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Asymmetric photoelectron emission from chiral molecules using a high repetition rate laser
摘要： In the chiro-optical phenomenon known as photoelectron circular dichroism, the angular distribution of electrons ionized from chiral molecules by circularly polarized light pulses has been found to be anti-symmetric with respect to the direction of the light propagation. To study this phenomenon, chiral molecules were multiphoton ionized with a femtosecond laser in our laboratory. Using a simple stereo-detection setup, direct measurements of the asymmetry for the exemplar aromatic chiral molecule 1-phenylethanol were made using 260 nm pulses produced at a rate of 1 MHz. It was found that the asymmetry had a linear dependence on Stokes’ S3 parameter indicating that the photoelectron circular dichroism is due to a single photon process from the excited state of the molecule. This is in contrast to previous and new results for camphor where a more complex dependence on S3 suggested that selective excitation of molecules with certain orientations was influential.
关键词： photoelectron circular dichroism,circularly polarized light,asymmetry,Stokes’ S3 parameter,chiral molecules
更新于2025-09-23 15:19:57
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Photoinduced Chirality Switching of Metal-Inorganic Plasmonic Nanostructures
摘要： Chiral plasmonic nanodevices whose handedness can be switched reversibly between right and left by external stimulation have attracted much attention. However, they require delicate DNA nanostructures and/or continuous external stimulation. In this study, those issues are addressed by using metal-inorganic nanostructures and photoinduced reversible redox reactions at the nanostructures, namely site-selective oxidation due to plasmon-induced charge separation (PICS) under circularly polarized visible light (CPL) and reduction by UV-induced TiO2 photocatalysis. We irradiate gold nanorods (AuNRs) supported on TiO2 with right- or left-CPL to generate electric fields with chiral distribution around each AuNR, and to deposit PbO2 at the sites where the electric fields are localized, for fixing the chirality to the AuNR. The nanostructures thus prepared exhibit circular dichroism (CD) based on longitudinal and transverse plasmon modes of the AuNRs. Their chirality given by right-CPL (or left-CPL) is locked until PbO2 is re-reduced under UV light. After unlocking by UV, the chirality can be switched by left-CPL (or right-CPL) irradiation, resulting in reversed CD signals and locking the switch again. The handedness of the chiral plasmonic nanodevice can be switched reversibly and repeatedly.
关键词： plasmon-induced charge separation,circular dichroism,chiral plasmonic nanodevice,nanofabrication,circularly polarized light
更新于2025-09-19 17:13:59
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Development of a liquid crystal laser using a simple cubic liquid crystalline blue phase platform
摘要： A liquid crystal laser using a polymer-stabilized simple cubic blue phase (BPII) platform has been scarcely reported because the polymer stabilization of a BPII is relatively di?cult compared to that of a body-centered-cubic BP (BPI). In this study, we succeeded in fabricating a dye-doped polymer-stabilized BPII laser with wide operating-temperature ranges over 15 (cid:1)C including room temperature. A narrow and sharp single laser peak with a full width at half maximum of approximately 2 nm was derived from the photonic band edge e?ect of the BPII-distributed feedback optical resonator. As a result, the laser emission was a circularly polarized light, which matched the chirality of the proposed pure BPII.
关键词： liquid crystal laser,circularly polarized light,photonic band edge effect,polymer-stabilized,BPII,simple cubic blue phase
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) - Controlling Light Polarization from Helical Travelling-Wave Nanoantennas
摘要： Light polarization is a key factor of modern photonics. Tailoring surface plasmons (SPs) in anisotropically-shaped metallic nanostructures introduces the prospect of polarization control at small scale [1]. However, the resulting components remain much larger than the wavelength of light. Here, we present a travelling-wave helical plasmonic antenna (TW-HPA) that overcomes this limit [2]. Due to its non-resonant nature, it differs from existing helical plasmonic structures [3-5], thus extending the concept of travelling-wave helical antenna [6] to optics. Our TW-HPA consists of a narrow gold-coated wire wound up in a screw-like shape forming a tiny helix (Fig. 1a). The gold-coated wire sustains a cutoff-free axially symmetric travelling SPs [7], locally excited with the dipolar mode of a rectangular aperture nanoantenna right at the helix's pedestal. In the course of propagation, the plasmon wire mode acquires orbital angular momentum (OAM). Due to the sharp curvatures, the OAM of the SP mode match the spin angular momentum (SAM) of free-space propagating photons [8]. On the basis of this OAM-to-SAM transfer, individual TW-HPA can produce circularly polarized directional light on the subwavelength scale through a swirling-plasmon effect. Such TW-HPAs can then be closely packed to build micron scale arrangements of tiny circularly polarized light sources of desired handedness and tunable intensities, which could open new perspectives in a large panel of photonic applications requiring local addressing, such as detectors, displays, optomagnetic recording as well as quantum information. By optically coupling four TW-HPAs of opposite handedness (Fig.1b), we obtained a phase plate occupying a volume smaller than a cubic wavelength whose polarization properties have never previously been demonstrated. Switching between left and right circular polarizations (LCP and RCP) occurs when the incident linear polarization is rotated by an angle of 52°, instead of 90° as for standard quarter wave plates. Based on the spin-orbit interaction of light, our method is versatile, robust and leads to ultracompact plasmonic polarizers and unconventional phase plates. Taken as individual or coupled structures, TW-PHAs may pave the way towards highly integrated polarization-encoded optics, particularly for the generation and control of spin-encoded photon qubits in quantum information and optical spintronics.
