We propose an optical and electrical hybrid LSI package with high bandwidth of 2.4 Tb/s and parallel multi-mode optical links at 1.3 μm using a polymer optical waveguide and our original optical I/O module. We report a silicate based organic-inorganic hybrid polymer optical circuit fabrication including waveguide, mirror and connector on electrical LSI package substrate. We also present about the propagation loss, bending loss and coupling loss at 1.3 μm using a MMF and a Si photonics transmitter. The propagation loss of the multimode polymer waveguide is 0.3 dB/cm at 1.3 μm. The minimum bending radian and value generated additional loss is 5 mm and 0.2 dB, respectively. The coupling loss of butt-coupling and mirror coupling from the polymer optical waveguide to the MMF is 0.4 dB and 1.2 dB, respectively. In addition, we measure the optical characteristics of LSI package substrate using our Si photonics transmitter integrated with vertical polymer waveguide. Owing to adoption of multi-mode transmission, large 1-dB alignment tolerances were obtained with efficient optical coupling.

The ever-increasing demand for bandwidth requires advanced interconnect solutions satisfying functional and economic constraints. A new interconnect called electrical tube (E-TUBE) is proposed as a cost-and-power-effective all-electricaldomain wideband waveguide solution for high-speed, high-volume, and short-reach communication links. Unlike conventional optical solutions, the E-TUBE achieves state-of-the-art performance in terms of bandwidth-per-carrier frequency, power, and density without any precision manufacturing process. The E-TUBE exhibits a frequencyindependent loss-profile and has 20GHz bandwidth over the V band. The inherent frequency response of the E-TUBE enables a single-sideband signal transmission and renders double data throughput without any physical overhead. Transmission up to 14Gb/s signals over 1.2m has been tested using 73GHz carrier frequency (f_C). The IC is fabricated in 40nm CMOS and the figure-of-merit of the interface is 0.52J/b/m×*fC (Radio frequency circuits only: 0.3J/b/m×*fC).

We report on the development and optimization of key performance properties of multimode silicone polymer waveguides, manufactured for 850 nm optical propagation. These developments are based on photopatternable, mechanically flexible, low-loss, gradient index waveguides. Cross sectional waveguide core sizes ranging from 40 μm x 50 μm to greater than 60 μm x 60 μm are assessed with optical analysis of component losses such as crossings and coupling between OM4 fiber and waveguide. Assessments of these values, led to optimization of waveguide size and lower total optical system losses. Methods of manufacture, preparation, and analysis are discussed in detail along with performance results.

The fabrication of optical interconnects has been widely investigated for the generation of optical circuit boards. Twophoton absorption (TPA) lithography (or high-precision 3D printing) as an innovative production method for direct manufacture of individual 3D photonic structures gains more and more attention when optical polymers are employed. In this regard, we have evaluated novel ORMOCER-based hybrid polymers tailored for the manufacture of optical waveguides by means of high-precision 3D printing. In order to facilitate future industrial implementation, the processability was evaluated and the optical performance of embedded waveguides was assessed. The results illustrate that hybrid polymers are not only viable consumables for industrial manufacture of polymeric micro-optics using generic processes such as UV molding. They also are potential candidates to fabricate optical waveguide systems down to the chip level where TPA-based emerging manufacturing techniques are engaged. Hence, it is shown that hybrid polymers continue to meet the increasing expectations of dynamically growing markets of micro-optics and optical interconnects due to the flexibility of the employed polymer material concept.

The operation speed of high-performance computers has increased dramatically over the last decades. For sustaining their growth, multimode fiber (MMF) links have been gradually deployed, and on-board interconnection is the next step. Polymer optical waveguides (POWs) have been expected as one of the key components for on-board interconnects: they are expected to connect the light source/ photo detector on-board and an MMF off-board. As a unique fabrication method for POWs, we developed the Mosquito method to obtain graded index (GI) circular core polymer waveguides and confirmed their low propagation loss compared to conventional step-index (SI) core waveguides. However, the connection loss of the light source to waveguide, and the waveguide to an MMF is a concern: insertion of the polymer waveguide between the light source and MMF would increase the optical loss. So, in this paper, a tapered GI core polymer waveguide is proposed for reducing the connection loss between the laser sources and fibers/waveguides by inserting it between the source and MMF. In the Mosquito method, a liquid core monomer is dispensed from a thin needle attached to a syringe into a cladding monomer, using a microdispenser. Hence, the core diameter is axially varied by changing the needle-scan velocity. First, the optimum refractive index profiles in the tapered core are theoretically predicted using the BPM method. Next, the refractive index profile formed in the core during the Mosquito method is also estimated by solving the Fick’s diffusion equation. Finally, we successfully fabricate a GI tapered core polymer waveguide as designed.

