| 1. |
- Anderson, Dan, 1943, et al.
(författare)
-
Parabolic similarity solutions of the Nonlinear Schrödinger and Wigner-Moyal equations
- 2008
-
Ingår i: in Proceedings of SIAM Conference on Nonlinear Waves and Coherent Structures, July 21-24, 2008, Rome, Italy, Society for Industrial and Applied Mathematics (SIAM), Philadelphia, PA, USA. ; , s. 56-
-
Konferensbidrag (refereegranskat)
|
|
| 2. |
- Cattani, F., et al.
(författare)
-
Multihump soliton-like structures in interactions of lasers and Bose-Einstein condensates
- 2011
-
Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 94:5, s. 53003-
-
Tidskriftsartikel (refereegranskat)abstract
- An investigation is made of multihump and periodic solutions of the semiclassical coupled equations describing laser radiation copropagating with a Bose-Einstein condensate. Solutions reminiscent of optical vector solitons have been found and have been used to gain understanding of the dynamics observed in the numerical simulations, in particular to shed light on the phenomenon of jet emission from a condensate interacting with a laser.
|
|
| 3. |
- Ceoldo, D., et al.
(författare)
-
Kerr frequency combs in a bichromatically pumped nonlinear fiber ring cavity
- 2016
-
Ingår i: 42nd European Conference on Optical Communication, ECOC 2016; Dusseldorf; Germany; 18 September 2016 through 22 September 2016. - 9783800742745 ; , s. 538-540
-
Konferensbidrag (refereegranskat)abstract
- We report numerical and experimental studies of four-wave mixing processes emerging from dual-frequency pumping of a passive fibre ring cavity. We observe the emission of a periodic train of nearly-background-free soliton pulses associated with Kerr frequency combs.
|
|
| 4. |
- Erkintalo, M., et al.
(författare)
-
Frequency combs in quadratically nonlinear resonators
- 2016
-
Ingår i: Optics InfoBase Conference Papers. - 2162-2701. - 9781943580170 ; , s. paper NM3A.1-
-
Konferensbidrag (refereegranskat)abstract
- We describe the physics and modelling of frequency combs and corresponding temporal patterns in coherently driven, quadratically nonlinear resonators.
|
|
| 5. |
- Erkintalo, M., et al.
(författare)
-
Numerical modelling of frequency comb generation in nonlinear resonators
- 2016
-
Ingår i: 16th International Conference on Numerical Simulation of Optoelectronic Devices, NUSOD 2016, Sydney, Australia, 11-15 July 2016. - 2158-3234. - 9781467386036 ; , s. 187-188
-
Konferensbidrag (refereegranskat)abstract
- We present a comprehensive review of recent work on numerical modelling of frequency comb generation in coherently-driven nonlinear resonators. Specifically, we discuss modelling and nonlinear dynamics of frequency combs generated in Kerr nonlinear microresonators, emphasizing links to similar dynamics studied in macroscopic fibre cavities. In addition to established Kerr frequency comb generators, we will also discuss emerging comb generation platforms based on continuously-driven quadratically nonlinear resonators.
|
|
| 6. |
- Hansson, Tobias, 1983, et al.
(författare)
-
Bichromatically pumped microresonator frequency combs
- 2014
-
Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934. ; 90:1
-
Tidskriftsartikel (refereegranskat)abstract
- A study is made of the nonlinear dynamics of bichromatically pumped microresonator Kerr frequency combs described by a driven and damped nonlinear Schrodinger equation, with an additional degree of freedom in the form of the modulation frequency. A truncated four-wave model is derived for the pump modes and the dominant sideband pair, which is found to be able to describe much of the essential dynamical behavior of the full equation. The stability of stationary states within the four-wave model is investigated, and numerical simulations are made to demonstrate that a large range of solutions, including cavity solitons, are possible beyond previously considered low-intensity patterns.
|
|
| 7. |
- Hansson, Tobias, 1983-, et al.
