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Ultrafast all-optical digital comparator using quantum-dot semiconductor optical amplifiers
摘要： In this investigation, three types of 160 Gb/s all-optical digital comparators using quantum-dot semiconductor optical amplifiers (QD-SOAs) are constructed. These configurations have different combination patterns of logic gates and QD-SOAs. Based on numerical simulations, we investigate and evaluate the performance of the devices in terms of the number of logic gates and QD-SOAs, and the value of the extinction ratio (ER). In addition, we demonstrate the effect of amplified spontaneous emission (ASE) noise on the ER and Q-factor. The results show that two of the three configurations are superior to the other configuration in terms of circuit complexity, value of ER, and sensitivity to injection current. Moreover, these two configurations achieve ER values over 10 dB and Q-factor over 9, even when intense ASE noise is considered. The proposed configurations have several advantages such as high quality, easy configuration, insensitivity to injection current, and strong noise robustness, which are favorable for practical applications. This investigation also facilitates the specification of the pros and cons of each configuration, and the determination of the appropriate comparator according to the desired requirements.
关键词： Logic gates,All-optical digital comparator,Amplified spontaneous emission (ASE),Quantum-dot semiconductor optical amplifier (SOA)
更新于2025-09-19 17:15:36
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Ehrenfest+R dynamics. I. A mixed quantum–classical electrodynamics simulation of spontaneous emission
摘要： The dynamics of an electronic system interacting with an electromagnetic field is investigated within mixed quantum–classical theory. Beyond the classical path approximation (where we ignore all feedback from the electronic system on the photon field), we consider all electron–photon interactions explicitly according to Ehrenfest (i.e., mean-field) dynamics and a set of coupled Maxwell–Liouville equations. Because Ehrenfest dynamics cannot capture certain quantum features of the photon field correctly, we propose a new Ehrenfest+R method that can recover (by construction) spontaneous emission while also distinguishing between electromagnetic fluctuations and coherent emission.
关键词： quantum electrodynamics,electromagnetic field,Ehrenfest dynamics,spontaneous emission,mixed quantum-classical theory
更新于2025-09-19 17:15:36
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Amplified spontaneous emission (ASE) and laser effects in ?2-LiYF4: Ce, Tb micro- and nanocrystals
摘要： β-NaYF4 crystals family are interesting materials and have potential for various applications. Here we present our research regarding amplified spontaneous emission (ASE) and laser effects of three materials: LiY0.7 F4: (Ce0.2 Tb0.1), NaY0.5 F4: (Ce0.4 Tb0.1) and LiLuY0.7 F4: (Ce0.2 Tb0.1), prepared by hydrothermal synthesis method. The luminescent active ion is Tb3+. β- LiY0.7 F4: (Ce0.2 Tb0.1) crystals with a hexagonal plate shape have ASE threshold at 400 mW/cm2, excitation with λex = 365 nm and a laser threshold at 490 J for a doped PMMA rod with a length of 25 mm. Laser line was observed at 542 nm.
关键词： β-LiYF4: Ce, Tb micro- and nanocrystals,Laser effect,Amplified spontaneous emission (ASE),Hydrothermal growth
更新于2025-09-19 17:13:59
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Imitating the effect of amplified spontaneous emission pedestal at relativistically intense laser interaction with nanostructured solid targets
摘要： We investigated the effect of focusing sub-nanosecond laser radiation with varied fluence onto the surface of different flat and nanostructured targets utilized in ultra-high intensity laser-plasma experiments. Thus, we modeled the action of the prepulse, referred to as an amplified spontaneous emission pedestal, typically present for a relativistic (with peak intensity over 1018 W cm?2) laser pulse with naturally limited contrast. The suppressed melting threshold was detected for the sub-wavelength scale structured material. Local melting leading to distortion of initial structures was detected at a fluence of ~0.2 J cm?2 and below, or 3–5 times lower compared to the flat substrate melting threshold. It is also demonstrated that the threshold lowering is dependent on the production method of the structures, which may be attributed to increased absorption and suppressed heat transfer into the bulk.
关键词： high intensity laser interaction,amplified spontaneous emission pedestal,laser melting,sub-nanosecond pulse,nanostructures
更新于2025-09-19 17:13:59
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Semiclassical analysis of dark-state transient dynamics in waveguide circuit QED
摘要： The interaction between superconducting qubits and one-dimensional microwave transmission lines has been studied experimentally and theoretically in the past two decades. In this work, we investigate the spontaneous emission of an initially excited artificial atom which is capacitively coupled to a semi-infinite transmission line, shorted at one end. This configuration can be viewed as an atom in front of a mirror. The distance between the atom and the mirror introduces a time delay in the system, which we take into account fully. When the delay time equals an integer number of atom oscillation periods, the atom converges into a dark state after an initial decay period. The dark state is an effect of destructive interference between the reflected part of the field and the part directly emitted by the atom. Based on circuit quantization, we derive linearized equations of motion for the system and use these for a semiclassical analysis of the transient dynamics. We also make a rigorous connection to the quantum optics system-reservoir approach and compare these two methods to describe the dynamics. We find that both approaches are equivalent for transmission lines with a low characteristic impedance, while they differ when this impedance is higher than the typical impedance of the superconducting artificial atom.
