After an introduction about the physics and engineering of metamaterials, we will present a detailed photophysical study showing the influence of metal/dielectric metamaterials on the spontaneous emission and photo-induced electron transfer properties of organic semiconducting thin films. The results will demonstrate how the effects of the plasmonic structures on the photonic density of states and the effective dielectric permittivity of the organic media can be controlled to boost the performance of organic optoelectronic materials and devices.

Programmable meta-imagers based on reconfigurable intelligent surfaces or dynamic metasurface antennas constitute a promising low-cost hardware layer for agile intelligent sensing in applications including security screening. However, their calibration via near-field scans is tedious, time consuming and not easily compatible with large-scale operations. In this talk, we review recent efforts on physical-model based wave control in metasurface-tunable complex media and discuss its applications to the frugal calibration of intelligent meta-imagers. Frugal here refers to the number of calibration measurements, the number of the parameters to be stored for later use, and the requirement or not for phase-sensitive measurements.

Tailored sub-wavelength structures of select materials, such as plasmonic metasurfaces and polymeric bragg reflectors, enable strong electromagnetic (EM) interactions that can be tuned to select frequencies across the spectrum. While such systems can be independently tailored towards precise colorimetric outputs in both static and dynamic configurations, new opportunities emerge in hybridized forms that enable more precise spectral control. Optimization of the nanophotonic response was achieved through the use of gaussian process regressions (GPRs) and artificial neural networks (ANNs) to predict colors and spectra of nanoscale metasurface patterns. In addition to the forward model, the inverse functions were also approximated for use in direct design prediction. Spectra were measured, as well as simulated with Lumerical.software Machine-learned models were trained to approximate each respectively. Corresponding experiments were performed to validate and improve the models, isolating metasurface parameters to targeted colorimetric response.

Xolography is a volumetric 3D printing method utilizing dual-color photoinitiators to fabricate layer-free objects from photopolymer resins, ranging from millimeters to centimeters in size. It enables fast, continuous printing producing objects with smooth surfaces and free of internal interfaces immediately after printing and postcuring. Xolography has the potential to revolutionize prototyping and fabrication of optical elements by allowing their rapid additive manufacturing without the need for additional surface treatment.

Single-layer-CVD graphene is grown and integrated into passive electronic interfaces through a cost-effective optical fabrication approach. Raman characterizations are carried out to verify the single-layer nature of the grown graphene. The realized antenna-free, non-gated, and passive electronic device with Ge/Au contacts to graphene shows radiation detection (94 GHz) and thermosensing (6K-120 K) based on the radiation-induced thermoelectric effects in graphene. Further, a Ti/Au contacted graphene electronic device is fabricated and characterized through current-voltage measurements at cryogenic temperatures (7-140 K). Ti-Au contacted electronic device shows thermo-resistive sensing that is applicable to negative temperature coefficient (NTC) thermistors. Application and future scopes of these graphene radiation detectors and thermosensors can be in temperature monitoring in graphene-integrated electronic and quantum devices, terahertz communications, thermal imaging, space, and environmental monitoring.

Energy derived from mechanical deformation is one of the cleaner energy options known as piezoelectric. Polyvinylidene fluoride (PVDF) has been identified to hold the characteristics of piezoelectric and dielectric properties due to good energy storage capacity and electrical breakdown strength. However, lower piezoelectricity limits its applicability, and therefore, advancement is needed, potentially through doping or filler like barium titanate (BaTiO₃ or BTO). Several fabrication approaches have been proposed, yet spin coating is desirable vis. for its reliability, ease of replicable, cost-effectiveness, and uniform coating. In this study, thin films were fabricated using spin coating with 5 wt.% and 12 wt.% BTO/PVDF compositions at 1000 rpm and 4000 rpm. The morphological characteristics of the materials were studied using Fourier transform infrared (FTIR) and scanning electron microscope (SEM) analysis techniques. The results showed that the 5wt.% BTO/PVDF film at 4000 rpm and annealed at 120 °C for 6 hours exhibited a maximum relative beta (β) fraction of around 94%. SEM images revealed the uniform distribution of BTO particles with less agglomeration in the PVDF matrix, indicating that adding BTO promotes nucleation sites for forming a more ordered crystalline structure. Despite that, further validation of crystallinity percentage is required to assess the enhancement made by the BTO fillers in a polymer matrix entirely. Overall, the experiment demonstrated that spin coating can effectively enhance the β-phase of PVDF (β-phase is desirable due to relatively high dielectric constant and piezoelectricity) with the addition of ceramic fillers such as BTO.

This paper presents the optical and acoustic characterization of an additively printed transparent polymer. Digital light processing DLP technic is used for printing transparent polymer when the acoustic and optical transmission were measured by ultrasonic transducers and UV spectroscopy. The 3D acoustic characterization of the polymer has shown slight anisotropic behavior with a longitudinal and shear velocities of 2488 m/s and 1133 m/s respectively. On the other hand, an anisotropic optical transmission and reflection have been shown. The obtained results are interesting in the development of acoustical and optical devices.

