Role of wavelength in photocarrier absorption and plasma formation threshold under excitation of dielectrics by high-intensity laser field tunable from visible to mid-IRстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 7 октября 2020 г.
Аннотация:The development of high power mid-IR laser applications requires a study on laser-induced damage threshold (LIDT) in the mid-IR. In this paper, we have measured the wavelength dependence of the plasma formation threshold (PFT) that is LIDT precursor. In order to interpret the observed trends numerically, a model describing the laser-induced electron dynamics, based on multiple rate equations, has been developed. We show both theoretically and experimentally that PFT at mid-IR wavelengths is controlled by a transition from weak- to strong-field regime of free carrier absorption. In the case of MgF2, this transition occurs around 3 - 4 um corresponding to the region of the lowermost PFT. The region of the uppermost PFT is reached around 1 um and is governed by an interplay of photoionization and weak-field free carrier absorption which manifests itself in both MgF2 and SiO2. The PFT observed in considered materials exhibits a universal dependence on the excitation wavelength in dielectrics. Thus, the presented results pave the route towards efficient and controllable laser-induced material modifications and should be of direct interest to laser researchers and application engineers for the prevention of laser-induced damage of optical components in high-intensity mid-IR laser systems.