Analysis of quarter-wave-shifted DFB laser

Design of narrow-linewidth phase-shifted distributed feedback lasers

“…where A o and <x i n are related to the peak gain g m and carrier density n through g m = A o n -<x In ; d, W and L are the active layer thickness, width and length, T is the confinement factor, B eff the recombination coefficient, a 0 the absorption and scattering losses and a m = 2<x th the power mode threshold gain computed using coupled mode theory [4]. The external efficiency normalised to the internal efficiency rji is CL rji P r + P t a m + a 0 and the minimum linewidth Av min [5] l + a 2 ) cc m (a m + a 0 )…”

Laterally-corrugated ridge-waveguide distributed feedback lasers at 980 nm

“…The degeneracy can be lifted by introducing a quarter-wave phase-shift section. The added phase-shift ensures single-mode lasing in the center of the grating stop-band (Utaka et al 1984), as illustrated in Fig. 1b.…”

Optical modeling of laterally-corrugated ridge-waveguide gratings

“…One solution for this DFB emission degeneracy problem is the introduction of a quarter-wave phase-shift section, which enables the propagation of the optical field in a narrow wavelength range (gap mode) within the grating stopband (Utaka et al 1984). For the DFB lasers with phase-shift sections and no supplementary facet-reflection phase-shifts, the gap mode can be placed in the center of the grating stopband, ensuring the highest possible side-mode suppression ratio (SMSR) for a given κ L-product and, accordingly, a high single-longitudinal-mode yield.…”