Abstract

With rapid progress of modern technologies in epitaxial growth and a lithography, many challenges for sophisticated optoelectronic devices, incorporating low-dimensional structures inside for example, have been increasingly attempted. One of those is the effort to materialize quantum wire (QWR) gain coupled (GC) distributed feedback (DFB) lasers, in which a purely periodic-gain structure is expected to offer a high yield, single mode emission without facet coatings or quarter-wave-shifted gratings, high immunity from feedback and low chirp under high speed modulation. In this presentation, a challenging work, successful fabrication of the so-called one-step QWR GC-DFB lasers in directions perpendicular to the wire axis is targeted along with a high-density of QWR array lasers in directions parallel to the wire. Fig. 1 shows schematic and cross-sectional scanning-electron-microscopic views of the QWR lasers in the DFB direction. The V-grooves, fixed at the third-order-diffraction gratings (~0.36μm), were formed on an (001) GaAs substrate by homemade-holographic photolithography and wet chemical etching. In this device, the emission wavelength is 827 nm at room temperature (RT), corresponding to the Bragg wavelength under the assumption of the refractive index of the QWR active media being 3.4. More strikingly, no two-mode degeneracy is found here, which is possibly an indicative of the GC DFB effect as expected. On the other hand, a stable lasing operation is achieved in the wire direction at relatively low threshold currents (less than 70 mA) under RT pulsed operation, as shown in Fig. 2. The emission wavelength is 828.5 nm, which is consistent with the peak values of the gain spectra taken from the quantum wires of the same dimension. Improved data will be presented at the conference.

© 2000 IEEE