(författare)
-
Bistable solitons in third-harmonic generation frequency combs
- 2023
-
Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE.
-
Konferensbidrag (refereegranskat)abstract
- We present a theoretical model for describing dissipative solitons and optical frequency combs formation in a dispersive and nonlinear χ(3)-based cavity system that is phase-matched for third-harmonic generation. We consider the importance of the stability properties of the homogeneous solution in generating various types of multi-frequency combs, and demonstrate a novel type of bistable cavity solitons.
|
|
| 8. |
- Hansson, Tobias, 1983, et al.
(författare)
-
Complex temporal dynamics in optical cavities
- 2015
-
Ingår i: 2015 Spatiotemporal Complexity in Nonlinear Optics, SCNO 2015, Como, Italy, 31 August-4 September. - 9781467380614
-
Konferensbidrag (refereegranskat)abstract
- We overview recent advances in the modeling and understanding of complex spatiotemporal dynamics associated with the generation of optical frequency combs in microresonators.
|
|
| 9. |
|
|
| 10. |
- Hansson, Tobias, 1983, et al.
(författare)
-
Dynamics of Frequency Comb Generation and Design of Planar Microring Resonators
- 2014
-
Ingår i: Proceedings of SIAM Conference on Nonlinear Waves and Coherent Structures, Cambridge UK, August 2014.
-
Konferensbidrag (refereegranskat)abstract
- We study the generation of optical frequency combs from microresonators and show that a truncated dynamical model can capture the essential nonlinear dynamics of both stable and chaotic patterns. We also present an analytical approach for obtaining linear and nonlinear design parameters of planar microring resonators. Closed form approximations for the eigenmode/eigenfrequency problem are derived for resonators possessing a large radius to width ratio and examples are presented for silicon microrings.
|
|
| 11. |
- Hansson, Tobias, 1983, et al.
(författare)
-
Dynamics of microresonator frequency comb generation: models and stability
- 2016
-
Ingår i: Nanophotonics. - : Walter de Gruyter GmbH. - 2192-8614 .- 2192-8606. ; 5:2, s. 231-243
-
Forskningsöversikt (refereegranskat)abstract
- Microresonator frequency combs hold promise for enabling a new class of light sources that are simultaneously both broadband and coherent, and that could allow for a profusion of potential applications. In this article, we review various theoretical models for describing the temporal dynamics and formation of optical frequency combs. These models form the basis for performing numerical simulations that can be used in order to better understand the comb generation process, for example helping to identify the universal combcharacteristics and their different associated physical phenomena. Moreover, models allow for the study, design and optimization of comb properties prior to the fabrication of actual devices. We consider and derive theoretical formalisms based on the Ikeda map, the modal expansion approach, and the Lugiato-Lefever equation. We further discuss the generation of frequency combs in silicon resonators featuring multiphoton absorption and free-carrier effects. Additionally, we review comb stability properties and consider the role of modulational instability as well as of parametric instabilities due to the boundary conditions of the cavity. These instability mechanisms are the basis for comprehending the process of frequency comb formation, for identifying the different dynamical regimes and the associated dependence on the comb parameters. Finally, we also discuss the phenomena of continuous wave bi- and multistability and its relation to the observation of mode-locked cavity solitons.
|
|
| 12. |
- Hansson, Tobias, 1983, et al.
(författare)
-
Frequency comb generation beyond the Lugiato-Lefever equation: multi-stability and super cavity solitons
- 2015
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 32:7, s. 1259-1266
-
Tidskriftsartikel (refereegranskat)abstract
- The generation of optical frequency combs in microresonators is considered without resorting to the mean-field approximation. New dynamical regimes are found to appear for high intracavity power that cannot be modeled using the Lugiato-Lefever equation. Using the Ikeda map, we show the existence of multi-valued stationary states and analyze their stability. Period doubled patterns are considered, and a novel type of super cavity soliton associated with the multi-stable states is predicted.
|
|
| 13. |
- Hansson, Tobias, 1983, et al.
