Generation of ultra-compressed solitons with a high tunable wavelength shift in Raman-inactive hollow-core photonic crystal fibers

The fission of N-solitons is a key mechanism leading to the supercontinuum generation and creation of hyper-compressed pulses and solitons featuring strong wavelength tuning [1, 2]. Recent advances in manufacturing PCFs filled with Raman-inactive gases [3] provide a strong motivation to focus the studies on the fission driven by the third-order dispersion (TOD) [4], and potential applications of this setting to photonics. In the absence of the Raman-induced self-frequency shift and the Raman-associated noise, fission-produced strongly compressed solitons, once generated, may propagate keeping constant internal frequencies. A higher-order N-soliton, u = NP₀sech(T/T₀) is launched into the fiber, where T₀ and P₀ are width and peak power of the corresponding fundamental soliton. If the TOD dispersion/3₃ is very small, it can be considered as a perturbation added to the second-order dispersion, ß₂. In this case, the peak power of each fundamental soliton emerging after the splitting of the N-soliton is given by the classical result, P_j = P₀(2N - 2j + 1)² [5]. If ß₃ is larger, it leads to a significant increase in the largest fundamental-soliton's peak power and compression degree, along with the increase of the wavelength shift. However, further increase of/3₃ leads to a loss of the peak-power enhancement. For optimal pulse compression and wavelength conversion, universal optimal value of TOD strength parameter δ₃ = β3/(6β₂Τ₀) was found. This optimal value is valid for any pulse duration, second- and third-order dispersion coefficients, depending solely on order N of the injectedsoliton (Fig. 1(a)). The optimal pulse-compression degree significantly exceeds the well-known analytical prediction [5], as shown in Figs. 1(b, d).