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Maturation of the Meniscal Collagen Structure Revealed by Polarization-Resolved and Directional Second Harmonic Generation Microscopy
摘要： We report polarization-resolved Second Harmonic Generation (p-SHG) and directional SHG (forward and backward, F/B) measurements of equine foetal and adult collagen in meniscus, over large field-of-views using sample-scanning. Large differences of collagen structure and fibril orientation with maturation are revealed, validating the potential for this novel methodology to track such changes in meniscal structure. The foetal menisci had a non-organized and more random collagen fibrillar structure when compared with adult using P-SHG. For the latter, clusters of homogeneous fibril orientation (inter-fibrillar areas) were revealed, separated by thick fibers. F/B SHG showed numerous different features in adults notably, in thick fibers compared to interfibrillar areas, unlike foetal menisci that showed similar patterns for both directions. This work confirms previous studies and improves the understanding of meniscal collagen structure and its maturation, and makes f/B and p-SHG good candidates for future studies aiming at revealing structural modifications to meniscus due to pathologies.
关键词： Second Harmonic Generation,meniscus,directional SHG,polarization-resolved,collagen
更新于2025-09-23 15:21:01
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Temporal Evolution of Polarization Resolved Laser-Induced Breakdown Spectroscopy of Cu
摘要： Polarization-resolved laser-induced breakdown spectroscopy based on a temporal investigation of polarized Cu plasma emission is presented by a gated detector with a width of 10 ns and a delay time range of 10 ns–2 μs. Polarization-resolved spectra show that the delay time plays a crucial role in plasma polarization for both continuum and discrete emissions. The polarization degree of continuum emission is shown to be stronger than the polarization degree of discrete emissions at delay times less than 500 ns, while this trend is inverse in a delay time range of 750 ns–1 μs. The mechanism for polarized continuum emission is proposed to have dynamic polarizability of a core, while the polarized discrete emission is driven by the interaction of the plasma with the surrounding environment. The latter may lead either to a deviation of plasma from local thermodynamic equilibrium or generation of self-magnetic fields.
关键词： Polarization-resolved laser-induced breakdown spectroscopy,Polarization,Laser-induced breakdown spectroscopy,Local temperature equilibrium,Self-generated magnetic field
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Polarization-Resolved High Harmonic Spectroscopy of Interlocked Attosecond Bursts
摘要： High-harmonic spectroscopy is an important tool for investigation of nonlinear atom-laser interaction. Polarization-resolved high harmonic spectroscopy is becoming a promising method for exploring chiral quantities, in particular as numerous techniques have been demonstrated experimentally for generating bright and applicable high-order harmonics with highly helical polarization. In this context, a simple direct mapping (ideally, analytical formula) between the harmonics polarization and time-domain description of the HHG process would be very useful. Here, we present an analytic mapping between ellipticities of the high harmonics and variables of an interlocked pair of attosecond pulse trains - relative emission directions, relative delay, and their ellipticities – in a new scheme for generation of bright helically polarized high harmonics. In this scheme, HHG is driven by a two-color pulse, a fundamental frequency and its second harmonic, where the two colors are slightly elliptically polarized with opposite helicity and perpendicular ellipse major axes. In the time domain, the HHG emission consists of a pair of nearly linearly polarized attosecond pulse trains (APTs), yet with very different polarization axes. The ellipticities of the harmonics vary from linear to circular by tweaking the ellipticity of the pump. We discovered that the underlying mechanism for this ultra-sensitive polarization knob is dominantly induced by phase shifts between the pair of interlocked APTs. The ellipticity of the attosecond bursts and their relative emission angles play a secondary, yet still easily measured, role. Obtaining an analytic formula for the ellipticities of the high harmonics as a function of the APTs variables allow us to probe the APTs by ellipticity-resolved high harmonic spectroscopy. We demonstrate this approach experimentally.
关键词： High-harmonic spectroscopy,attosecond pulse trains,helical polarization,polarization-resolved,two-color pulse
更新于2025-09-12 10:27:22
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Polarimetric Three-Dimensional Topological Insulators/Organics Thin Film Heterojunction Photodetectors
摘要： As a state of quantum matter with insulating bulk and gapless surface states, topological insulators (TIs) have huge potential in optoelectronic devices. On the other hand, polarization resolution photoelectric devices based on anisotropic materials have overwhelming advantages in practical applications. In this work, the 3D TIs Bi2Te3/organics thin film heterojunction polarimetric photodetectors with high anisotropic mobility ratio, fast response time, high responsivity, and EQE in broadband spectra are presented. At first, the maximum anisotropic mobility ratio of the Bi2Te3/organics thin film can reach 2.56, which proves that Bi2Te3 can serve as a sensitive material for manufacturing polarization photoelectric devices. Moreover, it is found that the device can exhibit a broad bandwidth and ultrahigh response photocurrent from visible to middle wave infrared spectra (405?3500 nm). The highest responsivity (Ri) of the device can still reach 1.93 AW?1 at 3500 nm. In addition, the ultrahigh external quantum efficiency is 4534% with a fast response time (1.42 ms). Excellent properties mentioned above indicate that TIs/organics heterojunction devices are suitable for manufacturing high-performance photoelectric devices in infrared region.
