Anti-Reflection Subwavelength Gratings for InP-based Integrated Waveguide Facets
Summary
Controlling reflections caused by waveguide facets is crucial for the optimal performance of many photonic integrated circuits. Reflections originate from the abrupt transitions between the waveguide materials to air occurring at the facet location. Inspired by the structure of the cornea of nocturnal insects, where arrays of nano-sized cones minimize reflections and enhance the insect鈥檚 sight, in this graduation work, similar nano-sized triangles were imprinted on photonic waveguides. As these nano-sized triangles are much smaller than the wavelength, they effectively create a smooth transition between materials, and thus, minimize reflections.
First, the shape of the nano-sized triangles was simulated using finite-difference-time-domain (FDTD) simulation in order to find the best geometry to minimize reflections. Then, different test structures, such as a Mach-Zehnder interferometer, were designed to systematically study the anti-reflection properties of arrays of nano-sized triangles. After in-house fabrication on a 3-inch wafer, lab measurements were performed. Reflection reductions as low as -30dB were measured and compared to simulations, verifying the effectiveness of the arrays.
The final work was very promising and submitted to and published by Optics Letters.
Experience during master
Lukas: The graduation work covered almost all aspects of research, from an initial design idea to design and simulations, and eventually characterization of these structures. This provided a very good foundation to start a PhD in the PhI-group afterwards!鈥