Abstract
Optical coherence tomography (OCT) has enabled clinical applications that revolutionized in vivo medical diagnostics. Nevertheless, its current limitations owing to cost, size, complexity, and the need for accurate alignment must be overcome by radically novel approaches. Exploiting integrated optics, we assemble the central components of a spectral-domain OCT system on a silicon chip. The spectrometer comprises an arrayed-waveguide grating with 136-nm free spectral range and 0.21-nm wavelength resolution. The beam splitter is realized by a non-uniform adiabatic coupler with its 3-dB splitting ratio being nearly constant over 150 nm. With this device whose overall volume is 0.36 cm(3) we demonstrate high-quality in vivo imaging in human skin with 1.4-mm penetration depth, 7.5-µm axial resolution, and a signal-to-noise ratio of 74 dB. Considering the reasonable performance of this early OCT on-a-chip system and the anticipated improvements in this technology, a completely different range of devices and new fields of applications may become feasible.
Highlights
Optical coherence tomography (OCT) is a well-established optical technique in the medical sciences for acquiring micrometer-scale-resolution cross-sectional images of specimen in a non-invasive way [1]
The signal-to-noise ratio (SNR), axial resolution, and imaging range were measured by placing a mirror in the sample arm, which was moved for depth-ranging measurements
The obtained volumetric images of human skin in multiple locations and subjects demonstrate that our partially integrated spectral-domain OCT” (SD-OCT) system with a 7.5-μm axial resolution, 1.4-mm depth range, and 74-dB SNR is capable of acquiring high-quality in vivo OCT images of human skin
Summary
Optical coherence tomography (OCT) is a well-established optical technique in the medical sciences for acquiring micrometer-scale-resolution cross-sectional images of specimen in a non-invasive way [1]. State-of-the-art OCT systems operate in the frequency domain, either with a broad-band light source and a spectrometer, called “spectral-domain OCT” (SD-OCT), or with a rapidly wavelength-tuned laser, called “swept-source OCT” (SS-OCT) [2] Both systems typically contain a combination of fiber and free-space components which add to the instrument size and cost, affect its mechanical stability, and require active alignment. We present an important step toward a cheap, compact, and maintenance-free SDOCT system by integrating its central components, the beam splitter and spectrometer, on a silicon chip [Fig. 1(a)] With this device whose overall volume is 0.36 cm which is significantly (~two orders of magnitude) smaller compared to bulky counterparts (spectrometer and splitter) we demonstrate in vivo imaging in human skin, delivering averaged cross-sections of sufficient quality for medical diagnosis. Integrated optics holds a great promise for mass-produced OCT systems with significantly reduced costs and smaller footprints which can make them affordable and accessible for wider groups of researchers
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