Absorption saturation analysis of Cr^2+:ZnSe and Fe^2+:ZnSe

Passively Q-switched Er:YAG laser operating at 1617 nm at low pump power level

“…First, the slope of the Cr:ZnSe absorption cross section is raising between 1617 and 1645 nm [7]. We considered absorption cross sections at 1645 and 1617 nm to be 0.95 × 10 −22 m 2 and 0.8 × 10 −22 m 2 , respectively, [15]. Hence, the Cr:ZnSe saturable absorber favors the emission at 1617 nm as its small signal transmission at 1645 nm is higher.…”

Passive Q-Switching of a Tm3+:YLF Laser at 2.3 μm with a Cr2+:ZnSe Saturable Absorber

“…Pulsed operation of 2.3-µm Tm 3+ lasers can also be obtained by employing the technique of passive Q-switching, where a saturable absorber (SA) is placed inside the cavity to generate a pulse train whose repetition frequency and pulse duration are determined by the parameters of the saturable absorber and resonator. Divalent Cr or Fe doped II-VI media such as Cr 2+ :ZnSe, Cr 2+ :ZnS, Cr 2+ :CdSe, Fe 2+: ZnS, and Fe 2+ :ZnSe have ultrabroad absorption bands which extend to 2.3 µm and hence can potentially be used as saturable absorbers at this wavelength [10][11][12]. Our present study focused on the passive Q-switching applications of Cr 2+ :ZnSe, whose saturation characteristics were previously investigated between 1.5 μm and 2.8 μm [13][14][15].…”

Nonlinear Change in Refractive Index and Transmission Coefficient of ZnSe:Fe<sup>2+</sup> at Long-Pulse 2.94-μm Excitation

“…Meanwhile, there is no-as far as we know-any data about the mechanisms and values of nonlinear refractive-index ∆n in ZnSe:Fe 2+ at ~3-µm excitation. The other problem, insufficiently addressed to date is quenching of ZnSe:Fe 2+ fluorescence, in terms of Fe 2+ lifetime reduction in regard to temperature and Fe 2+ concentration, at in-band excitation [1]- [3] [5] [19]- [21].…”

“…In Sections II and III, we study experimentally the nonlinear changes in transmission and refractive index of ZnSe:Fe 2+ at sub-mJ pulsed 2.94-µm probing by means of the Z-scan technique. [Note that the sole work [19], where the Z-scan technique was applied for ZnSe:Fe 2+ , was targeted at a study of its nonlinear transmission only, not ∆n.] In Section IV, we model the problem of propagation of pulsed ~3-µm radiation through ZnSe:Fe 2+ , where the two key nonlinearities are addressed, stemming from saturation of the resonant transition 5 E→ 5 T 2 (Fe 2+ ) and from light-induced heating.…”