Solitonic spectral transformations in double core photonic crystal fiber

Abstract

Nonlinear propagation of femtosecond pulses in double core square lattice PCF made of multicomponent glass was investigated experimentally at excitation wavelength 1250 nm in the anomalous dispersion region. The obtained results expressed soliton fission and self frequency shift in the anomalous region, inspected by IR registration, with increasing complexity by increasing excitation energy. The visible registration, inspecting the normal dispersion region, exhibited soliton induced dispersive wave generation with blue shifting feature suggesting nonlinear phase change effect on the phase matching condition. The width of the overall spectral feature approached two octaves at approximately 10 nJ excitation energy in 6 cm long fiber sample. The knowledge about the evolving processes was extended by numerical simulation of the nonlinear propagation in the near IR region in reasonable correspondence with the experimental results. Furthermore, separate registration of the visible spectral features originating from the two fiber cores was ensured exhibiting significant differences between the multipeak spectra. The two core spectral content differences was possible to further alternate by rotation of the excitation polarization direction with application potential for polarization switched directional coupler accompanied by frequency conversion. Finally, single versus double core excitation conditions were compared. The double core excitation resulted in smoother spectral features, both in the case of IR and visible registration, at requirement at expense higher excitation energies needed for broadband supercontinuum generation.

Ultra flat supercontinuum generation in silicate dual core microstructured fiber

“…The reason for the remarkable flatness smoothness of the spectra appears to be the nonlinear intermixing between the two cores that effectively smoothens out any modulations. Some suspicion for the existence of this smoothening has been reported previously [22] but here the effect is presented to its full extent and this to our knowledge for the first time. To identify the underlying mechanisms for the smoothening requires additional modeling tools which are not available at this time.…”

“…However multifrequency generation in dual core fibers has already been observed [20]. First prediction of distinct advantages over single core PCF in context of nonlinear frequency conversion was given by Bugar et al [22]. In this case authors considered properties of different dual core PCF than considered in current paper.…”

“…In this case authors considered properties of different dual core PCF than considered in current paper. The dual core PCF presented in [22] has a photonic cladding arranged in the square pattern lattice with filling factor of d/Λ = 0.66 and lattice constant of Λ = 1.99 µm. A heavy lead-silicate glass synthesized in-house (n D = 1.57) is used for the fiber development in that case.…”