Characteristics of the ground-state lasing operation in V-groove quantum-wire lasers

Lasing from the ground subband transition, which has long been attempted in one-dimensional (1-D) structures, has been achieved for the first time with vertically stacked, AlGaAs-GaAs multiple quantum-wire (QWR) lasers, fabricated by flow-rate modulation epitaxy on V-groove substrates. Direct experimental evidence is provided by the consistency of the photon energies of the lasing and photoluminescence peaks, in the temperature range 4.5 K-300 K. It is further ensured by numerical calculation of the electronic subband energy states with the corresponding QWR structure. The lasers with cavity lengths of 350 μm, show fundamental transverse mode, typical threshold current of 5 mA, an internal quantum efficiency of 18.5%, ultrahigh characteristic temperature T_o approx. 322 K above room temperature, and remarkably low wavelength-tuning rates of current (<0.012 nm/mA) and temperature (<0.19 nm/°C). Ultrafast lasing behaviors at the ground (n = 1) and the second (n = 2) transition of the QWR are also investigated in terms of the gain-switching method, using a characteristic of the wavelength shift from the n = 1 to the n = 2 subband with shortening the cavity length.