Senior HW Engineer – Signal and Power Integrity

Every board Lumai builds has to run multi-gigabit links and feed high-current ASIC and FPGA rails. Getting those right before the board is fabricated is the difference between a working system and a respin cycle. This role owns the modelling, the stackups, the materials and the design rules that make it work, and has a direct say in the decisions that prevent the respin.

You will own signal and power integrity across our boards and packages. That means pre-layout channel studies that set routing topologies, stackups, materials and constraints; post-layout analysis of critical channels, including insertion and return loss, crosstalk, and eye and COM analysis with IBIS-AMI models; optimisation of vias, breakouts, connector launches and the transitions into our optical engines; and PDN impedance targets, decoupling strategies and DC drop analysis for high-current rails.

What is genuinely hard is that the channels cross boundaries - chip, package, interposer, board and optical engine - and a model is only as good as its weakest corner. You will spend as much time at the bench as in the tool, correlating what you predicted against what the hardware does, and feeding that back into design rules.

By month six, you will have signed off the critical channels on at least one board, built the model libraries and design guidelines the team reuses, and be the person whose analysis decides when a layout is ready to release.

• Run pre-layout channel studies to set routing topologies, stackups, materials and design constraints for high-speed interfaces.

• Carry out post-layout SI analysis of critical channels: insertion and return loss, crosstalk, and eye and COM analysis using IBIS-AMI models.

• Design and optimise vias, breakouts, connector launches, and the transitions into optical engines and co-packaged components.

• Set PDN impedance targets, design decoupling strategies, and run DC drop and AC PDN analysis for high-current ASIC and FPGA rails.

• Support package, interposer and board co-simulation with the ASIC team to keep channel and power integrity sound end to end.

• Correlate simulation with lab measurements using TDRs, VNAs and oscilloscopes, and feed the results back into models and design rules.

• Evaluate and characterise PCB materials, connectors and cable assemblies with suppliers and fabricators.

• Build up our SI/PI methodology, model libraries and design guidelines so they can be reused across projects.

Must-have

• A degree in electronic engineering, physics or a related discipline, plus proven SI/PI experience on high-speed PCB and/or package designs.

• Proficiency with at least one major EM and circuit simulation suite, such as Ansys HFSS/SIwave, Keysight ADS or Cadence Sigrity/Clarity.

• Strong understanding of transmission line theory, S-parameters, crosstalk, loss mechanisms and channel compliance metrics such as eye diagrams and COM.

• Experience with IBIS and IBIS-AMI models for SerDes and memory interface simulation.

• Solid knowledge of PDN design, including impedance targeting, decoupling optimisation and DC IR drop analysis.

Strong preference for

• Hands-on measurement with VNAs, TDRs and high-speed oscilloscopes, and the ability to correlate measurements with simulation.

• 56G/112G PAM4 channels, or PCIe Gen5/6 compliance.

• Package and interposer co-simulation, including chip-package-board analysis.

• Low-loss PCB materials and fabrication tolerances and their effect on high-speed performance.

• Scripting (Python, MATLAB) to automate simulation and post-processing.

Lumai is the optical compute company building the next generation of AI infrastructure. Spun out of optics research at the University of Oxford in 2021, we compute with light instead of electrons. Our 3D optical technology carries out the matrix multiplications at the heart of AI inside beams of light travelling through free space, which lets it go beyond the limits of both silicon GPUs and integrated photonics.

In April 2026 we launched Iris Nova, the world's first optical computing system to run billion-parameter large language models in real time, using up to 90% less energy than conventional GPU-based systems. Iris Nova, the first server in the family, is now available for evaluation by hyperscalers, neoclouds, enterprises and research institutions. Aura and Tetra will follow.

Our work won the Falling Walls Award for Science Breakthrough of the Year 2025 and 'Best Overall Technology' at the OCP Future Technologies Symposium. We are headquartered in Oxford.

You'll work on a new kind of computer. Optical computing for AI has been promised for decades. We have a working system running real models, and the hard part left is taking it to volume.

Your work ships. We are moving from first product to volume production, so what you build this year goes into the servers our customers run.

You'll work across disciplines. Optical engineers, machine learning researchers, and hardware and software engineers solve problems together. You will learn things that don't appear on your job description.

The work matters beyond Lumai. AI's appetite for energy is one of the defining constraints of the next decade. Our mission is sustainable intelligence at global scale: AI that is faster, cheaper to run and far less power-hungry.

You'll join early. You'll have a real say in how we build the product, the team and the way we work.

Lumai is an equal opportunity employer. We make hiring decisions based on skills, experience and potential, and we welcome applications from people of all backgrounds. If you need an adjustment at any stage of the hiring process, let us know and we will do our best to support you.