关键词： quantum optics,circuit quantization,spontaneous emission,dark state,superconducting qubits,microwave transmission lines
更新于2025-09-19 17:13:59
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - LDPC Channel Coding in Ultraviolet Communication System
摘要： We review the physics underlying the process of spontaneous emission, with a special focus on spontaneous emission into a resonator mode. We define the mode volume, verify the fundamental modal dimensions, present the spectral mode profile, the coherence time, the Q-factor, the Fühtbauer–Ladenburg equation, and the Purcell factor, and discuss their influence on different types of lasers. We obtain the relation between peak emission cross section, radiative lifetime, and emission linewidth. By interpreting spontaneous emission as stimulated emission driven by vacuum fluctuations, we derive the spontaneous-emission rate into a resonator mode and establish physical expressions for the fractions of spontaneous emission and total decay from the upper laser level into this mode. Furthermore, we discuss coupling of the atomic system with the coherent field inside a lasing resonator mode, resulting in the formation of a Mollow triplet, and demonstrate that it leads to a reduction of the spontaneous-emission rate into a coherently occupied resonator mode by a factor of 2.
关键词： Lasers,laser modes,optical resonators,spontaneous emission,luminescence
更新于2025-09-19 17:13:59
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Optimization of the pulse width and injection time in a double-pass laser amplifier
摘要： We have optimized the input pulse width and injection time to achieve the highest possible output pulse energy in a double-pass laser ampli?er using two Nd:YAG rods. For this purpose, we have extended the Frantz–Nodvik equation by simultaneously including both spontaneous emission and pump energy variation. The effective pump energy of the ?ash lamp was 8.84 J for each gain medium. The energy of 1 J could be ampli?ed to an output energy of 12.17 J with the maximum achieved extraction ef?ciency of 63.18% when an input pulse having a pulse width of 168 μs is sent 10 μs after the absorbed pump energy becomes the maximum value.
关键词： pump energy variation,input pulse optimization,spontaneous emission,Frantz–Nodvik equation,pulse overlap
更新于2025-09-19 17:13:59
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Atoma??photon entanglement near a plasmonic nanostructure
摘要： We investigate the atom–photon entanglement between a four-level double V-type quantum system and a linearly polarized ?eld near a plasmonic nanostructure in the presence of a static magnetic ?eld. It is demonstrated that the magneto-optical effect can affect the atom–photon entanglement only when the atom is near the plasmonic nanostructure. We show that atom–photon entanglement increases when the quantum system is placed near the plasmonic nanostructure in order to modi?cation of the spontaneous decays of the quantum system. It is demonstrated that the degree of entanglement (DEM) increases by increasing the intensity of the linearly polarized ?eld when the quantum system is close to the surface of the plasmons. Moreover, we ?nd that near the plasmonic nanostructure, the static magnetic ?eld has a major role in increasing the steady-state DEM so that the DEM is completely demolished in the absence of the static magnetic ?eld. Finally, it is shown that the atom–photon entanglement near a plasmonic nanostructure is destroyed by free space decay rate.
关键词： degree of entanglement,static magnetic ?eld,atom–photon entanglement,plasmonic nanostructure,spontaneous emission
更新于2025-09-19 17:13:59
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Purcell-Enhanced Spontaneous Emission from Perovskite Quantum Dots Coupled to Plasmonic Crystal
摘要： Lead halide perovskite quantum dots (PQDs) have recently been proposed as scalable and color-tunable single emitters, but their slow spontaneous emission (1-10 ns) creates a mismatch with high-speed nanophotonic devices. Here we demonstrate Purcell enhanced emission rate in hybrid structure of PQDs coupled to plasmonic crystal at room temperature. A series of planar devices are produced in large scale via chemistry assembly using colloidal PQDs, Ag nanocubes and polyvinyl pyrrolidone (PVP) as building blocks. By varying the PVP spacer thickness as well as Ag nanocube surface density, a tunable photoluminescence enhancement is realized in both steady and time resolved measurements. We show a 3.5-fold enhancement in the total fluorescence intensity and simultaneously an increase in the emission rate of a factor of 4.5. Finally, a proof-of-concept tag using PVP spacer encoded inks is demonstrated, providing a promising approach for information security based on Purcell-enhanced emission.
关键词： perovskite quantum dots,plasmonic crystal,information security,spontaneous emission,Purcell-enhanced emission
更新于2025-09-16 10:30:52
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Greatly amplified spontaneous emission of colloidal quantum dots mediated by a dielectric-plasmonic hybrid nanoantenna
摘要： Optical nanoantennas can efficiently harvest electromagnetic energy from nanoscale space and boost the local radiation to the far field. The dielectric-metal nanogap is a novel design that can help to overcome the core issue of optical loss in all-metal nanostructures while enabling photon density of states larger than that in all-dielectric counterparts. This article reports that a crystalline spherical silicon nanoparticle on metal film (SiNPoM) nanoantenna can largely enhance the spontaneous emission intensity of quantum dots by an area-normalized factor of 69 and the decay rate by 42-fold compared with quantum dots on glass. A high total quantum efficiency of over 80%, including ~20% for far-field radiation and ~60% for surface plasmon polaritons, is obtained in simulation. Thanks to not only the low optical loss in dielectric nanoparticles but also the appropriate gap thickness which weakens the non-radiative decay due to the quenching from metal. Mie resonant modes additionally provide the flexible control of far-field emission patterns. Such a simple optical nanoantenna can be combined with various nanoscale optical emitters and easily extended to form large area metasurfaces functioning as active regions in light-emitting devices in applications such as advanced display, wireless optical communication, and quantum technology.
关键词： silicon nanoparticle,spontaneous emission,Purcell effect,plasmonics,nanoantenna
更新于2025-09-16 10:30:52