Open AccessSaturation in the principal (excited) channel of four-level medium as an effective two-level configuration
Author(s) -
Jihad S. Addasi
Publication year - 2021
Publication title -
optica applicata
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.204
H-Index - 28
eISSN - 1899-7015
pISSN - 0078-5466
DOI - 10.37190/oa210207
Subject(s) - excited state , singlet fission , saturation (graph theory) , singlet state , atomic physics , triplet state , population , excitation , channel (broadcasting) , physics , materials science , molecular physics , quantum mechanics , telecommunications , mathematics , demography , combinatorics , sociology , computer science
Saturation of complex molecules affects the nonlinear processes occurring in the medium. The medium can be described by two-, three-, and four-level configurations. The principal singlet-singlet and excited triplet-triplet channels of a four-level, N-type, configuration were used to study a nonlinear medium, which was excited by radiation with two frequencies. Under weak population of energy levels in the triplet-triplet channel (a small ratio of the total probability of spontaneous and irradiate transitions for both channels p 23 / p 31 ), the principal (singlet-singlet) channel is similar to a two-level configuration. At the same time, the effective population of the energy levels in the triplet-triplet channel (the ratio p 23 / p 31 is large and the radiation intensity in the principal channel is high) makes the excited (triplet-triplet) channel coincide with the two-level configuration. The saturation intensity of radiation in principal (excited) channel, as effective two-level configuration, and nonlinear processes in this channel can be controlled by external radiation acting on excited (principal) channel. Finally, the average excitation of molecules into the energy levels in the triplet-triplet channel (ratio p 23/ p 31 ≈ 1) makes the four-level configuration similar to the three-level configuration with effective level as a result of combination between second singlet level S 2 and first triplet level T 1 .