Few-Mode Cr-Doped Crystalline Core Fibers for Fiber Amplifier

A few-mode Cr-doped crystalline core fiber (FMCDCCF) is demonstrated. The fiber fabrication is a modified laser-heated pedestal growth (LHPG) technique that consists of over cladding a Cr:YAG crystal rod with silica and then fine tuning its core size with multiple core reduction through the LHPG system. The FMCDCCF exhibits a core diameter of 2 μm and a
V
-value around 3.77 to provide the few-mode characteristics. The optical properties of the FMCDCCF are similar to that of a pristine Cr
⁴⁺
:YAG crystalline. A gross gain of the FMCDCCF is measured around 2.3 dB at a wavelength of 1.4 μm.