Dominic F. G. Gallagher

Photonic integrated circuits (PICs) are considered as the way to make photonic systems or\nsubsystems cheap and ubiquitous. PICs still are several orders of magnitude more expensive than their microelectronic counterparts, which has restricted their application to a few niche markets.Recently, a novel approach in photonic integration is emerging which will reduce the R&D and prototyping costs and the throughput time of PICs by more than an order of magnitude. It will bring the application of PICs that integrate complex and advanced photonic functionality on a single chip within reach for a large number of small and larger companies and initiate a breakthrough in the application of Photonic ICs. The paper explains the concept of generic photonic integration technology using the technology developed by the COBRA research institute of TU Eindhoven as an example, and it describes the current status and prospects of generic InP-based integration technology.

With the rapid growth of the telecommunications industry over the last 5 to 10 years has come the need to solve ever more complex electromagnetic problems and to solve them more precisely than ever before. The basic EME (EigenMode Expansion) technique is a powerful method for calculation of electromagnetic propagation which has been well known amongst academic environments and also in microwave fields, representing the electromagnetic fields everywhere in terms of a basis set of local modes. It is at the same time a rigorous solution of Maxwell's Equations and is able to deal with very long structures. We discuss here progress that the authors and others have made recently in applying and extending it to integrated, fibre, and diffractive optics - including development of efficient ways of modelling tapers and other smoothly varying structures, new more efficient boundary conditions and improved mode finders. We outline the advantages it has over other techniques and also its limitations. We illustrate its application with a variety of real life examples, including diffractive elements, directional couplers, tapers, MMI's, bend modelling, periodic structures and others.

A new method for designing an echelle-type diffraction grating for wavelength division multiplexing (WDM), which is tuned to a single stigmatic point, is introduced. The new grating is defined by the mode and wavelength of operation in a slab waveguide, the position of the waveguides, the order of diffraction, and an arbitrary path, which is called the grating line, upon which individual facets are positioned, blazed, and curved via the outlined algorithm. A systematic design process for echelle gratings (EGs) is presented, covering all the key aspects of this device. A series of rules to improve the performance of any EG WDM device is outlined. A simulated comparison between this device, a standard Rowland grating, and a two stigmatic point grating, was undertaken with the new design performing better and comparably in each case, respectively.

In this letter, we report about design, fabrication, and testing of echelle grating (EG) demultiplexers in the O-band (1.31-μm) for silicon-based photonic integrated circuits. In detail, flat band perfectly chirped EGs and two-point stigmatic EGs on the 300-nm thick silicon-on-insulator platform designed for 4 × 800-GHz spaced wavelength-division multiplexing featuring a low average crosstalk (-30 dB), a precise channel spacing, optimized interchannel uniformity (0.7 dB) and insertion losses (3-3.5 dB) are presented. Wafer-level statistical performance analysis shows the EG spectral response to be stable over the wafer in terms of crosstalk, channel spacing, and bandwidth with minimal wavelength dispersion (<;0.8 nm), thus highlighting the intrinsic robustness of high-order gratings and chosen fab pathways as well as the full reliability of 3-D vectorial modeling tools.