关键词： polarization resolved,inorganics/organics heterojunction,photodetector,Bi2Te3 thin film,MWIR photodetectors
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Impact of Strain on the Second-Harmonic Generation in Transition Metal Dichalcogenide Monolayers
摘要： Second-harmonic generation (SHG) is a powerful measurement technique to analyse the symmetry properties of crystals. Mechanical strain can reduce the symmetry of a crystal and even weak strain can have an immense impact on the SHG intensity along different polarization directions [1]. The impact of strain on the SHG can be modelled with a second-order nonlinear photoelastic tensor [2,3]. We find that the photoelastic tensors depends highly on the excitation wavelength. We investigated the influence of strain on SHG for MoS2, MoSe2, WS2, and WSe2 monolayers. In order to quantify the strain induced anisotropy in the polarization resolved SHG we define two parameters. The Distortion (cid:1830) = (cid:4672), which is the ratio of the minima to the maxima of the envelope function of the polarization resolved SHG and the Intensity (cid:1835) = (cid:2024)((cid:1827)(cid:2870) + (cid:1828)(cid:2870)), which is the integral of the SHG intensity over all polarization directions. Our investigation allows for highly sensitive, non-invasive strain matrix imaging at the submicron scale as well as strain engineering of the conversion efficiency of SHG for all investigated materials.
关键词： Second-harmonic generation,strain,photoelastic tensor,polarization resolved SHG,transition metal dichalcogenide monolayers
更新于2025-09-11 14:15:04
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In-Plane Optical Anisotropy of Low-Symmetry 2D GeSe
摘要： As a new member of 2D materials, GeSe has attracted considerable attention recently due to its fascinating in-plane anisotropic vibrational, electrical, and optical properties originating from the low-symmetry crystal structure. Among these anisotropic properties, the anisotropic optical property, as a new degree of freedom to manipulate optoelectronic properties in 2D materials, is of great importance for practical applications. However, the fundamental understanding of the optical anisotropy of GeSe is still under exploration, severely restricting its utility in polarization-sensitive optical systems. Here, a systematic study about the in-plane optical anisotropy of GeSe is reported, including its anisotropic optical absorption, reflection, extinction, and refraction. The anisotropic band structure of GeSe is experimentally observed for the first time through angle-resolved photoemission spectroscopy, explaining the origin of the optical anisotropy. The anisotropic reflection and refraction of GeSe are further directly visualized through the angle-dependent optical contrast of GeSe flakes by azimuth-dependent reflectance difference microscopy and polarization-resolved optical microscopy, respectively. Finally, GeSe-based photodetectors exhibit a polarization-sensitive photoresponsivity due to the intrinsic linear dichroism. This study provides fundamental information for the optical anisotropy of GeSe, forcefully stimulating the exploration of novel GeSe-based optical and optoelectronic applications.
关键词： polarization-resolved optical microscopy,azimuth-dependent reflectance difference microscopy,birefringence,angle-resolved photoemission spectroscopy,germanium monoselenide
更新于2025-09-10 09:29:36
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Polarization-resolved and polarization- multiplexed spike encoding properties in photonic neuron based on VCSEL-SA
摘要： The spike encoding properties of two polarization-resolved modes in vertical-cavity surface-emitting laser with an embedded saturable absorber (VCSEL-SA) are investigated numerically, based on the spin-flip model combined with the Yamada model. The results show that the external input optical pulse (EIOP) can be encoded into spikes in X-polarization (XP) mode, Y-polarization (YP) mode, or both XP and YP modes. Furthermore, the numerical bifurcation diagrams show that a lower (higher) strength of EIOP is beneficial for generating tonic (phasic) spikes; a small amplitude anisotropy contributes to wide (narrow) tonic spiking range in XP (YP) mode; a large current leads to low thresholds of EIOP strength for both XP and YP modes. However, the spike encoding properties are hardly affected by the phase anisotropy. The encoding rate is shown to be improved by increasing EIOP strength. Moreover, dual-channel polarization-multiplexed spike encoding can also be achieved in a single VCSEL-SA. To the best of our knowledge, such single channel polarization-resolved and dual-channel polarization-multiplexed spike encoding schemes have not yet been reported. Hence, this work is valuable for ultrafast photonic neuromorphic systems and brain-inspired information processing.
关键词： VCSEL-SA,spike encoding,neuromorphic systems,polarization-resolved modes,brain-inspired information processing
更新于2025-09-10 09:29:36
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Synthesis, structural and optical‐vibration properties of Ba <sub/>3</sub> Sc <sub/>4</sub> O <sub/>9</sub> and Sr <sub/>3</sub> Sc <sub/>4</sub> O <sub/>9</sub> ceramics
摘要： Ba3Sc4O9 and Sr3Sc4O9 ceramics were synthesized by conventional solid‐state reactions at 1200°C, being further sintered at 1300°C in order to produce ceramic bodies suitable for exploring their structural and optical vibration properties. Optimized experimental conditions were employed to unveil the complex vibrational spectra of these ceramics by polarized Raman scattering. A reliable and comprehensive set of phonon features was obtained from these experiments: The 30 theoretically expected optically active lattice modes for each material were in fact observed, from which 15 could be assigned as totally symmetric A‐polar modes and 15 attributed as degenerate (and asymmetric) E‐polar ones. Differences between experimental data of Ba‐containing and Sr‐containing samples are discussed in terms of their ionic radii and molar masses. The knowledge of the optical phonon features reported here can help to understand the exceptional luminescence properties of Ba3Sc4O9 and Sr3Sc4O9 rhombohedral phases when doped with trivalent ions, as recently reported by the literature.
关键词： luminescence,ceramics,phosphors,Ba3Sc4O9 and Sr3Sc4O9,polarization‐resolved Raman spectroscopy
更新于2025-09-04 15:30:14