7-cell hollow-core photonic bandgap fiber with broad spectral bandwidth and low loss

Application of Hollow-Core Photonic Crystal Fibers in Gas Raman Lasers Operating at 1.7 μm

“…In 2005, they further reduced the fiber loss to 1.2 dB/km at 1620 nm [33], which is currently the lowest loss of PBG-HCFs. Figure 2c shows the schematic cross section of PBG-HCFs with a broad transmission band and low loss demonstrated by the Beijing University of Technology in 2019 [34]. The minimum loss of 6.5 dB/km at 1633 nm and a 3 dB bandwidth at 458 nm were achieved, which is the broadest bandwidth in PBG-HCFs.…”

“…The fiber core of an HC-PCF is an air hole, so the refractive index of the fiber core is less than that of the fiber cladding and the law of total reflection is not suitable for HC-PCFs. According to the light guide mechanism, there are two major classifications of HC-PCFs, namely photonic bandgap hollow-core fibers (PBG-HCFs) [31][32][33][34][35] and anti-resonance hollow-core fibers (AR-HCFs) (or inhibited-coupling fibers) [36][37][38][39][40][41][42][43][44][45][46][47][48][49].…”

Light guiding properties of negative-curvature hollow-core fiber

“…Fig. PBGF [36], (b) kagome fiber [41], (c) a sing ring negative curvature hollow core fiber (SR-NCF), which consists of single ring cladding tubes surrounding the central hollow region [53], (d) nested nodeless hollow core fiber NANF [54] Ref. [49].…”

“…A scanning electron microscope (SEM) image of the cross section of a PBG fiber is shown in Fig. 1.3(a) [36]. The guiding mechanism in PBG fiber is the photonic bandgap effect [27,28,35].…”

“…Another issue in PBG-type HCF is the presence of surface modes, the surface modes formed at the intersection of silica membrane, surface modes narrow the available bandwidth [38]. The bandwidth in PBG-type HCF is 458 nm with the minimum loss of 6.5 dB/km at 1633 nm, which hinders a wide range of applications [36].…”