Broadband emission centered at ∼1 µm with a Gaussian‐like spectrum by stacking In‐flushed QD layers

Abstract

We have grown a stack of In‐flushed InAs quantum dot (QD) layers to realize a broadband emission centered at ∼1 µm with a Gaussian‐like spectrum as a light source for optical coherence tomography (OCT). The In‐flush process, which enables control of the height of the QD, was optimized to control the emission wavelength and intensity of self‐assembled InAs/GaAs QDs. A partial capping layer of GaAs was deposited on as‐grown InAs/GaAs QDs with various thicknesses (dcap), and a rapid annealing of the sample was executed with the proper annealing temperature. By optimizing dcap and the annealing temperature for each QD layer, a broadband Gaussian‐like spectrum with a 102‐nm‐bandwidth was obtained. The coherence function of the emission spectrum exhibits a 4.5‐µm axial resolution for OCT images without distinct side lobes. These results demonstrate the effectiveness of the In‐flushed QDs as a light source to obtain high‐quality OCT images. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Optical characterization of In-flushed InAs/GaAs quantum dots emitting a broadband spectrum with multiple peaks at ~1 μm

“…This indicates that an axial resolution that is less than 5 μm in air can be achieved using this as a light source in OCT system. Furthermore, precise control of the emission wavelength can be executed by the variation of d cap , as previously reported [ 14 , 15 ], and further broadening and control of the center wavelength can be expected. Thus, the In-flushed QDs offer a novel approach for developing a broadband light source centered at 1.05 μm.…”

“…However, the InAs/GaAs QDs typically emit light of approximately 1.2–1.3 μm wavelength; therefore, we have developed various methods to control the emission wavelength of InAs QDs [ 13 ]. For the adjustment of the emission wavelength to the 1 μm regime, we have utilized the In-flush technique [ 14 , 15 ]. The In-flush technique was previously developed for setting the QD height to a constant value and obtaining a highly homogeneous QD emission wavelength [ 16 ].…”

“…The In-flush technique was previously developed for setting the QD height to a constant value and obtaining a highly homogeneous QD emission wavelength [ 16 ]. This method can also be applied to the control of the InAs QD emission wavelength and enables the creation of a broadband light source by combining the emission–wavelength-controlled QDs [ 14 , 15 , 17 – 19 ]. In our previous work regarding the control of the emission wavelength via the In-flush method, we have found that the In-flushed QDs exhibit multiple emission peaks in the emission spectrum at the ~1 μm regime [ 14 ].…”

Integration of Emission-Wavelength-Controlled InAs Quantum Dots for Ultra-Broadband Near-Infrared Light Source

“…According to a precise estimation using the coherence function of the spectrum, an axial resolution of 4.5 μm in air can be achieved using this structure as a light source in an OCT system [59].…”

“…As described in section 1, light with a center wavelength of 1.05 μm is recognized as an alternative probe for aqueous tissue, such as the human eye, because of the long penetration depth in biological samples [53]. To adjust the emission wavelength of conventional InAs/GaAs QDs, which emit approximately 1.2–1.3 μm, to the 1 μm regime, the In-flush technique, which was previously developed for QD height control [54], can be utilized [55–59]. In this section, the wavelength control technique is introduced and the potential of the obtained QDs as a broadband light source for OCT is discussed.…”