Showing papers on "Insertion loss published in 2018"

High-Performance Hybrid Silicon and Lithium Niobate Mach-Zehnder Modulators for 100 Gbit/s and Beyond

Abstract: Optical modulators are at the heart of optical communication links Ideally, they should feature low insertion loss, low drive voltage, large modulation bandwidth, high linearity, compact footprint and low manufacturing cost Unfortunately, these criteria have only been achieved on separate occasionsBased on a Silicon and Lithium Niobate hybrid integration platform, we demonstrate Mach-Zehnder modulators that simultaneously fulfill these criteria The presented device exhibits an insertion loss of 25 dB, voltage-length product of 22 Vcm, high linearity, electro-optic bandwidth of at least 70 GHz and modulation rates up to 112 Gbit/s The high-performance modulator is realized by seamless integration of high-contrast waveguide based on Lithium Niobate - the most mature modulator material - with compact, low-loss silicon circuits The hybrid platform demonstrated here allows for the combination of 'best-in-breed' active and passive components, opening up new avenues for enabling future high-speed, energy efficient and cost-effective optical communication networks

Frequency-Selective Rasorber With Interabsorption Band Transparent Window and Interdigital Resonator

Abstract: A novel frequency-selective rasorber (FSR) is proposed in this paper which has a nearly transparent window between two absorption bands. The FSR consists of a resistive sheet and a bandpass frequency-selective surface (FSS). The impedance conditions of absorption/transmission for both the resistive sheet and the bandpass FSS are theoretically derived based on equivalent circuit analysis. The insertion loss of FSR at the resonant frequency of lossless bandpass FSS is proven to be only related to the equivalent impedance of the resistive sheet. When the resistive sheet is in parallel resonance at the passband, a nearly transparent window can be achieved regardless of lossy properties. An interdigital resonator (IR) is designed to realize parallel resonance in the resistive element by extending one finger of a strip-type interdigital capacitor to connect the two separate parts of the capacitor. The IR is equivalent to a parallel LC circuit. Lumped resistors are loaded around the IR to absorb the incident wave at lower and upper absorption bands. With the bandpass FSS as the ground plane, the absorption performances at both the lower and upper bands around the resonant frequency are improved compared to a metal-plane-backed absorber structure. The FSR passband is designed at 10 GHz with an insertion loss of 0.2 dB. The band with a reflection coefficient below −10 dB extends from 4.8 to 15.5 GHz. A further extension to dual-polarized FSR is designed, fabricated, and measured to validate the proposed design.

Broadband passive isolators based on coupled nonlinear resonances

Abstract: Isolators are devices that transmit waves only in one direction, and are widely used to protect sensitive equipment from reflections and interference These devices inherently require the breaking of Lorentz reciprocity, which can be achieved with an external bias, such as a magnetic field, that breaks time-reversal symmetry Alternatively, nonlinear effects can be used, which offer a route to fully passive devices that do not require any form of external bias However, the nonlinear isolators developed so far have limitations in terms of insertion loss, isolation, bandwidth and isolation intensity range Here, we show that any isolator formed from one nonlinear resonator suffers from these limitations, and that they can be overcome by combining multiple nonlinear resonators with suitable intensity dispersion We theoretically show, and then experimentally demonstrate using a microwave circuit, that the combination of one Fano and one Lorentzian nonlinear resonator, and a suitable delay line between them, can provide unitary transmission, infinite isolation, broad bandwidth and broad isolation intensity range We also show that a larger number of resonators can be used to further increase the isolation intensity range without diminishing the other metrics of the device Passive isolators that offer unitary transmission, infinite isolation and large non-reciprocal intensity range can be created by combining Fano and Lorentzian nonlinear resonators, separated by suitably designed delay lines

Inverse design and demonstration of a compact on-chip narrowband three-channel wavelength demultiplexer

Abstract: In wavelength division multiplexing schemes, splitters must be used to combine and separate different wavelengths. Conventional splitters are fairly large with footprints in hundreds to thousands of square microns, and experimentally demonstrated multimode-interference-based and inverse-designed ultracompact splitters operate with only two channels and large channel spacing (>100 nm). Here we inverse design and experimentally demonstrate a three-channel wavelength demultiplexer with 40 nm spacing (1500, 1540, and 1580 nm) with a footprint of 24.75 μm2. The splitter has a simulated peak insertion loss of −1.55 dB with under −15 dB crosstalk and a measured peak insertion loss of −2.29 dB with under −10.7 dB crosstalk.

