Nonlinear performance of asymmetric coupler based on dual-core photonic crystal fiber: Towards sub-nanojoule solitonic ultrafast all-optical switching

Abstract

We demonstrate ultrafast soliton-based nonlinear balancing of dual-core asymmetry in highly nonlinear photonic crystal fiber at sub-nanojoule pulse energy level. The effect of fiber asymmetry was studied experimentally by selective excitation and monitoring of individual fiber cores at different wavelengths between 1500 nm and 1800 nm. Higher energy transfer rate to non-excited core was observed in the case of fast core excitation due to nonlinear asymmetry balancing of temporal solitons, which was confirmed by the dedicated numerical simulations based on the coupled generalized nonlinear Schrödinger equations. Moreover, the simulation results correspond qualitatively with the experimentally acquired dependences of the output dual-core extinction ratio on excitation energy and wavelength. In the case of 1800 nm fast core excitation, narrow band spectral intensity switching between the output channels was registered with contrast of 23 dB. The switching was achieved by the change of the excitation pulse energy in sub-nanojoule region. The performed detailed analysis of the nonlinear balancing of dual-core asymmetry in solitonic propagation regime opens new perspectives for the development of ultrafast nonlinear all-optical switching devices.

All-optical switching based on soliton self-trapping in dual-core high-contrast optical fibre

“…The structure of the dual-core fibre was initially optimized by the proper choice of material used for manufacturing fibers. The choice of the two glasses used for the cores or for the cladding was a result of an extensive research, including synthesis of a complementary glass to the highly nonlinear lead-bismuth-galliumsilicate (PBG-08) glass, used already earlier also in the case of the air-glass DC PCF structure [7,8]. The precise composition of the complementary borosilicate type glass was tuned in order to match the thermo-mechanical properties of the high refraction index, guiding PBG-08 glass.…”

“…Furthermore, we set 2 = 2 /2 , where c is light velocity, and = 2 2 / , where 2 is nonlinear refractive index of the guiding PBG-08 glass equal to 4.3 • 10 −19 2 / [14]. In order to estimate the pulse energy before the fibre in-coupling process, we will use 32 % in-coupling efficiency, which corresponds to the measured value in the case of the air-glass PCF having core from the same glass [8]. Therefore, for the sech 2 pulse shape we get, for in-coupled pulse peak power for pulse energy E 0 = 0.88 • • 0.32 FWHM .…”

“…In terms of switching energies, the in-coupled ones are presented, because the in-coupling efficiency could be different in the case of air-glass and all-solid fibre. In the frame of the overview of the all results above, the pulse energy before the in-coupling optics is presented, taking into account the experimentally determined 32 % in-coupling efficiency in the case of the real DC PCF fibre [8]. However, it represents an overestimation of the required pulse energy, because the simple all-solid structure should have significantly higher in-coupling efficiency.…”

Applicable ultrafast all-optical switching by soliton self-trapping in high index contrast dual-core fibre

“…The experimental setup to test solitonic switching in all-solid DC fiber will be the same as the one used for air-glass PCF. A detailed description of it is reported in Curilla et al manuscript [15]. The input pulse wavelength will be kept around 1500 nm and its temporal width around 75 fs, in order to achieve the same values of SC values we have predicted in the frame of this paper.…”

“…In the case of dual-core PCF excited in anomalous dispersion region, our group achieved this level of switching contrast, however, only in a limited spectral region of the nonlinearly broadened spectra [14]. Simultaneously, a numerical model based on the coupled GNLSE has been developed, which allowed us to obtain comparable numerical results to the experimental ones in the case of different types of dual-core PCFs [14,15]. Our recent focus is the design and development of a dual-core fiber, which will support high contrast all-optical switching.…”