this diode operates to 232 mw facet before catastrophic failure at a current density of 15 ka cm 2 the longer windows are more effective at blocking the current injection and reducing heating near the laser facets resulting in higher maximum output powers than the shorter window lasers the best device with longer windows operates without failure to 248 mw facet at a current of u02dc 1 1 a 18 2 ka cm 2 this is a u02dc 25 improvement in maximum output power over the best non window device the total external differential quantum efficiency u03b7 is u02dc 60 for all three devices u02dc 500 u03bcm cavities shown in fig4 the threshold currents of all three devices are 24 26 ma the inset of fig4 shows the longitudinal mode spectra of a non window device below threshold at 15 ma and above threshold at 25 ma near field nf patterns of both the window and non window devices are typically single lobed with a full width at half maximum fwhm of 10 11 u03bcm this fwhm corresponds to the width u02dc 10 5 u03bcm of these ridge waveguide devices the windows investigated in this example are too short to cause a broadening of the nf which reduces the power density at the laser facets and further increases the maximum output power therefore it is believed.