Optically pumped, indirect-gap Al(x)Ga(1-x)As lasers

We demonstrate optically pumped lasers with active layers of indirect-gap Al(x)Ga(1-x)As operating up to room temperature. The emission wavelength is 609 nm at 20 K and 639 nm at 300 K, respectively. The laser threshold shows a weak sensitivity on the lattice temperature. The relevant parameters of the electron-hole plasma close to threshold are determined from gain spectroscopy using the variable stripe-length method.