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On‐chip spatial and polarization multiplexing has emerged as a powerful strategy to boost the data transmission capacity of integrated optical transceivers. State‐of‐the‐art multiplexers require accurate control of the relative phase or the spatial distribution among different guided optical modes, seriously compromising the optical transmission bandwidth and performance of the devices. To overcome this limitation, a new approach based on the coupling between guided modes in integrated waveguides and optical beams free‐propagating on the chip plane is proposed. The engineering of the evanescent coupling between the guided modes and free‐propagating beams allows spatial and polarization multiplexing with state‐of‐the‐art performance. A two‐polarization multiplexed link and a three‐mode multiplexed link using standard 220‐nm‐thick silicon‐on‐insulator technology have been developed. The two‐polarization link shows a measured −35 dB crosstalk bandwidth of 180 nm, while the three‐mode link exhibits a −20 dB crosstalk bandwidth of 195 nm. These links are used to demonstrate error‐free operation (bit‐error‐rate <10−9) in multiplexing and demultiplexing of two and three non‐return‐to‐zero signals at 40 Gbps each, with power penalties below 0.08 and 1.5 dB for the two‐polarization and three‐mode links, respectively. The approach demonstrated for two polarizations and three modes is transferable to future implementation of more complex multiplexing schemes. [ABSTRACT FROM AUTHOR]

Flexible control of the modal confinement in silicon photonic waveguides is an appealing feature for many applications, including sensing and hybrid integration of active materials. In most cases, strip waveguides are the preferred solution to maximize the light interaction with the waveguide surroundings. However, the only two degrees of freedom in Si strip waveguides are the width and thickness, resulting in limited flexibility in evanescent field control. Here, a new strategy that exploits metamaterial engineering of the waveguide core and cladding is proposed and demonstrated to control the index contrast in the vertical and horizontal directions, independently. The proposed dual‐material geometry yields a substantially increased calculated bulk sensitivity in the air (0.35 RIU [refractive index unit]/RIU) compared to the best case scenario for a strip waveguide (0.3 RIU/RIU). To experimentally demonstrate the potential of this approach, dual‐metamaterial ring resonators operating with the transverse‐magnetic polarized mode in 220‐nm‐thick waveguides with air as upper‐cladding are implemented. Micro‐ring resonators implemented with strip and dual‐metamaterial waveguides exhibit the same measured quality factors, near 30 000. Having similar measured quality factors and better calculated bulk sensitivity than strip waveguides, the proposed dual‐metamaterial geometry stands as a promising approach to control modal confinement in silicon waveguides. [ABSTRACT FROM AUTHOR]

Wideband polarization beam splitters (PBS) are a key building block in polarization management circuits for wavelength division multiplexing applications. A broadband PBS on a 300-mm silicon nitride (SiN) photonic platform is reported based on phase-controlled directional coupler (DC). Unlike classical DC-based PBS made on silicon, the proposed configuration leverages the comparatively lower birefringence in SiN to yield wideband and efficient splitting. A semi-analytical approach, based on transfer matrix modeling and 3-D finite difference time domain, has been used to design and optimize the structure for O-band operation. The proposed PBS has been experimentally demonstrated showing insertion loss (IL) lower than 0.6 dB and extinction ratio (ER) as high as 10 dB over 95-nm bandwidth for both polarizations. Furthermore, this simplified architecture eases cascading, allowing the demonstration of IL below 1.1 dB and ER larger than 24 dB over 85-nm wavelength range in a dual-stage configuration. [ABSTRACT FROM AUTHOR]

Optical interconnects for system-in-package applications can be designed for various bit rates. In this paper, an optimization study is conducted to find the optimal parameters for electrooptical links, based on a silicon photonic technology. We focus on the bit rate to achieve highest possible power efficiencies. This paper takes all the elements of an electrooptical link into account: serialization stage, ring-resonator-based modulator, thermal stabilization, modulator driver, laser, receiver, deserialization stage, and clock-phase generation. The optimization is based on a simulation-supported database for single-ended transimpedance amplifiers (TIAs). For all the other, elements of the link simulation-based power consumption models are presented. Furthermore, an analytical solution for the TIA bandwidth and bit rate relationship is derived based on the system jitter, the TIA noise, transimpedance, bandwidth and minimal output swing, and the available input signal. Optimal bit rates are derived and discussed for a 65-nm CMOS and a 28-nm fully depleted silicon-on-insulator technology. We found that the optimal bit rates increase with more aggressive technology scaling and smaller photodiode capacitances, but decrease if lower static power consumptions can be achieved (e.g., by efficient thermal tuning of ring-resonator modulators). We conclude that further research should aim for lower tuning powers instead of higher speed. [ABSTRACT FROM PUBLISHER]