(författare)
-
Generalized dressing method for nonlinear evolution equations describing partially coherent wave propagation in noninstantaneous Kerr media
- 2011
-
Ingår i: Physical Review E. - 2470-0045 .- 2470-0053. ; 84:5, s. 056601-
-
Tidskriftsartikel (refereegranskat)abstract
- A generalized dressing method is presented for integration of the nonlinear evolution equation of the coherent density function describing partially coherent wave propagation in a noninstantaneous Kerr media. As an example an exact, partially coherent multisource N-soliton solution is derived. It is also demonstrated how this method is applicable for construction of solutions to the equivalent coupled system of nonlinear Schrodinger equations of the self-consistent multimode theory.
|
|
| 14. |
|
|
| 15. |
- Hansson, Tobias, 1983, et al.
(författare)
-
Mid-infrared octave spanning frequency comb generation in silicon microrings
- 2014
-
Ingår i: European Conference on Optical Communication (ECOC) 2014. Cannes, France, September 2014.
-
Konferensbidrag (refereegranskat)abstract
- We numerically show that octave-spanning Kerr frequency comb generation in the MIR spectral region may be obtained from planar microring resonators, by combining analytical dispersion engineering with generalized nonlinear envelope equation simulations of the temporal frequency comb dynamics.
|
|
| 16. |
- Hansson, Tobias, 1983, et al.
(författare)
-
Mid-infrared soliton and Raman frequency comb generation in silicon microrings
- 2014
-
Ingår i: Optics Letters. - : The Optical Society. - 0146-9592 .- 1539-4794. ; 39:23, s. 6747-6750
-
Tidskriftsartikel (refereegranskat)abstract
- We numerically study the mechanisms of frequency comb generation in the mid-infrared spectral region from cw-pumped silicon microring resonators. Coherent soliton comb generation may be obtained even for a pump with zero linear cavity detuning, through suitable control of the effective lifetime of free carriers from multiphoton absorption, which introduces a nonlinear cavity detuning via free-carrier dispersion. Conditions for optimal octave spanning Raman comb generation are also described.
|
|
| 17. |
|
|
| 18. |
- Hansson, Tobias, 1983, et al.
(författare)
-
Multi-stability and super cavity solitons in microresonator frequency combs
- 2015
-
Ingår i: Integrated Photonics Research, Silicon and Nanophotonics, IPRSN 2015, Boston, United States; 27 June - 1 July 2015. - 9781557520005
-
Konferensbidrag (refereegranskat)abstract
- Frequency comb generation in microresonators is considered beyond the meanfield approximation. We show the appearance of multi-valued stationary states and predict the existence of a novel type of super cavity solitons.
|
|
| 19. |
- Hansson, Tobias, 1983
(författare)
-
Nonlinear Dynamics of Coherent and Partially Coherent Optical Waves
- 2009
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In optics an important nonlinear effect is manifested by the fact that the refractive index, in addition to its frequency dependence, also depends on the intensity of the light. Nonlinear effects are present within a wide range of optical applications e.g. the fast growing fields of fiber-optic communication and all-optical signal processing. In recent years, the possibility of using sources with partial coherence has attracted strong interest as the degree of coherence plays a significant role for the propagation properties of the light and its interaction with the medium. Several approaches have been suggested for describing the nonlinear dynamics of partially coherent light and in this thesis we treat four of them, presenting their characteristic evolution equations and initial source conditions. An important feature of nonlinear wave propagation is the modulational instability. In this thesis the quasilinear evolution of the modulational instability beyond its initial linear stage is analyzed. A new exact solution of the Wigner-Moyal equation, which determines the evolution of partially coherent light beams in nonlinear media, is derived. This solution represents a dynamic self-similar soliton solution with a parabolic intensity profile. Similarly, using two different formalisms, exact self-similar solutions are also obtained for partially coherent beams propagating in logarithmically saturable media. Finally, the mutual interaction of coherent solitons and partially coherent soliton stripes in logarithmic saturable media are analyzed.