The all optical routing is novel approach for establishment of transparent information flow in optical networks. The diffraction limit of light is major factor which backseats the photonic components and mitigated by integrated all optical components. In this paper, an all-optical signal router with two optical inputs using nonlinear plasmonic Mach-Zehnder interferometer (MZI) is proposed. The nonlinearity in MZI structure is achieved by using nonlinear Kerr-material, which is also responsible for switching of optical signal across two output ports. The study of proposed device is carried out using finite-difference-time-domain (FDTD) method and verified using MATLAB.

Nanocomposites are a promising new dielectric material for on-chip and chip-to-chip waveguides that operate at millimeter (mm)-wave frequencies because of their higher relative permittivity compared to neat polymers and their compatibility with printed circuit board processing. For dielectric waveguides, extremely low loss is critical; thus, understanding the origins of loss is an important step for these applications. In this paper, we investigate the sources of loss in TiO₂/polypropylene (PP) nanocomposites, in which polypropylene-graft-maleic anhydride (PP-g-MA) is added as a compatibilizer. Compared to nanocomposites made without PP-g-MA, we find that PP-g-MA improves the distribution of nanoparticles in the PP matrix and significantly lowers loss. We also examine the contribution to dielectric loss from PP-g-MA by measuring samples that contain no TiO₂ nanoparticles, and find that while increasing the amount of PP-g- MA in PP results in a higher loss, it is small compared to the loss that comes from the addition of TiO₂ nanoparticles.

A rich variety of plasmonic modulators and switches is emerging. They offer ultra-compact size in the order of a few micrometers, bandwidths from the MHz to the THz, low power consumption and they operate across a large spectral range. Some plasmonic devices are latching and others offer linear performance. Plasmonic devices not only come in a variety of shapes but also rely on various physical phenomena such as the thermal effect, the free carrier dispersion effect, the Pockels effect, the material phase change effect or they may rely on electrochemical metallization effects. After a discussion on the physics of plasmonics we will conclude the talk with a discussion of the opportunities and challenges related to plasmonics in optical communications and in particular with respect to applications in optical interconnects.

The need for additional IO bandwidth for data center device interconnection is well established. Optical interconnects can deliver required bandwidth along with energy and space efficiency at a cost that encourages adoption. To this end, we are developing an optical transceiver incorporating multimode VCSEL emitters in a coarse wavelength division multiplex (CWDM) system capable of transmission at 25Gbps per channel, 100Gbps/fiber, and a maximum aggregate bidirectional data rate of 1.2Tbps. Electrical connection to the transceiver can be made by solder reflow or LGA connector, and optical connection is made by means of a custom optical connector supporting CWDM transmission.

As parallel optics data rates transition from 10 Gbps to 25 Gbps and beyond, VCSELs and photodiodes (PDs) are evolving to support the higher transmission rates. In order to maintain system performance as speeds increase and tolerances become tighter, an improved method is needed to efficiently couple VCSEL/PD array optical outputs to fiber optic networks. The mechanical-optical interface (MOI) is a monolithic component with an array of collimating lenses designed for efficient coupling between the on-board active components and a detachable fiber optic connector. This paper describes the design and implementation of a next generation MOI to match high speed VCSEL/PD requirements. Improvements to an earlier design were made to accommodate a wider variety of transceiver architectures by taking into account chip driver and wire-bond clearance requirements, while also optimizing the optical design to maximize coupling performance. Monte Carlo simulation results and the sensitivity analysis used to optimize optical performance with respect to VCSEL/PD alignment and coupling requirements are presented. Empirical testing results are shown to validate the optical model and subsequent system performance; eye-diagram results of a 25 Gbps error-free link are provided across a broad operating temperature range. Environmental and mechanical testing of the component after alignment and adhesion to the circuit substrate validates part and epoxy interaction and performance.

Multi-socket server boards have emerged to increase the processing power density on the board level and further flatten the data center networks beyond leaf-spine architectures. Scaling however the number of processors per board puts current electronic technologies into challenge, as it requires high bandwidth interconnects and high throughput switches with increased number of ports that are currently unavailable. On-board optical interconnection has proved the potential to efficiently satisfy the bandwidth needs, but their use has been limited to parallel links without performing any smart routing functionality. With CWDM optical interconnects already a commodity, cyclical wavelength routing proposed to fit the datacom for rack-to-rack and board-to-board communication now becomes a promising on-board routing platform. ICT-STREAMS is a European research project that aims to combine WDM parallel on-board transceivers with a cyclical AWGR, in order to create a new board-level, chip-to-chip interconnection paradigm that will leverage WDM parallel transmission to a powerful wavelength routing platform capable to interconnect multiple processors with unprecedented bandwidth and throughput capacity. Direct, any-to-any, on-board interconnection of multiple processors will significantly contribute to further flatten the data centers and facilitate east-west communication. In the present communication, we present ICT-STREAMS on-board wavelength routing architecture for multiple chip-to-chip interconnections and evaluate the overall system performance in terms of throughput and latency for several schemes and traffic profiles. We also review recent advances of the ICT-STREAMS platform key-enabling technologies that span from Si in-plane lasers and polymer based electro-optical circuit boards to silicon photonics transceivers and photonic-crystal amplifiers.

