Abstarct: In the recent years the infra-red (IR) laser diodes with the wavelength of 1.3 and 1.5 micrometers have found great interest in optical fibers communications. These researches are aimed towards more efficient laser diodes. Threshold current (Ith) and temperature sensitivity (known by the characteristic temperature T0) are two important parameters in the operation of a laser diodes. A device with a low Ith and T0 is desirable and it means that the radiative to nonradiative recombination current ratio is big and the variation of Ith with temperature is small. For these achievements different structure, including strained and unstrained quantum well(s), have been used. Using hydrostatic pressure is a useful method in finding the radiative and nonradiative current ratio in threshold current of the device. Here in this thesis we have tried to use the physical theoretical model to analyze the reported experimental data for the threshold current of IR laser diodes (emitting at 1.3 and 1.5 micrometer). These samples are contained quantum well(s) of InGaAs(P), with and without strain, which are examined at high (300K) and low temperatures (~100K) under hydrostatic pressure (up to 10kbar).