We report dispersions resulting from a slot device (SD) in silica-based arrayed-waveguide grating (AWG). A SD is used to produce flattened passbands and we show the dependence on the bandwidth, the crosstalk, the ripple, and the chromatic dispersion (CD) of the passband in the presence of such a device. A comparison with other known techniques is also given. The device has been developed on a high index silica-based PLC platform but can be implemented on higher index contrast platforms.
Silicon Carbide is a potentially useful compound for use in silicon based photonics because cubic silicon carbide (3C- SiC), possesses a first order electro-optic (Pockels) effect, something absent in pure silicon. This means the material is potentially suitable for high speed optical modulation. Furthermore, the wide bandgap (2.2 eV) of 3C-SiC makes the devices suitable for use over the visible and near infrared spectrum range as well as the longer communication wavelengths, and also means the material can tolerate high temperatures. However, relatively little work has been carried out in SiC for photonics applications. In this paper we will discuss design and fabrication of both SiC waveguides and modulators for silicon based photonics. The fabrication process utilizes ion implantation of oxygen into SiC to form the lower waveguide boundary. Subsequently, ribs are etched and contacts are added to form the optical modulators. Consideration of both Pockels modulators and plasma dispersion modulators has been made, and both will be discussed here. These devices have potential for optical modulation, but are also compatible with silicon processing technology. We have demonstrated waveguiding in 3C-SiC, established a processing recipe for the SiC wafers which enables fabrication of 3-dimensional devices, and demonstrated optical modulation. Performance of the resultant devices is compared to other silicon based devices in terms of operating speed and efficiency.
The realisation of two-dimensional Si/Si1-xGex/Si strained layer low-loss waveguides (1.7 dB/cm at 1.3micrometers ) is reported. The waveguide structure is grown using selective epitaxy. This fabrication method insures loosened cut-off and critical thickness conditions as demonstrated previously by the room-tem-perature operation of vertical emitting SiGe/Si LED. The main difference from other fabrication methods is the local deposition of the SiGe in a finite stripe region while in the conventional fabrication of rib waveguides the SiGe layer is deposited on an entire wafer and then patterned by reactive ion etching. The relative high amount of Ge (19%) incorpo-rated in selectively grown waveguides, and reduced thickness (0.6micrometers ) of Si cap layer are improvements from the previous reported SiGe/Si waveguides where thick Si cap layers (few microns) and reduced Ge concentrations (<10%) are necessary in order to obtain waveguiding.
Optical networks are becoming a reality as the physical layer of high-performance telecommunication networks. The deployment of wavelength-division multiplexing (WDM) technology allows the extended exploitation of installed fibers now facing an increasing traffic capacity demand. Performances of such systems can be degraded by wide variations of the optical channel power following propagation in the network. Therefore a tilt control of optical amplifiers in WDM networks and dynamic channel power regulation and equalisation in cross-connected nodes is necessary. An important tool for the system designer is the variable optical attenuator (VOA). We present the design and the realization of newly developed VOAs using the ASOC technology. This technology refers to the fabrication of integrated optics components in silicon-on-insulator (SOI) material. The device is based on the light absorption by the free-carriers that are injected in the core of a rib waveguide from a p-i-n diode. The devices incorporate horizontally and vertically tapered waveguides for minimum fiber coupling loss. The p-i-n diode for carrier injection into the active region of the rib waveguide was optimised in order to enhance the attenuation. One major advantage of the ASOC technology is the possibility of monolithic integration of many integrated optics devices on one chip. In the light of this the paper illustrates the result of characterisation of multichannel VOAs.
We analyse theoretically the feasibility of a vertical (SiGe/Si)n/Si quantum well structures for enhanced spontaneous emission light emitting diodes. The structure can be grown by selective epitaxy on silicon-on-insulator substrate. A design of a LED emitting at 1.3 micrometers wavelength is carried out.
We have designed and fabricated waveguide optical modulators using cubic silicon carbide-(3C-SiC)-on-insulator rib waveguides. A refractive index change is induced in the rib via the plasma dispersion effect. These types of devices have potential for relatively high-speed silicon-based photonics compatible with silicon processing technology, as compared to pure silicon. Furthermore, the wide bandgap (2.2 eV) of 3C-SiC makes the devices suitable for use over the visible and near infrared spectrum range as well as the longer communication wavelengths. We have demonstrated waveguiding in 3C-SiC, fabricating the waveguides by ion implantation of oxygen into a silicon carbide layer. We have also established a processing recipe for the SiC wafers which enables fabrication of 3- dimensional devices. The work reported here describes the fabrication of the devices and presents preliminary experimental results for the waveguide losses and the modulation of the refractive index as a function of applied current. An efficient waveguide modulator for a single polarization is reported.
