Lumerical Solutions, a provider of photonic design software, has announced the filing of a provisional patent application titled, ‘Method to improve the accuracy of mode matching methods such as eigenmode expansion or rigorous coupled wave analysis.’
This patent targets applications in the field of silicon photonics and integrated optics including tapers, spot size converters, y-branch splitters, directional couplers and waveguide Bragg gratings incorporating smoothly varying refractive index profiles.
The provisional patent application, filed with the US Patent and Trademark Office on April 1st, 2014, describes a Continuously Varying Cross-sectional Subcell (CVCS) method to enhance standard eigenmode expansion (EME) calculation techniques, particularly in waveguide structures with continuously-varying cross sections or material properties.
The standard EME method represents continuously varying structures, such as tapers, with a staircase approximation to resolve geometrical or material variations along the direction of propagation. This leads to non-physical reflections and calculation inaccuracies. The typical workaround involves increasing the number of expansion interfaces, which results in increased computational costs, both in terms of time and memory.
Lumerical’s CVCS method avoids this staircasing effect, through extensive benchmarking versus 3D finite-difference time-domain (FDTD) simulations for a wide variety of waveguide structures, offers excellent accuracy at a fraction of the time for longer structures.
‘The EME method is ideally suited to rapidly evaluate long waveguide structures where other rigorous methods such as FDTD can be computationally intensive and time consuming,’ said James Pond, CTO of Lumerical Solutions. ‘It took a great deal of effort for my team to develop an extension to the standard EME approach, valid in both 2D and 3D, that offers FDTD-like accuracy for long structures employing continuous material or geometric variations. I am excited to work with our customers to apply this new solver to their most challenging waveguide component designs and help them get the results they have come to expect when working with Lumerical.’
‘In discussions with customers during our product planning sessions, there was very strong interest in seeing Lumerical develop an eigenmode expansion propagation tool,’ stated Bill De Vries, director of product marketing at Lumerical Solutions. ‘We are working alongside leading customers during development to ensure it meets their expectations regarding compute time, accuracy and usability. Given our progress, I am confident our EME will be a very powerful addition to Lumerical’s photonic design and analysis software.’