- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Dynamical distortions of structural signatures in molecular high-order harmonic spectroscopy
摘要： We study the signature of two-center interferences in molecular high-order harmonic spectra, with an emphasis on the spectral phase. With the help of both ab initio computations based on the time-dependent Schr?dinger equation and the molecular strong-field approximation (SFA) as developed by Chiril? et al. [Phys. Rev. A 73, 023410 (2006)] and Faria [Phys. Rev. A 76, 043407 (2007)], we observe that the phase behavior is radically different for the short and the long trajectory contributions. By means of Taylor expansions of the molecular SFA, we link this effect to the dynamics of the electron in the continuum. More precisely, we find that the value of the electric field at recombination time plays a crucial role in the shape of the destructive interference phase jump.
关键词： molecular spectroscopy,spectral phase,strong-field approximation,two-center interferences,time-dependent Schr?dinger equation,high-order harmonic generation
更新于2025-09-23 15:23:52
-
Dynamically tunable perfect absorption based on the phase transition of vanadium dioxide with aluminum hole arrays
摘要： Integrating plasmonic nanostructures with functional materials can further control over the optical resonant responses. A perfect absorber (PA) consisting of aluminum (Al) ring array intercalated with vanadium dioxide (VO2) disk is presented. The resonance wavelength of absorption peak can be tuned over a wide range in the visible (Vis) and near-infrared (NIR) regimes. The absorption peak shifts from 770 nm to 1336 nm while VO2 undergoes a structural transition from metallic phase (m-VO2) to insulator phase (i-VO2), resulting in a relative 73.5% wavelength shift. In addition, the absorption peak is strongly dependent on the height and radius of the ring disk as well as the period of lattice. Our work also suggests that the designed VO2-based absorber has the potential to overcome the di?culty in performing dynamically tunable resonances and near-unity absorbance with wide angle of incidence as well as weak polarization dependence.
关键词： Vanadium dioxide (VO2),Visible and near-infrared spectral,Phase change material,Perfect absorption
更新于2025-09-23 15:21:01
-
Qualitative and Quantitative Distinction of <i>ortho</i> -, <i>meta</i> -, and <i>para</i> -Fluorotoluene by Means of Chirped Femtosecond Laser Ionization
摘要： Femtosecond-laser ionization mass spectrometry (fs-LIMS) is demonstrated to be a powerful analytical method providing access to the qualitative distinction of structural isomers of ortho-, meta-, and para-fluorotoluene. The key point of the approach presented is a systematic variation of the spectral phase of the fs-laser pulses, which characteristically affects the fragmentation pattern observed in the mass spectra. Variation of the linear chirp parameter is also helpful for rationalizing the fragmentation mechanism. Ultimately two ternary mixtures of the three title isomers are quantitatively analyzed in situ with an accuracy of 5% for the molar fractions.
关键词： structural isomers,Femtosecond-laser ionization mass spectrometry,fragmentation pattern,spectral phase,quantitative analysis,fluorotoluene
更新于2025-09-23 15:19:57
-
[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) - Video-Rate Phase Retrievals from Dispersion Scan Traces using Artificial Neural Networks
摘要： The full characterization of ultrashort pulses is crucial for all their applications. Lately, the dispersion scan (d-scan) technique has been developed, which stands out by its simplicity [1, 2]. Therefore, it is a promising candidate for a low-maintenance pulse characterization technique. The reconstruction of the spectral phase from a d-scan measurement relies on optimization algorithms [3, 4]. Considering the fact that the spectral phase of the pulses is directly imprinted on the d-scan trace, the phase reconstruction can also be regarded as an image recognition task. During the last few years, artificial neural networks have shown excellent performance in different fields, e.g. image recognition [5]. Here we present the retrieval of spectral phases from d-scan traces using deep neural networks (DNN) that is more than 3000 times faster than conventional optimization algorithms (16 ms) [6]. Our DNN is an optimized variant of the DenseNet-BC architecture that has already shown great performance in image recognition tasks [7]. Training our shallow variant of the DenseNet takes only 12 h using a low cost GPU (NVIDIA GeForce GTX 1080 Ti). After training with up to 1.5 × 106 different, randomly generated traces, we can employ the network for reconstruction of the spectral phases from a d-scan traces. Fig. 1(a) and (b) show a randomly generated d-scan trace and its corresponding reconstruction, respectively. The spectral intensity (black curve), the original spectral phase (blue curve) and the retrieved phase (red dashed curve) are depicted in Fig. 1(c). Additionally, Fig. 1(d) compares the original and the reconstructed temporal pulse shapes (same color code). The consistency between the original and the retrieved phases and their corresponding temporal shapes shows the excellent performance of the DNN. Furthermore, to prove the fidelity of phase reconstruction from experimentally measured traces, we retrieved the spectral phase from a Ti:sapphire based amplifier system [8]. Compared to a differential evolution optimization algorithm, we observe identical full width at half maximum pulse durations, as well as nearly identical temporal pulse shapes. We believe that DNNs combined with single-shot d-scan setups [9] enable video-rate measurements with an inherent error estimation due to the redundancy in the data.
关键词： deep neural networks,spectral phase retrieval,dispersion scan,ultrashort pulses
更新于2025-09-11 14:15:04
-
Phase control of plasmon enhanced two-photon photoluminescence in resonant gold nanoantennas
摘要： Plasmonic nanoantennas emit two-photon photoluminescence, which is much stronger than their second harmonic generation. Unfortunately, luminescence is an incoherent process and therefore generally not explored for nanoscale coherent control of the antenna response. Here, we demonstrate that, in resonant gold nanoantennas, the two-photon absorption process can be coherent, provided that the excitation pulse duration is shorter than the dephasing time of plasmon mode oscillation. Exploiting this coherent response, we show the pure spectral phase control of resonant gold nanoantennas, with effective read-out of the two-photon photoluminescence.
关键词： two-photon photoluminescence,gold nanoantennas,plasmonic nanoantennas,spectral phase control,coherent control
更新于2025-09-10 09:29:36