Measuring Propagation Loss Due to Distance Traveled Through a Waveguide

This research project conducted through the OPT101: Introduction to Optics class that I took during my freshman fall semester. During the project, we were assembled into groups and given the opportunity to work with one of the professors/researchers at the Institute. My group was paired with professor Jaime Cardenas working with measuring propagation loss in waveguides.

During the lab sessions, we worked with photonics integrated circuitry with loss spiral waveguides in order to measure the effect of increased travel distance on the amount of propagated energy loss. The importance to the loss spirals is that they are all the same length, making the increase in distance discrete and linear. Therefore, as you will see in our results, the relationship between the energy loss and path length can be fit by a linear curve.

There are many reasons why energy could be lost as it travels through a medium. Optical waveguides work through the concept of total internal reflection. Essentially, optical waveguides/fibers consist of an inner "core" and an outer "cladding". The relationship between the refractive index of the materials of these parts is such that incident light that enters the waveguide past a certain angle gets trapped within the waveguide. This relationship is described in further detail in the "Background Information" section of the project poster linked below. In order to get 100% energy propagation, every interaction between the light and the core/cladding boundary would have to result in 100% reflection and there would have to be no environmental influences on the waveguide. This, of course, is not the case. The conclusion of the experiment is that through a combination of loss sources energy is dissipated linearly. One can assume from these results that the main contribution to this loss is most likely absorption. Scattering is another possible contribution to loss but since that is reliant of imperfections in the waveguide, this would be difficult to quantify.

This project was such a valuable experience because, for many of us, this was our first hands-on experience working with optical technology and it introduced us to so many interesting concepts and instruments that we got to explore. Thank you very much to Professor Jaime Cardenas and his team of graduate students for the access to their equipment, their guidance, and their time. Thank you to Professor Tom Brown for facilitating this project. And thank you to Scott Carney and the Institute of Optics for printing the poster for the presentation and for the access to the Institute's facilities.