This PDF file contains the front matter associated with SPIE Proceedings Volume 12888, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Tunable light sources gain considerable interest as key components in various spectroscopic systems, e.g. for gas or chemicals detection. A novel approach to employ new active materials for such sources is aimed by the TAGGED consortium and relies on the integration of electrically biased graphene membrane with electrostatically actuated membrane which will allow tuning of source wavelength in visible or IR range. In this work, preliminary results of optical characterization of electrically biased graphene chips are presented. Graphene was grown on a copper foil using chemical vapor deposition technique. After the growth it was transferred over the trenches of silicon chips. Fabricated chips contain several test structures for suspending the graphene membranes, and electrical contacts to the membranes for biasing. Presented results pave the way to fully integrated miniaturized opto-electric-mechanical tunable light sources.

We report on the spatial and temporal coherence of interlayer exciton ensembles as photoexcited in MoSe₂/WSe₂ heterostructures and characterized by point-inversion Michelson-Morley interferometry. Below 10 K, the measured spatial coherence length of the interlayer excitons reaches values equivalent to the lateral expansion of the exciton ensembles. In this regime, the light emission of the excitons turns out to be homogeneously broadened in energy with a high temporal coherence. At higher temperatures, both the spatial and temporal coherence lengths decrease, most likely because of thermal processes. The presented findings point towards a spatially extended, coherent many-body state of interlayer excitons at low temperature.

Laser-induced graphene (LIG) has drawn immense interest among researchers worldwide since its development in 2015. The laser writing strategy used to synthesize LIG is particularly advantageous, as it enables the direct patterning of graphene with micron-sized features. There have been many attempts to reduce the feature size of LIG in recent years, however, the studies have shown wide variations in the methods and findings. As such, this work presents a rigorous study on the irradiation of polyimide via an ultraviolet (355-nm) laser to realize micron-scale, high-quality LIG. Our work shows that there is often a tradeoff between micron-scale features and high-quality material, as the tightly focused beams that are demanded for small features are predisposed to ablation of the material. This work investigates such LIG synthesis by correlating the characteristics of the material, via scanning electron microscopy and Raman spectroscopy, to the optical fluence incident on the polyimide substrate, providing a measure of applied optical energy per unit area. The findings reveal that—given suitable attention to the optical fluence—high-quality LIG with Raman 2D-to-G peak height ratios approaching 0.7 can be synthesized with feature sizes down to 18 ± 2 μm. Furthermore, optical fluences between 40 to 50 J/cm² produced the optimal LIG characteristics, as such optical fluences promote graphenization while minimizing ablation. The authors hope the findings of this study provide a foundation for the use of LIG in future integrated technologies.

We report enhanced nonlinear optics in integrated nanophotonic chips through the use of integrated with 2D graphene oxide (GO) films. We investigate nanophotonic platforms including silicon, silicon nitride and high index doped silica. Due to the high Kerr nonlinearity of GO films and low nonlinear absorption we observe significant enhancement of third-order nonlinear processes. In particular, in silicon we observe an increase in both the Kerr nonlinearity and nonlinear figure of merit of up to 20 times. These results show the strong capability of GO films for improving the nonlinear optical performance of integrated photonic devices.

In this paper, we introduce a novel nanophotonic multilayer structure comprising graphene, polymer, and PbSe to modulate electromagnetic waves within mid-IR atmospheric windows. Through finite-difference time-domain analysis and micro-genetic algorithms, we achieve a tunable perfect absorber, with optimized control over absorption and emission in the mid-IR range. By adjusting the graphene's chemical potential from 0 eV to 1 eV, we demonstrate a dynamic shift in peak absorptance from 4 μm to 4.22 μm and maintain high absorption at incident angles up to 52 degrees, marking significant advancements in mid-IR radiation management.

Atomically thin two-dimensional transition metal dichalcogenides have garnered tremendous attention from researchers owing to their distinct electrical and optical properties. Improving the photoluminescence of these two-dimensional atomic semiconductors is imperative for their seamless integration into photonic and optoelectronic devices. Concurrently, the advent of two-dimensional materials such as graphene and transition metal dichalcogenides has ushered in opportunities within the realm of valleytronics. Valleytronics endeavors to exploit valley degrees of freedom for information processing, mirroring the principles of spin-based spintronics and charge-based electronics. Notably, these materials demonstrate a unique spin-valley locking mechanism, thereby enabling modulation of the electronic valley degree of freedom through light. In the present study, we fabricated cost-effective nanocone structures via colloidal lithography and subsequently integrated them with a monolayer of WSe₂. Through this methodology, we amplified both the photoluminescence and valley polarization enhancement of the WSe₂ monolayer by harnessing plasmonic hotspots.