Fully-automated optimization of grating couplers.

Abstract: We present a gradient-based algorithm to design general 1D grating couplers without any human input from start to finish, including a choice of initial condition. We show that we can reliably design efficient couplers to have multiple functionalities in different geometries, including conventional couplers for single-polarization and single-wavelength operation, polarization-insensitive couplers, and wavelength-demultiplexing couplers. In particular, we design a fiber-to-chip blazed grating with under 0.2 dB insertion loss that requires a single etch to fabricate and no back-reflector.

Cavity-Free Optical Isolators and Circulators Using a Chiral Cross-Kerr Nonlinearity

Abstract: Optical nonlinearity has been widely used to try to produce optical isolators. However, this is very difficult to achieve due to dynamical reciprocity. Here, we show the use of the chiral cross-Kerr nonlinearity of atoms at room temperature to realize optical isolation, circumventing dynamical reciprocity. In our approach, the chiral cross-Kerr nonlinearity is induced by the thermal motion of $N$-type atoms. The resulting cross phase shift and absorption of a weak probe field are dependent on its propagation direction. This proposed optical isolator can achieve more than 30 dB of isolation ratio, with a low loss of less than 1 dB. By inserting this atomic medium in a Mach-Zehnder interferometer, we further propose a four-port optical circulator with a fidelity larger than 0.9 and an average insertion loss less than 1.6 dB. Using atomic vapor embedded in an on-chip waveguide, our method may provide chip-compatible optical isolation at the single-photon level of a probe field.

Ultra-compact mode (de) multiplexer based on subwavelength asymmetric Y-junction.

Abstract: We propose and experimentally demonstrate a novel multimode ultra-compact mode (de)multiplexer for highly integrated on-chip mode-division multiplexing systems. This device is composed of a wide divergence angle asymmetric Y-junction based on subwavelength structure and optimized using an inverse design method. The proposed device occupied a footprint of only 2.4 × 3 µm2. The measured insertion loss and crosstalk were less than 1dB and –24 dB from 1530 nm to 1590 nm for both TE0 mode and TE1 mode, respectively. Likewise, a three mode multiplexer is also designed and fabricated with a compact footprint of 3.6 × 4.8 µm2. Furthermore, our scheme could also be expanded to include more modes.

High-speed silicon modulators for the 2 μm wavelength band

Abstract: The 2 μm wavelength band has become a promising candidate to be the next communication window. We demonstrate high-speed modulators based on a 220 nm silicon-on-insulator platform working at a wavelength of 1950 nm, using the free carrier plasma dispersion effect in silicon. A Mach–Zehnder interferometer modulator and a microring modulator have been characterized. At 1950 nm, the carrier-depletion modulator operates at a data rate of 20 Gbit/s with an extinction ratio of 5.8 dB and insertion loss of 13 dB. The modulation efficiency (V π ·L π ) is 2.68 V·cm at 4 V reverse bias. The device operation is broadband, and we also characterize its performance at 1550 nm. At 1550 nm, an open eye is obtained at 30 Gbit/s. The difference in bandwidth is caused by the bandwidth limit of the 2 μm measurement setup. We also show a ring modulator paired with a low power integrated driver working in hybrid carrier depletion and injection mode at a data rate of 3 Gbit/s with power consumption of 2.38 pJ/bit in the 2 μm wavelength range. This work is a proof of principle demonstration and paves a route toward a full silicon-based transceiver in the 2 μm window.

Gigahertz speed operation of epsilon-near-zero silicon photonic modulators

Abstract: Optical communication systems increasingly require electro-optical modulators that deliver high modulation speeds across a large optical bandwidth with a small device footprint and a CMOS-compatible fabrication process Although silicon photonic modulators based on transparent conducting oxides (TCOs) have shown promise for delivering on these requirements, modulation speeds to date have been limited Here, we describe the design, fabrication, and performance of a fast, compact electroabsorption modulator based on TCOs The modulator works by using bias voltage to increase the carrier density in the conducting oxide, which changes the permittivity and hence optical attenuation by almost 10 dB Under bias, light is tightly confined to the conducting oxide layer through nonresonant epsilon-near-zero (ENZ) effects, which enable modulation over a broad range of wavelengths in the telecommunications band Our approach features simple integration with passive silicon waveguides, the use of stable inorganic materials, and the ability to modulate both transverse electric and magnetic polarizations with the same device design Using a 4-μm-long modulator and a drive voltage of 2 Vpp, we demonstrate digital modulation at rates of 25 Gb/s We report broadband operation with a 65 dB extinction ratio across the 1530–1590 nm band and a 10 dB insertion loss This work verifies that high-speed ENZ devices can be created using conducting oxide materials and paves the way for additional technology development that could have a broad impact on future optical communications systems

