Why Subwavelength Grating (SWG) design is the future of silicon photonics?

Whilst many applications (datacom, telecom, sensing, 5G, LIDAR, quantum computing…) could benefit from photonics adoption, when coming down to massive technology adoption scalability is a must, and integrated photonics is still making its way through.

So far integrated photonics have been developed under different platforms and design approaches in order to meet the needs of different applications ( e.g,  quantum circuits exploit nonlinearities in waveguides whilst LIDAR circuits need to handle high power), often trading off performance on certain properties to benefit critical requirements.

As per the table below, Alcyon design combination of nanometric-thick silicon and SWG provides with an outstanding performance along most critical features, without needing to penalize one to favour another. Consequently, SWG silicon photonics designs can be transversal used to develop end application, which ends up on reusable technology that can reduce the time and cost from development time, fabrication, testing and optimization.

Whilst nanometric-thick silicon platform stands behind the good design behaviour in terms of compactness and opto-electronics. SWG design can claim its contribution to remarkably support key features such as like large evanescent field, low nonlinearity and low thermal sensitivity, following its confinement engineering capability. Additionally, SWG advanced metamaterial engineering of dispersion and birefringence enables performance far beyond other design techniques on critical application requirements such as ultra-wideband, ultra-narrowband and polarization management.

In summary, the combination of Nanometric-Thick Silicon and SWG supports consistently an outstanding performance for key features across most applications, which make of it a sound foundation stone to build a complete integrated photonic industry upon.

Acknowledgement: We want to thank Carlos Ramos, from Université Paris-Saclay, for his contribution to this analysis

7 things I wish I knew before designing my first Photonic Integrated Circuit

An informal introduction to PICs design: ‘We’re not in Kansas anymore’

From Science to the real world

The first thing you realize when designing a PIC is that scientific papers are a good reading material, but not a user’s manual. Actual PICs design requires software tools, fabrication deviation and characterization knowledge. So, be prepared to invest time, money and brainpower to bring your idea to life. From our experience, it is important not only to be able to simulate and layout your idea but also to consider that different fabrication processes (and  even foundries) can severely impact your theoretical performance, so be prepared for characterize and optimize (but that’s another topic to address)

Software saves time…

Software can make your life much easier and, we don’t mean only in terms of usability and time, which is already quite something. But choosing the right software can be of big help if you are planning to reuse /escalate your design capabilities. Additionally, most of commercial software tools are incorporating functionalities that can help you bridging the simulation to reality gap, such as convergence tests, montecarlo simulations… Understanding the software modules can really help you to speed up your design by choosing the right tool.

…but not money

Even though you can find open photonic design software tools, if your design is going to be fabricated or included in a bigger structure, you will probably need to go for proprietary tools. The good news are that most of these tools are licensed module based, so you may be able to encompass your software investment to your design phase. The bad news is that going for an end customer design will probably require the full suite, so our advice is get a good understanding of your alternatives and your requirements and plan and budget in advance.

Programming skills

Yes, even with the most comprehensive software suite, at some point you will require programming for layout development, scripting simulations, geometrical structure modifications, integration with other simulation tools or even combination with other designs. So, do not leave aside programming as it underpins photonics design just as much as Maxwell equation resolution.

It is not only about software, hardware plays a role

Most of Photonic design tools conversation pivot around software capabilities, but software runs on hardware….and hardware has the ability to make your software fly or just crawl. Thus, plan your design environment considering that hardware needs to be capable of fully powering your software tools (RAM, cores, servers/cloud…

Design ahead for fabrication

Unless you just want to have a theoretical useless design, our recommendation is that you plan ahead for fabrication and characterization. Consider in your design as much input from the foundry you are planning to fabricate with as possible, e.g., minimum minimum feature spacing, available materials and thicknesses for the different layers, maximum core layer thickness deviation, waveguide propagation losses, to name a few. Remember that fabrication is not only costly but time consuming, so you will probably want to ensure that your design is as feasible as possible in terms of fabrication processes.

Layout for characterization

And finally you have your chip home, and it is time for measurements, and oopsss!…Anticipating your design layout will facilitate its characterization not only in terms of lab set up but also to anticipate the parameters and corresponding test structures that can be interesting in order to measure the design performance properly.

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