro-optomechanical resonators. We obtain high quality factors up to 9600, allowing us to read out the driven nanomechanical response with integrated optical interferometers with high sensitivity. We are able to excite higher order mechanical modes up to 115 MHz and observe the nanomechanical response also under ambient conditions. [ABSTRACT FROM AUTHOR]

Nanophotonic integrated circuits offer unique advantages for studying the interaction of light fields with mechanical structures. Because nanoscale waveguides are closely size-matched to nanomechanical devices, strong optomechanical interactions arise which can be harnessed in optical systems. The additional mechanical degrees of freedom provided by optomechanical devices are of particular interest for material systems in which tunability of the optical properties is not readily available. Here, suitable materials for the realization of chip-based optomechanical circuits are discussed and analyzed in terms of performance and the achievable quality factors. In particular, materials that offer large electronic band gaps are of interest, because in this case broadband optical transparency is achieved, combined with reduced free carrier effects. Several device geometries that can be used for enhancing optical forces are presented which address both an increase in the field gradient and the net optical force through resonant enhancement. Combining a variety of optomechanical components into full circuits thus provides a new route toward functional nanophotonic circuits with applications in sensing and optical signal processing in a chip-scale framework. [ABSTRACT FROM PUBLISHER]

Abstract: In this work, we study the formulation of beam propagation in an elliptical reflector in nanophotonic integrated circuits (NPICs). We introduce a Gaussian beam mode analysis with Effective Refractive Index Approximation (EIA) applied to planar waveguides. The wavelength-scale waveguides in NPICs lead to large diffraction angle of the input beam and phase aberration in the reflected beam. However, this aberration can be shown to be negligible under first order approximation (FOA). With the Gaussian beam formulation, we study the Near Field and Far Field scenarios in the incident and reflected beams and propose a design methodology that utilizes the two scenarios to minimize footprint of associated devices. Specifically, we use Finite-Difference Time-Domain (FDTD) simulation to show that applying such methodology in designing a waveguide crossing using elliptical reflectors not only minimizes the device footprint but also creates a novel crossing that outperforms the conventional Direct Waveguide Crossing (DWC) in terms of the lowest order mode transmission efficiency and crosstalk. [Copyright &y& Elsevier]

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 Ge2Sb2Te5 (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 Neumann neuromorphic computing. [ABSTRACT FROM AUTHOR]

In this paper, the accuracy of coupled-mode theory (CMT) and mode-matching (MM) method in estimating the scattering due to geometric perturbations in photonic crystal waveguides (PCWs) is examined. Two CMT formulations are considered: the instantaneous virtual grating and the conventional CMT. The two CMT formulations and the MM method are compared against the finite-difference frequency-domain (FDFD) method combined with the adjoint variable (AV) method. The results obtained with the AV/FDFD and MM methods agree very well, proving the validity of the latter for the sensitivity analysis of PCW structures. It is also deduced that although both CMT formulations lead to almost identical results, they can provide only a first approximation to the perturbation-induced scattering. [ABSTRACT FROM PUBLISHER]

Bigradient all‐dielectric metamaterials provide subwavelength‐scale on‐chip metalenses solution for dense photonic integrated circuits by structural engineering. (DOI: 10.1002/inf2.12264) [ABSTRACT FROM AUTHOR]

The field of silicon nanophotonics has attracted considerable attention in the past decade because of its unique advantages, including complementary metal–oxide–semiconductor (CMOS) compatibility and the ability to achieve an ultra-high integration density. In particular, silicon nanophotonic integrated devices for on-chip light manipulation have been developed successfully and have played very import roles in various applications. In this paper, we review the recent progress of silicon nanophotonic devices for on-chip light manipulation, including the static type and the dynamic type. Static on-chip light manipulation focuses on polarization/mode manipulation, as well as light nanofocusing, while dynamic on-chip light manipulation focuses on optical modulation/switching. The challenges and prospects of high-performance silicon nanophotonic integrated devices for on-chip light manipulation are discussed. [ABSTRACT FROM AUTHOR]

By cascading compact and low-loss Mach–Zehnder interferometers (MZIs) embedded within nanophotonic circuits we realize thermo-optically tunable optical filters for the visible wavelength range. Through phase tuning in either arm of the MZI, the filter response with maximum extinction can be shifted beyond one free-spectral range with low electrical power consumption. The working wavelength of our device is aligned with the emission wavelength of the silicon vacancy color center in diamond around 740 nm where we realize a filter depth beyond 36.5 dB. Our approach allows for efficient isolation of the emitted signal intensity in future hybrid nanodiamond-nanophotonic circuits. [ABSTRACT FROM AUTHOR]