Photonics packaging remains one the most challenging steps in the optoelectronic system industry and therefore responsible for more than 80% of the total cost of a fully assembled device. The conventional methods of coupling light from an optical fiber into a device require active alignment in a serial process which is extremely time consuming and costly. Several advanced types of fiber to waveguide connectivity solutions have already been reported based on diffractive gratings, reflective curved mirrors, microlenses
on 45°-angled fibers, facet mirrors of V-grooved silicon optical benches, V-grooves with integrated optical micro-systems, etc. However, most of these solutions provide small coupling efficiency, need active alignment and/or require complicated manufacturing methods. Moreover, additional components are usually required (e.g. lens/micro mirror arrays, fiber bundles) that adds up to the complexity and cost of the packaging, as well as making the final product bulky. In fact, it is essential to have a compact in-plane optical interconnector to photonic integrated circuits (PIC), to waveguides in electro optical boards, but also to active optical devices (e.g. lasers, LEDs and detectors).
Here, a novel wafer-scale, in plane solution for interconnecting optical devices with fibers and fiber arrays is presented. Micro-optical structures on glass wafers and in conjunction with SiN waveguides and corresponding grating couplers were designed, optimized, and fabricated (Figure 1). Our “plug-and-play” technology is based on micro-optical reflection elements, fabricated from reflowed comb-like structures. The reflow process results in automatically smooth mirror walls, which is the key for low optical losses, whereas the reflecting element enables a compact packaging solution. Excess losses of these structures as low as 0.35 dB are obtained.
In addition, to easily enable passive fiber array coupling and packaging, the reflecting micro-optical elements are combined with integrated self-alignment structures. Successful assembly of a 12-fiber ribbon is demonstrated (Figure 2). The implementation of such a replication technology will enable the production of reflecting micro-optical interconnects with extreme compactness, thus providing significant technical advantages and degrees of freedom both to component suppliers and to device/system integrators.