The Nb₂CT_x MXene was synthesized and optically characterized utilizing Photo-induced Force Microscopy (PiFM), a nanoscale imaging technique combining AFM topography mapping and infrared spectroscopy. In both bulk and single/few layered MXene flakes, absorption peaks were observed in the 770 - 1860 cm^-1 investigated range. The local IR spectra is compared with broader Fourier-transform infrared (FTIR) and Raman spectroscopy to analyse the material composition. Our findings notably highlight the presence of a characteristic peaks related to surface functional group in both far-field and near-field measurement. The spectra also indicate a strong contribution of niobium oxide in the synthetized material.

Ternary 2D materials, potential candidates for next generation technology showcase boundless opportunities by providing greater degree of freedom through integration of various elements with compositional variety. GeSeTe is a chalcogenide compound with great environmental stability and phase changing feature, making it eligible for many advanced photonics and optoelectronics devices such as ultrafast optical switching, optical modulator, parametric amplifier to name some. In this work, Ternary 2D GeSeTe nanosheets were synthesized employing facile LPE method, followed by extensive characterization have been conducted to comprehend various features of the prepared nanosheets such as thickness, optical absorption etc. Then, the NLO responses of the prepared nanosheets under NIR regime have been realized employing Zscan methods. The obtained nonlinear absorption coefficient varies from -73 ~ -4.5 cm/GW and -220 ~ -35 cm/GW at 1062 nm and 1560 nm wavelengths respectively indicating superior SA characteristics of GeSeTe nanosheets. The sample nanosheets switched its nonlinear absorption from SA to RSA with increased input intensity enabling potential opportunities for GeSeTe in optical limiting devices. Furthermore, the nonlinear refraction n₂ was recorded to be -9.5×10^{- 4} cm²/GW and -5×10^-4 cm²/GW at 1062 nm and 1560 nm respectively. To the authors' best knowledge, it is the very first time the NLO responses of GeSeTe nanosheets have been investigated and the achieved responses confirms the superior NLO features of GeSeTe that could be widely utilized in various photonics and optoelectronics devices.

Modern optoelectronic technologies rely heavily on UV photodetectors, which transform UV light stimuli into electrical signals and are used to measure UV radiation levels useful in military communication, medicine and biology. In this work, we report a novel approach to mitigate dark current in Gr-GaS heterojunction by utilizing van der Waals contacted Au electrodes. The all van der Waals photodetector shows self-powered characteristics with rectification ratio of ~10², sub femto ampere dark currents and excellent photo response properties under illumination at 375nm. With detection ability of sub microwatt per square centimeter light of 375 nm at zero bias voltage, the device shows a self-powered responsivity of 16.21mA/W and specific detectivity of 2.12X10¹² Jones with appreciable response times (rise/ fall) of 201.99ms/220.44ms with a linear dynamic range of 53.15dB. Such high-performance Gr-GaS-Au all van der Waals UV photodetector presented in this work is comparable to previously reported results, suggesting that it has great potential for UV-A band detection for weak light signals.

Due to the recent development of detection technology, there is an increasing demand for coating technology that has electromagnetic (EM) wave absorption/reflection characteristics for multi-band including S-band in addition to the existing X-band single wavelength absorption characteristics. In this work, a promising electromagnetic wave absorption and shielding material, MXene/metal oxide composite, was successfully designed and developed. The excellent electromagnetic wave absorption and shielding performance of the composite materials contribute to the synergistic effect of the MXene and the metal oxide, whereby the dielectric properties and electromagnetic wave loss can be easily controlled to obtain appropriate impedance matching conditions and excellent electromagnetic wave dissipation ability.

Transition metal dichalcogenides (TMDs) are widely utilized in spintronic and optoelectronic technologies due to their two-dimensional nature. In recent times, there has been a notable surge of interest in transition-metal disulfides, specifically molybdenum disulfide (MoS₂) and tungsten disulfide (WS₂), as exceptional materials for investigating fundamental physics in the realm of two-dimensional materials. The synthesis of Mo_xW_(1−x)S₂ alloys through experimental techniques has played a pivotal role in harnessing the unique properties of both MoS₂ and WS₂. Notably, trilayer TMDs exhibit properties such as tunable bandgap, higher exciton binding energy, and interlayer interaction, all of which contribute to the emergence of novel optical phenomena, including new optical modes and excitonic resonances. In this study, we investigate the potential of trilayer Mo_xW_(1−x)S₂ alloys using first-principle computational techniques. The analysis showed an indirect bandgap that ranged from approximately 1.34 to 1.39eV as the composition of the alloy varied from 74% Mo to 33% Mo. This tunability of the bandgap allows for precise control over the energy levels at which electronic transitions occur, enabling the material to adapt to specific device requirements. With an increasing percentage of tungsten (W) in the alloy, there was a pronounced peak shift in the out-of-plane absorption spectrum. The peak wavelength shifted from 1.95eV to 1.70eV, indicating that the material’s absorption properties could be tailored by adjusting the alloy composition. These findings open up possibilities for designing TMD-based photodetectors capable of detecting a wide range of light wavelengths.