Figure 4
Influence of the grating depth on the laser threshold and efficiency. (a) Laser threshold, expressed as pump energy density and power density (left and right axis, respectively; error ~ 10%); and (b) laser efficiency (error ~ 10%) vs grating depth for four series of DFB lasers with different values of the initial resist layer thickness, s0 (see legend). The full lines are guides to the eye. Dashed lines indicate, for each series, the device with no residual layer (s = 0). For all the lasers, a simple grating development system was used. Data for a laser (denoted as R-240, see legend) with s0 = 240 nm and prepared by using a much more complex anisotropic dry development system are shown.
