Simulating ring resonators - a first.

The multi-topology MT-FIMMPROP photonic simulation tool from Photon Design, which uses its unique, patented and well respected, EigenMode Expansion (EME) computational method, can now simulate ring resonator designs - a first in the photonics industry. The company quantified the performance of its new EME capability in a recent white paper. It concluded that EME delivered equivalent accuracy to industry-standard, Finite Difference Time Domain (FDTD) tools, but was over 100 times faster using a workstation PC, with no cloud processing necessary. Engineers run many simulations to fine-tune photonics designs, so the shorter runtimes provided by EME enable practical, iterative workflows. In addition, the efficiency of the MT-FIMMPROP software itself, also plays a valuable part in engineers achieving optimal, photonic design results.

Dominic Gallagher, CEO of Photon Design, said: “Photon Design’s MT-FIMMPROP is the only EME-based simulation tool to successfully model ring resonators. Our EME delivers the accuracy of FDTD at far faster simulation speeds and without the need for expensive, pay-per-simulation, cloud computing; often needed for FDTD.

“Our recently published white paper showed that MT-FIMMPROP can process a typical 30um-radius ring resonator in just 11 seconds, on a laptop PC. By comparison, FDTD took four hours for a much smaller and simpler, 12um-radius ring resonator, using a workstation PC. FDTD is slower because it requires more than 11 trillion calculations to process the 12um example, with its computational load increasing eight-fold every time the device size doubles. Had FDTD been used for the 30um ring resonator, the simulation would have taken 15 times longer again.

“MT-FIMMPROP is an efficient computational modeller. Unlike FDTD, which processes the entire device bounding box, EME only processes the ring-resonators’ computational regions, which typically make up less than 5% of the device volume. It also enables engineers to combine and reuse repeated computational regions to avoid both design and process duplication. This simplifies the design process, reduces runtimes and actively supports an iterative photonic design approach.”

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One hundred times faster than standard.

Photon Design has published a white paper comparing the processing speed and accuracy of the company’s EigenMode Expansion (EME) simulation tools, with the more commonly used, Finite Difference Time Domain (FDTD) alternative. The white paper uses actual design examples to objectively benchmark both computational methods. 

It concludes that Photon Design’s EME results were equally rigorous as those of leading FDTD vendors, but simulations were completed in around 15 seconds, on a workstation PC, whereas FDTD simulations took many hours. Even with expensive, state-of-the-art cloud GPU, the FDTD simulation took 20 minutes for a 12um radius ring resonator, whereas Photon Design’s EME took just 11s for an even more demanding, 30um ring resonator example.

Dominic Gallagher, CEO of Photon Design, said: “FDTD is the most prevalent computational method used by photonic simulation CAD vendors, but it’s slow to process. The misconception within the industry that FDTD’s longer runtime leads to higher rigour, is clearly dispelled in our white paper. EME and FDTD deliver similar simulation results across a range of devices, however, EME achieves these results significantly faster.

“Processing speed is as important as simulation accuracy, when designing photonic devices. To achieve optimal results, engineers often run more than a hundred separate simulations during the photonic design process, whilst fine tuning a design. EME runtimes make this workflow practical, whereas one hundred FDTD simulations would take many days. To meet time restraints and project deadlines, engineers are often forced to produce a design with fewer iterations with FDTD, compromising the quality of the results.”

Processing speed and accuracy are both key when selecting photonics simulation software, which Photon Design’s EME-based tools provide.

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Multi-junction VCSEL simulation.

Photon Design has enabled pioneering, multi-junction Vertical-Cavity Surface-Emitting Laser (VCSEL) simulation, within its HAROLD simulation tool. Multi-junction VCSELs deliver higher optical power than traditional VCSELs, while retaining their compact, efficient, manufacturable and reliable design. Instead of one gain junction, a multi-junction VCSEL has several junctions stacked vertically within its epitaxy.

Efficiency comes from using the same current across the multiple gain junctions. This enables either a higher optical power for the same current, or a longer lifetime and reliability from delivering single-junction power levels with less current and therefore generating less heat. The high power and efficiency of multi-junction VCSELs is contributing to their rapid uptake in many markets, including high-speed datacoms, machine vision, longer-range automotive LiDAR and consumer 3D sensing applications such as facial recognition.

Dr Dominic Gallagher, CEO of Photon Design, said: “Photon Design’s HAROLD simulation tool supports the demanding design requirements of multi-junction VCSELs, providing 3D optical, electrical and thermal simulations. HAROLD shows engineers how additional junctions can raise output power, before efficiency then declines as a result of losses in what is now a larger epitaxy structure. HAROLD provides designers with band diagrams using 3D drift-diffusion modelling of the energy-band structure; thermal analysis of current-induced temperature gradients and their effect on gain; and rigorous output-power predictions from combining the 3D optical profile of the DBR gratings with simulated gain spectra.”

