1,720,991 research outputs found
Rate equation analysis of slow-light photonic crystal lasers
Full text linkSlow-light (SL) in active photonic crystal (PhC) waveguides enhances the modal gain per unit length [1], with application to shorter lasers [2]. Recently, we have proposed a coupled-Bloch-mode (CBM) approach [4] to analyze active PhC structures. Essentially, the presence of material gain in a line-defect waveguide is viewed as a weak perturbation to a reference structure with purely real refractive index. In the SL regime, the optical gain induces a distributed feedback (DFB) between the counterpropagating Bloch modes of the reference waveguide. The active waveguide is efficiently described by a scattering matrix [5], which accounts for the SL gain enhancement and gain-induced DFB. In particular, this effect reveals that SL semiconductor optical amplifiers may benefit from a smaller linewidth enhancement factor (LEF) [5], as they would experience a weaker backscattering
Modulation properties and nonlinear dynamics induced by optical feedback in distributed-feedback quantum cascade lasers
Full text linkThis study explores the dynamic behavior of distributed-feedback quantum cascade lasers (QCLs) through numerical simulations based on the Effective Semiconductor Maxwell-Bloch Equations (ESMBEs). First, we analyze the intrinsic intensity modulation response of QCLs, demonstrating that the modulation bandwidth is fundamentally constrained by the population grating induced by the standing-wave pattern in the QCL cavity, namely, spatial hole burning (SHB). We then extend the ESMBEs framework to incorporate the effects of an external target, enabling the investigation of multimode nonlinear dynamics in QCLs subject to external optical feedback (EOF). Our findings identify fast SHB and a non-zero linewidth enhancement factor as key physical mechanisms governing the emergence of complex multimode behavior and the eventual transition to chaos. Notably, we reveal that QCL destabilization under EOF arises from interactions between internal longitudinal modes and external cavity modes, rather than from undamped relaxation oscillations, as typically observed in conventional semiconductor lasers. Furthermore, we examine the evolution of the system's dynamics as a function of feedback strength, demonstrating the onset of photonic chaos at feedback levels two orders of magnitude higher than those required in traditional diode lasers, in agreement with experimental observations existing in the literature. Finally, we assess the correlation dimension of the attractor of the resulting nonlinear dynamics. Beyond fundamental insight, this work introduces the use of ESMBEs as a predictive framework for experimental interpretation and device design, enabling the engineering of QCLs for mid- and long-infrared free-space applications, including high-speed transmission, chaos-based LiDAR, and random number generation. (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International (CC BY-NC-ND) license (https://creativecommons.org/licenses/by-nc-nd/4.0/)
Few-GHz repetition rate frequency combs in IIIV/SiN external cavity lasers
No full textWe study the dynamics of hybrid integrated lasers with dispersive effective reflectivity implemented through coupled microrings in a SiN platform. We investigate the self-generation of optical frequency combs and characterize them in terms of bandwidth, spectral line separation, phase and amplitude noise
Numerical Study of Optical Frequency Combs in mid-IR Quantum Cascade Lasers: Effective Semiconductor Maxwell-Bloch Equations
Full text linkIn this paper a theoretical model based on Effective Semiconductor Maxwell-Bloch Equations (ESMBEs) is proposed for the description of the dynamics of a multi-mode mid-Infrared (mid-IR) Quantum Cascade Laser (QCL) in Fabry Perot (FP) configuration, in order to investigate the spontaneous generation of frequency combs in this device. In agreement with recent experimental results our numerical simulations show both chaotic and regular multimode regimes. In the latter case we identify self-confined structures travelling along the cavity, and furthermore the instantaneous frequency is characterized by a linear chirp behaviour
Simulation of Quantum Dot Fabry-Perot Comb Lasers: Role of the Carrier Grating
No full textWe report a systematic analysis of multi-mode dynamics and in Quantum Dot single section lasers using a Time Domain Travelling Wave model. We observed that the inclusion of the carrier grating effect in our model reduces the multi-mode instability threshold and eventually leads to the generation of optical frequency combs
A simple coupled-bloch-mode approach to study active photonic crystal waveguides and lasers
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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