1220–1280-nm Optically Pumped InAs Quantum Dot-Based Vertical External-Cavity Surface-Emitting Laser

We report an InAs quantum dot-based optically pumped vertical external-cavity surface-emitting laser (VECSEL), with a continuously variable emission wavelength from 1220 to 1280 nm through the use of epitaxial gradient across the wafer. We demonstrate the performance of two designs of this VECSEL. The first design, 4 × 3, makes use of a resonant periodic gain structure where three dot-in-a-well (DWELL) layers are located at the antinode of the E-field standing wave, with a total of four sets being used. The second design, 12 × 1, makes use of a single DWELL layer per antinode which is repeated 12 times for the same total of 12 DWELL layers. We demonstrate the lasing performance of the two structures as a function of distance from the center of the wafer and use known radial composition gradients in the molecular beam epitaxy reactor to achieve 50 nm continuous wavelength variation in the 4 × 3 structure and 60 nm in the 12 × 1 structure. We also demonstrate that the performance of the 12 × 1 structure is significantly improved compared to the 4 × 3 structure for all measured laser parameters, possibly due to increased pump absorption in the former structure's thicker barriers.