Power threshold and optical gain of a third order mode optically pumped AlGaAs laser

We have characterized in detail the performance of an optically pumped semiconductor laser device which emits radiation on the third order laser mode. The sample was grown by molecular beam epitaxy and consists of an Al0.11Ga0.89As quantum well sandwiched between an Al0.50Ga0.50As/Al0.25Ga0.75As/AlAs double heterojunction. The structure was specially designed to emit laser radiation at 775 nm on the third order mode and used as a pump source towards generating twin photons at 1.55 mum on the fundamental mode via parametric fluorescence by utilizing the principle of modal phase matching between fundamental and third order laser modes in III-V semiconductors. The spectral and pumping power dependencies of the single pass optical gain of the structure were measured by varying the length of the excited region on the sample and recording the corresponding amplified spontaneous emissions. A maximum gain of 120 cm(-1) was measured. The threshold for laser emission of barlike samples with surface waveguide ridges was measured systematically vs cavity length and sample temperature. The optimum cavity length for obtaining the lowest threshold was greater than 1.2 mm. Threshold equal to 42 kW/cm(2) was measured at room temperature for a 1.44 mm long cavity, and the characteristic temperature which expresses the threshold in the exponential form was equal to 117 K. The transverse angular dependence of the third order mode laser radiation was measured for different pumping powers for processed as well as unprocessed samples. (C) 2002 American Institute of Physics.