Growth and Optical Characterizations of InAs-QDs Emitting at 1ƒÊm with a Broadband Spectrum for a Light Source of Biomedical Optical Coherence Tomography
Nobuhiko OZAKI, Yuji HINO, Shunsuke OHKOUCHI, Naoki IKEDA and Yoshimasa SUGIMOTO
Abstract:Emission wavelengths of self-assembled InAs quantum dots (QDs) were controlled at around 1.05ƒÊm by using the In-flush technique. A rapid annealing (In-flush) process after the growth of the GaAs capping layer, which partially covers the InAs-QDs, reduces the height of the InAs-QDs to the thickness of the capping layer. Using this technique, the emission wavelengths of the QDs were precisely controlled by varying the thickness of the capping GaAs layer. The central emission wavelength was suitably controlled in the range of approximately 0.95-1.22ƒÊm. This method enables the realization of a broadband 1.05ƒÊm light source with a bandwidth of beyond 200 nm via a combination of In-flushed QDs. Such a broadband light source with a wavelength of 1.05ƒÊm is applicable to optical coherence tomography (OCT), thereby enabling high resolution and large penetration depth in the OCT images. In addition, we have grown a sample including stacked layers of In-flushed QDs and obtained an emission spectrum with a central peak at 1.09ƒÊm and a bandwidth beyond 100 nm. These results suggest that an axial resolution of approximately 5ƒÊm will be achieved by the use of the light source in OCT. Key Words:Quantum dot, Molecular beam epitaxy, In-flush, Broadband near-infrared light source, Biomedical optical coherence tomography (OCT)