Abstracts Track 2024

Area 1 - Optics
Area 2 - Photonics

Area 1 - Optics

Nr: 10
Title:

Approaching the Thin-Film Absorption Limit with Monolayer Semiconductor Superlattices
Authors:

Sara Elrafey, Lennart M. Heijnen, Rasmus H. Godiksen and Alberto G. Curto
Abstract: Strongly absorbing materials are needed for nanoscale optoelectronics and strong light-matter coupling applications. The absorption limit of ultrathin films is 50%. The strong excitonic resonance in monolayer WS2 provides 16% absorptance. Here we demonstrate that monolayer WS2 superlattices provide higher absorption while preserving the exciton emission. We show that an artificial superlattice structure increases absorptance to 31%. Our results put forward superlattices as a platform for developing novel two-dimensional semiconductor devices.
Nr: 11
Title:

Plasmonics for Manipulating Light in Optoelectronics Devices
Authors:

Mohamed Abdelkhalik, Toni López, Thomas-Jan van Raaij, Aleksandr Vaskin, Anton Matthijs Berghuis, Xavier Garcia-Santiago and Jaime Gómez Rivas
Abstract: Controlling the optical enlivenment of optoelectronics devices such as micro-LEDs is essential to enhance its performance via structuring the device at the scale of the wavelength of light. Micro-Light emitting diodes (µLEDs) are attracting a broad interest because of their low power consumption, compact size and high brightness. However, µLEDs suffer from low outcoupling efficiency due to the high refractive index mismatch between air and the semiconductor. Recent progress in nanophotonics has led to the demonstration that metasurfaces integrated with emitters can provide an opportunity for tailoring the emission. Importantly, the emission pattern can be tailored to enhance the light outcoupling by the interplay of resonant modes of the metasurface. This tailoring relies on the near-field coupling of the emitters and the resonant nanostructures forming the metasurface. In this contribution, we describe a system of aluminum (Al) nanoparticles in a periodic array defining metasurfaces, which are fabricated onto a GaN/sapphire wafer to tailor the emission of InGaN quantum wells (QWs). We designed and fabricated arrays of Al nanodisks with a resonant response at 570 nm (green emission). We have measured the photoluminescence emission of InGaN QWs by varying the lattice constant of the Al arrays. Near-field coupling of the QWs with the arrays leads to the re-shaping of the far-field emission and the beaming of the generated light into a narrow solid angle, which is relevant for several applications. We have measured the angular emission pattern of the metasurfaces for different lattice constants using back-focal plane imaging in a Fourier microscope. A high outcoupling enhancement factor of 5.2 is obtained within a narrow solid angle with a simple square array of Al nanoparticles. In addition, we have performed simulations based on the reciprocity principle and achieved a very good agreement with the experimental data.
Nr: 15
Title:

Conical Diffraction Vector Beams in Linear and Nonlinear Regime
Authors:

