We describe the design and performance of ridge waveguide1,2 distributed feedback lasers operating in the 1.51-1.58-μm spectral region. A schematic diagram of a ridge DFB laser is shown in Fig. 1. The base structure and epitaxial regrowth over the grating were obtained by liquid phase epitaxy. Second-order diffraction gratings were defined by electron-beam writing in the top cladding layer and transferred by ion-beam milling. This procedure yields deep gratings, shown in Fig. 2, with the groove-to-period ratio as small as 10% and very efficient coupling to the radiation field.
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