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Analyzing the effect of higher order nonlinearity on dispersion relation and optical multistability generation in oppositely directed coupler
摘要： We report the influence of higher order nonlinearity on dispersion relation and multistability in oppositely directed coupler with negative index material channel. The study shows that the high intensity electric field shifts the photonic bandgap down in energy. When the positive index material channel of the coupler is influenced by quintic nonlinearity the group velocity of upper branch of dispersion curve (δ–q curve) falls to zero in positive q region and the loop in the lower branch shifts to positive q region. But the minima in upper branch and loop in the lower branch are observed at negative q region when the negative index material channel is influenced by χ(5) nonlinearity. As the curvature of the dispersion relation determines the group velocity dispersion the study report the possibility for dispersion engineering in oppositely directed coupler. Also we observed that the quintic nonlinearity enhances formation of multi stable states.
关键词： Oppositely directed coupler,Multistability,Optical switching,Negative index materials
更新于2025-09-23 15:23:52
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Experimental Study of Multistability in a Multimode Vertical-Cavity Laser
摘要： The coexistence of various spatial distributions of laser intensity in a multimode vertical-cavity surface-emitting laser (VCSEL) at ? xed DC values was experimentally demonstrated. Their structures were characterized by different integrated intensities, polarization states, and sets of wavelengths. Spatial multistability was shown to lead to the appearance of multistability in the laser intensity and polarization multistability and was characterized by a strong local dependence of the laser intensity hysteresis behavior on the pump current. The effect of the diode-laser temperature on the manifestation of multistability was also investigated.
关键词： local properties,vibrational resonance,VCSEL,multistability
更新于2025-09-23 15:21:01
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Frequency characteristics of a gas coupled-cavity ring laser
摘要： Based on a theoretical model describing the lasing dynamics in a gas ring laser (GRL) with coupled cavities, we have investigated the frequency characteristics of radiation. The conditions are found under which an increase in the scale factor is the largest. The regime of frequency locking of counterpropagating waves is studied. It is shown that the lock-in region in a GRL with an antiphase optical coupling of the cavities remains the same as without an additional cavity. The conditions are determined under which multistability of the radiation characteristics arises in a coupled-cavity GRL. In the numerical solution of the equations of the considered theoretical model, three branches of the frequency response are found.
关键词： multistability of radiation characteristics,gas ring laser,lock-in regime,coupled cavities,regime of beatings
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Symmetry Properties and Coexistence of the Mode-Locked States in Semiconductor Lasers
摘要： Coexistence of multiple dynamical states of operation is known in multimode lasers. In this work, we examine the symmetry properties of various laser models based on the delay differential equation (DDE) approach [1], and explain a vast class of experimental observations in mode-locked semiconductor lasers. In these models, the complex electric field amplitude ( )E t is presented by the equation having the form: 1 (cid:16) (cid:74) (cid:5) E t ( ) exp( (1) where dot means differentiation with respect to time, (cid:74) is the width of a Lorentzian bandwidth limiting element T(cid:77)(cid:32) (cid:58) is the term accounting the frequency detuning (cid:58) between one of the (such as a filter or gain profile); cavity modes and the transmittance peak of the filter; T is the cold cavity round trip time; is a function describing gain, saturable losses or/and nonlinearity. ) i R t T E t T (cid:77) R t T(cid:16) E t ( ) (cid:32) (cid:16) (cid:16) (cid:16) (cid:14) ) ( ( ) ( ) The phase parameter (cid:77) is 2(cid:652)-periodic translationally symmetrical. Continuous variation of the phase parameter (cid:77) allows for ‘unwrapping’ and overcoming this periodicity, unveiling translational symmetry in the system. The translational symmetry explains the appearance of multiple coexisting branches in the system, and multistability of the invariant solutions. We study this effect for several different systems, namely, a mode- locked single-section semiconductor laser, a mode-locked semiconductor laser with optical feedback, and a figure-eight semiconductor laser with a nonlinear amplifying loop mirror. By means of numerical continuation technique, we show that variation of the frequency detuning is the key to unveiling translationally symmetrical branches of laser mode-locked regimes, and their multistability. The multistable operations can demonstrate either slightly different repetition rates or/and very different temporal pulse profiles varying from Gaussian pulses to square waves. In order to corroborate our theoretical results experimentally, we explore single-section semiconductor quantum dash (Qdash) laser, and demonstrate switching and coexistence of two mode-locked operation states. The mode-locked regime repetition rate decreases with the pump current as a result of a thermally induced increase of the cavity length (see Fig. 1(a)). At 150 mA, the rf spectrum jumps discretely by approximately 2 MHz. This is accompanied by a jump in the optical spectrum of approximately 2 nm. After the jump, the repetition rate starts to decrease again until the next jump. This change of the cavity length induces the variation of the longitudinal mode spacing and, therefore, detuning between the dominant cavity mode and the peak of the gain profile, physically corresponding to the parameter (cid:77) in the model. The numerical bifurcation diagram plotted for the repetition rate evolution of the mode-locked operation is shown in Fig. 1(b), and the corresponding time traces are given in Fig. 1(c). The translational symmetry is ubiquitous in DDE laser models, and possibly, more effects of multistability related to multimode laser operation can be explained in this way.
关键词： delay differential equation,symmetry properties,mode-locked states,semiconductor lasers,multistability
更新于2025-09-12 10:27:22
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Vortex Multistability and Bessel Vortices in Polariton Condensates
摘要： Vortices are topological objects formed in coherent nonlinear systems. As such they are studied in a wide number of physical systems and promise applications in information storage, processing, and communication. In semiconductor microcavities, vortices in polariton condensates can be conveniently created, studied, and manipulated using solely optical means. For nonresonant excitation with a ring-shaped pump a stable vortex can be formed, leading to bistability with left- and right-handed vorticity. In the present work we report on a much richer vortex multistability, with optically addressable vortices with topological charges m ? (cid:2)1, (cid:2)2, and (cid:2)3, all stable for the same system and excitation parameters. This unusual multistable behavior is rooted in the inherent nonlinear feedback between reservoir excitations and condensate in the microcavity. For larger radius of the ring-shaped pump we also find a Bessel vortex with its characteristic spiralling phase in the high density region and pronounced self-stabilization ability. Our theoretical results open up exciting possibilities for optical manipulation of vortex multiplets in a compact semiconductor system.
关键词： Vortices,Polariton condensates,Bessel vortex,Nonlinear feedback,Multistability
更新于2025-09-09 09:28:46
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Optical bistability and multistability via both coherent and incoherent fields in a three-level system
摘要： We have investigated the optical bistability and multistability behaviors in a three-level V-type system via both coherent and incoherent fields inside a unidirectional ring cavity. We find that the appearance and disappearance of optical bistability (OB)/optical multistability (OM) can easily be controlled by adjusting systemic parameters. Our scheme opens up a new possibility for realizing transition from OB to OM or vice versa for potential applications in information networks and processing with increased capacity.
关键词： optical bistability,optical multistability,incoherent field
更新于2025-09-04 15:30:14