Combining FSS and EBG Surfaces for High-Efficiency Transmission and Low-Scattering Properties

Abstract: In this communication, we propose a method to achieve high-efficiency transmission and wideband scattering reduction at two distinctive frequency bands by combining frequency-selective surface (FSS) and electromagnetic bandgap (EBG) surface. Such FSS-EBG surface is composed of two-layered metallic patterns. The bottom FSS layer works as a filter for allowing in-band signal to pass and reflecting out-of-band signal, while the top EBG layer adopts 0 and $\pi $ reflection phase cells with a chessboard distribution to reduce the backward scattering wave. As a proof-of-concept demonstration, the planar and cylindrical surfaces are, respectively, designed to verify such two functionalities. Our FSS-EBG surface can make the antenna signal transmit at S-band with small insertion loss and simultaneously provide wideband low-scattering property at X–Ku band, which is suitable to be used as the stealth antenna radome. In addition, the possibility of integrating polarization conversion function into the passing band is numerically demonstrated.

Stacked Microstrip Linear Array for Millimeter-Wave 5G Baseband Communication

Abstract: A 42-element microstrip parasitic patch antenna is developed in the millimeter-wave band for fifth-generation mobile communication base stations. A metalized elliptical stripline-to-embedded-microstrip transition with adaptive via-hole arrangement as well as a 20 dB Chebyshev tapered six-way power divider is proposed to have an insertion loss of 0.045 dB. To confirm the feasibility of the antenna, it has been measured to provide a 6.3% fractional bandwidth from 26.83 to 28.56 GHz at VSWR of less than 1.96. The array antenna gains of more than 21.4 dBi have been realized with sidelobe levels of better than –19.1 dB, operating within 27.5–28.5 GHz in both the azimuth and elevation directions.

Design Space Exploration of Microring Resonators in Silicon Photonic Interconnects: Impact of the Ring Curvature

Abstract: A detailed analysis of fundamental tradeoffs between ring radius and coupling gap size is presented to draw realistic borders of the possible design space for microring resonators (MRRs). The coupling coefficient for the ring-waveguide structure is estimated based on an integration of the nonuniform gap between the ring and the waveguide. Combined with the supermode analysis of two coupled waveguides, this approach is further expanded into a closed-form equation that describes the coupling strength. This equation permits to evaluate how the distance separating a waveguide from a ring resonator, and the ring radius, affect coupling. The effect of ring radius on the bending loss of the ring is furthermore modeled based on the measurements for silicon MRRs with different radii. These compact models for coupling and loss are subsequently used to derive the main optical properties of MRRs, such as 3-dB optical bandwidth, extinction ratio of resonance, and insertion loss, hence identifying the design space. Our results indicate that the design space for add-drop filters in a wavelength division multiplexed link is currently limited to 5–10 $\mu$ m in radius and gap sizes ranging from 120 to 210 nm. The good agreement between the results from the proposed compact model for coupling and the numerical FDTD and experimental measurements indicate the application of our approach in realizing fast and efficient design space exploration of MRRs in silicon photonic interconnects.

Low-Profile Dual-Polarization Frequency-Selective Rasorbers Based on Simple-Structure Lossy Cross-Frame Elements

Abstract: The low-profile dual-polarization frequency-selective rasorbers with very simple structures are investigated. Based on an equivalent circuit model, the operating principle and design method are first studied. One rasorber using lossy cross-frame elements and double-square loops is then proposed, which exhibits two absorption bands at the two sides of one passband. Moreover, the rasorbers with reduced cell size are further developed to stabilize the angular response. Under normal incidence, an insertion loss of about 0.26 dB is obtained at 4.25 GHz, the fractional bandwidth for reflection less than −10 dB is over 100%, and the thickness is around ${\text{0.1}}\,\lambda _{L}$ . For demonstration, the rasorber prototypes are fabricated and measured, while reasonable agreements are observed accordingly.

