High-power tunable quantum fountain unipolar lasers

We report on high-power GaAs/AlGaAs quantum fountain unipolar lasers emitting at 14-15 mu m under optical pumping by a pulsed CO2 laser. Two kinds of devices were investigated: edge lasers with side-facet pumping and broad-area lasers with a patterned top grating for coupling the pump at normal incidence. Collected optical powers as high as 4.16 W corresponding to an estimated power per facet of 17.6 W have been achieved in TM00 mode for broad-area lasers. The lasing wavelength is shown to be tunable (Delta lambda/lambda approximate to 2.5%) by changing the pump wavelength. Broad-area lasers exhibit excellent beam quality with very low in-plane divergence in TM00 mode. Mode hopping is observed under intense pumping. (C) 2000 Published by Elsevier Science B.V. All rights reserved.