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Quantum dots of two-dimensional Ruddlesdena??Popper organica??inorganic hybrid perovskite with high optical limiting properties
摘要： Hybrid perovskites have been investigated for various potential applications because of their tunable optical properties. In this paper, we report the synthesis of quantum dots (QDs) of two-dimensional (2D) Ruddlesden–Popper (RP) hybrid perovskite using a top-down approach. The QDs of the developed 2D RP perovskite exhibit high and sharp photoluminescence in the ultraviolet region. The sharp peak in the absorption spectrum and the intense photoluminescence in the ultraviolet region indicate strong quantum confinement in these particles, which is further confirmed by x-ray photoelectron spectroscopy. These QDs show superior nonlinear optical scattering and absorption properties with the optical z-scan technique and strong nonlinear absorption property with the photoacoustic z-scan technique. Evaluating the nonlinear optical properties using two complementary techniques provides a deeper understanding of the nonlinear mechanism involved in the optical limiting process. The two-photon absorption coefficient obtained by optical z-scan is 7.2 × 102 cm/GW, which is larger than that of most perovskite nanocrystals and nanosheets. Our studies, therefore, reveal a new class of material, 2D RP perovskite QDs, which show important nonlinear properties that are important for optical limiting applications.
关键词： Ruddlesden–Popper perovskite,optical limiting,nonlinear optical properties,Quantum dots,two-photon absorption
更新于2025-09-23 15:21:01
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On the photo-activation of the S <sub/>0</sub> ?→?S <sub/>1</sub> transition in polyenes
摘要： The evidence provided in this work allows us to conclude that the electronic transition S0 → S1 either for the diphenylhexatriene molecule or for the diphenyloctatetraene molecule is dipole allowed and induced by one‐photon absorption. Consequently, the model to explain the photophysics of these polyenes does not need the existence of an underlying 21Ag excited electronic state, to the converse of what Hudson and Kohler proposed, that the transition S0 → S1 must be induced by two‐photon absorption.
关键词： two‐photon absorption,excitation spectra,photophysics of polyenes
更新于2025-09-19 17:15:36
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Enhanced Small-Signal Responsivity in Silicon Microring Photodetector Based on Two-Photon Absorption
摘要： We experimentally investigated methods of enhancing the small-signal responsivity of a silicon pin microring photodetector based on two-photon absorption for detecting small optical signals in the telecommunication wavelength range. Two approaches are demonstrated, the first exploiting the bistability effect in the nonlinear microring resonator while the second employing an optical bias at a different wavelength to increase the differential responsivity. We achieved a small-signal responsivity of 180 mA/W with the first approach and 141 mA/W with the second approach, both of which represent almost 10-fold enhancement over direct detection of small optical signals by the same silicon pin microring detector. Our techniques have potential applications in amplitude demodulation, heterodyne detection, and optical power monitoring in WDM communication channels.
关键词： microring resonator,photodetector,two-photon absorption,Silicon photonics
更新于2025-09-19 17:13:59
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Sensitive Infrared Photon Counting Detection by Nondegenerate Two-Photon Absorption in Si APD
摘要： We report on the sensitive detection of photons at broadband infrared wavelengths based on the nondegenerate two-photon absorption in the Si avalanche photodiodes. The detected 1700~1850 nm infrared photon energy is lower than Si band gap and the energy difference is complemented by a high intensity pump laser field at 1550 nm. It is thus possible to capitalize on the low noise property of large band gap materials for detecting low energy photons. And the linear intensity response of the detector to the incident infrared photons was observed when the power of pump laser was about 12.42 μW, indicating the dominance of nondegenerate two-photon absorption in the infrared photon detection. An enhancement factor of 20 was observed for the incident signal photon numbers of ~0.14×106 photons per pulse. We offer an alternative to sensitive detection of infrared light. This may also provide new ideas for broadband infrared photon detection in different applications such as optical comb laser ranging, infrared bio-image and so forth.
关键词： Infrared photon detection,silicon avalanche photodiode,nondegenerate two photon absorption
更新于2025-09-16 10:30:52
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[IEEE 2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC) - Fukuoka, Japan (2019.7.7-2019.7.11)] 2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC) - High-Responsivity Silicon Microring Photodetector Based on Two-Photon Absorption
摘要： We report a silicon pin microring photodetector based on two-photon absorption with responsivity enhanced by optical resonance and optical biasing. A small-signal responsivity of 100mA/W was achieved, which is the highest reported TPA-based silicon photodetectors.
关键词： microring resonator,silicon photonics,photodetector,two-photon absorption
更新于2025-09-16 10:30:52
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High-order harmonic generation from diatomic molecules in an orthogonally polarized two-color laser field
摘要： In this study, a two photon absorbing (TPA) material consisting silver nanoparticles and triphenylamine-thiol derivative (TBS) has been prepared through interfacial coordination effect according to soft-hard-acid-base principle. The interfacial structure and morphology of the hybrid are researched in detail. Linear and nonlinear optical properties of the hybrid are studied. Upon interfacial coordination, the hybrid shows red-shifted UV–Vis absorption, causing from enhanced electronic drawing strength due to existence of Ag atom. The results also indicate that the surface Plasmon resonance (SPR) effect of Ag nanoparticles (~6 nm) brings about enhancement in single photon fluorescence emission and two photon absorption. Compared with free TBS, Ag-TBS hybrids show higher TPA cross-section (δ), which is 8784 GM for TBS and up to 103876 GM for Ag-TBS hybrid, showing ~12 fold increase. Due to excellent TPA property, the hybrids have good application in the field of optical power limiting and its limiting threshold is 0.49 J/cm?2. This type of interfacial coordination induced hybrid provides a promising strategy to regulate linear optical properties and optimize nonlinear performance.