Marsal Nicolas, Waqar Iqbal, Yulija Shiposh, Anton Kohutych, Alexander Grabar and Germano Montemezzani
Abstract: Conical diffraction (CD) refers to a linear optical phenomenon that produces specific types of vector beams with spatially dependent polarizations. This phenomenon occurs when a focused beam travels along one of the optic axes of a biaxial crystal [1]. Even when an input wave is uniformly polarized, CD creates a double circular ring with spatially varying linear polarization in a fashion that any two diametrically opposite points on the rings always possess orthogonal linear polarization. [1,2]. CD beams have demonstrated compelling capabilities and potential across various applications in contemporary photonics. These applications include but are not limited to optical trapping, free-space optical communication, super-resolution imaging, polarimetry, among others [2]. A significant advancement in this domain involves investigating cascaded configurations, wherein two or more crystals are arranged sequentially with their optical axes aligned. This configuration leads to an increase in the number of rings by a factor of 2N−1, where N represents the number of crystals in the cascade. More complex setups involving series of biaxial crystals and intermediary adjustments in wavevector space can yield non-circular vector structures [3]. Also, in the framework of polarization holography, such vector beams could provide efficient recording that could be achieved with any combination of the input polarizations of the object and reference waves. Our contribution is divided in two parts and related to the previous topics: (i) exploring how the circular rings produced by cascaded configurations can be altered by conducting specific manipulations between the individual biaxial crystals and (ii) exploring the combination of CD with the recording of holograms in a nonlinear photorefractive material, all the processes of linear CD and nonlinear storage within the same medium. Firstly, we will present our numerical and experimental work based on CD in a cascaded configuration leading to non-circular structures with either concave or convex characteristics and complex polarization distributions. This can be achieved through intermediary manipulations in wave-vector space by means of two crossed cylindrical lenses positioned in a peculiar manner. Note that these manipulations not only impact the shape, intensity, and polarization distribution of the CD structures but also influence the associated fractional optical angular momentum values. All the different aspects have been investigated in detail. Secondly, in a more classical experiment involving only one biaxial SPS crystal, we explore the combination of CD with the recording and storage of holograms in a nonlinear photorefractive material. We demonstrate that efficient holograms can be recorded when the object wave undergoes conical diffraction, regardless of the combination of polarizations between the object and reference waves. [1]. M. V. Berry, J. Opt. A: Pure Appl. Opt. 6, 289–300 (2004). [2]. A. Turpin, Y. V. Loiko, T. K. Kalkandjiev and J. Mompart, Laser Photonics Rev. 10, 750 (2016). [3]. M. W. Iqbal, N. Marsal, and G. Montemezzani, Sci. Rep. 12, 7317 (2022)
Nr: 23
Title:

Reversible Environmental Effects on the Spontaneous and Stimulated Emission Properties of Lead Halide Perovskites Films
Authors:

Marco Anni, Stefania Milanese, Giovanni Morello and Maria Luisa De Giorgi
Abstract: Lead halide perovskites are receiving huge attention due to their capability to combine easy deposition and processing with excellent optical and electrical properties, allowing their potential applications to solar cells, LEDs, photodetectors and lasers. However, these materials typically show poor environmental stability, with irreversible degradation when exposed to light, heat, and air environment. Rather interestingly, recent studies evidenced that reversible effects of the interaction with the atmosphere are possible, resulting in modulation of the electrical conductivity or of the photoluminescence (PL) intensity, thus opening the way to possible application to electrical or optical gas sensors. In this work we report on a detailed investigation of the environmental effects on the spontaneous and stimulated emission properties of fully inorganic CsPbBr3 nanocrystals thin films, with nanocrystals synthesized by hot-injection and co-precipitation methods. The NCs realized by co-precipitation show a clear PL intensity increase in air, with respect to vacuum, due to revesible defect passivation, that modifies both the number of emitting nanocrystals (static effect) and the exciton non-radiative relaxation pathways (dynamic effects). On the contrary, in nanocrystals realized by hot-injection the lower surface defects density results in a reverible PL quenching in air, ascribed to moisture induced solvation of the nanocrystals surface. We also demonstrate that these NCs show Amplified Spontaneous Emission (ASE) under pulsed pumping in the nanosecond regime, with a low threshold both in vacuum and in air. In addition we report, for the first time, the evidence of reversible modulation of the Amplified Spontaneous Emission (ASE) intensity, showing a reversible quenching in air about 6.5 times stronger than the spontaneous emission one. This last result evidence the stronger environmental sensitivity of ASE and could be useful for future perovskite applications to optical gas sensors. Finally, the air sensitivity of four different NCs with different kind of surface ligands is explored, evidencing a strong ligand dependence of the environmental effects and the possibility to tune it by acting on the ligand choice.
Nr: 67
Title:

Advancements in Raman Probe Development and Spectra Preprocessing Evaluation for Identifying Large Hydroxyapatite: Based Samples
Authors:

