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Rolled-up photonic structures

We implement thin film roll-up technology to fabricate novel photonic devices.

Material thin film systems fabricated by standard physical or chemical deposition methods are bound to have residual mechanical stresses which can arise from either lattice mistmatch, thermal mistmatch or interface dislocations. Typically, these accumulated stresses are not desired for technological applications as they can lead to defects such as cracks, delamination and buckling (wrinkles) in the thin films.

When properly engineering the residual stress of a given thin film system, novel self-assembled structures can be obtained. One example are the so called rolled-up microtubular structures obtained by releasing a properly stressed thin film system via the removal of a sacrificial layer, which allows the film to  roll-up or down into itself and form Swiss-roll like structures.

These tubular structures represent an interesting route to fabricate novel multilayered devices, when compared to the standard multiple deposition steps approach, given that for every turn of the roll one gains an additional layer in the film stack present at the tube wall.

In this project, we are developing novel photonic devices by exploiting the rolled-up approach using dielectric and metallic materials. We rely on micro and nanofabrication techniques available both in our institute and at the EPFL's cleanroom facility. The self-assembled structures are then structurally characterized by means of scanning electron miscroscopy (SEM), and optically characterized by reflection and transmission optical microscopy. FDTD simulations are also performed to design and understand our multilayered devices.

 Experimental techniques:  Thin film deposition (thermal evaporation, sputtering), photolithography, e-beam lithography, reactive ion etching, scanning electron microscopy, atomic force microscopy, focused ion beam patterning,  polarized light microscopy, FDTD simulations (Lumerical).

Main investigator

Involved people