Automated fiber pigtailing of precision optical components

Problem statement

Nowadays, electronic and optical systems are becoming increasingly smaller. This allows integrating a large amount of functionality in a small package, e.g. smartphones. Additionally, more and more electronic systems are being replaced by optical systems. Examples can be found in sensing (optical sensors can be much more sensitive than electrical sensors) or telecommunication in which optical fibers enable Terabit per second data rates. Also for optical systems, integration and miniaturization plays an important role since it will allow for example higher bandwidth, more sensors or more functionality per unit area.

However, when optical structures reduce in size, coupling the light in and out becomes increasingly challenging. At the Cmst research group (Elis department,, various technologies are available to integrate light sources and detectors in very thin (~40 micron) foils, so that they even become mechanically flexible. Furthermore, polymer processing technologies enable us to fabricate very small and single mode optical waveguides (typical dimensions between 1 and 10 micron). The challenge is to couple these light sources and detectors to these optical waveguides or to optical fibers, i.e. so-called “pigtailing”. Unfortunately, traditional methods of pigtailing do not allow us to achieve these very small dimensions.


Figure 1: different possibilities for coupling light sources/detectors to waveguides or fibers.

Figure 2: Realizations at Cmst: (left) light sources and detectors coupled to mechanically stretchable optical waveguides and (right) a miniature laser coupled to an optical fiber using a 45 degree mirror.

Goals of the thesis

During the thesis, we will develop a new technology to precisely couple light in and out of single mode optical waveguides or fibers. Based on a literature study, different approaches of light coupling will be assessed and the most suited concept will be selected. This can for example be direct butt-coupling of a light source and waveguide, or using dedicated coupling structures such as an intermediate mirror or lenses (see Fig. 1 and 2). Afterwards, these components can be fabricated in the UGent cleanrooms and can then be assembled. For assembling the precision components and assuring the required micrometer positioning resolution, an automated setup will be constructed based on computer controlled motorized positioning stages available at Cmst (Fig. 3).

Figure 3: Motorized translation stages and controller with nanometer-level performance available at Cmst.

The work is divided in the following parts:

- Design/modeling/simulation of the coupling structures and the interaction with the waveguide or fiber.
- Fabrication of coupling structures such as mirrors, or lenses.
- Building an automated setup for precision assembly of the miniature optical components

Together with the master student, the focus of the master thesis can be slightly shifted towards one of the specified parts.


Ardoyen (clean rooms) en thuis