Interconnects have been more important in high-performance computing systems and high-end servers beside its improvements in computing capability. Recently, active optical cables (AOCs) have started being used for this purpose instead of conventionally used copper cables. The AOC enables to extend the transmission distance of the high-speed signals dramatically by its broadband characteristics, however, it tend to increase the cost. In this paper, we report our developed quad small form-factor pluggable (QSFP) AOC utilizing cost-effective optical-module technologies. These are a unique structure using generally used flexible printed circuit (FPC) in combination with an optical waveguide that enables low-cost high-precision assembly with passive alignment, a lens-integrated ferrule that improves productivity by eliminating a polishing process for physical contact of standard PMT connector for the optical waveguide, and an overdrive technology that enables 100 Gb/s (25 Gb/s × 4-channel) operation with low-cost 14 Gb/s vertical-cavity surfaceemitting laser (VCSEL) array. The QSFP AOC demonstrated clear eye opening and error-free operation at 100 Gb/s with high yield rate even though the 14 Gb/s VCSEL was used thanks to the low-coupling loss resulting from the highprecision alignment of optical devices and the over-drive technology.

Increased data rates have motivated the investigation of advanced modulation schemes, such as four-level pulseamplitude modulation (PAM4), in optical interconnect systems in order to enable longer transmission distances and operation with reduced circuit bandwidth relative to non-return-to-zero (NRZ) modulation. Employing this modulation scheme in interconnect architectures based on high-Q silicon photonic microring resonator devices, which occupy small area and allow for inherent wavelength-division multiplexing (WDM), offers a promising solution to address the dramatic increase in datacenter and high-performance computing system I/O bandwidth demands. Two ring modulator device structures are proposed for PAM4 modulation, including a single phase shifter segment device driven with a multi-level PAM4 transmitter and a two-segment device driven by two simple NRZ (MSB/LSB) transmitters. Transmitter circuits which utilize segmented pulsed-cascode high swing output stages are presented for both device structures. Output stage segmentation is utilized in the single-segment device design for PAM4 voltage level control, while in the two-segment design it is used for both independent MSB/LSB voltage levels and impedance control for output eye skew compensation. The 65nm CMOS transmitters supply a 4.4V_ppd output swing for 40Gb/s operation when driving depletion-mode microring modulators implemented in a 130nm SOI process, with the single- and two-segment designs achieving 3.04 and 4.38mW/Gb/s, respectively. A PAM4 optical receiver front-end is also described which employs a large input-stage feedback resistor transimpedance amplifier (TIA) cascaded with an adaptively-tuned continuous-time linear equalizer (CTLE) for improved sensitivity. Receiver linearity, critical in PAM4 systems, is achieved with a peak-detector-based automatic gain control (AGC) loop.

The field of silicon photonics is attracting a lot of attention due to the prospect of low-cost and compact circuits that integrate photonic and microelectronic elements on a single chip. Such silicon chips have applications in optical transmitter and receiver circuits for short-distance communications as well as for long-haul optical transmissions. Silicon photonics has proven to be a successful platform for many functional elements such as low-loss waveguides, filters, multiplexers/demultiplexers, optical modulators and Ge-on-Si photodiodes. On-going developments for advanced photonic integrated circuits include compact and energy-efficient silicon modulators, temperature-insensitive passive devices and hybrid III-V on Silicon lasers. The European COSMICC project gathers key industrial and research partners in the field of silicon photonics, CMOS electronics, printed circuit board packaging, optical transceivers and datacenters, aiming at developing low-cost and low-energy consumption 50 Gb/s 4-wavelength coarse wavelength division multiplexing optical transceivers that will be packaged on-board. Combining CMOS electronics and Si-photonics with innovative high-throughput fiber attachment techniques, the developed solutions will be scalable beyond 1 Tb/s to meet the future data-transmission requirements in data-centers and super computing systems.

Glass waveguides fabricated by ion-exchange are a promising technology for short reach on-board optical interconnects. We developed an optical connector concept for the interconnection of multimode glass waveguides to fiber ribbon cables. Our concept is based on the MXC expanded beam connector, and it uses a modified version of the US Conec PRIZM MT ferrule that is installed on the edge of the glass waveguide panel by adhesive bonding. The paper will discuss the connector concept, the assembly process, the demonstrator platform and the characterization results.

