Two all-optical switching schemes of 1560 nm femtosecond pulses using soft glass asymmetric dual-core fibers

Abstract

We present a study of nonlinearly governed all-optical switching of C-band femtosecond pulses using all-solid dual-core fibers with slight asymmetry between the cores. The fibers are made of a thermally matched pair of soft glasses ensuring high index contrast between the core and the cladding. Two dual-core fibers with lower and higher levels of dual-core asymmetry were examined by two different experimental approaches targeting nonlinear switching of 1560 nm, 75 fs solitonic pulses. When using the less asymmetric fiber, an effective self-switching of 1560 nm, 75 fs low-energy pulses was demonstrated; in the case of more asymmetric fiber, a cross-switching of identical pulses was achieved driven by 270 fs, 1030 nm control pulses. The fiber length was optimized in both cases by the cut-back method. The self-switching approach employed in the case of less asymmetric fiber resulted in 35 mm optimal length, at which the highest switching contrast of 20.1 dB with broadband character in the spectral range 1450-1650 nm was observed. The cross-switching in the more asymmetric fiber was performed with even higher switching contrasts exceeding 25 dB at more homogeneous spectral dynamics in the C-band at 14 mm optimal length. Both outcomes represent high application potential with some complementary advantages. The simpler self-switching scheme requires only a single sequence of pulses and subnanojoule switching energy levels. However, in applications where even higher switching contrasts are required, crossswitching can be performed by employing more complex experimental schemes with higher energy control pulses.