Effect of the active region width in GaAs semiconductor injection lasers on single-frequency stimulated emission conditions

Results are presented of an experimental investigation of the radiative characteristics of single-channel semiconductor injection lasers operated under cw conditions (77°K) with different active region widths (1.5–11μ). It is shown that two-sided horizontal confinement of the active region, using Ge-doped layers of an Al_xGa_1–xAs solid solution, makes it possible to produce a structure exhibiting good waveguide properties and low leakage currents. A study was made of the threshold, spectral, and watt-ampere characteristics of the radiation and the field distribution in the near- and far-field zones. An investigation of a large number of single-channel lasers showed that these emit a single axial mode over a broad range of the injection current. The maximum radiation power under single-frequency conditions was greater than 100 mW (in both directions). It was established that single-frequency emission terminated and a transition to multimode emission took place at a radiation power density of ~(1–2)×10⁵ W/cm² in the channel.