Abstract
We present results of experimental investigation of the chaotic and quasi-periodic regime in the chirped-pulsed (dissipative soliton) Cr:ZnS and Cr:ZnSe mid-IR oscillators with significant third-order dispersion. The instability develops when the spectrum edge approaches resonance with a linear wave either due to power increase or by dispersion adjustment. In practice, this occurs when the spectrum edge reaches zero dispersion wavelength. The analysis suggests a three-oscillator chaos model, which is confirmed by numerical simulations. The regime is long-term stable and can be easily overlooked in similar systems. We show that chaotic regime is accompanied by a characteristic spectral shape and can be reliably recognized by using wavelength-skewed filters and by second-harmonic or two-photon absorption detectors.
Highlights
Mode-locked oscillators operating in the all-normal (β2 > 0) dispersion regime (ANDi) have established themselves as versatile sources of energy scalable chirped picosecond pulses, which can be further compressed to well below hundred femtosecond duration
At relatively low third-order dispersion (TOD) [Fig. 5(a)] the pulse corresponds to that of the approximate model of Fig. 4: it consists of a linearly chirped central part and the two tails at spectrum edges, which are very well localized in frequency at resonance positions R1 and R2
We conclude that our model adequately describes the experiment and that the TOD is responsible for the onset of the chaotic instability: as the resonant wavelength approaches the pulse spectrum, the corresponding dispersive wave merges with the pulse edge and becomes strongly amplified
Summary
Mode-locked oscillators operating in the all-normal (β2 > 0) dispersion regime (ANDi) have established themselves as versatile sources of energy scalable chirped picosecond pulses, which can be further compressed to well below hundred femtosecond duration. The main interest in implementing such sources is the possibility to generate high-energy pulses directly from an oscillator, avoiding complex and costly amplifier schemes. These chirped-pulse oscillators (CPO) operate in the dissipative soliton (DS) regime, which is somewhat more complex than a soliton-like compensation of self-phase modulation by anomalous dispersion as in conventional femtosecond lasers. It is important to establish the physical mechanisms, properties, and find practical rules to help recognising such regimes
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