In this work, the simplified modeling of silicon phase modulators is presented along with a comparison among different options of modulators. The proposed simplified model enables a substantial reduction in computational effort while maintaining a good accuracy. The presented model is validated against complete 3D-simulations by means of the design of four different modulators. Furthermore, with the help of the model a deep insight on the performances tradeoffs in the choose and design of silicon modulators is provided.
A new technological platform aimed at making prototypes and feasibility studies has been setup at STMicroelectronics using 300mm wafer foundry facilities. The technology, called DAPHNE (Datacom Advanced PHotonic Nanoscale Environment), is devoted at developing and evaluating new devices and sub-systems in particular for wavelength division multiplexing (WDM) applications and ring resonator based applications. Developed in the course of PLAT4MFP7 European project, DAPHNE is a flexible platform that fits perfectly R&D needs. The fabrication flow enables the processing of photonic integrated circuits using a silicon-on-insulator (SOI) of 300nm, partial etches of 150nm and 50nm and a total silicon etching. Consequently, two varieties of rib waveguides and one strip waveguide can be fabricated simultaneously with auto-alignment properties. The process variability on the 150nm partially etched silicon and the thin 50nm slab region are both less than 6 nm. Using a variety of different implantation configurations and a back-end of line of 5 metal layers, active devices are fabricated both in germanium and silicon. An available far back-end of line process consists of making 20 μm diameter copper posts on top of the electrical pads so that an electronic integrated circuit can be bonded on top the photonic die by 3D integration. Besides having those fabrication process options, DAPHNE is equipped with a library of standard cells for optical routing and multiplexing. Moreover, typical Mach-Zehnder modulators based on silicon pn junctions are also available for optical signal modulation. To achieve signal detection, germanium photodetectors also exist as standard cells. The measured single-mode propagation losses are 3.5 dB/cm for strip, 3.7 dB/cm for deep-rib (50nm slab) and 1.4 dB/cm for standard rib (150nm slab) waveguides. Transition tapers between different waveguide structures are as low as 0.006 dB.
In this paper we report on advances in DUV dry photolithography both for etching and implantation of silicon photonic devices. We explain why silicon patterning is a critical building block in silicon photonics and what are the challenges related to that process. Furthermore, it also occurs that some silicon photonic devices need implantation lithographic conditions which are also specific to the technology. For that purpose, we developed a dedicated DUV 193nm implantation lithography to address that need.
In this paper, we communicate on the design, fabrication, and testing of optical modulators for Silicon-based photonic
integrated circuits (Si-PICs) in the O-band (1.31 μm), targeting the 100GBASE-LR4 norm (4 wavelengths at 25 Gbit/s).
The modulators have been conceived to be later coupled with hybrid-III-V/Si lasers as well as echelle grating
multiplexer, to create a hetero-integrated optical transmitter on a silicon-on-insulator (SOI) platform. The devices are
based on a Mach-Zehnder Interferometer (MZI) architecture, where a p-n junction is implanted to provide optical
modulation through carrier depletion. A detailed study focusing on the best doping scheme for the junction, aimed at
optimizing the overall transmitter performance and power-efficiency is presented. In detail, the trade-off between low
optical losses and high modulation efficiency is tackled, with a targeted CMOS-compatible voltage drive of 2.5 V.
Process simulations of the junction are realized for the doping profile optimization. Modulators of different lengths are
also investigated to study the compromise between extinction ratio, insertion losses and bandwidth. Furthermore,
coplanar-strip (SGS) travelling-wave electrodes are designed to maximize the bandwidth, to reach the targeted bit rate of
25 Gbit/s. Measurements show modulation efficiencies up to 19 °/mm (or 2.4 V.cm) for a 2.5 V input voltage, with
doping-related losses below 1 dB/mm, in line with theoretical estimates, and well-suited to enhance the Si-PIC
transmission and power-efficiency. Finally, an electro-optical (EO) bandwidth at 1.25 V bias is measured above 28 GHz.
We present 40 Gbit/s optical modulators based on different types of phase shifters (lateral pn, pipin, and interleaved pn junction phase). Those structures were processed both on 200 and 300mm SOI wafers, available in large-scale microelectronic foundries. Both Ring Resonators (RR) and Mach Zehnder (MZ) modulators were fabricated. As an example, MZ modulator based on 0.95 mm long interleaved pn junction phase shifter delivered a high ER of 7.8 dB at 40 Gbit/s with low optical loss of only 4 dB. Ring modulator was also fabricated and characterized at high-speed, exhibiting 40 Gbit/s.
We demonstrate the feasibility of producing advanced silicon photonic devices for future data communication nodes at 40Gbps using CMOS compatible processes in a 300mm wafer fab. Basic building blocks are shown together with various wavelength division multiplexing solutions. All the devices presented are integrated on 220nm SOI or locally grown epitaxial germanium.
Development of fast silicon photonics integrated circuit is mainly driven by the reduction of the power consumption. As a result, photodetectors with high efficiency, high speed and low dark current are needed to reduce the global link consumption. Germanium is now considered as the ideal candidate for fully integrated receivers based on SOI substrate and CMOS-like processes. We report on low power and high speed waveguide-integrated Ge photodetectors. Butt coupled lateral PIN structure photodiodes have been fabricated by Germanium selective growth and ion implantation at the end of silicon waveguide. Three types of photodiodes are reported, with dark current as low as 6nA at 1V reverse bias, optical bandwidth over 40GHz at zero bias and responsivity up to 0.8A/W at a wavelength of 1550nm. Such devices are suitable for data rate over 40Gbps and can be easily integrated with other photonic devices to fabricate wafer scale integrated circuits for datacom and telecom applications.
We report a Germanium lateral pin photodiode integrated with selective epitaxy at the end of silicon waveguide.
A very high optical bandwidth estimated at 120GHz is shown, with internal responsivity as high as 0.8A/W at
1550nm wavelength. Open eye diagram at 40Gb/s was obtained under zero-bias at wavelength of 1.55μm.