CMOS-compatible Hybrid Research Articles

Octave-spanning supercontinuum generation in a CMOS-compatible thin Si3N4 waveguide coated with highly nonlinear TeO2.

Supercontinuum generation (SCG) is an important nonlinear optical process enabling broadband light sources for many applications, for which silicon nitride (Si3N4) has emerged as a leading on-chip platform. To achieve suitable group velocity dispersion and high confinement for broadband SCG the Si3N4 waveguide layer used is typically thick (>∼700 nm), which can lead to high stress and cracks unless specialized processing steps are used. Here, we report on efficient octave-spanning SCG in a thinner moderate-confinement 400-nm Si3N4 platform using a highly nonlinear tellurium oxide (TeO2) coating. An octave supercontinuum spanning from 0.89 to 2.11 µm is achieved at a low peak power of 258 W using a 100-fs laser centered at 1565 nm. Our numerical simulations agree well with the experimental results giving a nonlinear parameter of 2.5 ± 0.5 W-1m-1, an increase by a factor of 2.5, when coating the Si3N4 waveguide with a TeO2 film. This work demonstrates highly efficient SCG via effective dispersion engineering and an enhanced nonlinearity in CMOS-compatible hybrid TeO2-Si3N4 waveguides and a promising route to monolithically integrated nonlinear, linear, and active functionalities on a single silicon photonic chip.

Numerical Investigation and Design of Electrically-Pumped Self-Pulsing Fano Laser Based on III-V/Silicon Integration

A self-pulsing III-V/silicon laser is designed based on the Fano resonance between a bus-waveguide and a micro-ring resonator, partially covered by the graphene as a nonlinear saturable absorption component. The Fano reflector etched on the straight waveguide is used as one of the cavity mirrors in the coupling region to work with the graphene induced loss and nonlinearity to achieve pulsed lasing in GHz repetition frequency. The detailed lasing characteristics are studied numerically by using the rate equation and finite-difference time-domain (FDTD) simulations. The results show that the CMOS compatible hybrid laser can generate picosecond pulses with repetition rate at 1~3.12 GHz, which increases linearly with the injection current.

Wide-range, ultra-compact, and high-sensitivity ring resonator biochemical sensor with CMOS-compatible hybrid plasmonic waveguide

A ring resonator-based biochemistry sensor with a wide range, ultra-compact footprint, and high sensitivity is proposed, which utilizes a suspended slot hybrid plasmonic (SSHP) waveguide. The waveguide consists of a suspended Si nanowire separated from a Cu metal surface by a nanoscale air gap. The hybridization of fundamental mode of a Si channel waveguide with the surface plasmon polariton (SPP) mode of Cu-Si interface achieves a strong light confinement, high waveguide sensitivity (Sw), and low optical loss, showing a great potential in integrated optical sensor. The sensitivity, the detection limit and the detection range of the SSHP waveguide-based biochemistry sensor with a miniaturized radius of 1 µm are numerically demonstrated as 458.1 nm/RIU, 3.7 × 10-5 RIU and 0.225 RIU, respectively. These superior performances as well as the fully CMOS compatibility enable the integrated optical sensing applications.

CMOS-compatible hybrid bi-metallic TE/TM-pass polarizers based on ITO and ZrN.

Transverse-magnetic (TM) and transverse-electric (TE) pass polarizers based on a silicon-on-insulator platform are studied and analyzed. The proposed structures are CMOS-compatible based on indium tin oxide and zirconium nitride as alternative plasmonic materials. The bi-metallic combination of the plasmonic materials exhibit large coupling between one of the modes (TE or TM) in the silicon core and the surface plasmon mode, while the other mode can propagate with low losses. The numerical simulations for the TE-pass polarizer predict 32.7dB extinction ratio (ER) and 0.13dB insertion loss (IL) at a compact device length of 1.5μm. Additionally, the TM-pass polarizer has 31.5dB ER and 0.17dB IL at a device length of 2μm at an operating wavelength of 1.55μm.

Long Range Multilayer Hybrid Plasmonic Waveguide Components and Integrated Circuit

In this work, CMOS compatible hybrid insulator metal insulator (HIMI) planar plasmonic waveguide based components such as, racetrack ring resonator, y-splitter, coupler and dual parabolic profile nano antenna have been proposed and investigated at 1.55 μm operating wavelength for the first time. The proposed components are analyzed at various parametric variations using CST microwave studio. The proposed racetrack ring resonator offers 153.88 nm free spectral range, 0.3232 nm FWHM and 46.57 dB extinction ratio at 0.40 μm radius and 0.49 μm separation length. Y-splitter divides equal power of 46.85% in both output arms and coupler couples till 86.5% power in coupled arm. The dual parabolic profile nano antenna offers a gain, bandwidth and efficiency of 7.99 dB, 203 THz and 84.56 % respectively. Using all the components, HIMI plasmonic integrated circuits have also been designed and investigated for on chip applications. Proposed components work very efficiently in chip scale integrated circuit. This investigation provides groundwork for future chip scale applications.

