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We developed a near-infrared (NIR) superluminescent diode (SLD) based on self-assembled InAs quantum dots (QDs) and demonstrated high-axial-resolution optical coherence tomography (OCT) imaging using this QD-based SLD (QD-SLD). The QD-SLD utilized InAs QDs with controlled emission wavelengths as a NIR broadband light emitter, and a tilted waveguide with segmented electrodes was prepared for edge-emitting broadband electroluminescence (EL) spanning approximately 1–1.3 μm. The bandwidth of the EL spectrum was increased up to 144 nm at a temperature of 25 °C controlled using a thermoelectric cooler. The inverse Fourier transform of the EL spectrum predicted a minimum resolution of 3.6 μm in air. The QD-SLD was subsequently introduced into a spectral-domain (SD)-OCT setup, and SD-OCT imaging was performed for industrial and biological test samples. The OCT images obtained using the QD-SLD showed an axial resolution of ~4 μm, which was almost the same as that predicted from the spectrum. This axial resolution is less than the typical size of a single biological cell (~5 μm), and the practical demonstration of high-axial-resolution OCT imaging shows the application of QD-SLDs as a compact OCT light source, which enables the development of a portable OCT system.

Herein, we report an emission wavelength control technique for self-assembled InAs quantum dots (QDs) grown via molecular beam epitaxy using an As2 source (As2-QDs). The As2-QDs exhibited photoluminescence with a shorter center wavelength and larger bandwidth than those of the QDs grown using an As4 source. In addition, the emission center wavelength could be controlled by adjusting the time between the growth and capping of the As2-QDs. We utilized the multilayer stack of emission-wavelength-controlled As2-QDs to fabricate an electrically-driven light source and demonstrated its broadband (approximately 130 nm) emission in the 1–1.3 μm wavelength range.