Ultra-Broadband Mode Converter and Multiplexer Based on Sub-Wavelength Structures

Abstract: Current bandwidth capacity provided by wavelength-division multiplexing and polarization-division multiplexing is insufficient to keep up with the increasing bandwidth demand required for new services. Mode-division multiplexing technology paves the way to further increase transmission and bandwidth capacities in photonic interconnects. In this work, we propose an ultra-broadband two-mode converter and de/multiplexer based on a sub-wavelength engineered multimode interference coupler, a 90 $^{\circ }$ phase shifter, and a symmetric Y-junction for the silicon-on-insulator platform. Sub-wavelength grating waveguides enable dispersion engineering to further increase the bandwidth operation of conventional multimode interference coupler and, subsequently, of mode de/multiplexer based on them. Full three-dimensional simulations of the designed mode converter and de/multiplexer show insertion loss below than 0.84 dB and crosstalk lower than $-$ 20 dB over an unprecedented bandwidth of 300 nm (1.4–1.7 $\mu$ m). The overall footprint of the proposed device is only 36 $\mu$ m $\times$ 3.7 $\mu$ m.

A Negative Group Delay Microwave Circuit Based on Signal Interference Techniques

Abstract: A novel self-matched negative group delay (NGD) microwave circuit based on the signal interference technique is proposed to eliminate the performance degradation due to the temperature-dependent resistance variation. The proposed circuit consists of unequal power dividing/combining structures and coupled-line phase shifter, which can be directly synthesized with prescribed NGD time and insertion loss (IL). To verify the proposed method, an NGD circuit with a size of $0.41\lambda _{g}\times 0.41\lambda _{g}$ is designed and fabricated. From the measured results, NGD time of −2.09 ns at the center frequency of 1.016 GHz is obtained with NGD bandwidth of 14.2% (0.944–1.088 GHz), in which the IL is less than 18.1 dB and the return loss is greater than 33 dB.

Pseudo-Linear Time-Invariant Magnetless Circulators Based on Differential Spatiotemporal Modulation of Resonant Junctions

Abstract: In this paper, we present voltage-mode and current-mode differential magnetless nonreciprocal devices obtained by pairing two single-ended (SE) circulators, each consisting of three first-order bandpass or bandstop LC filters, connected in either a wye or a delta topology The resonant poles of each SE circulator are modulated in time with 120° phase-shifted periodic signals, resulting in synthetic angular-momentum biasing achieved through spatiotemporal modulation (STM) We tailor the two SE circulators to exhibit a constant 180° phase difference between their STM biases Unlike conventional differential time-variant circuits, for which only the even or odd spurs are rejected, we show that the proposed configuration cancels out all intermodulation products, thus making them operate alike linear time-invariant (LTI) circuits for an external observer In turn, this property enhances all metrics of the resulting circulator, overcoming the limitations of SE architectures, and improving insertion loss, impedance matching, bandwidth, and noise figure We show that this differential architecture also significantly relaxes the required modulation parameters, both in frequency and amplitude We develop a rigorous small-signal model to guide the design of the proposed circuits and to get insights into their pseudo-LTI characteristics Then, we validate the theory with simulations and measurements showing remarkable performance compared to the current state-of-the-art of magnetless nonreciprocal devices

A 300-mm Silicon Photonics Platform for Large-Scale Device Integration

Abstract: A 300-mm silicon photonics platform for large-scale device integration was developed, leveraging 40-nm complementary metal-oxide-semiconductor technology. Through fabrication using this technology platform, wire waveguides were obtained with low propagation losses for the C-band (0.4 dB/cm) and O-band (1.3 dB/cm). Several types of wavelength filters, including a coupled resonator optical waveguide (CROW), an arrayed waveguide grating, and a cascaded Mach–Zehnder interferometer, were also demonstrated, with low crosstalk and low insertion loss. A polarization rotator Bragg grating with multiple reflection peaks having polarization independence was also obtained. In terms of wafer-scale uniformity, a small standard deviation of 0.7 nm in resonant wavelength for the CROW was confirmed. A grating coupler also exhibited low wafer-scale variations in the maximum coupling efficiency and the diffraction wavelength in optical coupling with a single-mode fiber. Extraction of fabrication deviations for the waveguides was performed using the spectral variation of microring resonators and grating couplers. The extracted wafer-scale variations in waveguide width and height and grating depth well reproduced the results of physical measurements, with subnanometer-level accuracy. The developed technology can thus enable manufacturing of high-speed, low-power optical interconnects.

