Integrated-optics Based Multi-Beam Imaging for Speed Improvement of OCT Systems

The speed improvement is a game-changer in optical coherence tomography (OCT) imaging because it opens up for new and very exciting applications. The frame rate of an OCT system is limited by the speed of the camera or the sweep rate of the light source. This problem can be overcome by multiple-beam imaging, in which different locations on the sample are illuminated by an array of light simultaneously. This technique allows parallel imaging from multiple sample locations and therefore improves OCT axial scan rate by a factor equal to the number of beams used simultaneously which can go up to very high frequency ranges (e.g. MHz) easily. In this work, we introduce a compact integrated-optics based multiple-beam illumination design in which several waveguides with certain length differences are combined with wavelength-independent couplers for space-division multiplexing. Electrodes will be placed on each beam path in order to separate desired signal from unwanted reflections at the optical surfaces or tissue. The imaging speed will be improved by the number of the beam paths used. In addition to fast imaging, the proposed design will be very compact which makes it very suitable to be used in endoscopic probes. The proof-of-concept of this idea was experimentally demonstrated using a design which consists of 2 times 4 parallel OCT channels that are realized with a total of 6 Y-couplers. Each individual OCT channel has an optical path length delay with respect to the other channels.