Polymer optical waveguides with graded-index (GI) circular cores are fabricated using the Mosquito method, in which the positions of parallel cores are accurately controlled. Such an accurate arrangement is of great importance for a high optical coupling efficiency with other optical components such as fiber ribbons. In the Mosquito method that we developed, a core monomer with a viscous liquid state is dispensed into another liquid state monomer for cladding via a syringe needle. Hence, the core positions are likely to shift during or after the dispensing process due to several factors. We investigate the factors, specifically affecting the core height. When the core and cladding monomers are selected appropriately, the effect of the gravity could be negligible, so the core height is maintained uniform, resulting in accurate core heights. The height variance is controlled in ±2 micrometers for the 12 cores. Meanwhile, larger shift in the core height is observed when the needle-tip position is apart from the substrate surface. One of the possible reasons of the needle-tip height dependence is the asymmetric volume contraction during the monomer curing. We find a linear relationship between the original needle-tip height and the core-height observed. This relationship is implemented in the needle-scan program to stabilize the core height in different layers. Finally, the core heights are accurately controlled even if the cores are aligned on various heights. These results indicate that the Mosquito method enables to fabricate waveguides in which the cores are 3-dimensionally aligned with a high position accuracy.

The paper compares the results of panel- and wafer-level processing of display glass integrated single mode optical waveguides. The comparison is based on measurements of the same optical structures processed using panel- and waferlevel technology. Additionally, large panels of 440 mm x 305 mm where manufactured to prove the scalability of the single-mode process. Measurements are done by optical back scattering reflectometry using a Luna OBR 4600 and a fiber-based propagation loss measurement setup. Based on these results of diverse processing equipment and substrate dimensions, a comprehensive statistic is shown and error estimation made to compare the different technologies.

Pluggable optics are being pushed to their limits in terms of face plate density and power consumption requirements within emerging mega data centers and HPCs applications. Future applications seek silicon photonics based optical engines with ability for high channel count and throughput beyond 1Tb/s. In this paper, we show our results in development of single mode polymer-based optical-electrical PCBs (OEPCBs) supporting the emerging Si-Pho host PCB platforms with multi-terabit on-board routing capability for chip-to-chip communications. Single mode polymer waveguides (SM-PWGs) are fabricated using new photopatternable optical silicone materials (WG-2211/WG-2511-WG2711) on conventional PCBs. Test platform PCB shows designs with varying core sizes (20/15/12/9/7µm) and channel lengths (5-15cm). The measurements results show single-mode waveguides loss as less 0.4 dB/cm at 1310nm. Furthermore, the result show new waveguide material to be compliance for both rigid and flexible PCBs. OEPCB compliance evaluation test results shown in the paper includes results of lamination, chemical compliance, drilling, and plating tests. The results shown in the paper show first time ever fabrication of single mode polymer waveguide OEPCBs in production environment.

Optical communication networks – long-haul and short-reach as well as classical and quantum-based networks of the future – require modulators that actively alter the phase, amplitude, wavelength, and polarization of light. For decades, lithium niobate electro-optic (EO) modulators have met the requirements for EO modulation in long-haul networks. However, as optical links continue to present ever-greater advantages at shorter length scales, other more compact and integrable material platforms have been investigated, including silicon, indium phosphide, and, most recently, two-dimensional materials. Although much progress has been made on Si and InP and there is much promise for 2D materials, no technology to date has been shown with the concomitant properties of high EO bandwidth, wide optical range, low voltage, and compact size. To address this need, we have taken the approach of developing thin film BaTiO3 as an optoelectronic platform for high frequency, low voltage, and compact modulators. Epitaxial BaTiO3 films are a silicon-compatible optoelectronic material with among the highest known EO coefficient, more than 10 times larger than that of LiNbO3. Using BaTiO3 thin films with 1 mm long interaction length, we have previously demonstrated intensity modulators with voltage-length products nearly an order of magnitude smaller than that of silicon. We have also shown the potential for high frequency operation by demonstrating modulation out to 50 GHz and 28 GHz 3 dB EO bandwidth. Here we demonstrate the high-frequency and low-voltage phase modulation of light using epitaxial thin film BaTiO3. Clear EO phase modulation of 1550 nm light is measured out to 50 GHz using an optical spectral analysis method. We also show that, by incorporating low dimensional, photonic crystal (PC) waveguides to enhance the EO coefficient, the operating voltage can be significantly reduced.

Vertical-cavity surface-emitting lasers and multi-mode fibers is the dominating technology for short-reach optical interconnects in datacenters and high performance computing systems at current serial rates of up to 25-28 Gbit/s. This is likely to continue at 50-56 Gbit/s. The technology shows potential for 100 Gbit/s.

A one-dimensional (1D) photonic crystal (PC) slot waveguide was proposed and experimentally demonstrated for integrated silicon-organic hybrid modulators. The 1D PC slot waveguide consists of a conventional silicon slot waveguide with periodic rectangular teeth on its two rails. This structure takes advantage of large mode overlap in a conventional slot waveguide and the slow light enhancement from the PC structure. Its simple geometry makes it resistant to fabrication imperfections and helps reduce the propagation loss. The observed effective EO coefficient in an actual Mach-Zehnder interferometer modulator is as high as 490 pm/V owing to slow light effect.

