Theoretical study on nonlinear properties of four level systems under nano-second illumination

Abstract

In this work, we report the theoretical results of the single beam transmittance of an absorber by employing the rate equation approach, utilizing 10 ns laser pulses. With the appropriate choice of lifetimes of the participating levels in the transition and their corresponding absorption cross-section, it is possible to control the onset of different phenomena like saturable absorption, reverse saturable absorption, and double saturable absorption. We discuss how to increase the saturable and optical limiting nature of the system by appropriate changes of spectroscopic parameters. We discuss the estimation of spectroscopic terms from their contribution in the single beam transmittance.

Nonlinear absorption study in four and five energy level systems

“…The lifetime's effect on the transmittance curve is shown in figure 2. In four level absorption process, the transmittance get saturates two times in the entire transmittance profile and the transmittance have the steps in the absorption processes as: linear absorption/transmittance followed by first saturation in the absorption/transmittance followed by second saturation in the absorption/transmittance [21]. As The transmittance curve as a function of absorption cross-sections illustrated in figure 3.…”

“…Four level non-cascade system is discussed in the Ref. [21]. In this section, we will discuss five level non The population dynamics among the five levels in the differential equations form as given in equation 3.…”

“…The rate equations 1(a)-1(e) are numerically solved and obtained the population in each energy level [21].…”

“…In figure 5 Four level non-cascade system is discussed in the Ref. [21]. In this section, we will discuss five level non-cascade system.…”

“…But still, no article has discussed absorption cross-sections and lifetimes effect in the nonlinear absorption process. In this article we have shown, how one can see the single saturable absorption (SSA) [21], double saturable absorption (DSA) [21] and saturable with reverse saturable absorption (SRSA). In addition to this, we systematically study the influence of spectroscopic parameters in the transmittance curve through SBT.…”