High-sensitivity and low-temperature magnetic field sensor based on tapered two-mode fiber interference.

Abstract: A high-sensitivity and low-temperature fiber-optic magnetic field sensor based on a tapered two-mode fiber (TTMF) sandwiched between two single-mode fibers has been proposed and demonstrated. The section of TTMF has a specifically designed transition region as an efficient tool to filter higher-order modes, where the uniform modal interferometer just involved with LP01 and LP11 modes is achieved. The transmission spectral characteristics and the magnetic response of the proposed sensors have been investigated. The experimental results show that a maximum sensitivity of 98.2 pm/Oe within a linear magnetic field intensity ranging from 0 to 140 Oe can be achieved. Significantly, the temperature cross-sensitivity problem can be resolved owing to the lower thermal expansion coefficient of the TTMF. Finally, with its low insertion loss, compactness, and ease of fabrication, the proposed sensor would find potential applications in the measurement of a magnetic field.

Novel Surface Plasmon Polariton Waveguides with Enhanced Field Confinement for Microwave-Frequency Ultra-Wideband Bandpass Filters

Abstract: In this paper, a novel planar waveguide based on spoof surface plasmon polaritons (SSPPs) using fish-bone corrugated slot structure is first proposed in the microwave region. Low-dispersion band can be realized by such structure with tight field confinement of SSPPs, resulting in size miniaturization of the proposed waveguide. The high frequency stopband of the proposed ultra-wideband bandpass filter (BPF) is created by using this proposed waveguide, while the low frequency stopband is properly designed through introducing the microstrip-to-slotline transition. The 2-D E-fields distribution, surface current flow, and energy flow patterns are all calculated and illustrated to demonstrate the electromagnetic (EM) characteristics of the proposed ultra-wideband BPF. The BPF tuning characteristics is explored to provide a guideline for facilitating the design process. To validate the predicted performance, the proposed filter is finally designed, fabricated, and measured. Measured results illustrate high performance of the filter, in which the reflection coefficient is better than −10 dB from 2.1 to 8 GHz with the smallest insertion loss of 0.37 dB at 4.9 GHz, showing good agreement with numerical simulations. The proposed surface plasmon polariton waveguides are believed to be significantly promising for further developing plasmonic functional devices and integrated 2-D circuits with enhanced confinement of SSPPs in microwave and even terahertz bands.

A Very Low Loss 220–325 GHz Silicon Micromachined Waveguide Technology

Abstract: This letter reports for the first time on a very low loss silicon micromachined waveguide technology, implemented for the frequency band of 220–325 GHz The waveguide is realized by utilizing a double H-plane split in a three-wafer stack This ensures very low surface roughness, in particular on the top and bottom surfaces of the waveguide, without the use of any surface roughness reduction processing steps This is superior to previous micromachined waveguide concepts, including E-plane and single H-plane split waveguides The measured average surface roughness is 214 nm for the top/bottom of the waveguide, and 16313 nm for the waveguide sidewalls The measured insertion loss per unit length is 002–007 dB/mm for 220–325 GHz, with a gold layer thickness of 1 $\mu$ m on the top/bottom and 03 $\mu$ m on the sidewalls This represents, in this frequency band, the lowest loss for any silicon micromachined waveguide published to date and is of the same order as the best metal waveguides

Integrated Resonators in an Ultralow Loss Si 3 N 4 /SiO 2 Platform for Multifunction Applications

Abstract: Integrated optical resonators are key building blocks for an ever-increasing range of applications including optical communications, sensing, and navigation. A challenge to today's photonics integration is realizing circuits and functions that require ultralow loss waveguides on-chip while balancing the waveguide loss with device function and footprint. Incorporating Si3N4/SiO2 waveguides into a photonic circuit requires tradeoffs between waveguide loss, device footprint, and desired device specifications. In this paper, we focus on the design of resonator based circuits in the silicon nitride platform and the balancing of desired properties like quality factor ${\text{Q}}$ , free spectral range, finesse, transmission shape with waveguide design, and footprint. The design, fabrication, and characterization of two resonator-based circuit examples operating at 1550 nm are described in detail. The first design is a thin core, large mode-volume bus-coupled resonator, with a 2.72 GHz free spectral range and a measured intrinsic ${\text{Q}}$ of 60 million and loaded ${\text{Q}}$ on the order of 30 Million, representing the highest reported loaded ${\text{Q}}$ for a large mode volume resonator with a deposited upper cladding. The second circuit is a thicker core, smaller footprint, low loss flat passband third-order resonator filter with an ultrahigh extinction ratio of 80 dB tunable over 100% of the free spectral range and insertion loss under 1.3 dB.

