Emission wavelength from a confinement quantum dot (QD) strongly depends on its size and composition. As the application of the wideband light source for optical coherence tomography (OCT), we fabricated InP and InAsP quantum dots on GaInP lattice-matched to GaAs(001) with an intentionally broadened size and composition distribution. The growth technique is droplet hetero-epitaxy using organometallic vapor phase epitaxy system. In particular, InAsP QDs showed a broad PL spectrum with the central wavelength at 845 nm and a large FWHM of 100 nm. This FWHM value improves the resolution of OCT by 4-5 times from the conventional one.
[Show abstract][Hide abstract] ABSTRACT: There have been three basic approaches to optical tomography since the early 1980s: diffraction tomography, diffuse optical tomography and optical coherence tomography (OCT). Optical techniques are of particular importance in the medical field, because these techniques promise to be safe and cheap and, in addition, offer a therapeutic potential. Advances in OCT technology have made it possible to apply OCT in a wide variety of applications but medical applications are still dominating. Specific advantages of OCT are its high depth and transversal resolution, the fact, that its depth resolution is decoupled from transverse resolution, high probing depth in scattering media, contact-free and non-invasive operation, and the possibility to create various function dependent image contrasting methods. This report presents the principles of OCT and the state of important OCT applications. OCT synthesises cross-sectional images from a series of laterally adjacent depth-scans. At present OCT is used in three different fields of optical imaging, in macroscopic imaging of structures which can be seen by the naked eye or using weak magnifications, in microscopic imaging using magnifications up to the classical limit of microscopic resolution and in endoscopic imaging, using low and medium magnification. First, OCT techniques, like the reflectometry technique and the dual beam technique were based on time-domain low coherence interferometry depth-scans. Later, Fourier-domain techniques have been developed and led to new imaging schemes. Recently developed parallel OCT schemes eliminate the need for lateral scanning and, therefore, dramatically increase the imaging rate. These schemes use CCD cameras and CMOS detector arrays as photodetectors. Video-rate three-dimensional OCT pictures have been obtained. Modifying interference microscopy techniques has led to high-resolution optical coherence microscopy that achieved sub-micrometre resolution. This report is concluded with a short presentation of important OCT applications. Ophthalmology is, due to the transparent ocular structures, still the main field of OCT application. The first commercial instrument too has been introduced for ophthalmic diagnostics (Carl Zeiss Meditec AG). Advances in using near-infrared light, however, opened the path for OCT imaging in strongly scattering tissues. Today, optical in vivo biopsy is one of the most challenging fields of OCT application. High resolution, high penetration depth, and its potential for functional imaging attribute to OCT an optical biopsy quality, which can be used to assess tissue and cell function and morphology in situ. OCT can already clarify the relevant architectural tissue morphology. For many diseases, however, including cancer in its early stages, higher resolution is necessary. New broad-bandwidth light sources, like photonic crystal fibres and superfluorescent fibre sources, and new contrasting techniques, give access to new sample properties and unmatched sensitivity and resolution.
Reports on Progress in Physics 02/2003; 66(2). DOI:10.1088/0034-4885/66/2/204 · 17.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A technique called optical coherence tomography (OCT) has been developed
for noninvasive cross-sectional imaging in biological systems. OCT uses
low-coherence interferometry to produce a two-dimensional image of
optical scattering from internal tissue microstructures in a way that is
analogous to ultrasonic pulse-echo imaging. OCT has longitudinal and
lateral spatial resolutions of a few micrometers and can detect
reflected signals as small as ~10-10 of the incident optical
power. Tomographic imaging is demonstrated in vitro in the peripapillary
area of the retina and in the coronary artery, two clinically relevant
examples that are representative of transparent and turbid media,
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