Grating couplers can be more efficient than end-fire coupling, in coupling light into a thin film waveguide. The aim of this work is to fabricate a low cost, highly efficient silicon waveguide grating coupler which is to be use data the telecommunication wavelength of 1.3 micrometers . Silicon-on-insulator (SOI) is chosen for fabricating the gratings as it is low cost using the exiting silicon technology. Unibond wafers were used because they offer flexibility in the choice of the thickness' of both the silicon film and the buried oxide layer, and they have low optical waveguide loss. The wafers used in this work have a Si film thickness of 1.14 μm and a SiO2 buried layer thickness of 0.67 μm. Gratings that have asymmetrical profiles, such as blazed gratings are known to have higher directionality than the symmetrical rectangular gratings, and hence a higher output efficiency. Using perturbation theory, Si blazed gratings with an optimum grating height were predicted to have a maximum output efficiency of the order of 90% towards the substrate. The design and fabrication of the blazed gratings will be discussed in this paper.
In this work planar and rib (beta) -SiC-on-insulator waveguides were investigated. The waveguides were fabricated by two different methods. In the first a technological process similar to that of SIMOX was used, a buried SiO2 layer was formed by a two-step high-energy ion implantation of oxygen in SiC/Si wafers. For the second type of waveguides we used heteroepitaxy of SiC on SOI. The losses have been measured at 1.3 and 1.55micrometers . Rib waveguides were fabricated using dry-etching. These types of waveguides have great potential for high-speed silicon-based photonic devices compatible with silicon technology.
In integrated optics, grating couplers are used when conventional end-fire methods are cumbersome and less efficient in coupling light in and out of thin-film waveguides. Our aim is to fabricate a high efficiency grating coupler for integrated optics applications at infra-red wavelengths and for thin-film waveguides which can be used for sensor applications. In this paper, theoretical output efficiencies of silicon (Si) rectangular, ideal right-angled blazed and non-ideal trapezoidal gratings are presented. Using perturbation theory, Si rectangular gratings with optimum grating heights exhibit a maximum predicted output efficiency towards the surface at the order of 80% and Si right-angled blazed gratings have predicted efficiencies approaching 100%. The fabrication method consists of using electron beam lithography and reactive ion etching. Ion beam milling is also considered with the aim of creating blazed profiles by tilting the silicon-on-insulator (SOI) wafer. In our work, smart cut SOI Unibond wafers are used as the base material for fabricating the grating couplers as they offer good flexibility in choosing the guiding layer and buried layer thickness'. These waveguides are chosen to have an Si film thickness of 0.92 micrometer and an SiO2 buried layer thickness of 0.67 micrometer in order to use the transverse resonance effect to improve the output coupling efficiency. Si rectangular with various grating heights, designed at the first order of diffraction, were fabricated and characterized. The highest efficiency grating yet reported in SOI was produced, having the coupling efficiency in excess of 70%.
In this work planar planar (beta) -SiC-on-insulator waveguides were investigated. The waveguides were fabricated by two different methods. In the first a technological process similar to that of SIMOX was used, and therefore a buried SiO2 layer was formed by high energy ion implantation of oxygen in SiC/Si wafers. For the second type of waveguides we used heteroepitaxy of SiC on SOI(SIMOX). The losses have been measured at 0.633, 1.3 and 1.55 micrometer in both TE and TM polarization. A detailed analysis of the different loss mechanisms is presented. These types of waveguides have potential for high-speed silicon-based photonic devices compatible with silicon technology.
We have designed waveguide modulators using (beta) -SiC-on- insulator waveguides and the Pockels effect. A 2D semiconductor device simulator was used to determine the electric field configuration in a double-Schottky diode structure. This allowed us to evaluate the local modulation of the refractive index as a function of applied external bias and to determine the effective index modulation of the guided mode. The optical simulations were performed using the Spectral Index and the Effective Index methods. Different 2D geometries are analyzed and the material parameters needed for fabricating such a device are determined. Application to Mach- Zehnder intensity modulators is described. Such devices have potential for high-speed Si-based photonic devices compatible with silicon technology.