Optical coherence tomography (OCT) is a non-invasive optical technique for high-resolution cross-sectional imaging of specimens, with many applications in clinical medicine and industry (e.g. materials testing, quality assurance, and process control). Current state-of-the-art OCT systems operate in the frequency domain, using either a broadband light source and a spectrometer, known as “spectral-domain OCT” (SD-OCT), or a rapidly tunable laser, known as “swept-source OCT” (SS-OCT). Both systems contain a multitude of fiber and free-space optical components, which make these instruments costly and bulky. The size and cost of an OCT system can be decreased significantly by the use of integrated optics. A suitable fabrication technology and an optimum design may allow one to fabricate very compact, low-cost, and rugged OCT systems. In this talk, I will first introduce the theory of OCT by focusing on SD-OCT systems. System specifications related to design parameters such as axial resolution, imaging depth range, and sensitivity roll-off will be presented. The miniaturization of OCT systems and the pertaining integrated optics components will be discussed, which includes performance-enhanced novel AWG designs as well as ultra-broadband 3dB splitters. Finally, in vivo images taken by the partially-integrated SD-OCT system will be demonstrated.
We demonstrated an inexpensive, simple and ultra-sensitive refractive index (RI) sensor based on a long tapered tip optical fiber combined with a straightforward image analysis method. The tapering length was optimized through beam propagation simulations and trapezoidal tip fibers were fabricated using a single-step chemical etch process. A simple measurement setup was built that consists of a single wavelength light source (λc= 660 nm), a cuvette, an objective lens, and a camera. The sensitivity of the fibers was measured using saline solutions with different concentrations. The light rays exiting the fiber tip along the tapered section form a circular interference pattern on the camera, whose size in the central part very strongly depends on the surrounding refractive index. By analyzing the areal changes in the center of the fringe patterns for different saline solutions, we obtained an unprecedented sensitivity value of 24160 dB/RIU (refractive index unit), which is the highest value reported so far among intensity-modulated fiber refractometers. We also performed beam propagation simulations to predict the behavior of the tapered tip fiber sensor. The experimental results are consistent with the simulations. This sensor is ultra-sensitive, simple, easy-to-fabricate, and low-cost, which makes it a promising tool for on-site measurements and point-of-care applications such as DNA tests based on loop-mediated isothermal amplification.
We present a new approach to Micropipette Aspiration (MPA), a pioneering method in mechanobiology, that introduces an all-optical readout to retrieve both applied stress and material response. Our technique, i.e. Hydraulic Force Spectroscopy, expands on the current MPA experimental possibilities, allowing for frequency-dependent complex moduli measurements of soft suspended bodies over a large bandwidth, with nanometric resolution. This is achieved by oscillating the pressure on the sample by tens of Pascals with a multifrequency signal, by means of a fast pump. Our goal is to use this technique to define new label-free biomarkers for different applications, e.g. embryo viability control.
Conference Committee Involvement (1)
Emerging Technologies for Cell and Tissue Characterization
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