Micro-Opto-Mechanical Structures for the Infrared Spectral Range Fabricated by Two-Photon Polymerization

Since initial applications in the latter twentieth century, the field of micro-optics has greatly expanded. Micro-optics now encompasses research in areas such as integrated optics, micro-electromechanical systems (MEMS), quantum technology, sensing, energy harvesting, and metamaterials. In its current stage, dynamically tunable micro-optics are crucial to providing additional processing power without increasing volume. Micro-structured optics comprise a subsection of micro-optics where the optical response is manipulated by some sub-wavelength or wavelength scale structure. One challenge in developing micro-structured optics are restrictions in terms of geometric freedom and extensive development times. As a solution to some of these challenges, rapid prototyping techniques such as two-photon polymerization (TPP) have been employed in the development of complex two- and three-dimensional optics. TPP provides nano-scale feature sizes, resolutions which surpass the diffraction limit of the light source. In search of ways to add additional degrees of tuning in micro-optics, the unique properties of TPP compatible resins can be exploited. In this study, dynamically tunable micro-structured optics are developed by TPP. Being a polymer, the fabricated structures have unique mechanical properties when compared with conventional glass and metal optics. The structures are designed such that their optical response is sensitive to induced mechanical stress or strain. Both sub-wavelength and wavelength-scale micro-structured arrays were investigated for this mechanical tuning. In each case, changes in the structure's geometry due to mechanical stimuli resulted in a change in the optical response. In combination with a MEMS device, the investigated structures could have applications in integrated optics, mechanical sensing and beamsplitting, and tunable bandgap filtering.