Hybrid Quantum Well/Quantum Dot Structure for Broad Spectral Bandwidth Emitters

• Published in: IEEE journal of selected topics in quantum electronics Vol. 19; no. 4; p. 1900209
• Main Authors: Siming Chen, Kejia Zhou, Ziyang Zhang, Orchard, J. R., Childs, D. T. D., Hugues, M., Wada, O., Hogg, R. A.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.07.2013; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Bandwidth; Broadband light source; carrier transport; hybrid quantum well (QW)/quantum dot (QD); Indium gallium arsenide; optical coherence tomography (OCT); Quantum dots; Spontaneous emission; superluminescent diode (SLD); Superluminescent diodes; Temperature; Temperature measurement
• ISSN: 1077-260X; 1558-4542
• DOI: 10.1109/JSTQE.2012.2235175

We report a hybrid quantum well (QW)/quantum dot active element for an application in broadband sources. These structures consist of an InGaAs QW and six InAs dot-in-well (DWELL) layers. The single QW is designed to emit at a wavelength coincident with the second excited state of the quantum dot. We compare two hybrid QW/quantum dot samples where the QW position is changed, and show that carrier transport effects make QW placement very important through current-voltage, capacitance-voltage, photocurrent, and temperature-dependent spontaneous emission measurements. Using the optimal structure, due to the combined effects of quantum dot ground states, first excited state, and QW emission, a positive modal gain spanning ~300 nm is achieved for the segmented contact device. The values for modal gain are further confirmed by simultaneous three-state lasing, which is studied spectroscopically. Finally, a hybrid QW/quantum dot superluminescent diode (SLD) is reported; the device exhibits a 3 dB emission spectrum of 213 nm, centered at 1230 nm with a corresponding output power of 1.1 mW. The hybrid SLD is then assessed for an application in an optical coherence tomography system; an axial resolution of ~4 μm is predicted.