Advances in active alignment engines for efficient photonics device test and assembly

The photonics market is advancing rapidly, with projected substantial growth in a large number of sectors incorporating this technology in the next decade. Anticipating devices with hundreds or even thousands of individual components and connections, manufacturers face the necessity of parallel optimization, making active alignment an optimal choice to meet production demands.

By Scott Jordan, Stefan Vorndran and Warren Harvard, Physik Instrumente L.P. (PI)

Over more than a half century, the pace of innovation in electronic communication and computing has consistently increased, giving rise to progressively smaller silicon microchips with enhanced processing power. This achievement is attributed to the exponential growth in the density of integrated circuit (IC) transistors, a development predicted by Gordon Moore, Intel confounder, in 1965 and commonly called Moore’s Law. However, there are inherent limits to reducing the physical feature size of silicon structures before quantum effects start influencing their functionality.

Optical feedback is the key to automated alignment. A fast, traditional way of finding first light followed by a gradient search for optimum coupling efficiency is shown above – a double spiral scan using a hexapod/piezo approach. The hexapod runs a coarse spiral scan (coarse meaning single digit microns), while the piezo stage fills in the gaps with high-speed sub-micron scans. Both fine and coarse scans can be executed simultaneously. (Image courtesy PI)

Fortunately, photonics has come to the aid of electronics, enabling the integration of miniaturized optical devices into various applications, from sensors in wearable devices, to LiDAR and ADAS cameras in autonomous vehicles. Photonics has the potential to surpass traditional electronics combining data throughput and efficiency with miniaturization, sparking a true revolution in the telecommunications and data communication sector. To sustain this growth, it is essential to address the remaining challenges and bottlenecks in photonic device manufacturing. The implementation of additional automation solutions, especially those ensuring fast and precise component alignment, is crucial to meet the demands of future advancements.

Limitations of labor-intensive device assembly
The assembly process of photonic devices typically includes meticulously aligning, gluing, and curing a combination of light sources, fibers, lenses, arrays, waveguides and chips. Each of these individual components must be accurately positioned to ensure the intended functionality and performance of the final product, as even slight misalignments on the orders of less than a millionth of a meter can severely impact device efficiency.

Testing and packaging of modern photonic devices can be a huge challenge across multiple degrees of freedom. The alignment of multi-channel devices, such as fiber-optical arrays, used to be a slow, repetitive process before modern parallel algorithms were developed. (Image courtesy PI).

Despite technological advancements, many manufacturers still rely on manual alignment techniques, using shims for error compensation or securing hardware with retaining rings. Beyond being time-consuming, these methods often involve specialized labor that is both costly and challenging to find.

The manual assembly of complex devices can take up to 20 minutes, creating a significant bottleneck in the production process at the component positioning stage. Additionally, traditional assembly tools like shims and jigs may struggle to meet the increasingly stringent tolerances required for manufacturing modern devices. An alternative alignment strategy is necessary to precisely indicate component positioning.