In this paper, we discuss a hybrid photonic packaging platform that reduces module size by enhancing the functionality of glass-based substrates, frames and caps featuring electrical, thermal, mechanical, and optical functions. Furthermore, the substrates can be functionalized with integrated optical waveguides by means of thermal ion exchange. New results for low loss bending’s will be discussed. The packaging approach offers the possibility to integrate beam forming optics and further (optical) components within the miniaturized photonic module. This serves clients who do not want to cope with alignment of single micro-optics, which is inherently a tight tolerance process, but instead want to have a surface-mountable device that provides certain optical inputs and outputs which can be interconnected in a defined manner, i.e. a collimated beam or fiber coupling. As an example, we present modular photonic subsystems that enable complex configurations such as master oscillator power amplifier (MOPA). Panel-level manufacturing and high precision automated assembly techniques on panel-level are demonstrated. Laser-based sealing processes using metal absorption structures are demonstrated to form metallic bonds between glass layers. Singulation of the panel stack at the end of the process chain ensures streamlined handling and allows for cost effective manufacturing.
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.
Demand for high integration of optoelectronic and micro-optical components into micro-electronic systems for communication, computing, medical, and sensing applications is increasing. Advanced hybrid packaging technologies are used to enhance glass-based substrates featuring electrical, thermal, and optical functionalities with laser diodes, modulators, isolators, photonic integrated circuits (PIC), beam-splitting components, and micro-lenses. Such glass-based substrates can be thin glass layers on large panels or more mini-bench-like boards that can be embedded into organic printed circuit boards (PCBs). Optical fiber interconnects, connectors, and electrical–optical integration platforms are used for higher level system integration and need to be miniaturized on module and board level to fulfill decreasing channel pitch requirements. We provide background on and discuss thin glass as a suitable base material for ion exchanged waveguide panels and interposers, precise glass structuring for posts and holders, the related high precision assembly techniques, and advanced fiber interconnects. Some examples of PCB photonic integration, micro-bench optical sub-assemblies, including PIC, and 3D optical resonator packages that combine most of these approaches will be shown.
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