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Laser design in Welsh University.

Photon Design has partnered with Cardiff University to deliver a two-day, laser design course, as part of its physics curriculum. Students begin the course with laser theory and end by producing practical laser designs and models. The students gain hands-on experience of Photon Design’s CAD software, using its FIMMPROP simulation tool to create laser component designs, circuit simulations, and layouts. Students then progress to Photon Design’s PICWave to produce a complete design workflow with three-dimensional, time evolving, laser modelling. The course provides hands-on experience of how advanced simulation tools can simplify and accelerate the laser design process, producing functional laser designs within just two days.

Alex Edwards, Scientific Advisor at Photon Design, who delivers the course, said, “The unique partnership with Cardiff University gives students valuable, real-world, industrial laser design experience, modelling physics in action. Within two days, students produce manufacturable laser designs, clearly demonstrating the simplicity, speed, and efficiency of the simulation tools and connecting academic theory to practical industry skills.

“The course includes simulating photonic components like MMIs, rings, and tapered waveguides with FIMMPROP. Introducing this EigenMode Expansion (EME)-based simulation tool is often pivotal for students, as they experience its impressive speed compared to the more familiar FDTD method. With EME, we conduct equally thorough simulations in seconds, not the hours required by FDTD, making it possible to iterate laser designs efficiently and an essential part of the process.

“PICWave offers students many advanced physics effects, essential for modelling cutting-edge lasers. This covers optical mode propagation, thermal effects, carrier diffusion, and how their combined coupling will impact laser gain, ensuring the laser design meets individual application requirements.

“Our partnership with Cardiff University provides valuable feedback that helps to enhance our laser simulation products, informing and improving our next-generation of laser simulation tools.”

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Quantum dot laser simulator.

Photon Design has officially released its HAROLD QD, quantum dot laser simulation tool.

HAROLD QD enables engineers to model a quantum dot (QD) laser’s multi-layer, graded epitaxy structure, including dot size and distribution. It has an eight-band, K.P-based modeller to calculate the energy levels of the quantum dots, where previously it was six-band. As an evolution of the company’s HAROLD, hetero-structure semiconductor and laser simulator, developed over many years, HAROLD QD enables engineers to produce 3-D stress and strain models for each quantum dot shape. From this, HAROLD QD also allows engineers to calculate QD laser gain and absorption spectra, which reliably match the results of quantum dot lasers in field tests.

Dr. Dominic Gallagher, CEO of Photon Design, said, “OFC is the leading, global exhibition for the optical communications and networking supply chain; an ideal platform to officially launch HAROLD QD. Quantum dot lasers are critical to next-generation data centres, AI, and HPC applications and HAROLD QD puts Photon Design at the forefront of their design. QD lasers offer unparalleled, high-temperature operation, when compared to existing lasers, along with superior modulation, data transmission performance and power efficiency. They also bring practical, silicon-based manufacturing benefits, where quantum dots can be grown directly on silicon waveguides.

“HAROLD QD enables engineers to work in a single, integrated environment for gain materials, including InP and silicon. Seamless integration into Photon Design’s PICWAVE, to give engineers three-dimensional, time evolving, quantum dot laser models will follow.”

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Driving coherent communications, Ai & data transmission.

Photon Design enables rigorous 3D simulations of entire, Thin Film Lithium Niobate (TFLN), Mach-Zehnder Modulators (MZM’s), within a single design environment. Designing fast modulators for high-speed data transmission is central to driving coherent communications, AI, and co-located optics-based processers. TFLN’s strong and near instant response to applied voltage, and its wafer-scale fabrication capability, make it the key material for MZMs and next-generation modulators

Dr. Dominic Gallagher, CEO of Photon Design, said, “MZM device simulation is critical to many, new and emerging, high-data rate, photonics technologies. Photon Design’s Multi-Topology (MT)-FIMMPROP simulator enables thorough, MZM, 3D simulation, with export to layout by GDS-II. It is unique in enabling engineers to use a single tool for designing MMIs, Y-splitters, and waveguide bends; investigating the waveguide’s response under voltage; building a circuit simulator; and producing a layout tool. Additionally, the MT-FIMMPRP’s electro-optic solver simulates the Pockles effect of the isotropic, TFLN material in MZMs, as it changes refractive properties with voltage, to switch phase. 