Multifunctional electrochromic (EC) materials which control multiple colors, various color density, and specular reflection are expected to be potential candidate for light-modulation device and novel reflective display device. Electrodeposition is also attractive method to create colors [1-6] because silver (Ag) nanoparticles exhibit various optical states based on their localized surface plasmon resonance (LSPR). LSPR bands of metal nanoparticles are affected by the size and shape. The control of LSPR, therefore, must enable dramatic changes in color for the surface where nanoparticles are deposited. We successfully demonstrate the first LSPR-based multicolor EC device enabling reversible control of six optical states—transparent, silver mirror, cyan, magenta, yellow and black. We will discuss the mechanism of electrodeposition and a wide range of its applications.
References; [1] Adv. Mater., 24, 122 (2012), [2)] Adv. Mater., 25, 3197 (2013), [3)] Chem. Mater., 26, 6477 (2014), [4] Nanoscale, 12, 23975 (2020), [5] Adv. Mater. Tech., 6, 200081 (2021), [6] Sol. Ener. Mater. & Sol. Cells, 251, 112 (2023)

The growing use of lasers increases the risk of accidental or intentional damage to human eyes and optical sensor systems. Current protection equipment is based on optical filters with fixed spectral transmission bands or shutter systems, but optical filters only work in predefined wavebands and shutter-systems are too slow to protect against pulsed laser radiation. Passive self-activated devices, in contrast, offer the potential for short response times with a simple design. Nonlinear optical materials with the capability to strongly attenuate intense laser beams are particularly interesting. In this work, we present our research on the protection capability of C60 and self-produced silver nanoparticles as functional materials in a real application case. A camera with CMOS sensor can be completely protected from being damaged up to a maximum measured input energy of 2 mJ. Therefore, it has been demonstrated that optical limiting materials can be suitable in laser protection applications.

Ultrashort pulsed laser welding of dissimilar materials has become an attractive alternative technique to commonly used adhesive bonding for joining optics to metal mounts / assemblies in the manufacturing of optical and laser systems. The laser welding process relies on very high peak intensities from an ultrashort (ps/fs) pulsed laser beam which is tightly focused through a transmissive optical component, providing a focal spot in the vicinity of the optic-metal interface. Nonlinear multi photon absorption in the optic and linear absorption in the metal results in a highly confined plasma, surrounded by a localised melt zone that rapidly cools to form a bond. For successful welding, the laser pulse repetition rate must be sufficiently high to provide thermal accumulation, to ensure a localised melt volume (the heat-affected zone, HAZ) surrounding the small plasma. The size of this HAZ is dependent on the laser processing parameters and material combinations used during the process and is typically on the ~100μm scale. As the laser spot translates across the material, this highly localised melt/plasma zone rapidly solidifies behind the beam and forms a strong bond (micro weld) between the two surfaces.

We present our recent results from the ultrashort pulsed laser welding of Er,Yb:Phosphate laser glass and Nd:YAG laser crystals to copper for a combination of mechanical mounting and thermal management (heatsinking) applications in laser systems. Er,Yb:Phosphate glass is a well-known and commonly used active medium for lasers emitting in the ‘eye-safe’ spectral range from 1.5-1.6μm. Nd:YAG is the most popular lasing media for solid state lasers typically emitting light in the 1.064μm spectral range. We investigate the influence of laser processing parameters such as pulse duration and repetition rate on the resultant welds. Analysis of welded parts includes shear strength and accelerated lifetime tests.

Long wavelength InGaN/GaN quantum well (QW) light emitting diodes (LEDs) are essential components of solid-state lighting and displays. However, efficiency of these devices is inferior to that of blue LEDs. To a large degree, this occurs because equilibration of injected holes between multiple QWs of the active region is hindered by the high GaN quantum confinement and polarization barriers. This drawback could be overcome by lateral hole injection via semipolar QWs present on facets of V-defects that form at threading dislocations in polar GaN-based structures. In this work we have tested the viability of this injection mechanism and studied its properties by time-resolved and near-field spectroscopy techniques on multiple QW devices. We have found that indeed the hole injection via the V-defects does take place, the mechanism is fast, and the hole spread from the V-defect is substantial making this type of injection feasible for efficient long wavelength GaN LEDs.

Estimating the time of fingerprint deposition at a crime scene provides clues to the duration since the crime. We have previously shown that when the fingerprint was continuously irradiated with an ultraviolet laser, the intensity of fluorescence presented just after impression decreases, and the other fluorescence appeared at longer wavelengths and its intensity became stronger over time. In this study, the possibility of estimating the elapsed time was examined using the aging function originally proposed by the research group of University of Amsterdam. Fingerprints were stored for up to two years, and fluorescence spectra were periodically measured by excitation with the ultraviolet laser, to calculate the aging rate of the aging function as dividing the former fluorescence intensity by the latter one. As a result, the aging rate were shown to increase in the order of greater UV influence and higher humidity. Furthermore, aged fingerprints were visualized using a fluorescence peak that increases with time.