关键词： Surface plasmon resonance,Interfacial coordination,Optical power limiting,Two photon absorption
更新于2025-09-16 10:30:52
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Two-photon absorption in a two-level system enabled by noise
摘要： We address the textbook problem of dynamics of a spin placed in a dc magnetic field and subjected to an ac drive. If the drive is polarized in the plane perpendicular to the dc field, then the drive photons are resonantly absorbed when the spacing between the Zeeman levels is close to the photon energy. This is the only resonance when the drive is circularly polarized. For a linearly polarized drive, additional resonances corresponding to absorption of three, five, and multiple odd numbers of photons is possible. Interaction with the environment causes the broadening of the absorption lines. We demonstrate that the interaction with environment enables the forbidden two-photon absorption. We adopt a model of the environment in the form of random telegraph noise produced by a single fluctuator. As a result of the synchronous time fluctuations of different components of the random field, the shape of the two-photon absorption line is non-Lorentzian and depends dramatically on the drive amplitude. This shape is a monotonic curve at strong drive, while, at weak drive, it develops a two-peak structure reminiscent of an induced transparency on resonance.
关键词： environment interaction,absorption spectrum,noise,two-photon absorption,telegraph noise,Floquet description,two-level system
更新于2025-09-12 10:27:22
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New Approach for Pulsed-Laser Testing That Mimics Heavy-Ion Charge Deposition Profiles
摘要： A novel approach for two-photon absorption (TPA) pulsed-laser testing produces extended charge deposition profiles that are analogous to those produced by heavy ions. In this approach, which utilizes an axicon rather than a spherical lens, the conventional Gaussian beam is replaced by a quasi-Bessel beam. The key feature of a quasi-Bessel beam, relevant to pulsed-laser single-event effects (PL-SEE) studies, is that its radial size (~1 μm) remains constant over the axial length of the beam (several 100s of μm) resulting in a charge-deposition profile that more closely mimics that produced by a heavy ion. This elongated charge distribution directly lends itself to a simple and intuitive description in terms of linear-energy transfer, or LET, facilitating laser/ion correlation studies. Experimental results comparing a conventional TPA PL-SEE focusing geometry and the axicon focusing geometry are presented for three different test vehicles: a 45-nm SOI nFET, a bulk silicon photodiode, and an LM 124 operational amplifier. Using the axicon approach, strong laser/ion correlation is observed in the silicon photodiode for single-event transients (SET) across a wide range of LETs. The correlation is achieved by “tuning” the laser to the desired LET rather than relying on pre-existing heavy-ion data and therefore this approach holds promise as a predictive tool.
关键词： single-event effect (SEE),silicon,Correlation methods,single-event transient (SET),heavy-ion testing,pulsed-laser,two-photon absorption,linear energy transfer (LET)
更新于2025-09-12 10:27:22
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Dependence of the Two-Photon Absorption Coefficient of Steel on the Pulse Duration During Its Ablation by Femto- and Picosecond Laser Pulses
摘要： The dependences of the depth of single-pulse ablation of the steel surface on the energy density of ultrashort laser pulses (0.3–12 ps) with a wavelength of 515 nm have the form different from the usual logarithmic one for linear absorption of radiation. Since the density of states of free conduction electrons in the s band is low, and the d band of strongly bound electrons with a high density of states is located around the Fermi level, these dependences have been approximated within the two-photon absorption model. The two-photon absorption coefficient increases almost linearly with the duration of laser pulses, which indicates the saturation of absorption and allows estimating the corresponding parameters of the electronic subsystem.
关键词： picosecond,two-photon absorption,femtosecond,ultrashort laser pulses,steel ablation
更新于2025-09-12 10:27:22
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Comparison of Sensitive Volumes Associated with Ion-and Laser-Induced Charge Collection in an Epitaxial Silicon Diode
摘要： A sensitive volume is developed using pulsed laser-induced collected charge for two bias conditions in an epitaxial silicon diode. These sensitive volumes show good agreement with absorption laser-induced collected charge at a variety of focal positions and pulse energies. When compared to ion-induced collected charge, the laser-based sensitive volume over predicts the experimental collected charge at low bias and agrees at high bias. A sensitive volume based on ion-induced collected charge adequately describes the ion experimental results at both biases. Differences in the amount of potential modulation explain the differences between the ion- and laser-based sensitive volumes at the lower bias. Truncation of potential modulation by the highly doped substrate at the higher bias results in similar sensitive volumes.
关键词： single-event transients,two-photon absorption,sensitive volume,single-event effects,Pulsed laser
更新于2025-09-12 10:27:22