Experimental investigation of selfsustained oscillations in stripe-geometry DH lasers

Experimental results on self-sustained oscillations in (GaAl) As double-heterostructure injection lasers are presented. A comparison is made between the emission properties of shallow proton bombarded stripe-geometry lasers with those of oxide-insulated stripe-contact lasers. The rate of increase of oscillation frequencies with injection current or output power is found to be greater for oxide-insulated lasers. Carrier density profiles are obtained from the spontaneous emission at short wavelength from the front facet, as well as from the luminescence through a window (open-back) in the substrate cladding. A model for narrow-stripe lasers has been used, which considers current spreading under the stripe by dividing the laser into three regions in the lateral plane. It is found experimentally that the width of the regions outside the stripe should be of the order of the stripe width, and the regions beyond these may be treated as optically absorbing, with an absorption factor ¿ of 0.06.