We demonstrate the hybrid silicon and electro-optic (EO) polymer modulator for low-driving voltage and high bandwidth applications. The designed hybrid waveguide was fabricated by the conventional photolithography technique, so that this widespread compatibility enabled the construction of the unique polymer photonic devices. The waveguide consists of the silicon core with a 50 nm-thick and 2 m-wide core and the EO polymer cladding. The optical mode calculation indicates that the large extension of the optical field into the EO polymer provides the EO coefficient of about 80 pm/V in the waveguide. Therefore, the half-wave voltage of the hybrid waveguide was recorded only 1.1 V at 1550 nm in the Mach-Zehnder modulator. The measured insertion loss was about 15 dB, which included the materials absorption loss of the EO polymer. The traveling-wave-electrodes were applied to the hybrid waveguide in order to evaluate the frequency response of the modulator up to 40 GHz by measuring the S21 parameter. The -3 dB bandwidth of 20 GHz and a 6 dB reduction in response at 40 GHz were measured. This bandwidth is mainly limited by the conductor loss of the electrode, which can be improved further by the fabrication. The hybrid waveguide showed the excellent temperature stability at 85C for longer than 2000 hours.

Mid-infrared (IR) fibers have been extensively investigated due to their applicability in chemical sensing and remote laser delivery, among others. Materials such as chalcogenides and fluoride glasses transmit mid-IR wavelengths with low practical losses. However, their low glass transition temperatures make them chemically unstable, even at room temperatures, resulting in performance degradation over time. Semiconductors, such as germanium, have a wide transmission window in the mid-IR region, and offer significantly improved chemical stability. In this research, germanium-core, borosilicate-cladded fibers were drawn by a ‘rod in tube’ method using a mini draw tower assembled in-house at 1000°C, which is significantly lower than the drawing temperatures of 2000-2200°C for conventional silica fibers. Typical drawn fibers had a 40 μm core diameter and 177 μm cladding diameter. Transmission electron microscopy (TEM) studies showed that diffusion of oxygen and silicon from the cladding to the core during the drawing process was minimal, with diffusion distances of the order of 10s of nm. This is encouraging for mid-IR transmission, since the presence of oxygen in the fiber core is known to increase transmission losses in the mid-IR spectrum. This low diffusivity is presumably due to the relatively low drawing temperature. Transmission losses through the fibers were measured with a quantum cascade laser (QCL) and the losses were found to be in the 3-9 dB/cm range in the spectral range of 5.75-6.3 μm.

Miniaturization of medical imaging devices will significantly improve the workflow of physicians in hospitals. Photonic integrated circuit (PIC) technologies offer a high level of miniaturization. However, they need fiber optic interconnection solutions for their functional integration. As part of European funded project (InSPECT) we investigate fiber bundle probes (FBPs) to be used as multi-mode (MM) to single-mode (SM) interconnections for PIC modules. The FBP consists of a set of four or seven SM fibers hexagonally distributed and assembled into a holder that defines a multicore connection. Such a connection can be used to connect MM fibers, while each SM fiber is attached to the PIC module. The manufacturing of these probes is explored by using well-established fiber fusion, epoxy adhesive, innovative adhesive and polishing techniques in order to achieve reliable, low-cost and reproducible samples. An innovative hydrofluoric acid-free fiber etching technology has been recently investigated. The preliminary results show that the reduction of the fiber diameter shows a linear behavior as a function of etching time. Different etch rate values from 0.55 μm/min to 2.3 μm/min were found. Several FBPs with three different type of fibers have been optically interrogated at wavelengths of 630nm and 1550nm. Optical losses are found of approx. 35dB at 1550nm for FBPs composed by 80μm fibers. Although FBPs present moderate optical losses, they might be integrated using different optical fibers, covering a broad spectral range required for imaging applications. Finally, we show the use of FBPs as promising MM-to-SM interconnects for real-world interfacing to PIC’s.

Data centers (DCs) are facing the challenge of delivering more capacity over longer distances. As line rates increase to 25 Gb/s and higher, DCs are being challenged with signal integrity issues due to the long electrical traces that require retiming. In addition, the density of interconnects on the front panel is limited by the size and power dissipation requirements of the pluggable modules. One proposal to overcome these issues is to use embedded optical transceivers in which optical fibers are used to transport data to and from the front panel. These embedded modules will utilize arrays of VCSEL or silicon-photonic transceivers, and in both cases, the capacity may be limited by the density of the optical connections on the chip. To address this constraint, we have prototyped optical fibers in which the glass and coating diameters are reduced to 80 and 125 microns, respectively. These smaller diameters enable twice as many optical interconnects in the same footprint, and this in turn will allow the transceiver arrays to be collinearly located on small chips with dimensions on the order of (5x5mm²)^1,2. We have also incorporated these reduced diameter fibers into small, flexible 8-fiber ribbon cables which can simplify routing constraints inside modules and optical backplanes.

