Researchers at the University of Sheffield (Sheffield, England) and the Chinese Academy of Sciences (Beijing) have reported the first demonstration of ultrabroadband superluminescent light-emitting diodes (SLEDs) with a multiple quantum-dot (QD) layer structure. The V-groove QD-SLED structure, fabricated via a rapid thermal annealing process, is based on a typical p-i-n configuration, beginning with a silicon-doped (100) gallium arsenide (GaAs) substrate. Five layers of indium arsenide (InAs) QDs make up the active region, in between a 1 µm cladding layer of n-Al0.5Ga0.5As and another 1 µm cladding layer of p-Al0.5Ga 0.5As.
After a 750°C rapid thermal annealing process, the electroluminescent emission spectra of three QD-SLEDs injected with 1200 mA of current exhibits a 3 dB bandwidth spanning 146 nm, from 892 to 1038 nm. The blueshifting of the emission peak to 984 nm is attributed mainly to state filling and higher-energy QD- and quantum-well-like states. The obtained continuous-wave output power at room temperature was as high as 15 mW. Broadband superluminescent sources have potential in numerous applications such as spectrum-sliced wavelength-division-multiplexing systems, fiber gyroscopes, and optical-coherence tomography. Contact Ziyang Zhang at [email protected].