Sofia Pessanha, Paulo A. Ribeiro and Valentina Vassilenko
Abstract: This paper addresses the challenge presented by the dimensions of certain objects that defy the limitations of microscope-coupled Raman spectrometers, rendering sample collection impractical due to their intrinsic value or nature. Specifically, materials like hydroxyapatite-based substances utilized in artistic and ornamental carvings, such as bone or ivory, fall into this problematic category. The primary focus of this study is to enhance analytical capabilities for large objects using a Raman microscope system. The research outlines an innovative approach involving a remote probe integrated with fiber optics, providing a detailed account of the design and performance aspects. It underscores the appropriateness of selected components in the analysis of nine objects sourced from private collectors. Results indicate that employing an 805 nm longpass dichroic mirror effectively directs the Near Infrared laser onto the samples, significantly mitigating the contribution of Rayleigh scattering to the spectrum. Additionally, various preprocessing methods for spectrum evaluation were explored to apply a chemometric approach for differentiating the studied artifacts, thereby contributing to a strategy for provenance recognition.
Nr: 6
Title:

TARDYS: A Laser-Inspired Technique to Unveil Dynamics in Complex Systems
Authors:

Andrés Aragoneses
Abstract: Revealing underlying regular behaviour in complex and chaotic systems is a current challenge. Determinism in chaos can be manifest in the form of temporal correlations or patterns in the dynamics of a measurable variable. These temporal dynamical structures are sometimes related to hidden global symmetries. Here we study the output intensity of a semiconductor laser with external optical feedback, and identify the temporal (approximate) symmetries in its dynamics. Based on these symmetries we define the Temporal And Reversible DYnamical Symmetry (TARDYS) quantifiers to evaluate the relevance of specific temporal correlations in a time series. We show that these symmetries are also present in other complex dynamical systems, allowing us extrapolate one system’s symmetries to characterize and distinguish chaotic regimes in other dynamical systems. These symmetries, intrinsic of the dynamics of the laser with feedback, can also be used as indicators in forecasting regular-to-chaos transitions in mathematical iterative maps. We envision that this can be a useful tool in experimental data, as it can extract key features of the deterministic laws that govern the dynamics of a system despite the lack of knowledge of those specific quantitative descriptions.

Area 2 - Photonics

Nr: 35
Title:

A Reflective Fiber Optic Probe Towards an In Vivo Biosensor for Pharmacokinetic Studies in the Brain: Design and Detection
Authors:

Pragnya Satapathy, Cátia Santa, Soohyun Park, Jakub Dostalek, Bastian Hengerer and Khulan Sergelen
Abstract: Abstract: Continuous monitoring of small drug molecules in the brain is complicated, at the same time, it is of fundamental importance to know the physiological activity, kinetics, and stability of the drug molecules for medicinal applications. The required sensor should address many parameters that are vital for in vivo sensing. The drug should be monitored selectively, quantitatively, reversibly, robustly, and continuously at the appropriate physiological ranges1. Owing to the required spatial and temporal resolutions, we have addressed and established our research to develop a reflective fiber optic probe sensor, which can be inserted in the targeted areas inside the brain of behaving rodents. Fiber optic surface plasmon resonance (FO-SPR) based biosensors are quite successful tools for biomarker detection due to their user-friendliness and adaptability to other sensitivity enhancement mechanisms2. In the case of our sensor, we have fabricated the FO-SPR probes with the smallest area of sensing and having higher sensitivity reported3. Aptamers are employed for selective sensing, and they are already tested for their affinity and reversible sensing in physiological conditions. The FO-SPR is cladded with a biocompatible, assay-integrated mechanical responsive material, which will further enhance the sensitivity, and has the capability for real-time optical in vivo sensing. REFERENCES 1. Shaver A, et. al. Optimization of Vancomycin Aptamer Sequence Length Increases the Sensitivity of Electrochemical, Aptamer-Based Sensors In Vivo. ACS Sens. 2022 doi: 10.1021/acssensors.2c01910 2. Dillen A, et al. A versatile One-Step Competitive Fiber Optic Surface Plasmon Resonance Bioassay Enabled by DNA Nanotechnology. ACS Sens. 2021 doi: 10.1021/acssensors.1c01447 3. Bello V, et. al. Design and Implementation of a dual-region self-referencing Fiber-Optic Surface Plasmon Resonance Biosensors. ACS Sens. 2022 doi: 10.1021/acssensors.2c01362