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Recent progress on narrow-linewidth crystalline bulk Raman lasers
摘要： Narrow-linewidth, solid-state Raman lasers are of signi?cant importance for numerous applications. In last decade, variety of methods have been utilized to suppress the spectral linewidth of Raman laser output. In this review we summarize the recent works of narrow-linewidth and/or single-frequency solid-state Raman lasers. The mechanisms and results are addressed while the positive and negative aspects of each technique are also discussed to give the readers a reference to choose a proper narrow-linewidth method for certain applications.
关键词： F-P etalon,Injection seeding,Narrow-linewidth laser,Single-frequency laser,Raman laser,Spatial hole burning
更新于2025-09-23 15:21:01
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Universal Output Characteristics of Single-Mode Operation in Low-Loss Large- <i>V</i> -Number Multimode Waveguide Lasers with Transverse Spatial Hole Burning
摘要： We study the performance limit of single-mode operation in low-loss large-V-number planar waveguide lasers, with transverse spatial hole burning as the dominating mechanism for transverse-mode competition. By introducing normalized variables, we develop a simple semianalytical model to describe the universal output characteristics of single-mode emission before the onset of high-order modes, which can be easily scaled to a wide range of laser configuration parameters. Our model is validated using exact numerical solutions, which show applicability beyond that of the low-loss approximation. Our analysis establishes a minimum criterion of the loss ratio between the fundamental and first higher-order mode for a robust single-mode operation. This criterion is much weaker than that of conventional wisdom based on the pure wave-propagation argument, which we attribute to a resonator enhancement effect. Our universal outcome can be denormalized to establish the relationship between single-mode extraction efficiency and optimum output coupling in a multimode laser with arbitrary modal loss ratios over a wide range of single-pass unsaturated gain and loss.
关键词： single-mode operation,transverse spatial hole burning,multimode waveguide lasers,large-V-number,low-loss
更新于2025-09-23 15:19:57
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Multimode dynamics and modeling of free-running and optically injected Fabry-Pérot quantum-dot lasers
摘要： We derive and apply a numerical model for the description of optically injected long-cavity Fabry-Pérot (FP) quantum-dot (QD) lasers, based on a multisection delay-algebraic-equation approach. In conjunction with experimental measurements, we characterize the multimode dynamics of the free-running laser as well as under external optical injection. We investigate the dynamics of the spatial hole burning (SHB) in the charge-carrier distribution, which is signi?cant in QD lasers and is furthermore a driving mechanism for the emergence of multimode dynamics. In the injected laser, we focus on the transition between the locking regions of neighboring FP modes, which could not be described using traditional multimode rate-equation models. For very strong injection, the individual locking cones are found to converge. For intermediate injection strength, an additional dynamic boundary between the unlocked states is found in a narrow dynamical region in between two neighboring locking cones. This region is characterized by a further unlocking of all laser modes. Furthermore, we ?nd the SHB to impose a threshold in the locking strength which must be overcome to lock a laser mode.
关键词： Fabry-Pérot quantum-dot lasers,multimode dynamics,locking regions,spatial hole burning,optical injection
更新于2025-09-16 10:30:52
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Numerical study of Riskena??Nummedala??Grahama??Haken instability in mid-infrared Fabrya??P??rot quantum cascade lasers
摘要： We review our recent theoretical studies on multimode instabilities in Fabry–Pérot cavity mid-infrared quantum cascade lasers (QCLs) caused by parametric excitation of Rabi flopping oscillations. Numerical simulations are based on the semiclassical traveling wave Maxwell–Bloch equations. QCLs with a few mm cavity without an absorber exhibit intermittent RNGH self-pulsations, while regular self-pulsations are possible in short-cavity QCLs, with the cavity length of 100 μm or smaller. However, the second threshold in short-cavity QCLs is significantly increased compared to the values for a few mm long devices. We provide here a new insight on RNGH instability via bifurcation analysis of the output waveform and studies of the recurrence period density entropy. We propose an interpretation of the broadening/narrowing of the optical spectrum of a QCL i.e. switching the RNGH instability on and off observed in experiment.
关键词： Quantum cascade laser,RNGH instability,Self-pulsations,Bifurcation diagram,Spatial hole burning
更新于2025-09-16 10:30:52
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Theory of Frequency-Modulated Combs in Lasers with Spatial Hole Burning, Dispersion, and Kerr Nonlinearity
摘要： Frequency-modulated (FM) frequency combs constitute an exciting alternative to generate equidistant spectra. The full set of Maxwell-Bloch equations is reduced to a single master equation for lasers with fast gain dynamics to provide insight into the governing mechanisms behind phase locking. It reveals that the recently observed linear frequency chirp is caused by the combined effects of spatial hole burning, group velocity dispersion, and Kerr nonlinearity due to asymmetric gain. The comparison to observations in various semiconductor lasers suggests that the linear chirp is general to self-starting FM combs.
关键词： dispersion,spatial hole burning,semiconductor lasers,Kerr nonlinearity,Frequency-modulated combs
更新于2025-09-12 10:27:22