in the case of ridges with 0 50 u03bcm residual upper cladding thickness fig6 d to address the foregoing coupling problem between closely spaced adjacent ridges the technique illustrated in fig7 a can be employed fig7 a shows a partial cross sectional view of a laser structure 50 that is configured in accordance with the embodiments of the invention illustrated in fig4 a 4c and 5 a 5 c for example the laser structure 50 includes at least first and second adjacent ridge waveguides 52 and 54 that are spaced from one another by a distance rr to reduce the coupling between the two ridge waveguides 52 and 54 a notch 56 is formed in the laser substrate 58 between the two ridge waveguides 52 and 54 the notch 56 is of a predetermined etch depth and width the impact of the coupling between the two adjacent ridges is significantly reduced thereby as illustrated in the graphs of fig7 b as compared to the graphs of fig6 d which shows the results of the same structure but without the notch it should be understood that the invention is applicable to laser structures in different material systems three examples of such structures are described below all of which have been demonstrated to allow etched facets a wafer is fabricated with an n inp cladding layer an n algainas sch separate confinement heterostructure layer algainas strained multi quantum well active layers a p algainas sch layer a p inp cladding layer and a highly doped p ingaas contact layer formed successively on an n type 100 inp substrate the active region consisted of five 6 nm compressively strained algalnas quantum wells separated by 10 nm tensile strained algalnas barrier layers.