THESIS
2004
xvi, 137, [4] leaves : ill. (chiefly col.) ; 30 cm
Abstract
Alignment is one of the most critical issues in optoelectronics packaging. A slight offset in any direction will affect the performance of the photonic devices. Nowadays passive alignment of optical fibers is attracting more attention due to its low manufacturing cost and short processing time when compared with active alignment. The position of the optical fiber in passive alignment is defined by the geometry of a V-groove. The epoxy is usually dispensed in a glob-top manner. However, the optical fiber may be lifted up due to the buoyancy effect. An additional cover plate is usually required to press the fiber against the wall of the V-groove. Although the fibers can be well aligned by the aforementioned method, the applied stress may deform the fibers or damage the cover plate, leadin...[
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Alignment is one of the most critical issues in optoelectronics packaging. A slight offset in any direction will affect the performance of the photonic devices. Nowadays passive alignment of optical fibers is attracting more attention due to its low manufacturing cost and short processing time when compared with active alignment. The position of the optical fiber in passive alignment is defined by the geometry of a V-groove. The epoxy is usually dispensed in a glob-top manner. However, the optical fiber may be lifted up due to the buoyancy effect. An additional cover plate is usually required to press the fiber against the wall of the V-groove. Although the fibers can be well aligned by the aforementioned method, the applied stress may deform the fibers or damage the cover plate, leading to subsequent reliability issues. In this study, a new method of dispensing epoxy with self-alignment capability is introduced. An innovative design of V-grooves on a silicon optical bench (SiOB) is developed. A "reservoir" is placed right next to the V-groove. The purpose of this reservoir is to let the epoxy flow into the gap between the optical fiber and the bottom of the V-groove. The excess epoxy may be drained away via the "canal". The reservoir/canal feature is patterned and etched together with the V-grooves so that there is no additional cost and time for fabricating the SiOB. It is observed that, if an appropriate amount of epoxy is flowing in the gap between the optical fiber and the V-groove, the optical fiber will not be lifted up by the buoyancy of the epoxy. On the contrary, the surface tension of running epoxy can pull down the fiber for passive alignment. With this new method, the optical fiber with greater than 60 μm of initial misalignment can be aligned with the centre of the V-groove within 0.5 μm of accuracy. During the course of the present research, the wet etching techniques on silicon are also studied. The effects of various etching parameters are investigated and some critical issues are identified.
Vertical Cavity Surface Emitting Lasers (VCSEL) are wildly used as light sources in various optoelectronic applications. As VCSELs are surface emitting devices, they are relatively difficult to be packaged with a silicon optical bench (SiOB). In this study, a new package structure with a chip-on-chip 3D optical interconnect feature is developed. The package consists of a SiOB and a flip chip mirror carrier. The light beam is deflected by two pairs of mirrors on both the SiOB and the flip chip mirror carrier. The optical path is coupled from one optical fiber to another through an "overpass" type of 3D interconnect. The flip chip mirror carrier is self-aligned during the reflow of flip chip solder joints. Furthermore, the newly developed V-groove passive alignment feature is also integrated with the SiOB. A prototype with the aforementioned configuration is fabricated in this study for illustration purpose. In practice, the flip chip mirror carrier may be replaced by other devices such as VCSELs and photo detectors.
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