|
|
| 20. |
- Hansson, Tobias, 1983
(författare)
-
Nonlinear Theory of Partially Coherent Optical Waves
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nonlinear effects arise in optics as a consequence of the medium properties being modified by the presence of light. Of particular interest are situations where the effect of the nonlinearity can be described by an intensity dependent refractive index and the subsequent interplay with dispersion and diffraction. Nonlinear optics finds many important applications, e.g. within fiber-optical communication and all-optical signal processing. In recent years, the possibility of using partially coherent light has additionally attracted strong interest as the degree of coherence may significantly influence the propagation properties of the light and its interaction with the medium.The present thesis is concerned with the nonlinear theory of partially coherent optical waves. Several approaches have been suggested for describing the nonlinear dynamics of partially coherent light and in this thesis four of them are considered, along with their characteristic evolution equations and initial source conditions. It is shown that the evolution of partially coherent waves in noninstantaneous Kerr media can be treated in the framework of inverse scattering with the presentation of a generalized dressing method along with a recursion relation for generating an infinite number of invariants. The theory is applied by considering the modulation instability beyond its initial linear stage and a new parabolic solution of the Wigner-Moyal equation, which is one of the equations describing the evolution of partially coherent waves, is derived. Wave propagation in saturable logarithmic media is further considered by the derivation of a dynamic self-similar solution using two different formalisms and an analysis of the mutual interaction of coherent solitons as well as partially coherent soliton stripes. Finally, considerations are made of some aspects of the collapse and blow up phenomena of radially symmetric beams.
|
|
| 21. |
|
|
| 22. |
|
|
| 23. |
- Hansson, Tobias, 1983, et al.
(författare)
-
Propagation of Partially Coherent Light in Nonlinear Media
- 2009
-
Ingår i: Progress in Electromagnetics Research Symposium (PIERS), August 18-21, 2009, Moscow, Russia, PIERS Proceedings, The Electromagnetics Academy, Cambridge, MA, USA. ; , s. 1391-1395
-
Konferensbidrag (refereegranskat)
|
|
| 24. |
- Hansson, Tobias, 1983, et al.
(författare)
-
Propagation of partially coherent solitons in saturable logarithmic media: A comparative analysis
- 2009
-
Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934. ; 80:3, s. 033819-
-
Tidskriftsartikel (refereegranskat)abstract
- Dynamic self-similar solutions of the nonlinear Schrodinger equation are derived describing the propagation of partially coherent solitons in media with saturable logarithmic nonlinearity. The analysis is based on both the Wigner and the coherent density formalisms and it is shown that although the approaches involve different analysis, the solutions for the evolution of the physically relevant intensity distributions are equivalent.
|
|
| 25. |
|
|
| 26. |
|
|
| 27. |
- Hansson, Tobias, 1983, et al.
(författare)
-
Self-similar collapse and blow up of laser beams in nonlinear Kerr media-Revisited
- 2011
-
Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018. ; 284:13, s. 3422-3427
-
Tidskriftsartikel (refereegranskat)abstract
- Some features of the blow up and collapse phenomena characteristic of the focusing nonlinear Schrodinger equation are discussed. Particular attention is given to recently found solutions describing self-similar collapse in the form of ring-shaped structures. The characteristic parameters of such collapsing rings are found and particular single-humped initial conditions giving rise to ring formation are also discussed. The possibility of self-similarly collapsing beams with parabolic intensity profiles is investigated and used to infer the blow up distance of initially Gaussian beams. The result is shown to be in good agreement with previous empirical results for the blow up distance. (C) 2011 Elsevier B.V. All rights reserved.
|
|
| 28. |
- Hansson, Tobias, 1983, et al.