Silicon photonics has emerged as a very promising technology platform for the implementation of high-performance, low-cost, ultra-compact circuits that can monolithically co-integrate electronic, opto-electronic and optic functionalities. However, Si neither has efficient light emission or detection in the telecom wavelength range, nor exhibits efficient electro-optic Pockels effect, hindering the implementation of integrated active devices like sources, detectors, or modulators. Current approaches relay on different materials to provide active functionalities in Si photonics, resulting in highly complex integration schemes that compromise cost-effectiveness. Semiconducting single-wall carbon nanotubes (SWNTs) are capable of emitting and detecting near-infrared light at room temperature and exhibit intrinsically fast electro-optic effects. They have also proven promising uses in micro-electronic devices, making them an ideal material to provide active functionalities in the Si photonic platform. In this work, we propose and experimentally validate the possible use of slot photonic waveguides to improve interaction between SWNTs and Si waveguide modes. Fabricated Si slot micro-ring shown an experimental $\sim 60\% $ photo-luminescence improvement compared to previous demonstration based on Si strip waveguide resonators. These results prove the potential of Si slot waveguides for the implementation of efficient SWNT-based Si photonic devices. [ABSTRACT FROM PUBLISHER]

Based on a transverse electric (TE)/transverse magnetic (TM) polarization diversity waveguide, we theoretically propose a TE-pass/TM-stop polarizer by etching a polarization dependent Bragg grating into the oxide layer of a silicon/thin SiO2 gap/metal cap hybrid plasmonic waveguide. The simulation results indicate that the device is characterized by high TE-transmission and large TM-reflection levels in a wide waveband from 1.48 to 1.7 μm combined with an excellent compactness (length less than 5 μm). Transmission and reflection extinction ratio are both larger than 17.1 dB in the 1.48-1.64 μm wavelength range, while losses are smaller than 1.36 and 0.69 dB for the TE and TM modes, respectively. [ABSTRACT FROM PUBLISHER]

Control of electromagnetic fields using graded photonic crystals (GPhCs) is explored using equations of Hamiltonian optics. Contrary to previous works devoted to the long-wavelength regime enabling homogenization of photonic metamaterials, attention is paid to short-wavelength light propagation for the possible use of dispersive phenomena and light path reconfiguring with wavelength. An analytical description of the dispersion diagram of a square PhCs is extracted using plane wave expansion calculations, making possible the description of arbitrary light paths in 2-D GPhC structures and fast optimization to find the conditions suited to make light follow prescribed paths. The validity of the approach is validated by comparison with finite-difference time-domain simulation. For purpose and illustration, a wavelength demultiplexing structure with four channels and an overall surface of 60 \mum\,\times\,60 \mum is proposed. The described methodology is applicable to the generalized 2-D chirp of PhC lattice or filling ratio parameters for electromagnetic field shaping. [ABSTRACT FROM PUBLISHER]

The evolution of silicon optical modulators is recalled, from the first effect demonstrations to the characterization of high-performance devices integrated in optical waveguides. Among possibilities to achieve optical modulation in silicon-based materials, the carrier depletion effect has demonstrated good capacities. Carrier depletion in Si and SiGe/Si structures has been theoretically and experimentally investigated. Large phase modulation efficiency, low optical loss, and large cutoff frequency are obtained by considering simultaneously optical and electrical structure performances. Integrated Mach-Zehnder interferometers and resonators are compared to convert phase modulation into intensity modulation. Finally, recent results on high-speed and low-loss silicon optical modulator using an asymmetric Mach-Zehnder interferometer are presented. It is based on a p-doped slit embedded in the intrinsic region of a lateral pin diode integrated in a silicon-on-insulator waveguide. This design allows a good overlap between the optical mode and carrier density variations. An insertion loss of 5 dB has been measured with a -3 dB bandwidth of 15 GHz. [ABSTRACT FROM AUTHOR]

Subwavelength grating (SWG) metamaterials have garnered a great interest for their singular capability to shape the material properties and the propagation of light, allowing the realization of devices with unprecedented performance. However, practical SWG implementations are limited by fabrication constraints, such as minimum feature size, that restrict the available design space or compromise compatibility with high-volume fabrication technologies. Indeed, most successful SWG realizations so far relied on electron-beam lithographic techniques, compromising the scalability of the approach. Here, we report the experimental demonstration of an SWG metamaterial engineered beam splitter fabricated with deep-ultraviolet immersion lithography in a 300-mm silicon-on-insulator technology. The metamaterial beam splitter exhibits high performance over a measured bandwidth exceeding 186 nm centered at 1550 nm. These results open a new route for the development of scalable silicon photonic circuits exploiting flexible metamaterial engineering. [ABSTRACT FROM AUTHOR]

The authors report on high speed operation of a Ge/SiGe multiple quantum-well waveguide photodetector. At -3~V, 10 Gb/s operation is demonstrated at wavelengths of 1405 and 1420 nm with a responsivity as high as 0.8 A/W. The device, 3 \mum wide and 80 \mum long, exhibits a dark current of 474 nA at a reverse bias of -1~V. These results pave the way for the use of Ge/SiGe multiple quantum-well structures as efficient active waveguide devices in silicon compatible integrated circuits. [ABSTRACT FROM PUBLISHER]

A comb slot photonic crystal waveguide geometry allowing flexible dispersion engineering of wide slot photonic crystal waveguides is proposed. Additionally, a figure of merit combining confinement within the slot and high group index is introduced to quantify the electromagnetic density within slow wave slot waveguides, and is applied to the proposed waveguide geometries. Group indices exceeding 130 and 90 over bandwidths of 1.5 and 2 nm are achieved for slots wider than 300 nm. The figure of merit exhibits sevenfold and fortyfold enhancements in comparison with classical slot waveguides with slot widths around 50 and 100 nm, respectively. [ABSTRACT FROM PUBLISHER]