NANOSENSORS’ Post

Nonlinear scattering losses are losses in optical fibers that occur when high optical power levels cause uneven attenuation of light. These losses are a result of the transfer of optical power between different modes at different frequencies, either in the forward or backward direction. Read More: https://lnkd.in/dmeDBvSd #Insights #Photonics #Industry #Article #Fiber #Optics

Compact terahertz harmonic generation in the Reststrahlenband using a graphene-embedded metallic split ring resonator array Harmonic generation is a result of a strong non-linear interaction between light and matter. It is a key technology for optics, as it allows the conversion of optical signals to higher frequencies. Owing to its intrinsically large and electrically tunable non-linear optical response, graphene has been used for high harmonic generation but, until now, only at frequencies < 2 THz, and with high-power ultrafast table-top lasers or accelerator-based structures. Here, we demonstrate third harmonic generation at 9.63 THz by optically pumping single-layer graphene, coupled to a circular split ring resonator (CSRR) array, with a 3.21 THz frequency quantum cascade laser (QCL). Combined with the high graphene nonlinearity, the mode confinement provided by the optically-pumped CSRR enhances the pump power density as well as that at the third harmonic, permitting harmonic generation. This approach enables potential access to a frequency range (6-12 THz) where compact sources remain difficult to obtain, owing to the Reststrahlenband of typical III-V semiconductors. https://lnkd.in/d-5iFX7M

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

Can light polarization be manipulated with materials a thousand times thinner than its wavelength? This breakthrough could be the key to next-generation optoelectronic devices. Traditionally, polarization control relies on bulky waveplates made from optically anisotropic crystals, with thicknesses comparable to the light's wavelength. In the terahertz (THz) range, these waveplates are typically 100 microns to 1 mm thick—far from ideal for integration with modern optoelectronics. In a recent study at the MeV-UED instrument at the Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, researchers have demonstrated a significant birefringent response in the nanoscale anisotropic semimetal WTe2 at THz frequencies. Astonishingly, they achieved tunable THz polarization using just a 50-nanometer thick layer of WTe2—an ultrathin broadband waveplate, about one-thousandth the thickness of a wavelength, capable of producing quasi-circularly polarized THz light. The polarization was characterized using a novel near-field approach, where the time-dependent deflection of diffracted femtosecond electrons was measured in the modulated THz electromagnetic field. This discovery paves the way for the use of anisotropic semimetals as naturally occurring waveplates in integrated, on-chip 2D optoelectronic devices. Additionally, it introduces a new method for directly characterizing the THz optical properties of nanoscale materials in the near field, especially for samples smaller than the diffraction limit. Congratulations to the team on this remarkable achievement! The future of optoelectronics is brighter than ever! #Research #Science #Photonics #Electrondiffraction #THzlight https://lnkd.in/dT65DxkY

Superconducting nanowire detectors are important for secure quantum communication and computation. We now have a detailed model that can model several important features of SNSPD from conventional superconductors and the special (unconventional) superconductors. We are sure that the time has come for SNSPDs that operate at significantly higher temperatures. For more information and results, please access the article here https://lnkd.in/g-z4WWaP #SNSPD #superconductivity #singlephoton #quantum technologies Souvik Haldar Arun Sehrawat

Well worth reading: New EURAMET Case Study - Improving the useability of high accuracy optical clocks It can be found on EURAMET - The European Association of National Metrology Institutes’ website: ⏱️ https://zurl.co/0X77 “TOPTICA helped develop an optical clock prototype using the compact ion trap created by the CC4C project. This clock prioritises both useability and portability for end users, fitting inside a 19” rack format while limiting relative uncertainty and frequency instabilities to the 10-17 range. The clock therefore outperforms the current best microwave clocks by about an order of magnitude.” “The ion trap, as well as knowledge transfer from PTB, has allowed TOPTICA to extend the prototype further into a commercial system.” We're excited to be leading the way in making high-precision time measurement more accessible than ever before and thank PTB (Physikalisch-Technische Bundesanstalt) for their support. #OpticalClocks #Photonics #TimeMeasurement