To solve the coupling issue in optical systems, we previously proposed a coupling method based on the selforganized lightwave network (SOLNET) formed by self-focusing in photo-induced refractive-index increase (PRI) materials such as photopolymers. SOLNETs are formed by an attractive force between light beams, providing Optical Solder that enables self-aligned couplings between optical devices, even if misalignments and core size mismatching exist. In the present work, in order to extend the lateral misalignment tolerance between nanoscale waveguides and between microscale and nanoscale waveguides, we propose the two-photon SOLNET, which is formed using twophoton photochemistry. Simulations based on the finite-difference time-domain method reveal that when write beams with wavelengths of 500 and 600 nm are respectively introduced into a two-photon PRI material from two 600-nm-wide waveguides opposed with a 32-μm distance and a 4200-nm lateral misalignment, a two-photon SOLNET is formed between them. The misalignment tolerance is 7-times larger than that in conventional one-photon SOLNETs, and 1.4- times larger than that in two-photon SOLNETs formed using 400-nm and 780-nm write beams. The two-photon SOLNET extends the lateral misalignment tolerance to <1000 nm for couplings between a 3-μm -wide waveguide and a 600-nm-wide waveguide, exhibiting a function of mode-size convertors. Preliminary experiments demonstrate that the two-photon SOLNETs are formed between multimode optical fibers by introducing a 448-nm write beam and a 780-nm (or 856-nm) write beam from the fibers into a photosensitive organic/inorganic hybrid material, SUNCONNECT®, with doped camphorquinon (or biacetyl).

Optical switch networks based on silicon photonics can provide high bandwidth, low latency, low power, and low cost interconnect fabrics for datacenter, cloud, and high-performance computing by eliminating the pin-constrained electronic switches and the multiple electrical-optical conversions necessary in traditional networks. Silicon photonics is also compatible with wavelength division multiplexing (WDM) allowing simultaneous routing of large bandwidth data streams. Adoption of photonic switches requires scaling to large port counts compared to current 4x4 and 8x8 demonstrations. For example, a 64-port switch implemented using thirty-two 4x4 and four 16x16 switches will be limited by losses in numerous subcomponents, including optical couplers, waveguide propagation losses, waveguide crossings, and phase shifters. To enable viable optical-link-loss budgets requires incorporation of optical gain in addition to improved efficiency in all subcomponents. We have developed a silicon photonic switch platform with integrated gain based on a carrier with active photonics. Optical switches are monolithically integrated into photonic carrier while semiconductor optical amplifiers (SOAs) and CMOS drive ICs are flip-chip attached. We demonstrated non-blocking 4x4 Si photonic switches with < 3-dB on-chip loss and < -20 dB crosstalk with about 4ns switching time. Photonic carriers and 4-channel SOA arrays were co-designed with custom precision packaging features enabling flip-chip bonding with high accuracy. The photonic carrier incorporates low-loss SiN waveguides with inverse taper structures for efficient coupling to/from the SOA arrays and off-carrier coupling. Photonic carriers with integrated 4-channel SOA arrays were fabricated achieving over 10 dB gain and demonstrating error-free 4x25-Gb/s WDM links for all 4 channels.

Content Addressable Memories (CAMs) are widely used in nowadays router applications due to their fast bit searching capabilities. However, address loop-up operation cannot still keep up with high data-rate speeds of optical packet payload due to the limited speeds offered by electronic technology, which hardly can reach a few GHz. Despite this limitation, optics has still not managed to penetrate in the area of address look-up and forwarding operations due to the complete lack of optical CAM-based solutions. To the best of our knowledge, the first all-optical binary CAM cell has been only recently experimentally demonstrated by our group using an all-optical monolithically integrated InP Flip-Flop and an optical XOR gate, revealing error-free operation at 10 Gbps for both Content Addressing and Content Writing operations. In this paper, we extend our previous work by presenting for the first time to our knowledge an all-optical Ternary CAM cell architecture that allows also for a third matching state of "X" or "don’t care", thus adding the necessary searching flexibility required by modern CAM-based solutions for supporting subnet-masked addresses. Moreover, we exploit the optical Ternary CAM cell towards deploying a complete CAM row formed by 4 Ternary CAM cells, demonstrating its operation through VPI simulations at 10 Gbps for an indicative 2 bit packet address and for both Content Addressing and Content Writing functionalities. The potential of this memory architecture to allow for up to 40 Gbps operation could presumably lead to fast CAM-based routing applications by enabling all-optical Address Lookup schemes.