(författare)
-
Single envelope equation modeling of multi-octave comb arrays in microresonators with quadratic and cubic nonlinearities
- 2016
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 33:6, s. 1207-1215
-
Tidskriftsartikel (refereegranskat)abstract
- We numerically study, by means of the single envelope equation, the generation of optical frequency combs ranging from the visible to the mid-infrared spectral regions in resonators with quadratic and cubic nonlinearities. Phase-matched quadratic wave-mixing processes among the comb lines can be activated by low-power continuous wave pumping in the near infrared of a radially poled lithium niobate whispering gallery resonator. We examine both separate and coexisting intracavity doubly resonant second-harmonic generation and parametric oscillation processes and find that modulation instabilities may lead to the formation of coupled comb arrays extending over multiple octaves. In the temporal domain, the frequency combs may correspond to pulse trains or even to a single pulse circulating in the cavity.
|
|
| 29. |
|
|
| 30. |
- Hansson, Tobias, 1983, et al.
(författare)
-
Soliton interaction in logarithmically saturable media
- 2009
-
Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018. ; 283:2, s. 318-322
-
Tidskriftsartikel (refereegranskat)abstract
- An analysis, based on the variational approach, is carried out of the interaction between two fully coherentsolitons as well as two partially coherent soliton stripes in a medium with logarithmic nonlinearity.For the coherent case, it is found that the interaction can be both attractive and repulsive depending onthe relative phase. The different interaction scenarios involve a bound system where the distancebetween the solitons oscillates with various magnitude of the oscillation amplitude, including total coalescence,and another where the solitons separate asymptotically. The effect of partial coherence on thesoliton interaction is also studied by analyzing the interaction between two partially coherent solitonstripes. It is found that the strength as well as the character (attractive/repulsive) of the interactionchanges for decreasing coherence. Thus, the general interaction properties of solitons in logarithmic nonlinearmedia are qualitatively similar to those of solitons in nonlinear Kerr media.
|
|
| 31. |
- Hansson, Tobias, 1983, et al.
(författare)
-
Theory of quadratic optical frequency combs
- 2016
-
Ingår i: International Conference on Transparent Optical Networks. - 2162-7339. - 9781509014675 ; 2016-August
-
Konferensbidrag (refereegranskat)abstract
- We present theoretical studies of optical frequency comb generation in dispersive quadratically nonlinear resonators. We introduce a mean field equation approach to model cavity enhanced second harmonic generation and find excellent agreement with recent experimental frequency comb observations. We also develop a more general approach based on a single envelope equation for both quadratic and Kerr nonlinear cavities. © 2016 IEEE.
|
|
| 32. |
- Jeong, H., et al.
(författare)
-
Evolution of Sommerfeld and Brillouin precursors in intermediate spectral regimes
- 2009
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 26:12, s. 2455-2460
-
Tidskriftsartikel (refereegranskat)abstract
- We study, numerically, the transitional behavior of precursors in the intermediate spectral regime between twocontrasting regimes for which analytical solutions exist. The two opposite regimes are, respectively, defined as(1) off-resonance carrier with a spectral pulse width comparable to the medium’s absorption linewidth and (2)on-resonance carrier with the spectral width of the pulse much narrower than the absorption linewidth. Beyondthese two regimes, there have been few studies of precursors. In this paper, we investigate precursordynamics for the intermediate spectral regime using the finite-difference time domain method. The parameterthat has the strongest influence on the precursor dynamics is found to be the plasma frequency, ωp. This researchis applicable for controlling transients in fast communication systems.
|
|
| 33. |
|
|
| 34. |
- Kim, A.V., et al.
(författare)
-
Extreme nonlinear optics in a Kerr medium: Exact soliton solutions for a few cycles
- 2008
-
Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934. ; 77, s. 043823 1-6
-
Tidskriftsartikel (refereegranskat)abstract
- Exact soliton solutions containing only a few cycles are found within the framework of a nonlinear full wave equation in a Kerr medium. It is proven numerically that they are stable and play a fundamental role in the pulse propagation dynamics. These wave solitons cover the range from the fundamental Schrodinger solitons, which occur for long pulses involving many field oscillations, to extremely short pulses, which contain only one optical period.
|
|
| 35. |
- Leo, F., et al.
