Abstract
In this paper, we present numerical studies of several different structures of anti-resonant, hollow core optical fibers. The cladding of these fibers is based on the Kagomé lattice concept, with some of the core-surrounding lattice cells removed. This modification, by creating additional, glass-free regions around the core, results in a significant improvement of some important optical fiber parameters, such as confinement loss (CL), bending loss (BL), and dispersion parameter (D). According to the conducted simulations (with fused silica glass being the structure’s material), CL were reduced from ~0.36 dB/m to ~0.16 dB/m (at 760 nm wavelength) in case of the structure with removed cells, and did not exceed the value of 1 dB/m across the 700–850 nm wavelength range. Additionally, proposed structure exhibits a remarkably low value of D—from 1.5 to 2.5 ps/(nm × km) at the 700–800 nm wavelength range, while the BL were estimated to be below 0.25 dB/m for bending radius of ~1.5 cm. CL and D were simulated, additionally, for structures made of acrylic glass polymethylmethacrylate, (PMMA), with similarly good results—DPMMA ∊ [2, 4] ps/(nm × km) and CLPMMA ≈ 0.13 dB/m (down from 0.41 dB/m), for the same spectral regions (700–800 nm bandwidth for D, and 760 nm wavelength for CL).
Highlights
The appearance of hollow core optical fibers [1] was a true revolution in the field of fiber optics.hollow core opticTalhfeiybearrse[c1a] pwaabsleaotrfugeuridevinoglultiigohnt iwnitthherefimeladrokfabfilbyelroowptliecvse. ls of optical losses and non-linearities, as ding light with remwaelrlkaasblpyrolovwidlienvgetlhs eofpoopsstiicbailliltoysfsoers eanngdinneoenr-ilningetahreitiireds,isapsersion, bi-refringence, etc. [2,3,4,5,6]
Where λk is the wavelength of the considered transmission window, d0 is the thickness of the first layer of high-index material, surrounding the core, k is 0,1,2, . . . , defining the transmission’s window order, and n is the material’s refractive index
The modal properties of these fibers were proven to be dependent mainly on the geometry of the very first layer of high refractive index material, surrounding the core. It was not very long until a truly single layer, microstructured cladding, hollow-core optical fiber was presented [14]. This idea, due to the simplicity of the cladding structure, and its susceptibility to modifications, has been extensively studied, resulting in the appearance of many different types of single-cladding-layer HC-ARFs with negative curvature of the core, such as nodeless [15], nested [11,16,17], dual core [18], split-cladding [19], or co-joined tube anti-resonant fibers [20]
Summary
The appearance of hollow core optical fibers [1] was a true revolution in the field of fiber optics. The modal properties of these fibers were proven to be dependent mainly on the geometry of the very first layer of high refractive index material, surrounding the core It was not very long until a truly single layer, microstructured cladding, hollow-core optical fiber was presented [14]. This idea, due to the simplicity of the cladding structure, and its susceptibility to modifications, has been extensively studied, resulting in the appearance of many different types of single-cladding-layer HC-ARFs with negative curvature of the core (we will refer to these fibers as NCHCFs), such as nodeless [15], nested [11,16,17], dual core [18], split-cladding [19], or co-joined tube anti-resonant fibers [20]. Our goals in this paper were to present that simple modifications of the negative curvature Kagomé HCFs core-cladding interface can significantly influence fiber CL and spectral bandwidth, and in turn, we propose a fiber structure that is well-suited for the delivery of high energy, ultrashort laser pulses with a wavelength range of 700 to 800 nm
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