Towards spectral-domain optical coherence tomography on a silicon chip

B.I. Akça, Kerstin Worhoff, V.D. Nguyen, J. Kalkman, Ton van Leeuwen, R.M. de Ridder, Markus Pollnau

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Optical coherence tomography (OCT) is a widely used optical imaging technology, particularly in the medical field, since it can provide non-invasive, sub-micrometer resolution diagnostic images of tissue. Current OCT systems contain optical fibers and free-space optical components which make these instruments bulky and costly. A significant decrease in the size and cost of an OCT system is possible through the use of integrated optics, allowing for compact and low-cost OCT systems, especially suited for applications in which instrument size may play an important role. In this work, we present a miniaturized spectral-domain OCT (SD-OCT) system. We design an arrayed waveguide grating (AWG) spectrometer in silicon oxynitride for the 1300-nm spectral range. The spectral range of the SD-OCT system near 1300 nm is specifically selected for skin imaging. We aim at 18-μm depth resolution (determined by the full width at half maximum values of the transmission spectrum of the AWG) and a 1-mm depth range (determined by the wavelength spacing per output waveguide). The free spectral range of 78 nm and wavelength resolution of 0.4 nm of the AWG are determined to meet these requirements. We use ahe fiber-based SD-OCT system with AWG spectrometer. The Michelson interferometer is illuminated using a superluminescent diode which has a Gaussian-like spectrum with a bandwidth of 40 nm and a central wavelength of 1300 nm. Via a circulator the light is coupled into a 90/10 beamsplitter. Polarization controllers are placed into both, sample and reference arm. The backreflected light is redirected through the optical circulator to the AWG spectrometer. The collimated beam is imaged with a camera lens onto a 46 kHz CCD linescan camera. The acquired spectra are processed by first subtracting the reference arm spectrum, then compensating the dispersion, and finally resampling to k-space. We achieve a depth range of 1mm. The measured signal-to-noise ratio (SNR) is 75 dB. The axial resolution (FWHM) is determined from a Gaussian fit to the point spread function in amplitude at various depths. A slight decrease in depth resolution is observed at higher depth ranges, which we attribute to misalignment and lens aberrations. As a demonstration of OCT imaging using the AWG spectrometer, an image of a layered phantom is recorded. The phantom consists of three layers of scattering medium (µs = 4 mm-1, refractive index n = 1.41) interleaved with non-scattering tape. We can observe all three scattering layers up to the maximum imaging depth of 1 mm.
Original languageEnglish
Title of host publicationInternational Laser Physics Workshop 2011
Place of PublicationMoscow
PublisherRAS - General Physics Institute
Number of pages1
Publication statusPublished - Jul 2011
Event20th International Laser Physics Workshop, LPHYS 2011 - Hotel Hollywood, Sarajevo, Bosnia and Herzegovina
Duration: 11 Jul 201115 Jul 2011
Conference number: 20


Conference20th International Laser Physics Workshop, LPHYS 2011
Abbreviated titleLPHYS
Country/TerritoryBosnia and Herzegovina
Other11-15 July 2011
Internet address




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