<P> A study of the reliability of semiconductor distributed feedback diode lasers is presented using the degree of polarisation of photoluminescence (DOP). Two figures of merit, v and w, are developed and used to characterise device aging times and performance. v measures the strain gradient between the top and middle of a device by calculating the difference in an area-averaged DOP between the middle and top of a fixed area of the device. w measures the average strain profile across the top of the device by taking the difference in an area-averaged DOP between the region immediately beneath the ridge and the regions to the immediate right and left of it. Further, the influence of aging and the nature of metal contact are explored as they relate to these metrics. </p> <P> Finite element fits to the DOP and rotated degree of polarisation of photoluminescence (ROP) are presented. The models thus generated are used to explain the nature of the strain observed in different devices. </p> / Thesis / Master of Applied Science (MASc)