“Accurately simulating a full MZM within a single design environment is only possible using EigenMode Expansion (EME) for processing, found in our MT-FIMMPROP simulator. EME can perform 3D simulations on a standard laptop, with results back within minutes. Whereas, the more commonly available FDTD-based simulators are barely viable, with equivalent results taking hours, not minutes to process, and often requiring expensive, cloud computing services for the calculations.

“EME’s simulation efficiency comes from only processing the active areas of the MZM, not the entire bounding box, wasting no resources simulating empty space. EME is unaffected by the MZM’s size, which can often be large in photonics terms, measuring 1600um in some cases. Since MZM design is an iterative process, design and simulation of MZMs using FDTD modelling is barely viable.”

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Photonic team to be strengthened.

Photon Design is expanding its Oxford-based team, in Britain, to include Application Engineers. This is to support growth and meet the increasing demand for its wide range of photonic simulation products.

Dr. Dominic Gallagher, CEO of Photon Design, said, “Application Engineering is a hybrid role involved in sales, product management, and engineering functions. It will facilitate alignment between customer requirements and our software development roadmap. Our Application Engineers will assist with technical and product support. As experienced software super-users, they have a comprehensive understanding of customer design challenges, offering expert support with simulations. The role will help accelerate the design process, improving performance and boosting productivity for customers. It will also create a structure where feedback is more easily captured to inform Photon Design’s R&D department, to ensure we remain an innovator at the forefront of the worldwide, photonic simulation industry.”

Photon Design will initially apply this approach to their laser simulation products, PICWAVE and HAROLD. By allowing engineers to concentrate on design and product enhancements, new product introductions will be accelerated. The laser simulation products which have already benefited from this approach include the new Quantum Dot gain model for entire laser waveguide cross sections; high-power VCSELs, for multi-junction devices; and extending quantum dot simulation functionality to include a full, 3D, time domain.

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Laser simulator.

Photon Design has announced that its quantum dot module for its HAROLD laser simulation tool, is now available as a release candidate for customer evaluation. The HAROLD module enables engineers to model a quantum dot (QD) laser's epitaxy structure, including dot size and distribution. Its eight-band K.P-based modeller predicts laser gain and absorption spectra, reliably matching the results of beta sample, quantum dot lasers in recent field tests.

Dr. Dominic Gallagher, CEO of Photon Design, said, “The HAROLD quantum dot simulator is at the forefront of quantum dot laser design. QD lasers operate reliably at higher temperatures than existing lasers, with superior modulation and data transmission performance, and heat and power savings. They also bring practical, silicon-based manufacturing benefits. Quantum dot lasers are expected to play a critical role in many, next-generation, laser applications, including supporting the move to optical architectures within data centres, AI, and HPC.

“The HAROLD quantum dot laser simulator is a release candidate which we are inviting customers to test and evaluate. It is a development of Photon Design’s long-established and well-respected, HAROLD, a mature simulation platform with an established library of material systems available to designers. When released, the HAROLD quantum dot module will have seamless integration into Photon Design’s PICWAVE simulator, giving engineers a full, three-dimensional, time evolving, quantum dot laser model.”

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PCL and PCSEL design enablement.

Photon Design Ltd., a leader in photonic simulation CAD software, is now providing PCSEL and PCL design solution for laser designers, by using a combination of its HAROLD and OmniSim, simulation tools. PCSELs (Photonic Crystal Surface-Emitting Lasers) and PCLs (Photonic Crystal Lasers) are rapidly becoming the first choice of laser for high-power, coherent applications in fast-growing markets, such as optical communications, sensing, and material processing. They have complex crystal structures that are challenging to model, but which are now made possible, entirely within Photon Design’s simulation tool portfolio.

Dr. Dominic Gallagher, CEO of Photon Design, said, “Engineers designing PCSELs and PCLs can use Photon Design’s HAROLD to simulate gain spectra in epitaxy structures. OmniSim, our FDTD-based, Dynamic Gain modeller, then simulates pulsed laser light propagation, over time, through the laser crystal lattice, including the effect of power.

“OmniSim’s Dynamic Gain modeller is new. Its Band Analyser provides band diagrams for photonic crystals, enabling designers to tune the laser structure to the desired wavelength, optimising the lattice, atoms and cavities in the structure using our Kallistos simulator. Finally, active FDTD simulations provide the operating wavelength and linewidth of the laser, which our Q-factor calculator produces at up to 85% quicker than the conventional, Fourier transform method, with equivalent levels of accuracy.” 

Photon Design is now a leader in PCSEL design with its HAROLD and OmniSim, simulation tools. Existing HAROLD users need only add OmniSim to begin designing crystal lasers.

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