Excitons are bound quasi-particles formed due to the coulomb interacting forces between Electrons and Holes of a semiconductor which can be excited by shining optical polarisation(optic pulse) in a coherent scheme inside a direct band-gap semiconductors like GaAs and InGaAs . In this paper review we talk about the transmission , absorption, spectroscopy techniques and quantum mechanical aspects used to characterise excitons to understand photoluminescence in a quantum-well or wire. Excitons can act as quantum degenerate state having application in quantum computing and ultrafast information processing which can be the cutting-edge technology of the century. It is crucial to understand the Exciton population and behaviour to control devices such as Lasers,LED's , Solar Cells . This quantum dot technology are applied QLED TV's, Efficient light sources , Nano-energy storage systems . Imaging and Diagnostics in Healthcare and Drug-delivery in Biomedicine play a fore front and real time application of these quasi-particles. #quantumwells #LatticePhysics #Exciton #photoluminescence #Semiconductor #Nanophysics #Interband #spectroscopy #Luminescensespectroscopy #QuasiparticleSpectroscopy.

I am delighted to share that follow up work on our Ta2NiSe5 parametric amplification results is now published in Nature Communications. This paper is also meaningful to me in a sense that it's my first work as a corresponding author. Huge congratulations to the brilliant Marios Michael from Harvard University for the hard work, and for the friendship that developed while working on this over the last 4 years. Also, big thanks to Simone Latini (currently at DTU - Technical University of Denmark) and Lukas Windgätter for the detailed DFT calculation, and Yuan Zhang for the time-resolved terahertz (THz) spectroscopy measurement. Shout out to the PIs: Richard Averitt from UC San Diego, Eugene Demler from ETH Zürich, and Angel Rubio from MPI for the Structure and Dynamics of Matter who were kind enough to allow me and Marios assume the leadership roles in this long and arduous effort. As the name suggests, photonic time crystals are analogous to photonic crystals. However, photonic crystals exhibit periodicity of the dielectric function in space, whereas photonic time crystals are periodic in time. In our work published in Nature Materials in January, we demonstrated light-induced parametric amplification at terahertz frequencies that contained information about the exciton condensate of Ta2NiSe5. It was also explained that this amplification was mediated by squeezing oscillations of infrared-active phonons coupled to the condensate. In this current paper, we showed that upon the optical excitation, the phonon squeezing oscillation initiates dynamics which turn Ta2NiSe5 into a photonic time crystal, leading to exciting prospects of non-resonant periodic modulation of quantum materials properties as well as realistic technological application of phonon-based THz photon sources. Here is the link to the photonic time crystal paper: https://lnkd.in/g9pDEJBG  As a recap, link to the parametric amplification paper: https://lnkd.in/gP6R-jud #photonic_time_crystal #terahertz_parametric_amplification #phonon_squeezing #nonlinear_optics

What can one learn from torturing a 2D Semiconductor?🤔 The photons with zero momentum can only initialize direct bandgap transitions, hence, conventional spectroscopy often ignores the rest of the band structure. Most excitons residing in other parts of the band structure remain 😶🌫️ invisible (dark) despite their significant technological importance. We realized that one can study dark excitons by stretching these crystals. In our latest research in Nature Communications 📝, we've developed a straining technique to "fingerprint" and "brighten" these elusive species. We show that mechanical stretching: ✔️Drastically changes the band structure ✔️Transforms the energy hierarchy of excitons ✔️ Tunes the brightness of excitons. Using these insights, we discovered dark excitons from different points in the momentum space of WSe₂ and WS₂ monolayers, controlled their coupling and hybridization, and achieved large energy tuning of localized quantum emitters. You can read more about our work here: 🔗 https://lnkd.in/dkPEHz4u Looking ahead: We are excited to explore the potential of our technique to break the symmetry of excitons, manipulate valley dynamics, and engineer exciton transport. The future seems bright as we continue tuning the "strain knob". Thank you, Denis Yagodkin, for being an equal partner in the journey. Especial shoutout to our collaborators Roberto Rosati, Joakim Hagel, Ermin Malic, Christoph Schattauer, Sarah Tobisch, and Florian Libisch for their theory calculations; Pablo H. López and Sebastian Heeg for optimizing the straining technique; Douglas James Bock, Bianca Höfer, Jan Niklas Kirchhof, Kenneth Burfeindt for their assistance; Cornelius Gahl and Kirill Bolotin for supervision. #Semiconductors #2D #Research #Strain #TMDs #Excitons #Photonics

An Optical Parametric Amplifier (OPA) is a device used to amplify and generate coherent optical signals in a nonlinear process called parametric amplification. The specific wavelength and power of an OPA depend on the design, pump laser, and nonlinear crystal used. Read More: https://lnkd.in/dRujDxcM #Insights #Photonics #Industry #Article #Optics