NANOSENSORS’ Post

In recent years, emerging interfacial ferroelectricity (a spontaneous and switchable electric field in the material), or Sliding ferroelectricity or Moiré ferroelectricity, has been a key focus in van der Waals #2dmaterials. Our latest study uncovers how ferroelectricity in parallel-stacked 3R-MoS2 can be directly probed using various modalities of far-field #spectroscopy, even at room temperature. Contrary to conventional electrostatic perceptions, we demonstrate that while layer-hybridized excitons (electric dipoles formed by electron-hole pairs) with out-of-plane dipole moments remain decoupled from out-of-plane ferroelectric ordering, intralayer excitons with in-plane dipole orientation are sensitive to it. This sensitivity lets us optically read and electrically control multi-state polarization with non-volatile switching. Additionally, ultrafast Kerr ellipticity reveals a link between spin-valley dynamics and ferroelectric order. You can read about it here: https://lnkd.in/eYyTgcef Why is this significant? Most experimental studies have been confined to visualizing ferroelectricity and indirect measurements in basic bilayer units using near-field probes (see to know more- https://lnkd.in/efrBDRxv) or sensing layers at low temperatures- precluding practical applications. Our work, however, potentially paves the way for next-gen devices with both logic and storage capabilities in standard optoelectric setups. A visionary goal would be to engineer the optical response in TMDs by exploiting the ferroelectricity-induced interaction, which can be highly localized, non-volatile, and reconfigurable. Universität Rostock Alexander von Humboldt Foundation #2D #MoS2 #quantummaterials #spectroscopy #optoelectronics #optics #naturecommunications

The growing demand for high-performance quasi-optic components, including polarizers, phase shifters, and waveplates, is driving innovation in materials and design. Among these, THz polarizers play a critical role in enabling selective polarization control, a cornerstone of THz spectroscopy and imaging applications. In our recent study, published in Optical Materials, we focused on metallic wire grid (MWG) structures and achieved groundbreaking advancements in polarization performance. By simply reducing the pitch of gold wire grids, we: - Achieved a remarkable polarization efficiency of 94.3%! - Reached an extinction ratio of ~22.1 dB. - Enhanced anti-reflection properties, showcasing their multifunctionality! The work is available here: https://lnkd.in/dmJ-wSDa. These results position MWG structures as an optimal choice for THz polarizers, with unmatched efficiency over a broad frequency range of 0.2–2.5 THz. The durable, low-maintenance nature of these structures, combined with their exceptional performance, makes them highly promising for diverse THz applications. This work addresses a critical gap in the field, demonstrating how precise micron-scale adjustments to the array pitch can fine-tune polarization performance—setting a new benchmark for THz polarizers. We believe these findings will significantly impact the design and development of advanced THz devices and inspire further innovation in quasi-optic technologies. A heartfelt thanks to Prof. Anjan Barman and Prof. Rajib Kumar Mitra for their exceptional guidance and unwavering support throughout this interesting work. #THzTechnology #OpticalMaterials #Polarizers #AntiReflectionPerformance

Two dimensional (2D) halide perovskites demonstrate intriguing optical properties. Interestingly, there is intense discussion with significant disagreement about the fundamental origin of the various photoluminescence (PL) characteristics in 2D perovskites. We have investigated the dual emission and correlated photoresponse in a 2D perovskite. Dual emission characteristics are ascribed to the existence of free exciton and bound exciton. The dynamics of bound excitations was studied at room temperature and low temperature which reveals interesting photophysics. Our study sheds light on the emission properties of 2D perovskite, laying the foundation for the strategic design of different optoelectronics devices. Fins our latest article in Small. #perovskite #wiley #photoemission #iit https://lnkd.in/gDwCVrJx