关键词： Light polarization,orbital angular momentum,surface plasmons,circularly polarized light,optical spintronics,quantum information,spin angular momentum,helical travelling-wave nanoantennas
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) - Comparative Study of Harmonic Generation in Air and Argon in Light Filaments Driven by Circularly Polarized Mid-IR Pulses
摘要： A generation of optical harmonics by circularly polarized light, which is in general forbidden in an isotropic medium, was recently observed in molecular gases where molecules were aligned and oriented by another linearly polarized laser pulse or by pulses with twisted polarization. In order to generate nth-harmonic with circularly polarized light, a molecule has to “absorb” n photons, having the same handedness, and to emit a single nth harmonic photon while fulfilling the energy and the momentum conservation laws, meaning a necessity to excite the molecule to appropriate rotational state. One can do this by means of intrapulse rotational Raman scattering, which prepares the molecule in the excited state through a subsequent absorption of (n-1) same-handed photons. All previously reported experimental studies on circular harmonic generation in molecular gases were performed with visible/near-IR drivers, in either gas jets or in standing cells and with pre-alignment of molecules by an additional laser pulses. Here we report on the studies of self-action of elliptically polarized mid-IR pulses on the generation of low-order harmonics in filaments ignited in air and in argon, representing a molecular and an atomic gas respectively. The harmonics were driven by 20-mJ, sub-100 fs mid-IR pulses, centred at 3.9 μm wavelength. In the experiments filamentation was assisted by focusing light with a spherical mirror of ROC=-2500 mm into an open-end tube, through which Ar gas was flown at slight overpressure. Polarization of the pulses was controlled by a broadband quarter wave plate (QWP). Spectra of 5th and 7th harmonics were recorded after the filaments with a grating spectrometer (HR4000, OceanOptics). Polarization state of the generated harmonics was analysed with a Glan-Taylor polarizer.
关键词： filaments,argon,circularly polarized light,mid-IR pulses,harmonic generation,air
更新于2025-09-11 14:15:04
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Optically Controlled Orbitronics on a Triangular Lattice
摘要： The propagation of electrons in an orbital multiplet dispersing on a lattice can support anomalous transport phenomena deriving from an orbitally induced Berry curvature. In striking contrast to the related situation in graphene, we find that anomalous transport for an L ? 1 multiplet on the primitive 2D triangular lattice is activated by easily implemented on site and optically tunable potentials. We demonstrate this for dynamics in a Bloch band where point degeneracies carrying opposite winding numbers are generically offset in energy, allowing both an anomalous charge Hall conductance with the sign selected by off-resonance coupling to circularly polarized light and a related anomalous orbital Hall conductance activated by layer buckling.
关键词： Berry curvature,anomalous transport,circularly polarized light,triangular lattice,orbital Hall conductance
更新于2025-09-11 14:15:04
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Photoactive Functional Soft Materials (Preparation, Properties, and Applications) || Photochemical Chirality Induction and Inversion in Soft Materials
摘要： Chirality or “handedness” is a prerequisite of the biological world, where life exists in a specific chirality. In living organisms, almost all the sugars are exclusively right‐handed (d‐isomer), amino acids are left‐handed (l‐isomer), and DNA coils assemble into right‐handed helices. The reason behind this homochirality is still an unresolved issue. Inspired by the natural homochirality, the scientific community has been interested in exploring the mechanism of transmission of chirality from the molecular level of monomeric units to the macro‐ or supramolecular level, as well as the origin of chirality. The supramolecular chirality in nature from self‐assembled achiral molecules and its specific handedness play a crucial role in the evolution of life and the development of supramolecular materials. While the chirality of molecules is of configurational and conformational origin, supramolecular level chirality arises from the organization of molecules, with formation of a chiral superstructure by means of long‐range positional and orientational orders of molecules.
关键词： Supramolecular,Polymers,Circularly Polarized Light,Photochromic Switches,Helical Structures,Liquid Crystals,Photochemical,Self-Assembly,Soft Materials,Chirality
更新于2025-09-09 09:28:46