Comparison of supercontinuum spectral widths in CCl₄-core PCF with square and circular lattices in the claddings

Abstract

In this study, we demonstrate the ability to generate a broad supercontinuum (SC) spectrum with a low peak power of square (S-PCF) and circular (C-PCF) lattice photonic crystal fibers with hollow-core infiltrated with carbon tetrachloride (CCl4). The dispersion and nonlinear characteristics have been numerically analyzed in detail and compared to select the optimal structures for SC generation and evaluate the SC generation efficiency for each PCF. With four optimal proposed structures, the all-normal dispersion of square PCF (#SF1) is found to be flatter and smaller. This results in its SC bandwidth reaching 901 nm at 1.095 μm pumping wavelength which is broader than that of circular PCF (#CF1) (768 nm at 0.98 μm wavelength) despite the lower nonlinear coefficient and higher confinement loss. For the anomalous dispersion regime, #CF2 fiber provides a wider SC spectrum (1753.1 nm) with a peak power of 10 kW compared to #SF2 (1689.6 nm) with a peak power of 13.75 kW thanks to the higher nonlinear coefficient and smaller confinement loss. With the higher nonlinearity of CCl4, the proposed fibers can be a new generation of optical fibers, suitable for low peak power all-fiber optical systems replacing glass core fibers.

Circular lattice benzene-core PCFs with flat near-zero dispersion for low-power broad-spectrum supercontinuum generation

“…Dispersion increases dramatically at short wavelengths (between 0.5 and 0.9 μm). This has been confirmed in several previous publications [26,29,43]. Also, as Λ increases, the dispersion becomes flatter and eventually monotonic.…”

“…For #F 2 , the SC spectrum can be extended from a part of the visible to MIR with even hundreds of times smaller power and short fiber length. Studies [14,29,31,48] also take advantage of the first air-hole ring diameter control model, but the SC spectral widths obtained are still limited with P values ranging from 0.45 to 10 kW. Moreover, with the same circular lattice, the work of Thuy et al [47] also showed a disadvantage in terms of spectrum broadening even using 7.4 and 24.7 times more peak power than ours.…”

“…Most work on SCG uses chloroform (CHCl [11,12,[24][25][26][27][28][29]. CS 2 has a high nonlinear refractive index n 2 = 514 × 10 −20 m 2 W −1 at 1064 nm [28], which is 100 times higher than n 2 = 2.74 × 10 −20 m 2 W −1 of silica (SiO 2 ) glass [30].…”

“…C 6 H 5 NO 2 and C 7 H 8 have relatively low transparency in the NIR region, which reduces the spectral broadening of PCFs [11,27]. The advantage of C 2 H 4 Br 2 , C 2 Cl 4 , CHCl 3 , and CCl 4 is that they have moderate toxicity, but their linear refractive index is lower than others, leading to reduced nonlinear coefficients [24][25][26]29]. On the other hand, C 6 H 6 has a high nonlinear refractive index n 2 = 168 × 10 −20 m 2 W −1 at 1.064 μm, which corresponds to C 6 H 5 NO 2 and C 7 H 8 .…”

“…As shown in table 1, the optical properties of PCFs are also highly dependent on the different types of geometric structures of the photonic cladding. Historically, accepted and realized standard configurations have cross-sections consisting of multiple layers of air holes arranged in hexagonal arrays around a core [20,28,29]. This configuration gives a flat dispersion curve close to zero, but the spectral bands are not very flat.…”