We are thrilled to announce the publication of our collaborative work with Prof. Juergen Brugger's group at EPFL Switzerland in Nature Communications. This study tackled the critical challenge of low carrier mobility in 2D MoS2 transistors, a key hurdle for the advancement of beyond-silicon electronics. By introducing controlled tensile strain via grayscale nanotopography, an 8-fold increase in electron mobility was achieved. This breakthrough was supported by tip-enhanced Raman spectroscopy (TERS), which provided critical insights into strain distribution at the nanoscale. This work paves the way for high-performance 2D materials in future nanoelectronics. Find out more here: https://lnkd.in/eM7j38YV - with Berke Erbas, Juergen Brugger, Siiri Bienz, Renato Zenobi #2dmaterials #nanoelectronics #ramanspectroscopy

💡 Scientists working at #laser #spectroscopy have successfully employed Ekspla’s lasers for about three decades. Laser spectroscopy encompasses a diverse array of techniques tailored for investigating different properties of matter. Among these, time-resolved Photoluminescence Spectroscopy (TRPL) stands out as a contactless method for characterizing recombination and transport in solid materials. Measuring TRPL requires exciting luminescence from a sample with a pulsed light source and then measuring the subsequent decay in photoluminescence as a function of time. Most experiments excite the sample with a pulsed laser source and detect the PL with a photodiode, streak camera, or photomultiplier tube set up for upconversion or single-photon counting. The system response time, wavelength range and sensitivity vary widely for each configuration. It is possible to apply the general methodology of time-resolved photoluminescence for lifetime imaging of the charge carrier dynamics. Nonradiative surface recombination at the boundaries of a semiconductor device can be a major factor limiting the efficiency in light-emitting and laser #diodes (LEDs and LDs), photovoltaic cells, and photodetectors. Therefore, the effective lifetime is a crucial parameter to obtain solar cells with a high conversion ratio. #Photoluminescence #microscopy also is a powerful optical method for the study of crystal defects in #semiconductors and organometallic complexes, with important applications in the manufacturing process of nanostructures, optoelectronic devices and solar cell systems. #femtosecondlasers #picosecondlasers #nanosecondlasers #tunablewavelength

⚠️ New paper out 📝 Are you interested in innovative materials for reconfigurable photonic applications or frequency comb generation?   In our latest research, we studied the linear and nonlinear optical properties of phase-change GeSe(1-x)Te(x) thin films. Here some key highlights: 🔍 ·      🌟 Significant refractive index contrast between amorphous and crystalline phases ·      📉 Low optical losses at the telecom 1550 nm wavelength ·      🔥 Thermal stability ·      💡 Remarkable intrinsic nonlinearity   These properties of GeSe(1-x)Te(x) thin films make them promising for their use in next-generation photonic linear/nonlinear devices and applications in photonic computing.   A special thanks to my co-authors and colleagues: Martina Tomelleri, Lara Karam, Jean-Baptiste DORY, Christophe Licitra, Benoit Charbonnier, Jean-Baptiste Jager, Aurélien Coillet, Benoit Cluzel, and Pierre Noé.   Here the full article: 📘 https://lnkd.in/duukdy3z CEA-Leti - Laboratoire ICB - Université de Bourgogne #PCMs #photonics #activecomponents #lowloss #neuromorphic #nonlinear

【Centimeter-scale single-crystal hexagonal boron nitride freestanding thick films as high-performance VUV photodetectors】 Journal of Materials Science & Technology ( IF 11.2 ) Pub Date : 2024-09-07 , DOI: 10.1016/j.jmst.2024.08.026 Large-scale hexagonal boron nitride (h-BN) single crystals are highly desirable not only as the substrate or dielectric for van der Waals heterostructures, but also the promising candidates in optoelectronics, electronics, detectors, as well as recently boomed room-temperature single-photon sources. Here, we report the synthesis of centimeter-scale single-crystal h-BN films with hundreds of micrometer thickness via the metal flux method. The growth control along the out-of-plane and in-plane directions of h-BN crystals is realized by the adjustment of NiCr alloy composition, from which the limited solubility of N atoms can be promoted by high diffusion in molten reactants. This also benefits to forming a distinct interface between the synthesized h-BN crystals and the metal ingot, giving rise to an easy exfoliation of the large area high-quality thick films. Such h-BN crystals have been demonstrated as both self-powered flexible and rigid vacuum-ultraviolet photodetectors, allowing for efficient photodetection in terms of high responsivity, rapid response speed, and high operational temperature. A maximum photoresponsivity of 3.35 mA/W is achieved at a wavelength of 185 nm with an operational temperature spanning to 500 °C (and possibly beyond). The large-area freestanding h-BN single crystal described herein reveals great potential as a high-performance photodetector, and versatile platform for other superb electronic and optoelectronic devices. https://lnkd.in/eiMwMA89

