| Sources in the mid-infrared wavelength regions (3-5μm) are important tools inthe field of scientific research due to the growing number of emerging applicationsfor them in the optical frequency metrology, remote sensing, environmental testing,strong-field physics and counter measures. As the further research and developmentof these fields, including strong-field physics, biomedical and civil engineering areas,mid-infrared pulses with high peak power and a few even single cycles are becomingvery indispensable. As the broadband laser systems approach the single-cycle regime,the phase of the carrier frequency with respect to the pulse envelope which can bedescribed by the concept of carrier-envelope phase (CEP) plays a crucial role inmany nonlinear experiments, such as attosecond science and ultra-short pulseapplications.This paper around generation of single-cycle mid-infrared pulses withcarrier-envelope phase stabilization and the main works are summarized as follows:1. In this paper, we summarize the research progress of the mid-infrared lasers andmid-infrared light with stabilized carrier-envelope phase and ultra-short pulses.We introduce the methods of generating the mid-infrared ultra-short pulses indetail and also compare the advantage and disadvantage of these methods. Weanalyze the generation and application of pulses with stabilized carrier-envelopephase and conclude that the combination of difference frequency generation(DFG) and optical parametric chirped pulse amplification (OPCPA) is the mainapproach of generating the ultra-short mid-infrared pulses with stabilizedcarrier-envelope phase.2. The coupled wave equations of the three-wave mixing have been derived fromthe Maxwell equation. Based on the coupled wave equations, the principle of phase matching and walk off effect in the optical parametric amplification (OPA)process are analyzed. We numerically simulate the phase matching conditions ofthe MgO-doped periodically poled Lithium Niobate (PPLN) crystal and thebiaxial KTiOAsO4(KTA) crystal, respectively. The walk-off effect of KTA isalso studied. Moreover, the investigation on the length of nonlinear crystal isperformed.3. The introduction of carrier-envelope phase is derived from the definition of thecarrier-envelope phase, and the relationship between the time domain and thefrequency domain of the carrier envelope phase is obtained according to thisdefinition. The research process and stabilized techniques of the carrier envelopephase are summarized. The master optical stabilized techniques andmeasurement of the carrier envelope phase are highlighted. Furthermore, weanalyze the self-stabilization principle of DFG process.4. We present a new approach, based on coherent wavelength multiplexing of bothidlers from difference frequency generation processes, to generate single-cyclemid-infrared pulses. The theoretical model for coherent synthesis between twoidlers generated from different DFG processes is established. The influences ofthese parameters, including the spectra superposition, the difference of two CEPs,the relative timing and the chirp ratio between the idlers on the synthesizedwaveform are numerically calculated and analyzed, which offers generalguidelines for the waveform optimization. It is found that there is an optimalwavelength difference, within which the shortest duration can be achieved; thesynthesized pulse has the shortest width when the CEP difference between bothidlers is0.8π; the energy of synthesized pulse is decreased as the relative timingis changed within a certain range; there is an optimal chirp ratio between twoidlers to make the synthesized pulse shortest. According to the optimal design ofthese parameters, we obtain a single cycle pulse centered at4233nm spanningfrom3000nm to7000nm. |
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