(författare)
-
Frequency-comb formation in doubly resonant second-harmonic generation
- 2016
-
Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934. ; 93:4
-
Tidskriftsartikel (refereegranskat)abstract
- We theoretically study the generation of optical frequency combs and corresponding pulse trains in doubly resonant intracavity second-harmonic generation (SHG). We find that, despite the large temporal walk-off characteristic of realistic cavity systems, the nonlinear dynamics can be accurately and efficiently modeled using a pair of coupled mean-field equations. Through rigorous stability analysis of the system's steady-state continuous-wave solutions, we demonstrate that walk-off can give rise to an unexplored regime of temporal modulation instability. Numerical simulations performed in this regime reveal rich dynamical behaviors, including the emergence of temporal patterns that correspond to coherent optical frequency combs. We also demonstrate that the two coupled equations that govern the doubly resonant cavity behavior can, under typical conditions, be reduced to a single mean-field equation akin to that describing the dynamics of singly-resonant-cavity SHG [F. Leo et al., Phys. Rev. Lett. 116, 033901 (2016)]. This reduced approach allows us to derive a simple expression for the modulation instability gain, thus permitting us to acquire significant insight into the underlying physics. We anticipate that our work will have a wide impact on the study of frequency combs in emerging doubly resonant cavity SHG platforms, including quadratically nonlinear microresonators.
|
|
| 36. |
- Leo, F., et al.
(författare)
-
Theory of Frequency Comb Generation in Cavity Enhanced Second Harmonic Generation
- 2016
-
Ingår i: 2016 Conference on Lasers and Electro-Optics, CLEO 2016, San Jose, United States, 5-10 June 2016. - 2160-9020. - 9781943580118
-
Konferensbidrag (refereegranskat)abstract
- We theoretically investigate frequency comb generation in dispersive quadratically nonlinear resonators. We introduce a single mean field equation to model cavity enhanced second harmonic generation and find excellent agreement with recent experimental frequency comb observations.
|
|
| 37. |
- Leo, F., et al.
(författare)
-
Walk-Off-Induced Modulation Instability, Temporal Pattern Formation, and Frequency Comb Generation in Cavity-Enhanced Second-Harmonic Generation
- 2016
-
Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 116:3
-
Tidskriftsartikel (refereegranskat)abstract
- We derive a time-domain mean-field equation to model the full temporal and spectral dynamics of light in singly resonant cavity-enhanced second-harmonic generation systems. We show that the temporal walk-off between the fundamental and the second-harmonic fields plays a decisive role under realistic conditions, giving rise to rich, previously unidentified nonlinear behavior. Through linear stability analysis and numerical simulations, we discover a new kind of quadratic modulation instability which leads to the formation of optical frequency combs and associated time-domain dissipative structures. Our numerical simulations show excellent agreement with recent experimental observations of frequency combs in quadratic nonlinear media [Phys. Rev. A 91, 063839 (2015)]. Thus, in addition to unveiling a new, experimentally accessible regime of nonlinear dynamics, our work enables predictive modeling of frequency comb generation in cavity-enhanced second-harmonic generation systems. We expect our findings to have wide impact on the study of temporal and spectral dynamics in a diverse range of dispersive, quadratically nonlinear resonators.
|
|
| 38. |
- Mangini, F., et al.
(författare)
-
Self-imaging dynamics in nonlinear GRIN multimode optical fibers
- 2020
-
Ingår i: Optics InfoBase Conference Papers. - : Optica Publishing Group. - 9781943580804
-
Konferensbidrag (refereegranskat)abstract
- We study nonlinear self-imaging dynamics in graded-index multimode optical fibers. Side-scattering of light that accompanies the propagation of intense femtosecond pulses permits us to directly measure the self-imaging period.
|
|
| 39. |
|
|
| 40. |
- Parra-Rivas, P., et al.
