On Chip Optical Waveguide Interconnect: the Problem of the In/Out Coupling (original) (raw)

Development of multi-step processing in silicon-on-insulator for optical waveguide applications

Journal of Optics A: Pure and Applied Optics, 2006

Multi-step processing for a silicon-on-insulator (SOI) platform was developed. It allows the incorporation of additional grooves and steps into the basic optical waveguide structures, so that light can be adiabatically coupled between waveguides with different cross-sections. The processes were based on simple fabrication methods easily scalable for mass production. Two options for the fabrication sequence were tested, both having one silicon etch step with an oxide mask and another etch step with a resist mask. The applicability of the developed processes was tested with different waveguide structures. An additional groove etched beside a bent 10 µm thick rib waveguide suppressed the bend losses to below 1 dB/90 • with a 5 mm bending radius. A waveguide mirror exhibited optical losses below 1 dB/90 • . The excess losses of a vertical taper between 10 and 4 µm thick rib waveguides were 0.7 dB. A converter between a rib and a strip waveguide showed negligible losses, below 0.07 dB.

Photosensor and optical waveguide coupling in silicon technology

Sensors and Actuators A: Physical, 1997

ARROW-type optical waveguides are designed for implementation on silicon using the materials (silicon dioxide and silicon nitride) and techniques (CVD, RIE) of CMOS integrated-circuit technology. Light is detected by a photodiode buried in the silicon substrate, which is made following the same process. The steps of this process are described and their influence on the optical properties of the guides is analysed. The optical signal attenuation in the waveguide-photodiode coupling region and the cut-off frequency of the system are measured in test devices. The advantages of the technological compatibility with CMOS circuits are discussed. © 1997 Elsevier Science S.A.

Silicon photonics beyond silicon-on-insulator

Journal of Optics

The standard platform for silicon photonics has been ridge or channel waveguides fabricated on silicon-on-insulator (SOI) wafers. SOI waveguides are so versatile and the technology built around it is so mature and popular that silicon photonics is almost regarded as synonymous with SOI photonics. However, due to several shortcomings of SOI photonics, novel platforms have been recently emerging. The shortcomings could be categorized into two sets: (a) those due to using silicon as the waveguide core material; and (b) those due to using silicon dioxide as the bottom cladding layer. Several heterogeneous platforms have been developed to address the first set of shortcomings. In such important heterogeneous integrated photonic platforms, the top silicon layer of SOI is typically replaced by a thin film of another optical material with a refractive index higher than the buried oxide (BOX) bottom cladding layer. Silicon is still usually preferred as the substrate of choice, but silicon has no optical functionality. In contrast, the second category of solutions aim at using silicon as the core waveguide material, while resolving issues related to the BOX layer. Particularly, one of the main drawbacks of SOI is that the BOX layer induces high optical loss in the mid-wavelength infrared (mid-IR) range. Accordingly, a host of platforms have been proposed, and some have been demonstrated, in which the BOX is replaced with insulating materials that have low intrinsic loss in the mid-IR. Examples are sapphire, lithium niobate, silicon nitride and air (suspended Si membrane waveguides). Although silicon is still the preferred substrate, sometimes a thin film of silicon, on which the optical waveguide is formed, is directly placed on top of another substrate (e.g., sapphire or lithium niobate). These alternative substrates act as both mechanical support and the lower cladding layer. In addition to the demands of mid-IR photonics, the non-SOI platforms can potentially offer other advantages and flexibilities. Examples are different, and sometimes interesting, guided mode properties (e.g., single-mode and single-polarization behavior), enhanced dispersion engineering (wideband anomalous regimes), as well as ease of fabrication and higher thermal conductivity in some cases. The objective of this article is to review this category of non-SOI photonic platforms that use silicon as the waveguide core layer and discuss their challenges and opportunities.

Hybrid Silicon Photonic Integrated Circuit Technology

IEEE Journal of Selected Topics in Quantum Electronics, 2000

In this paper, we review the current status of the hybrid silicon photonic integration platform with emphasis on its prospects for increased integration complexity integration. The hybrid silicon platform is maturing fast as increasingly complex circuits are reported with tens of integrated components including on-chip lasers. It is shown that this platform is wellpositioned and holds great potential to address future needs for medium-scale photonic integrated circuits.

Silicon photonic integrated devices for optical interconnects

Asia Communications and Photonics Conference 2013, 2013

Optical interconnects; Integrated optoelectronic circuits We present our latest update on key components in the integrated Si photonic interconnect system, including hybrid Si microring lasers, Si microring modulators, hybrid Si photodetector and passive waveguide devices.

Basic structures for photonic integrated circuits in Silicon-on-insulator

Optics Express, 2004

For the compact integration of photonic circuits, wavelengthscale structures with a high index contrast are a key requirement. We developed a fabrication process for these nanophotonic structures in Silicon-on-insulator using CMOS processing techniques based on deep UV lithography. We have fabricated both photonic wires and photonic crystal waveguides and show that, with the same fabrication technique, photonic wires have much less propagation loss than photonic crystal waveguides. Measurements show losses of 0.24dB/mm for photonic wires, and 7.5dB/mm for photonic crystal waveguides. To tackle the coupling to fiber, we studied and fabricated vertical fiber couplers with coupling efficiencies of over 21%. In addition, we demonstrate integrated compact spot-size converters with a mode-to-mode coupling efficiency of over 70%.

Hybrid Silicon Photonics for Optical Interconnects

IEEE Journal of Selected Topics in Quantum Electronics, 2011

In this paper, we review the hybrid silicon photonic integration platform and its use for optical links. In this platform, a III/V layer is bonded to a fully processed silicon-on-insulator wafer. By changing the bandgap of the III/V quantum wells (QW), lowthreshold-current lasers, high-speed modulators, and photodetectors can be fabricated operating at wavelengths of 1.55 µm. With a QW intermixing technology, these components can be integrated with each other and a complete high-speed optical interconnect can be realized on-chip. The hybrid silicon bonding and process technology are fully compatible with CMOS-processed wafers because high-temperature steps and contamination are avoided. Full wafer bonding is possible, allowing for low-cost and large-volume device fabrication.

On the route towards Si-based optical interconnects

Microelectronic Engineering, 2000

We have developed and fabricated a prototype of optical interconnects on a Si substrate. The original device design includes an aluminum-porous silicon light-emitting diode connected with a photodetector by an alumina waveguide. In order to minimize optical losses, the waveguide has been realized by subsequent deposition of three aluminum layers among which the intermediate one was doped with a titanium large refractive index layer. This multilayer structure was then anodically oxidized to form an Al O /Al O 1 TiO /Al O layered waveguide. In the integrated optoelectronic unit it provides up to 2 3 2 3 2 2 3 50% increase of the detector response with respect to a waveguide of pure Al O. Optical losses in the visible range have 2 3 been estimated to be about 1 dB / cm. Another method for increasing the detector response through the use of a microcavity is discussed.