College of Science, Thi-Qar University discussed a Ph.D. thesis on studying a theoretical study to improve the negative conversion coefficients of the quality factor of fiber LASER by the postgraduate student, Ms. Sarah Abd Al-Hussein.

The thesis aimed at proposing and studying mathematical models that include six equations as (F_ {3/2}) and (I_ {11/2} ) diagrams and four rate equations.

The thesis demonstrated simulating the dual generation of Nd:YAG POS LASER pulses and the characteristics of these pulses as a function of the concentration of the saturable absorber and simulating the effect of the length of the saturable absorber on the characteristics of the dual pulses of the PQS system.

The thesis included the conclusion of the effect of reflectivity (R_{21}) and (R_{22}) on the characteristics of the double pulses of the PQS system, explaining the absorption activity and photon losses by studying the saturable absorber for double wavelengths in the PQS LASER system.

The thesis concluded a good match regarding the behavior and structure of both the photons of the two pulses, the behavior of the variation in the inverse distribution density of the ions of the active medium, and the behavior of the time calibration of the density of the qualification of the two energy levels of the saturable absorber.