Anisotropic tapered polarization-maintaining large mode area optical fibers

Abstract

We demonstrate a novel type of tapered large mode area polarization-maintaining fiber. These birefringent fibers have an elliptical inner cladding and a core diameter that increases adiabatically from 8 µm to 70 µm. The polarization maintaining ability of the fiber samples was investigated by measuring the spatial distribution of polarization beat length by using optical frequency-domain reflectometry. The measurements show a clear correlation between the birefringence and the fiber core size, resulting in a modest 10-15% variation in polarization beat length along the fiber. There is no significant coupling of polarization modes or transverse modes in the tested fibers and, therefore, the linear polarization state of propagating light is preserved.

Ultra-large core birefringent Yb-doped tapered double clad fiber for high power amplifiers

“…The results of our measurements of mode beat for active T-DCF are in good agreement with the results of Ref. 19. Although the polarization beat length is not very high, 16mm (0.65 × 10 −4 ), the polarization extinction in the 4th piece of fiber wound with a diameter of 35cm was 30dB (Fig.…”

“…The ability to preserve polarization is another important property of an active anisotropic tapered fiber. Recently, the evolution of birefringence over the length of an anisotropic tapered fiber with a pre-stressed cladding and a core diameter of up to 70 μm was studied [19]. One of the important results of this study is the conclusion that, although birefringence in a tapered fiber varies with length, the changes are insignificant; less than10% at a tapering ratio of 7-10.…”

“…Thus, despite some reduction in birefringence with length, a tapered fiber remains birefringent and, as a result, maintains polarization. Another important conclusion of the paper [19] concerns the small coupling of the polarization modes in a tapered fiber with a large tapering ratio.…”

“…To date, Yb-doped birefringent T-DCFs with a relatively modest core diameter of 45μm [18], 56 μm [15] and 60 μm [14] have been demonstrated. Isotropic active T-DCFs with a large core diameter of 100μm [17] and even 200μm [8] and an anisotropic passive tapered fiber with a core size of 70μm [19] have also been demonstrated. However, a stable and powerful pulse amplifier requires the combination of a large MFD and polarization maintenance.…”

Large mode area double clad ytterbium tapered fiber with circular birefringency

“…The early works implemented the capabilities of the T-DCFs technology by utilizing the fibers without internal birefringence 1,3,4,5 . Recently, the family of scientific works has increased by experimental demonstration of the passive and active anisotropic tapers with an elliptical core of 70 μm size 9 and stress rods (PANDA type) 7,8 . To date, the PANDA type of the active T-DCF are the most common to maintain the polarization of the linearly polarized light.…”