(författare)
-
Locking of Domain Walls and Quadratic Frequency Combs in Doubly Resonant Optical Parametric Oscillators
- 2019
-
Konferensbidrag (refereegranskat)abstract
- The formation of frequency combs (FCs) in high-Q microresonators with Kerr type of nonlinearity has attracted a lot of attention in the past decade [1]. Recently it has been shown that FCs can be also generated in dissipative dispersive cavities with quadratic nonlinearities [2,3], opening a new possibility of generating combs in previously unattainable spectral regions. Previous work has shown that modulational instability (MI) induces pattern and FC formation in degenerate optical parametric oscillators (OPOs) [4]. However, the existence of dissipative solitons or localized structures (LSs) is still unclear. In this work we present the locking of domain walls (DWs) as an alternative mechanism to MI for the formation of LSs and FCs. DWs have been widely studied in the context of Kerr cavities and diffractive OPO cavities [5,6]. Here we show that similar structures can arise in dispersive quadratic cavities. To illustrate this, we consider a dispersive cavity with a quadratic medium phase matched for degenerate OPO and driven by the field B in at the frequency 2ω 0 in a doubly resonant configuration. The formation of dissipative structures in this type of cavity can be described by an infinite map for the slowly varying electric field envelopes A m , and B m , that are centered at frequency ω 0 and 2ω 0 , respectively [4], where m indicates the cavity round-trip number. With this map one may numerically explore the dynamics of the system. For example, Fig. 1(a)-(b) show the formation of a dissipative structure, after a sufficient number of round-trips (m = 2 · 10 4 ), from an initial noisy background. We see that i) both fields are phase locked and drift at the same velocity; ii) for the A field one can identify a sequence of DWs connecting two different, and coexisting, CW states, that form a disordered structure. Furthermore, the latter is composed of a sequence of LSs of different widths. One of them, LS 4 , is plotted in panel (c). We demonstrate that this ty...
|
|
| 41. |
- Ricciardi, Iolanda, et al.
(författare)
-
Experimental Observation of Optical Frequency Combs in Doubly Resonant Second Harmonic Generation
- 2019
-
Konferensbidrag (refereegranskat)abstract
- Continuously-driven microresonators, whose nonlinear response is dominated by the third-order Kerr nonlinearity, have proven to be valid alternatives to comb sources based on femtosecond mode-locked lasers [1]. More recenlty, the direct generation of optical frequency combs (OFCs) entirely through quadratic interactions has also been demonstrated in singly resonant cavity second harmonic generation (SHG) and in cw pumped nearly degenerate optical parametric oscillation [2,3]. Interestingly, theoretical studies on doubly resonant cavity SHG predicted the emergence of OFCs with a much lower threshold with respect to the singly resonant configurations, as well as rich nonlinear dynamics [4].
|
|
| 42. |
- Ricciardi, Iolanda, et al.
(författare)
-
Optical frequency combs in dispersion-controlled doubly resonant second-harmonic generation
- 2022
-
Ingår i: Optics Express. - Washington, DC, United States : Optica Publishing Group. - 1094-4087. ; 30:25, s. 45694-45704
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the experimental realization and a systematic study of optical frequency comb generation in doubly resonant intracavity second harmonic generation (SHG). The efficiency of intracavity nonlinear processes usually benefits from the increasing number of resonating fields. Yet, achieving the simultaneous resonance of different fields may be technically complicated, all the more when a phase matching condition must be fulfilled as well. In our cavity we can separately control the resonance condition for the fundamental and its second harmonic, by simultaneously acting on an intracavity dispersive element and on a piezo-mounted cavity mirror, without affecting the quasi-phase matching condition. In addition, by finely adjusting the laser-to-cavity detuning, we are able to observe steady comb emission across the whole resonance profile, revealing the multiplicity of comb structures, and the substantial role of thermal effects on their dynamics. Lastly, we report the results of numerical simulations of comb dynamics, which include photothermal effects, finding a good agreement with the experimental observations. Our system provides a framework for exploring the richness of comb dynamics in doubly resonant SHG systems, assisting the design of chip-scale quadratic comb generators.
|
|
| 43. |
|
|
