FOCUSLIGHT V-GROOVES
BUILDING THE FUTURE OF OPTICAL SYSTEMS THROUGH PHOTONIC INTEGRATION
THE ROLE OF ENGINEERED V-GROOVES IN NEXT-GENERATION PIC-FIBRE INTERFACES
As Photonic Integrated Circuit (PIC) channel counts continue to grow, wafer-level V-groove structuring techniques provide the precision, scalability, and design flexibility needed for high-performance fibre interfaces in advanced optical systems, writes Focuslight Market Intelligence & Strategic Marketing Manager Auri Ripoll , Senior Strategic Marketing Expert Dirk Hauschild , and Marketing Manager Zhichao He .
T he rapid growth of global data traffic – driven by telecom networks, data centres, and next generation high- performance computing – has created new performance and integration challenges for PICs. As channel counts climb and system architectures shift toward tighter integration, the optical packaging interface between fibre and PIC is emerging as one of the key factors influencing system performance, cost, and scalability. Industry-wide, packaging strategies must now deliver submicron alignment accuracy, volume scalability, and long- term reliability – often under challenging thermal and mechanical conditions. These requirements are further amplified in multi-channel, high-speed single- mode architectures, where the tolerance can approach a fraction of a micron, leaving minimal margin for assembly error.
Traditional fibre alignment approaches, including blade-diced V-grooves, have served the industry well in lower- channel-count systems. However, their inherent process limitations – such as sequential cut variability, substrate size restrictions, and limited geometry flexibility – are becoming more significant in the next-generation PIC packaging. This has opened the door for new wafer-level structuring techniques that can address these challenges, while supporting high-precision and scalable manufacturing compatible with semiconductor technologies and materials. THE LIMITATIONS OF TRADITIONAL V-GROOVES Blade-diced V-grooves have long been used for fibre alignment in photonic packaging, valued for their straightforward process and established manufacturing base. However, the sequential nature of mechanical dicing introduces cumulative errors that
become increasingly problematic at higher channel counts. Blade wear, mechanical drift, and environmental factors such as thermal expansion can lead to pitch deviations, roll angle errors, and height inconsistencies in the fibre seating surface. These variations increase assembly complexity, raise the need for active alignment, and may ultimately impact coupling efficiency and overall yield. Additional drawbacks include the potential for fibre damage from chipping or sharp-edge formation, possible size limitations on larger format substrates, and fixed tool geometries that reduce design flexibility. As systems adopt more complex fibre array layouts and customised pitches, the limitations of sequential blade-dicing can become a barrier to scalability. Figure 1 shows a typical distribution of the functional parameters of a sequential process that does not show a single centre of gravity value. The consequence of this random distribution is incompatibility with lithography-produced PICs, resulting in larger performance variation and more complex alignment and assembly processes. Wafer level simultaneous structuring Advances in wafer-level structuring are now enabling simultaneous definition of all fibre alignment features in a single process step. This shift from sequential cutting to batch structuring removes the accumulation of positional error across multiple channels, offering submicron relative accuracy across the entire array. The process is compatible with lithography-based PIC production platforms and supports a wide range of geometries – from standard telecom pitches to high-density arrays with more than 96 fibres. It also allows the use of diverse substrate materials, including
Lateral deviation from nominal position (grid error)
Figure 1: Random fibre pitch variation without a single centre of gravity value
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| ISSUE 42 | Q3 2025
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