Low-loss hollow-core silica fibers with adjacent nested anti-resonant tubes

Abstract

Abstract:We report on numerical design optimization of hollow-core antiresonant fibers with the aim of reducing transmission losses. We show that re-arranging the nested anti-resonant tubes in the cladding to be adjacent has the effect of significantly reducing leakage as well as bending losses, and for reaching high loss extinction ratios between the fundamental mode and higher order modes. We investigate two versions of the proposed design, one optimized for the mid-IR and another scaled down version for the near-IR and compare them in detail with previously proposed antiresonant fiber designs including nested elements. Our proposed design is superior with respect to obtaining the lowest leakage losses and the bend losses are also much lower than for the previous designs. Leakage losses as low as 0.0015 dB/km and bending losses of 0.006 dB/km at 5 cm bending radius are predicted at the ytterbium lasing wavelength 1.06 µm. When optimizing the higher-order-mode extinction ratio, the low leakage loss is sacrificed to get an effective single-mode behavior of the fiber. We show that the higher-order-mode extinction ratio is more than 1500 in the range 1.0-1.1 µm around the ytterbium lasing wavelength, while in the mid-IR it can be over 100 around λ = 2.94 μm. This is higher than the previously considered structures in the literature using nested tubes.

Hollow-core fibers for high power pulse delivery

“…The numerical analysis done here is consistent with their findings and represents an extension to fibers with non-touching tubes. The use of a large number of tubes (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) would greatly limit bend loss in this kind of fiber as shown in [13]. On the other hand it would limit the maximum obtainable ratio d/D, consequently limiting the suppression of HOM as described in the following.…”

“…nested tube design [15], offer lower loss and bend loss, but much work is still needed in the fabrication technology in order to target relevant fiber strustures with nested tubes. A novel anti-resonant hollow-core (AR-HC) fiber with an odd number of 7 tubes is introduced in contrast to the typically used 6, 8 or 10 tubes [13,15,16].…”

Antiresonant hollow core fiber with seven nested capillaries

“…1(a) using image processing tools. Moreover, to precisely model the fiber confinement loss, we utilized a circular perfectly matched layer (PML) and both mesh and PML parameters were carefully optimized [10,11]. Fig.…”

Low loss mid-IR transmission bands using silica hollow-core anisotropic anti-resonant fibers

“…Various HC-AR fiber designs have been proposed and implemented by several research groups in order to reduce the loss. HC-AR fibers with both circular AR tubes [1] and nested tubes inside the AR tubes [2], [4] have been investigated. The later designs confirm a significant loss reduction but increase design complexity.…”

“…We define ellipticity as η=r y /r x , where r x and r y are the radius of major and minor axis of the AR tubes respectively. We choose a core radius R c =47µm as reported in [2], [4] and silica strut thickness t=1.26 µm, which gives an anti-resonant first-order transmission window in the high-frequency mid-IR range (specifically around λ=2.94μm, the emission wavelength of Er:YAG lasers).…”