- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Nonlinear Optics || Nonlinear Optics in the Two-Level Approximation
摘要： Our treatment of nonlinear optics in the previous chapters has for the most part made use of power series expansions to relate the response of a material system to the strength of the applied optical field. In simple cases, this relation can be taken to be of the form ?P (t) = (cid:2)0χ (1) ?E(t) + (cid:2)0χ (2) ?E(t)2 + (cid:2)0χ (3) ?E(t)3 + · · · . However, there are circumstances under which such a power series expansion does not converge, and under such circumstances different methods must be employed to describe nonlinear optical effects. One example is that of a saturable absorber, where the absorption coefficient α is related to the intensity I = 2n(cid:2)0c|E|2 of the applied optical field by the relation α = α0 / (1 + I /Is), where α0 is the weak-field absorption coefficient and Is is an optical constant called the saturation intensity. We can expand this equation in a power series to obtain α = α0 [1 ? (I /Is) + (I /Is)2 ? (I /Is)3 + · · · ]. However, this series converges only for I < Is, and thus only in this limit can saturable absorption be described by means of a power series of the sort given by Eq. (6.1.1).
关键词： Rabi oscillations,two-level approximation,saturable absorber,optical Stark shifts,nonlinear optics
更新于2025-09-23 15:21:01
-
Coherent spin control of s-, p-, d- and f-electrons in a silicon quantum dot
摘要： Once the periodic properties of elements were unveiled, chemical behaviour could be understood in terms of the valence of atoms. Ideally, this rationale would extend to quantum dots, and quantum computation could be performed by merely controlling the outer-shell electrons of dot-based qubits. Imperfections in semiconductor materials disrupt this analogy, so real devices seldom display a systematic many-electron arrangement. We demonstrate here an electrostatically confined quantum dot that reveals a well defined shell structure. We observe four shells (31 electrons) with multiplicities given by spin and valley degrees of freedom. Various fillings containing a single valence electron—namely 1, 5, 13 and 25 electrons—are found to be potential qubits. An integrated micromagnet allows us to perform electrically-driven spin resonance (EDSR), leading to faster Rabi rotations and higher fidelity single qubit gates at higher shell states. We investigate the impact of orbital excitations on single qubits as a function of the dot deformation and exploit it for faster qubit control.
关键词： Rabi oscillations,silicon quantum dot,spin qubits,electrically-driven spin resonance,quantum dots
更新于2025-09-19 17:13:59
-
Coherent light matter interactions in nanostructure based active semiconductor waveguides operating at room temperature
摘要： Light matter coherent interactions require that the coherent state induced in the matter be maintained for the duration of the observation. The only way to induce and observe such interactions in room temperature semiconductors, where the coherence time is of the order of a few hundred femtoseconds, is to use ultrashort pulse excitations and an ultrafast characterization technique. For media comprising an ensemble of nanostructure semiconductors such as self-assembled quantum dots, the gain broadening inhomogeneity also affects the interaction. Moreover, when gain media in the form of an active waveguide, such as optical amplifiers, are used, the interaction is distributed and includes nonresonant incoherent phenomena that occur simultaneously with the coherent effects. Such a complex system can exhibit, nevertheless, clear coherent interactions even at room temperature. Using InAs/InP quantum dot and wirelike quantum dash amplifiers, Rabi oscillations, self-induced transparency, coherent control using spectral pulse shaping, Ramsey interference, and photon echo have been demonstrated. The characterization employed cross frequency resolved optical gating, and the experiments were accompanied by a comprehensive finite difference time domain model that solves the Maxwell and Lindblad equations. This work has major implications on the understanding of the details of dynamical processes in active semiconductor devices, on short pulse generation from semiconductor lasers, and on various future quantum devices.
