Refractive index variation in rare-earth doped specialty fiber can be possible through resonantly enhanced optical nonlinearity with the assistance of an optical pumping. The quantity of the variation under low-power optical pumping is enough to induce phase shift of 2π. By using this nonlinear effect in the specialty fiber, optical imaging system can perform phase shift-based optical imaging without mechanically controlled phase stepping. The pump-induced refractive index from the specialty fiber in reference arm of interferometer can produce optical delay depending on applied optical pumping power. At low optical power under few hundred mW, optical delay corresponding to 2π can be yielded in the reference arm efficiently. Contrast to the conventional mechanical phase stepping method, optically actuated phase stepping with the specialty optical fiber can avoid drawback of mechanical hysteresis and requirement of high voltage controllable electronics. The feasibility of the proposed method on optical imaging is suggested with demonstrating full range imaging in optical coherence tomography. Extended imaging range under optical phase stepping was successfully presented. The proposed method could be applied for detailed control of phase shift-based interferometry.

Date Published: 5 March 2015
PDF: 6 pages
Proc. SPIE 9317, Optical Fibers and Sensors for Medical Diagnostics and Treatment Applications XV, 931715 (5 March 2015); doi: 10.1117/12.2078368

Published in SPIE Proceedings Vol. 9317:
Optical Fibers and Sensors for Medical Diagnostics and Treatment Applications XV
Israel Gannot, Editor(s)