Multilevel rate-equation analysis to explain the recent observations of limitations to optical limiting dyes

Abstract

A theoretical rate-equation analysis is presented to investigate the molecular properties that are important for achieving high-fluence optical limiting. Critical conditions for achieving induced absorption are derived in terms of the material and laser parameters by employing a range of hierarchical energy-level models. The influences of stimulated emission and saturation of the excited-state absorption are seen to induce the regime of optical limiting to one of increasing transmittance. This is in direct agreement with recent experimental measurements.

Band Alignment of MoTe2/MoS2 Nanocomposite Films for Enhanced Nonlinear Optical Performance

“…[35,46] The density of grain boundary of MoTe 2 /MoS 2 nanocomposite films increases with increasing the film thickness. [47,48] When the pump laser with a wavelength of 800 nm (≈1.55 eV) excites the heterostructure samples, the electrons transit from the ground-state (S 0 , S 0 ′) to the first excited-state (S 1 , S 1 ′) of MoTe 2 and MoS 2 , respectively. [46] However, when the thickness is sufficiently thick (80 nm), the carriers actually participating in the NLO response reach a saturation due to the balance between all the influence factors.…”

“…We used a four-level energy model (Figure 4a) to analyze the SA NLO property. [47,48] When the pump laser with a wavelength of 800 nm (≈1.55 eV) excites the heterostructure samples, the electrons transit from the ground-state (S 0 , S 0 ′) to the first excited-state (S 1 , S 1 ′) of MoTe 2 and MoS 2 , respectively. The electrons populating at S 1 and S 1 ′ levels can either transit further to a higher energy level or relax back to the S 0 and S 0 ′ levels.…”

Linear and nonlinear optical properties of merocyanines derivatives of malonodinytriles

“…Such a complicated dependence of the NLO response on the photon density in the various intervals seems to be related to the possibility of describing nonlinear processes within different schemes: threeand four-level models of the excited state absorption under low and high photon fluxes [14,16,17]. In our opinion, one must pass from the three-level energy scheme to the multilevel scheme to interpret correctly the NLO response in the longer (nanosecond) time interval.…”

Optical Conduction Resonance in Self-Assembled Metal Nanoparticle Array-Dielectric Thin Films

“…However, if a sample exhibits strong nonlinear absorption, Beer's law needs to be modified to include the nonlinear absorption term. This work can be found in references [46][47][48][49]. Considering both linear and nonlinear absorption factors, when a laser beam propagates in a medium, the Figure 3: Computed resonance feature of photoconductivity S according to equation (6).…”