关键词： active semiconductor waveguides,coherent control,self-induced transparency,Rabi oscillations,coherent light matter interactions,nanostructure,Ramsey interference,photon echo,room temperature
更新于2025-09-16 10:30:52
-
Collective dynamics of inhomogeneously broadened emitters coupled to an optical cavity with narrow linewidth
摘要： We study collective effects in an inhomogeneously broadened ensemble of two-level emitters coupled to an optical cavity with narrow linewidth. Using second-order mean-field theory we find that the emitters within a few times the cavity linewidth exhibit synchronous behavior and undergo collective Rabi oscillations. Under proper conditions, the synchronized oscillations give rise to a modulated intracavity field which can excite emitters detuned by many linewidths from the cavity resonance. To study the synchronization in further detail, we simplify the model and consider two ensembles and study steady-state properties when the emitters are subjected to an incoherent drive.
关键词： collective dynamics,optical cavity,Rabi oscillations,inhomogeneous broadening,synchronization
更新于2025-09-12 10:27:22
-
Backaction effects in cavity-coupled quantum conductors
摘要： We study the electronic transport through a pair of distant nanosystems (Sa and Sb) embedded in a single-mode cavity. Each system is connected to source and drain particle reservoirs and the electron-photon coupling is described by the Tavis-Cummings model. The generalized master equation approach provides the reduced density operator of the double system in the dressed-states basis. It is shown that the photon-mediated coupling between the two subsystems leaves a signature on their transient and steady-state currents. In particular, a suitable bias applied on subsystem Sb induces a photon-assisted current in the other subsystem Sa which is otherwise in the Coulomb blockade. We also predict that a transient current passing through one subsystem triggers a charge transfer between the optically active levels of the second subsystem even if the latter is not connected to the leads. As a result of backaction, the transient current through the open system develops Rabi oscillations (ROs) whose period depends on the initial state of the closed system.
关键词： Rabi oscillations,Coulomb blockade,nanosystems,photon-mediated coupling,electronic transport,Tavis-Cummings model
更新于2025-09-12 10:27:22
-
The New Concept of Nano-Device Spectroscopy Based on Rabi–Bloch Oscillations for THz-Frequency Range
摘要： We considered one-dimensional quantum chains of two-level Fermi particles coupled via the tunneling driven both by ac and dc ?elds in the regimes of strong and ultrastrong coupling. The frequency of ac ?eld is matched with the frequency of the quantum transition. Based on the fundamental principles of electrodynamics and quantum theory, we developed a general model of quantum dynamics for such interactions. We showed that the joint action of ac and dc ?elds leads to the strong mutual in?uence of Rabi- and Bloch oscillations, one to another. We focused on the regime of ultrastrong coupling, for which Bloch- and Rabi-frequencies are signi?cant values of the frequency of interband transition. The Hamiltonian was solved numerically, with account of anti-resonant terms. It manifests by the appearance of a great number of narrow high-amplitude resonant lines in the spectra of tunneling current and dipole moment. We proposed the new concept of terahertz (THz) spectroscopy, which is promising for different applications in future nanoelectronics and nano-photonics.
关键词： ultrastrong coupling,Bloch-oscillations,THz-spectroscopy,Rabi-oscillations
更新于2025-09-11 14:12:44
-
Nonequilibrium Environment Dynamics in a Frequency-Dependent Polarizable Embedding Model
摘要： Hybrid quantum mechanical/molecular mechanical (QM/MM) models are some of the most powerful and computationally feasible approaches to account for solvent effects or more general environmental perturbations on quantum chemical systems. In their more recent formulations (known as polarizable embedding) they can account for electrostatic and mutual polarization effects between the QM and the MM subsystems. In this paper, a polarizable embedding scheme based on induced dipoles that is both able to describe electron evolution of the embedded QM system in an efficient manner as well as to capture the frequency dependent behavior of the solvent is proposed, namely ωMMPol. The effects of this frequency dependent solvent on a time-dependent model system — the Rabi oscillations of H+2 in a resonant field — are considered. The solvent is shown to introduce only mild perturbations when the excitation frequencies of the solvent and the solute are off-resonant. However, the dynamics of the H+2 are fundamentally changed in the presence of a near-resonant excitation solvent. The effectiveness of ωMMPol to simulating realistic chemical systems is demonstrated by capturing charge transfer dynamics within a solvated system.
关键词： charge transfer dynamics,polarizable embedding,Rabi oscillations,QM/MM models,frequency-dependent polarizability,electron dynamics
更新于2025-09-10 09:29:36