MEASUREMENT OF COUPLING COEFFICIENT AND COUPLING LENGTH OF GaAs/AlGaAs INTEGRATED TWIN-GUIDE INJECTION LASERS PREPARED BY LIQUID-PHASE-EPITAXY.

The integrated twin-guide (ITG) structure which consists of an active guide and a low-loss passive output guide is considered to be one of the suitable structures for realization of integrated optical circuits. This paper gives an experimental result on the measurement of the maximum coupling coefficient and the coupling length between the active waveguide and the passive output waveguide in GaAs/AlGaAs ITG injection lasers prepared by liquid-phase-epitaxy. Very high coupling efficiency between the active and the passive waveguides was experimentally confirmed. The maximum coupling coefficient and the coupling length were measured to be about 90% and 250 mu m, respectively. These values were in agreement with theory. At properly chosen parameters, the threshold current density on an ″ITG-type″ laser was as low as 3kA/cm**2 at room temperature.