This paper presents a bidirectional optical data transmission system as an enhancement of a contactless power transmission system (CPTS). The latter consists of two separate devices and is able to transmit up to 240W of electrical power using inductive resonant coupling. The optical system consists of two self-developed light-guiding structures and a short-reach free-space optical path. As source and sink of the optical system a light-emitting diode resp. a photodiode with a centroid wavelength of 850nm are used. The optical system is positioned within the CPTS; it transmits the PROFIBUS protocol. Due to the restrictions given by the applications areas of the CPTS, such as air gap up to 5°mm, misalignment up to 2 mm, tilting up to 5 and rotation angle up to 360°, different kinds of light-guiding structures are analyzed by simulation. Based on these results the most promising structures are selected and manufactured. Hereafter the attenuation and the near field characteristic of one light-guiding structure is analyzed. After this, the attenuation based on misalignment, variation of air gap, tilting and rotation between two light-guiding structures are analyzed by measurement. To check whether the requirements of the PROFIBUS has been satisfied by the complete data transmission system, the transient transmission behavior of the system was analyzed by a pseudo-random bit stream. In this paper the most important results of the design, the simulation and the measurement are explained. The presented results demonstrate the ability to design of such systems based on simulations and to evaluate the suitability of various geometries for present and future works.

Programmable switching nodes supporting Software-Defined Networking (SDN) over optical interconnecting technologies arise as a key enabling technology for future disaggregated Data Center (DC) environments. The SDNenabling roadmap of intra-DC optical solutions is already a reality for rack-to-rack interconnects, with recent research reporting on interesting applications of programmable silicon photonic switching fabrics addressing board-to-board and even on-board applications. In this perspective, simplified information addressing schemes like Bloom filter (BF)-based labels emerge as a highly promising solution for ensuring rapid switch reconfiguration, following quickly the changes enforced in network size, network topology or even in content location. The benefits of BF-based forwarding have been so far successfully demonstrated in the Information-Centric Network (ICN) paradigm, while theoretical studies have also revealed the energy consumption and speed advantages when applied in DCs. In this paper we present for the first time a programmable 4x4 Silicon Photonic switch that supports SDN through the use of BF-labeled router ports. Our scheme significantly simplifies packet forwarding as it negates the need for large forwarding tables, allowing for its remote control through modifications in the assigned BF labels. We demonstrate 1x4 switch operation controlling the Si-Pho switch by a Stratix V FPGA module, which is responsible for processing the packet ID and correlating its destination with the appropriate BF-labeled outgoing port. DAC- and amplifier-less control of the carrier-injection Si-Pho switches is demonstrated, revealing successful switching of 10Gb/s data packets with BF-based forwarding information changes taking place at a time-scale that equals the duration of four consecutive packets.

We report on a converged optically enabled Ethernet storage, switch and compute platform, which could support future disaggregated data center architectures. The platform includes optically enabled Ethernet switch controllers, an advanced electro-optical midplane and optically interchangeable generic end node devices. We demonstrate system level performance using optically enabled Ethernet disk drives and micro-servers across optical links of varied lengths.

We propose tunable grating structures implemented by the change of the effective refractive index based on thermo-optic effect in silicon. For resistive heating, p-i-n or pn junction was formed in the grating region and surrounding region was thermally isolated. Fabricated tunable gratings were characterized by fiber-to-fiber measurement and Fourier-imaging system with a variation of the bias voltage applied to the heater. From a p-i-n type structure showing the best data, we achieved a wide tuning of the central wavelength in a range of 40 nm with an efficiency of 0.41 nm/mW. When this tunable grating structure is applied in the radiator of the optical phased array, the radiation angle was actively manipulated in a range of 2.7° in the longitudinal direction.

An optical reconfigurable logic device is an optical equivalent of an FPGA, and all the basic digital logic functions can be realized. A tremendous advantage that the optical scheme has over the conventional electronic scheme is the elimination of gate latency and simultaneous availability of a logic function and its complementary at the output, which makes this approach extremely efficient. In this paper, an electro-optic polymer-based high-performance reconfigurable logic system is proposed. Compared to silicon, electro-optic polymers have the advantages of 1) large electro-optic coefficient and ultra-fast response speeds, and 2) easy solution-based processability, thus ultra-high speed logic systems on flexible and rigid substrates are possible. Although most polymer materials can be spun on to form a uniform layer, their patterning into a waveguide often relies on the use of reactive-ion etching (RIE), which is not only an expensive process, but also deteriorates the surface quality, thus negating any advantage provided by polymeric material systems. To address this problem, we utilize all-additive “printing” process comprising of nanoimprint lithography and ink-jet printing for developing low-loss and high surface-quality systems. The ring resonator, demonstrated with Q-factor of 20,720 and switching speed of 1 MHz, is used as an integral component of the logic device. Utilizing different configuration architectures of ring resonators, polymer-based optical logic gates are proposed. The R2R compatible printing processes will enable high-rate, low-cost, and large-area development of these devices on flexible as well as on rigid substrates, thus enabling high-performance integrated polymer based optical interconnect systems.

