Search Results (4)

The increasing demand for optical technologies with dynamic spectral control has driven interest in chromogenic materials, particularly for applications in tunable infrared metasurfaces. Phase-change materials such as vanadium dioxide and germanium–antimony–tellurium, for instance, have been widely used in the infrared regime. However, their reliance on thermal and electrical tuning introduces challenges such as high power consumption, limited emissivity tuning, and slow modulation speeds. Photochromic materials may offer an alternative approach to dynamic infrared metasurfaces, potentially overcoming these limitations through rapid, light-induced changes in their optical properties. This manuscript explores the potential of thiazolothiazole-embedded polymers, known for their reversible photochromic transitions and strong infrared absorption changes, for use in tunable infrared metasurfaces. The material exhibits low absorption and a strong photochromic contrast in the spectral range from 1500 ${\mathrm{cm}}^{-1}$ to 1700 ${\mathrm{cm}}^{-1}$, making it suitable for dynamic infrared light control. This manuscript reports on infrared imaging experiments demonstrating the photochromic contrast in thiazolothiazole-embedded polymer, and thereby provides compelling evidence for its potential applications in dynamic infrared metasurfaces. Full article

One-dimensional photonic crystals have been used in sensing applications for decades, due to their ability to induce highly reflective photonic bandgaps. In this study, one-dimensional photonic crystals with alternating low- and high-density layers were fabricated from a single photosensitive polymer (IP-Dip) by two-photon polymerization. The photonic crystals were modified to include a central defect layer with different elastic properties compared to the surrounding layers, for the first time. It was observed that the defect mode resonance can be controlled by compressive force. Very good agreement was found between the experimentally measured spectra and the model data. The mechanical properties of the flexure design used in the defect layer were calculated. The calculated spring constant is of similar magnitude to those reported for microsprings fabricated on this scale using two-photon polymerization. The results of this study demonstrate the successful control of a defect resonance in one-dimensional photonic crystals fabricated by two-photon polymerization by mechanical stimuli, for the first time. Such a structure could have applications in fields, such as micro-robotics, and in micro-opto–electro–mechanical systems (MOEMSs), where optical sensing of mechanical fluctuations is desired. Full article

Over the last several years, two-photon polymerization has been a popular fabrication approach for photonic crystals due to its high spatial resolution. One-dimensional photonic crystals with photonic bandgap reflectivities over 90% have been demonstrated for the infrared spectral range. With the success of these structures, methods which can provide tunability of the photonic bandgap are being explored. In this study, we demonstrate the use of mechanical flexures in the design of one-dimensional photonic crystals fabricated by two-photon polymerization for the first time. Experimental results show that these photonic crystals provide active mechanically induced spectral control of the photonic bandgap. An analysis of the mechanical behavior of the photonic crystal is presented and elastic behavior is observed. These results suggest that one-dimensional photonic crystals with mechanical flexures can successfully function as opto-mechanical structures. Full article

Metamaterials, in the form of perfect absorbers, have recently received attention for sensing and light-harvesting applications. The fabrication of such metamaterials involves several process steps and can often lead to nonidealities, which limit the performance of the metamaterial. A novel reciprocal plasmonic metasurface geometry composed of two plasmonic metasurfaces separated by a dielectric spacer was developed and investigated here. This geometry avoids many common fabrication-induced nonidealities by design and is synthesized by a combination of two-photon polymerization and electron-beam-based metallization. Infrared reflection measurements revealed that the reciprocal plasmonic metasurface is very sensitive to ultra-thin, conformal dielectric coatings. This is shown here by using Al₂O₃ grown by atomic layer deposition. It was observed experimentally that incremental conformal coatings of amorphous Al₂O₃ result in a spectral red shift of the absorption band of the reciprocal plasmonic metasurface. The experimental observations were corroborated by finite element model calculations, which also demonstrated a strong sensitivity of the reciprocal plasmonic metasurface geometry to conformal dielectric coatings. These coatings therefore offer the possibility for post-fabrication tuning of the reciprocal plasmonic metasurface resonances, thus rendering this novel geometry as an ideal candidate for narrow-band absorbers, which allow for cost-effective fabrication and tuning. Full article