Hybrid Insulator Metal Insulator Planar Plasmonic Waveguide-Based Components

This is the first report on investigation of CMOS compatible hybrid insulator metal insulator (HIMI) planar plasmonic waveguide-based components. In this letter, a realistic planar HIMI plasmonic waveguide, which offers good balance between propagation length (253 μm) and confinement (38%), has been studied at 1.55-μm operating wavelength for designing various waveguide components. Key components, such as 90°, Sand U-shaped bends, have been investigated and their transmission and loss characteristics have been analyzed at different bend radii. The components exhibit transmittance up to 80% at various bend radii within a confinement area of 0.25×0.04 μm 2 . This investigation could be fruitful in designing plasmonic integrated circuits for chip-scale applications.

Electro-Optical Modulation Based on Pockels Effect in BaTiO3With a Multi-Domain Structure

The influence of an in-plane multi-domain structure in BaTiO3 films grown on SrTiO3/Si buffers for highly efficient electro-optic modulation has been analyzed. The modulation performance can be significantly enhanced by rotating a certain angle, the optical waveguide, with respect to the BaTiO3 crystallographic axes. A robust electro-optical performance against variations in the domain structure as well as the lowest $V_{\pi }$ voltage can be achieved by using the rotation angles between 35° and 55°. Our calculations show that $V_{\pi }$ voltages below 1.7 V for a modulation length of 2 mm can be obtained by means of a CMOS compatible hybrid silicon/BaTiO3 waveguide structure.

A CMOS-Compatible Hybrid Plasmonic Slot Waveguide With Enhanced Field Confinement

The emerging field of nanophotonics requires plasmonic devices to be fully compatible with semiconductor fabrication techniques. However, very few feasible practical structures exist at present. Here, we propose a CMOS-compatible hybrid plasmonic slot waveguide (HPSW) with enhanced field confinement. Our simulation results show that the HPSW exhibits significantly enhanced field confinement as compared with the traditional low-index slot waveguides and the hybrid metal dielectric slot waveguides. By controlling the thicknesses of different layers, an optimized HPSW structure with a better tradeoff between field confinement and propagation length has been simultaneously achieved.

Hybrid electro-optic plasmonic modulators based on directional coupler switches

By breaking the diffraction limit, plasmonics enable the miniaturization of integrated optical signal processing units in a platform compatible with traditional CMOS technology. In such architectures, modulators and switches are essential elements for fast and low-power optical signal processing. This work presents the design of a CMOS-compatible hybrid plasmonic modulator based on directional couplers enhanced with a layer of electro-optic polymer. The modulator shows very broad operating window with low crosstalk values and very small footprint with respect to similar couplers and switches of the silicon photonics platform.

CMOS-compatible hybrid plasmonic modulator based on vanadium dioxide insulator-metal phase transition.

To extend the application of an emerging plasmonic material, vanadium dioxide (VO₂), in silicon photonics technology, we propose a complementary metal-oxide-semiconductor (CMOS)-compatible hybrid plasmonic modulator using an VO₂ insulator-metal phase transition. The optical device is based on a directional coupler that consists of a Si waveguide and a Si-SiO₂-VO₂-SiO₂-Si hybrid plasmonic waveguide. By electrically triggering the phase of VO₂ with a driving voltage of 2 V, the propagation loss of the hybrid plasmonic waveguide is switched, and hence the output optical power is modulated. The on/off extinction ratio is larger than 3.0 dB on the entire C-band.

Tailored Organic Electro-optic Materials and Their Hybrid Systems for Device Applications

Recent development of tailored organic electric-optic (OEO) materials and their applications in hybrid device systems has been reviewed. Hybrid systems encompass the optical and/or electrical components that form intimate contact with OEO materials, such as metal oxide barrier layers, solution processable passive waveguides, silicon nanoslots, and photonic CMOS chips, etc. These systems offer unique advantages combining excellent properties and simple processing for advanced photonic device platforms. Examples include the demonstration of low-Vπ and low-loss EO modulators in hybrid polymer sol−gel waveguides, CMOS-compatible hybrid polymer/silicon slotted waveguides, and EO polymer-clad silicon nitride ring resonator modulators. This review also provides a future prospect for the development of OEO materials and their hybrid systems.