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978-3-8439-4709-1, Reihe Mikrosystemtechnik
Marie Theresa Alt
Glass on Silicon for Thick Waveguides and Hermetic Miniaturized Laser Diode Packaging on Wafer-Level
234 Seiten, Dissertation Albert-Ludwigs-Universität Freiburg im Breisgau (2020), Softcover, B5
This thesis introduces novel technologies for hermetic micro-packaging of LDs and integrated glass-based multi-mode waveguides on wafer-level. Passive alignment structures facilitate the assembly of individual optical components for highly efficient coupling of laser light.
Two new processes were developed to pattern aluminum-borosilicate glass AF32®eco on silicon wafers with precise micro-machining: The first approach was based on fusion bonding and wet etching of glass foils while embedded glass structures were realized by glass reflow in the second process.
Both techniques were successfully applied to fabricate thick, stress-free and highly transparent multi-mode waveguides. The first prototypes of glass-silicon micro-optical housings were assembled with integrated edge-emitting LDs delivering wavelengths of 450 nm and 650 nm. Embedded waveguides were used as optical glass-feedthroughs to couple the light with minimal losses into optical fibers. Different feedthrough designs were explored, including tapered waveguides and beam combiners. The lowest measured total loss of the optical power transmitted from a blue and red packaged LD through attached glass fibers was -1.95 dB and -3.15 dB, respectively. Even though the LDs are already mounted in a hermetically sealed and polymer-free housing, these are the lowest losses ever published for passively aligned systems on wafer-level.
The novel technologies enabled the first thick glass structures for optical applications that can be realized in a complete silicon micromachining process. While demonstrating superior optical properties, these polymer-free approaches pave the way for future glass-based micro-optical systems for applications in implants or light engines in consumer applications like glasses for augmented reality.