Silicon photonics is a topic that draws much attention in the semiconductor industry. Even if mass production did not take off yet, there is a shared feeling that this technology will be full of promises. Silicon photonics is already addressing solutions in data-communication area and can potentially address new industrial segments such as long haul telecommunication cables, smart detectors, chemical sensors or even consumer products such as next generation computer peripheral cables. Consequently, STMicroelectronics is concentrating efforts in launching silicon photonic research activities that explore innovative solutions for future market demands. With a smart transition from discrete photonics to integrated photonics, ongoing developments in silicon photonics include the ability to co-integrate different materials within the same platform. Typically, epitaxially grown germanium is used to fabricate photodetectors. Moreover, a vast activity is also devoted at integrating III-V laser sources within the integrated circuit. Currently, various configurations are under evaluation to integrate a laser source within the silicon photonic chip. Furthermore, alternative non-metallic materials are also assessed to fabricate complementary passive devices. The rationale is to consider possible processes and designs to improve electrical power consumption budget, reduce optical transmission losses, achieve low cost production and introduce new functions within photonic systems. Developments made in the framework of COSMICC European project aim at demonstrating few pJ/bit data transmission for a 4-channel coarse wavelength division multiplexing transceiver bearing a data rate of 56 Gbps NRZ per channel. The demonstrator will make use of current and projected developments made by both STMicroelectronics and collaborators.

As data centers constantly expand, electronic switches are facing the challenge of enhanced scalability and the request for increased pin-count and bandwidth. Photonic technology and wavelength division multiplexing have always been a strong alternative for efficient routing and their potential was already proven in the telecoms. CWDM transceivers have emerged in the board-to-board level interconnection, revealing the potential for wavelength-routing to be applied in the datacom and an AWGR-based approach has recently been proposed towards building an optical multi-socket interconnection to offer any-to-any connectivity with high aggregated throughput and reduced power consumption.

Echelle gratings have long been recognized as the multiplexing block exhibiting smallest footprint and robustness in a wide number of applications compared to other alternatives such as the Arrayed Waveguide Grating. Such filtering devices can also perform in a similar way to cyclical AWGR and serve as mid-board routing platforms in multi-socket environments. In this communication, we present such a 3x3 Echelle grating integrated on thick SOI platform with aluminum-coated facets that is shown to perform successful wavelength-routing functionality at 10 Gb/s. The device exhibits a footprint of 60x270 μm², while the static characterization showed a 3 dB on–chip loss for the best channel. The 3 dB-bandwidth of the channels was 4.5 nm and the free spectral range was 90 nm. The echelle was evaluated in a 2x2 wavelength routing topology, exhibiting a power penalty of below 0.4 dB at 10^-9 BER for the C-band. Further experimental evaluations of the platform involve commercially available CWDM datacenter transceivers, towards emulating an optically-interconnected multi-socket environment traffic scenario.

The cost-effective integration of laser sources on Silicon Photonic Integrated Circuits (Si-PICs) is a key challenge to realizing the full potential of on-chip photonic solutions for telecommunication and medical applications. Hybrid integration can offer a route to high-yield solutions, using only known-good laser-chips, and simple freespace micro-optics to transport light from a discrete laser-diode to a grating-coupler on the Si-PIC. In this work, we describe a passively assembled micro-optical bench (MOB) for the hybrid integration of a 1550nm 20MHz linewidth laser-diode on a Si-PIC, developed for an on-chip interferometer based medical device. A dual-lens MOB design minimizes aberrations in the laser spot transported to the standard grating-coupler (15 μm x 12 μm) on the Si-PIC, and facilitates the inclusion of a sub-millimeter latched-garnet optical-isolator. The 20dB suppression from the isolator helps ensure the high-frequency stability of the laser-diode, while the high thermal conductivity of the AlN submount (300/W=m.°C), and the close integration of a micro-bead thermistor, ensure the stable and efficient thermo-electric cooling of the laser-diode, which helps minimise low-frequency drift during the approximately ~ 15s of operation needed for the point-of-care measurement. The dual-lens MOB is compatible with cost-effective passively-aligned mass-production, and can be optimised for alternative PIC-based applications.

Energy efficient Wavelength Division Multiplexing (WDM) is the key to satisfying the future bandwidth requirements of datacentres. As the silicon photonics platform is regarded the only technology able to meet the required power and cost efficiency levels, the development of silicon photonics compatible narrow linewidth lasers is now crucial. We discuss the requirements for such laser systems and report the experimental demonstration of a compact uncooled external-cavity mWatt-class laser architecture with a tunable Silicon Photonic Crystal resonant reflector

MIM plasmonic waveguides are considered in proposed work, due to their ability of confining the surface plasmons to deep subwavelength scale or beyond diffraction limit. By cascading various MIM waveguides Mach-Zehnder interferometer (MZI) is designed which has been used to design all-optical 3 × 8 line decoder. To attain the nonlinearity Kerr material has been used. The proposed device is studied and analyzed using finite-difference-time-domain (FDTD) method and MATLAB simulations.