Liquid crystal terahertz modulator with plasmon-induced transparency metamaterial.

Abstract: An electrically tunable terahertz (THz) modulator with large modulation depth and low insertion loss is performed with liquid crystal (LC) metamaterial. The modulation depth beyond 90% and insertion loss below 0.5 dB are achievable at normal incidence by exploiting plasmon-induced transparency (PIT) effect. The PIT spectra can be manipulated by actively controlling the interference between dipole mode and nonlocal surface-Bloch mode with LC. The incident angle tuning effect on PIT spectra shows that the large modulation depth and low insertion loss can remain over a wide range of working angles. The superior property and simplicity of design make this modulator promising in advanced terahertz communication.

Low-loss and broadband non-volatile phase-change directional coupler switches

Abstract: An optical equivalent of the field-programmable gate array (FPGA) is of great interest to large-scale photonic integrated circuits. Previous programmable photonic devices relying on the weak, volatile thermo-optic or electro-optic effect usually suffer from a large footprint and high energy consumption. Phase change materials (PCMs) offer a promising solution due to the large non-volatile change in the refractive index upon phase transition. However, the large optical loss in PCMs poses a serious problem. Here, by exploiting an asymmetric directional coupler design, we demonstrate PCM-clad silicon photonic 1 \times 2 and 2 \times 2 switches with a low insertion loss of ~1 dB and a compact coupling length of ~30 {\mu}m while maintaining a small crosstalk less than ~10 dB over a bandwidth of 30 nm. The reported optical switches will function as the building blocks of the meshes in the optical FPGAs for applications such as optical interconnects, neuromorphic computing, quantum computing, and microwave photonics.

A High-Transmittance Frequency-Selective Rasorber Based on Dipole Arrays

Abstract: This paper presents a frequency-selective rasorber whose transmission window locates at the higher frequency of absorption band. The accomplished rasorber is composed of dipole-like and slot arrays, and has realized the transmissive/absorptive performance. In every unit cell, each pair of dipole-like elements connected by vias is printed on the two sides of the substrate, and the coupling between long and short dipoles is suppressed by this structure. A guiding circuit is studied based on the analysis of the current path, and the insertion loss of transmission window is significantly reduced by the surface current at the pass-band that is hindered to pass through lossy elements. The presented rasorber acts as an absorber at the low frequencies, while providing a high transmittance window at 5.6 GHz. This design is elaborately optimized to achieve low reflection and angle-insensitive performance. Finally, the presented structure is validated by numerical simulations and experimental measurements. This rasorber could be used for secrecy communications among stealth facilities while providing stable broad-band absorptive properties.

Hybrid Photonic-Plasmonic Nonblocking Broadband 5 × 5 Router for Optical Networks

Abstract: Photonic data routing in optical networks is expected to overcome the limitations of electronic routers with respect to data rate, latency, and energy consumption. However, photonics-based routers suffer from dynamic power consumption, and nonsimultaneous usage of multiple wavelength channels when microrings are deployed and are sizable in footprint. Here, we show a design for the first hybrid photonic-plasmonic, nonblocking, broadband $5\times 5$ router based on 3-waveguide silicon photonic-plasmonic $2\times 2$ switches. The compactness of the router (footprint $ ) results in a short optical propagation delay (0.4 ps) enabling high data capacity up to 2 Tb/s. The router has an average energy consumption ranging from 0.1 to 1.0 fJ/bit depending on either DWDM or CDWM operation, enabled by the low electrical capacitance of the switch. The total average routing insertion loss of 2.5 dB is supported via an optical mode hybridization deployed inside the $2\times 2$ switches, which minimizes the coupling losses between the photonic and plasmonic sections of the router. The router's spectral bandwidth resides in the S, C, and L bands and exceeds 100 nm supporting wavelength division multiplexing applications since no resonance feature is required. Taken together this novel optical router combines multiple design features, all required in next-generation high data-throughput optical networks and computing systems.

