µ-optics Enable Scaling of PIC Applications

Application Note3 May 2023

Photonics technologies cover almost endless aspects of our modern life and wellbeing. The need ranges from information collection with cameras and sensors, to information processing and sharing through all kinds of devices and further to information storage in finally tangible recording means.

Authors: Myun-Sik Kim, PhD, Principal Strategic Business Development and Marco Müller, Global Marketing Manager, Axetris Switzerland

Worldwide data volume is expected to multiply incessantly, driven by IoT applications, cloud services and on-site processing that make it really skyrocket. That said, efficient optical signal transmission is a mission critical issue in modern data communication and continuous performance improvement of optical sub-assemblies is a future key success factor.

Nowadays, photonics systems get more and more complex. Often, the required optical setup may require the size of a living room table. No doubt that will work and the desired tasks can be accomplished with such bulky systems. However, you certainly recognize that such a system of highly populated optical components is very difficult to industrialize and to scale up for mass production. So, what could be the solution?

Photonic integrated circuits (PIC) seem to be the best approach among today's state-of-the-art options. When coupling light into- and out of the PIC or other forms of optical circuits, premium quality micro-lenses (shown in the first figure) can be also the best fit to maintaining high efficiency light coupling on one hand and vast scaling up to mass production requirements on the other.

Let's take a look at proven technologies in Telecom and Datacom, like the 100G to 400G small form factor transceivers. Optical sub-assembly (OSA) consists of the transmitter (TOSA) and the receiver (ROSA) modules, whose exemplary schematic is shown in figure 2.

Silicon micro-lens chip of sub-millimeter dimension empowers those optical sub-assembly modules by coupling light from a laser diode into the optical circuit and further toward optical fibers, see in the second figure.

Such an assembly scheme can be adopted wherever PICs employed. For instance, frequency modulated continuous wave (FMCW) light detection and ranging (LIDAR) and Quantum applications need interferometers, splitting optical paths, branching them in multiple outputs.

Those optical functions are now all available in PIC circuits of millimeter size chip dimension.

In addition to the optical characteristics, wafer-level MEMS processed micro-optics allow adding a wide range of mechanical structuring and metallization features to facilitate higher integration, smarter embedding and further miniaturization of optical sub-assemblies, see examples in the third figure.

Needless to mention that wafer-level micro-optics manufacturing is probably the smartest way to scale-up production output from prototype to multi-millions, exactly as PIC does.

Axetris supplies its global customer base with refractive micro-optical lenses, lens arrays and diffractive optical elements in silicon and fused silica. These cover the entire wavelength range.

Classic products in the micro-optics segment include collimators for high-power diode lasers, microlenses for fiber optic coupling, and arrays for edge-emitting laser diodes or VCSELs. In telecommunications, Axetris' aspherical and spherical microlenses and lens arrays are used primarily for high-speed components that require very high coupling efficiency.

Axetris customers benefit from excellent product value, high product quality and professional support.