We suggest a simple approach to achieve light amplification without population inversion in Landau-quantized graphene. We provide a detailed analysis of the interaction between the applied coherent and incoherent fields and a three-level cascade-type magnetized graphene. The optical response of the system is obtained by numerically solving the density matrix equation in the transient regime. Then, the analytical expressions for the steady-state populations in Landau levels and the coherence term related to the optical gain are derived using the perturbation theory. The results demonstrate that the proposed system can deliver optical gain without population inversion, making it applicable in graphene-based optical amplifiers and lasers operating at THz frequencies.
We suggest a simple approach to achieve light amplification without population inversion in Landau-quantized graphene. We provide a detailed analysis of the interaction between the applied coherent and incoherent fields and a three-level cascade-type magnetized graphene. The optical response of the system is obtained by numerically solving the density matrix equation in the transient regime. Then, the analytical expressions for the steady-state populations in Landau levels and the coherence term related to the optical gain are derived using the perturbation theory. The results demonstrate that the proposed system can deliver optical gain without population inversion, making it applicable in graphene-based optical amplifiers and lasers operating at THz frequencies.
In this study, we explore the interplay of laser beams with a graphene sample in a ladder configuration under various conditions of coherent and incoherent fields. We investigate how these interactions influence absorption and amplification, focusing on the effects of control field detuning, incoherent pumping, and varying decay rates. We first analyze the system’s response under resonance conditions, revealing symmetric gain profiles with distinct gain dips. As incoherent pumping is introduced, we observe a reduction in gain, highlighting the role of population transfer in modulating amplification. Furthermore, we examine the impact of control field detuning, which disrupts the symmetry of the gain profile and shifts the gain dip to nonzero detuning values. Additionally, by varying the decay rates of the intermediate state, we find that higher decay rates lead to asymmetric gain profiles and reduced amplification. Importantly, the gain observed in these graphene systems is inversionless. Our results provide insights into the tunability of graphene’s optical properties, demonstrating its potential for advanced optoelectronic applications that demand exact manipulation of light and material interactions.
Abstract In this paper, we investigated the behaviors of the absorptive-dispersive properties of weak probe light based on quantum coherence and interference in a Landau-quantized graphene nanostructure driven by coherent pumping fields. The linear dynamical properties of the grapheme are discussed with reference to the density matrix method and the perturbation theory. It is found that under certain conditions and by an appropriate selection of the parameters of the medium, the absorption, dispersion and group index of the weak probe light can be controlled. Moreover, the superluminal light propagation in the system is accompanied by amplification to make sure that the probe field is amplified as it passes through the system via adjusting the corresponding controllable parameters such as the intensity, the detuning and the relative phase of the applied fields. Moreover, it is observed that the probe amplification can be obtained in the presence or absence of population inversion by properly choosing the system’s parameters. We hope that these results may have useful application in future quantum communicational systems and networks.
Landau-quantized graphene (LQG) offers a magnetically controlled platform for manipulating coherent inter-Landau-level transitions of Dirac fermions. Such a platform provides compact control of terahertz and infrared photonic signals. Here, a closed-form susceptibility expression is derived using the density-matrix approach, where the real part of the susceptibility describes dispersion and the imaginary part describes absorption or gain. The numerical results show that tuning the control field modifies the probe response from a dispersive resonance regime to a transparency window and a gain-assisted response. The calculated group-index variation, approximately from 0.6 to 1.7, enables broad modulation of the probe group velocity, ranging from about 1.8 × 10 8 m/s to 5.2 × 10 8 m/s . The reduced-absorption region indicates an electromagnetically induced transparency response suitable for controlled probe-field transmission. Distinct spectral features are also observed in the absorption coefficient and electron energy-loss spectrum (ELS), indicating selective energy transfer near the LQG resonance and potential relevance for THz/IR modulation. In addition, the frequency-selective and sign-reversible photon-drag response suggests detuning-controlled optical momentum transfer. These tunable responses within the linear regime support LQG as a reconfigurable medium for quantum optical transport, synchronization, pulse routing, buffering, and chip-scale THz photonic interfaces.
We analyze transient properties of light amplification without population inversion (LWI) in a closed three-level @sV -type system and study the system evolution from transient LWI into steady-state LWI. From the time evolution of the atomic coherence and population distribution with and without an incoherent pump field, we elucidate the light amplification mechanism and derive the conditions under which the @sV system exhibits LWI in any state basis. We derive analytical solution for the steady-state LWI and discuss other mechanisms of light amplification such as stimulated Raman scattering and population inversion in the dressed states. \textcopyright{} 1996 The American Physical Society.
Abstract In this article, we discuss the dynamic and steady-state features of the absorption-dispersion of a graphene monolayer system, interacting with an elliptically polarized control and coherent pumping fields. We find that, under a proper condition of parameters selection, the absorption, dispersion and group index of the weakly probe field in a monolayer graphene system can be adjusted. We show that, under optimal conditions, the controlling of the group velocity can be possible to achieve the subluminal and superluminal light propagation. Moreover, we realize that the amplification of the probe light due to the presence and absence of population inversion can be obtained by the proper choice of controllable parameters. Our findings may be useful for high-speed optical communications based on a graphene monolayer system.
We analyze transient properties of light amplification in a coherently coupled three-level \ensuremath{\Lambda}-type system and study the system evolution from the transient regime into the steady state. From the time evolution of the atomic coherence and population distribution, we discuss the transient light amplification mechanism with and without population inversion. We also solve the density-matrix equations in the steady state and derive the conditions for the existence of specific light amplification mechanisms, such as light amplification without inversion in any standard state basis, light amplification by stimulated Raman scattering, and light amplification from population inversion in the dressed states.