Gallium nitride (GaN) vertical-cavity surface-emitting lasers (VCSELs) are semiconductor laser diodes with promising applications in various fields, including adaptive headlights, retinal scanning displays, point-of-care testing systems, and high-speed visible light communication systems. Their high efficiency and low manufacturing costs make them especially appealing for these applications. GaN-VCSELs are composed of two layers of special semiconductor mirrors, called distributed Bragg reflectors (DBRs), separated by active GaN-semiconductor layers, which form the optical resonant cavity, where laser light is generated. The length of this resonant cavity is crucial for controlling the target laser wavelength, called the resonance wavelength. #lasers #light #resonance #wavelength #communications https://lnkd.in/gNgkrAm8

In this dynamic industry, constant #innovation is at its core! Stumbled upon a great article on enhancing #FiberSensor sensitivity using an exceptional point (EP). The standout? The vital role of Fiber Bragg Grating #FBG - something we're already familiar with and utilising at Ensure 🚀👇 FBGs, integrated seamlessly into Ensure's ultra-narrow linewidth lasers #UNL play a pivotal role in our cutting-edge technology. These gratings act as precision markers, reflecting specific wavelengths with unparalleled accuracy. This unique ability ensures wavelength-stability✔️, reduces noise✔️, and heightens sensitivity✔️ in our lasers. Why does having a narrow linewidth matter? A narrow linewidth translates to a more focused and precise wavelength emission. This precision is crucial in fiber sensing applications, as it enhances the sensor's ability to detect subtle changes, delivering accurate and reliable results. Imagine, for instance, Pipeline Leak Detection powered by #UNLlaser in fiber sensing applications. With this technology, detecting the smallest anomalies in the pipeline becomes the difference between ❌ A potential undetected leak leading to environmental hazards, significant damage, and prolonged downtime vs. ✔️Accurate and timely identification of leaks, safeguarding the environment, preventing extensive damage & ensuring seamless operations. The narrow linewidth allows for precise monitoring, providing real-time insights and enhancing overall safety measures for critical infrastructure. 🛢️ The fusion of FBG technology with UNL lasers results in linewidths as narrow as 1~3 kHz, making our lasers a reliable cornerstone in DVS/DAS systems. #FiberOptics #FBGTechnology Article link: https://lnkd.in/evN3SFMD

Our latest paper published in Advanced Science today explores dark magnetic excitons in a 2D helical antiferromagnet, NiI2 (open access). We utilize photocurrent spectroscopy to reveal coherent many-body excitons that have only been seen in the past by optical absorbance in this material since selection rules forbid direct recombination, unlike some other 2D magnetic semiconductors that show strong photoluminescence. The photocurrent measurements in lateral and vertical devices confirm their ultra-narrow spectral width and a high degree of linear polarization. NiI2 is emerging as an interesting magnetic semiconductor with band-like transport and multi-ferroic phase transition down to the bilayer limit. The measurement is enabled by innovations in all-2D contact and encapsulation schemes (metal contacts don't work). Thus, this finding is a noteworthy advance in this field. Congratulations Dmitry Lebedev and Tyler Gish. https://lnkd.in/gsGD77MZ