We present a large-core fiber (LCF) with a reduced nonlinear property for a single-mode beam delivery of intense ultrashort pulses. A tapered-fiber mode filter was fabricated in an LCF with the core diameter decreased from to at the tapered waist region surrounded by index-matched liquid. By the tapered geometry, the high-order mode was rejected so that our mode-filtered LCF acted as a single-mode fiber despite the multimode property of the original LCF. It has been found that this fiber class is suitable for applications, such as an endoscopic multiphoton microscope, that demand a flexible short-distance () delivery medium of ultrashort pulses.
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