Low-loss optical single-mode waveguide platform in thin glass with wide spectral range

Current developments are pushing the integration of optical technologies deeper into the architecture of data centers,1 a trend in which co-packaging figures prominently due to its many inherent advantages2, 3. Several materials are used as a basis for these co-packaged platforms, but glass stands out for its many positive properties, such as high thermal and dimensional stability, great optical transparency, excellent high-frequency properties for electric circuits, and extremely low cost. To seize these advantages, we pursued an approach called electro-optical circuit board (EOCB), in which optical and electrical interconnections are realized by glass-integrated optical waveguides and electrical circuits on both sides of the glass board. An ion-exchange technique was developed to integrate low-loss optical single-mode waveguides into large-sized glass boards (457 mm x 303 mm). In the reported work, the next milestone in developing this process was achieved by reducing the diffusion metal mask opening's width from 6 μm to 3 μm by mask-less laser patterning. These smaller mask opening allow for optical waveguides with a more circular modal field shape resulting in smaller coupling losses to optical fibers. Additionally, the reduction of propagation losses of multi-mode waveguides for wavelengths down to the visible range was achieved. This opens up the field of sensing and quantum application to EOCBs.