63 research outputs found
Generation of stable and breathing flat-top solitons via Raman assisted four wave mixing in microresonators
Flat-top-soliton (or platicon) dynamics in coherently pumped normal dispersion microresonators is important for both fundamental nonlinear physics and microcomb generation in the visible band. Here we numerically investigate the platicon generation that is initiated via Raman assisted four wave mixing instead of mode interaction. To show the possibility of generating coherent combs in the visible band, we design an aluminum nitride (AlN) microresonator with normal dispersion and investigate the comb generation dynamics in simulations. Stable platicon Kerr combs can be generated in this AlN microresonator using a 780-nm pump. Moreover, we also observe a breather platicon dynamics induced by the narrow Raman gain spectrum of crystalline AlN, which shows distinct dynamics from the dark soliton breathers reported in previous work that are dominated by Kerr effect. A phase diagram bearing the influence of the pump detuning and pump power on the breathing dynamics of the breather platicon is also computed. Furthermore, a transition to chaotic breathing is numerically observed
Generation of stable and breathing flat-top solitons via Raman assisted four wave mixing in microresonators
Flat-top-soliton (or platicon) dynamics in coherently pumped normal dispersion microresonators is important for both fundamental nonlinear physics and microcomb generation in the visible band. Here we numerically investigate the platicon generation that is initiated via Raman assisted four wave mixing instead of mode interaction. To show the possibility of generating coherent combs in the visible band, we design an aluminum nitride (AlN) microresonator with normal dispersion and investigate the comb generation dynamics in simulations. Stable platicon Kerr combs can be generated in this AlN microresonator using a 780-nm pump. Moreover, we also observe a breather platicon dynamics induced by the narrow Raman gain spectrum of crystalline AlN, which shows distinct dynamics from the dark soliton breathers reported in previous work that are dominated by Kerr effect. A phase diagram bearing the influence of the pump detuning and pump power on the breathing dynamics of the breather platicon is also computed. Furthermore, a transition to chaotic breathing is numerically observed
Coherence memory and amnesia in a mode-locked laser
Self-organization of temporal modes in mode-locked lasers usually starts from
quantum noise. In this process, incoherent spontaneous emission is steered into
coherent ultrashort pulses by dissipation and nonlinearity. In this work, we
investigated self-organization dynamics in a mode-locked Mamyshev oscillator
starting from coherent pulse seeds as opposed to quantum noise. We observed
that the coherence of the seed can be remembered or forgotten depending on the
initial inverse population. The excessive nonlinearity in the coherence amnesia
regime can devastate the seed coherence, causing the oscillator to undergo a
chaotic transition lasting hundreds of round trips before regaining coherence.
Conversely, the oscillator converges in only a few round trips for the
coherence memory regime. A heterodyne technique was developed to record the
fast varying optical phase and characterize these two regimes. Dissipative
soliton molecules were synthesized from external pulse pair seeds via the
coherence memory pathway. In this case, a plateau of the generated pulse
spacing independent from seed pulse spacing, i.e., amnesia of the seed spacing,
was observed for close spaced seed pulse pairs. Moreover, we show that pulse
seeds can be used for laser reconfiguration and pulse pattern control. Our work
paves a way to control transient pulse dynamics and steady pulse forms on
demand in mode-locked lasers
Observation of Coexisting Dissipative Solitons in a Mode-Locked Fiber Laser
We show, experimentally and numerically, that a mode-locked fiber laser can operate in a regime where
two dissipative soliton solutions coexist and the laser will periodically switch between the solutions.
The two dissipative solitons differ in their pulse energy and spectrum. The switching can be controlled by an external perturbation and triggered even when switching does not occur spontaneously. Numerical
simulations unveil the importance of the double-minima loss spectrum and nonlinear gain to the switching dynamics
Microresonator soliton dual-comb imaging
Fast-responding detector arrays are commonly used for imaging rapidly changing scenes. Besides array detectors, a single-pixel detector combined with a broadband optical spectrum can also be used for rapid imaging by mapping the spectrum into a spatial coordinate grid and then rapidly measuring the spectrum. Here, optical frequency combs generated from high-Q silica microresonators are used to implement this method. The microcomb is dispersed in two spatial dimensions to measure a test target. The target-encoded spectrum is then measured by multi-heterodyne beating with another microcomb having a slightly different repetition rate, enabling an imaging frame rate up to 200 kHz and fill rates as high as 48 megapixels/s. The system is used to monitor the flow of microparticles in a fluid cell. Microcombs in combination with a monolithic waveguide grating array imager could greatly magnify these results by combining the spatial parallelism of detector arrays with spectral parallelism of optics
- …