Design and analysis of integrated all-optical $$2\times 4$$ decoder based on 2D photonic crystals

Abstract: In the development of the technology of all-optical integrated circuits, the logic gates play considerable role in the progress of optical components. As one of the main building-blocks of an optical system, a high-performance 2*4 all-optical decoder is proposed and studied based on nonlinear effects in a photonic crystal ring resonator. The proposed structure consists of 1*2 decoders which are combined to operate as a unique 2*4 decoder and this will let us to extend the design to decoders with increased inputs. An optical bias is used to interact with input signals, and each output port is enabled for a given code in the input code. Numerical simulation methods such as plane wave expansion and finite difference time domain are performed to study the operation of proposed structure. Results of simulations show that for an on-state output, the highest achievable power is about 87% and the lowest value is 40%. For the case of 40%, the on/off ratio of outputs is at least 2.22 which ensures the acceptable resolution needed for detection of on-state. Maximum cross-talk about −10 dB and insertion loss about −8.8 dB is obtained for proposed decoder.

Ultra-high-speed graphene optical modulator design based on tight field confinement in a slot waveguide

Abstract: We present a design of an ultra-fast in-line graphene optical modulator on a silicon waveguide with a bandwidth exceeding 100 GHz, very small power consumption below 15 fJ/bit, and insertion loss of 1.5 dB. This is achieved by utilizing the transverse-electric-mode silicon slot to tailor the overlap of graphene electrodes, thus significantly reducing the capacitance of the device while maintaining a low insertion loss and using conservative estimates of the graphene resistance. Our design is substantiated by comprehensive finite-element-method simulations and RC circuit characterization, as well as fabrication feasibility discussion.

Towards heterogeneous integration of optical isolators and circulators with lasers on silicon [Invited]

Abstract: Optical isolators and circulators are extremely valuable components to have in photonic integrated circuits, but their integration with lasers poses significant design and fabrication challenges. These challenges largely stem from the incompatibility of magneto-optic material with the silicon or III-V platforms commonly used today for photonic integration. Heterogeneous integration using wafer bonding can overcome many of these challenges, and provides a promising path towards integrating isolators with lasers on the same silicon chip. An optical isolator operating for TE mode with 25 dB of isolation, 6.5 dB of insertion loss, and tunability over 40nm is demonstrated and a path towards integrating this isolator with the heterogeneous silicon/III-V laser is described.

Frequency Selective Rasorber With Low Insertion Loss and Dual-Band Absorptions Using Planar Slotline Structures

Abstract: This letter proposes a dual-polarized frequency selective rasorber (FSR), which exhibits bandpass filtering response together with absorption performance at both sides of the passband. Although the design concept is modified from a three-dimensional FSR, the proposed FSR is implemented by cross-inserting a few identical printed circuit board pieces etched with planar slotline structures, thus releasing difficulties in fabrication and assembly. The bandpass characteristic is provided by lossless resonators constructed in the slotlines with center-loaded U-type strips, whereas the absorption bands are realized by lossy resonators formed in short-circuited slotlines with lumped resistors. Surface current distributions are illustrated to explain the operation mechanism. A prototype of the designed FSR is fabricated and measured. The measured results show that the minimum insertion loss in the passband is about 0.3 dB, and the absorption bandwidths are ranged from 1.6 to 2.3 GHz and from 3.6 to 4.6 GHz, respectively. To further demonstrate the design concept, another FSR with wider absorption bands is developed by introducing more lossy resonators. Moreover, the proposed FSRs feature stable performance under oblique incident angles.

16 × 16 Silicon Optical Switch Based on Dual-Ring-Assisted Mach–Zehnder Interferometers

Abstract: In this paper, we report a nanosecond 16 × 16 silicon electro-optic switch chip based on a Benes architecture. The switch adopts dual-ring-assisted Mach–Zehnder interferometers as the basic building blocks. In each switch element, both TiN microheaters and PIN diodes are integrated for ring resonance alignment and high-speed switching, respectively. A transfer-matrix-based theoretical model is established to analyze the switch performances. The 16 × 16 switch is characterized by measuring the optical transmission spectra and quadrature phase-shift keying (QPSK) data transmission through 16 representative optical paths. The insertion loss of the entire switch chip is 10.6 ± 1.7 dB and the crosstalk is less than −20.5 dB. The 32-Gb/s QPSK signal is successfully switched to different destination ports by reconfiguring the optical paths, verifying the signal integrity after switching.