Ingenieurwissenschaften und zugeordnete Tätigkeiten
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.
We demonstrate narrow band spectral intensity switching in dual-core photonic crystal fibers made of highly nonlinear glass under femtosecond excitation. The fibers expressed dual-core asymmetry, thus the slow and fast fiber cores were unambiguously distinguished according to their dispersion profiles. The asymmetry effect on the dual-core Propagation in anomalous dispersion region was studied both experimentally and numerically. The experimental study was carried
out using femtosecond laser amplifier system providing tunable pulses in range of 1500 nm - 1800 nm. The obtained results unveiled, that it is possible to improve nonlinearly the coupling between the two waveguides by excitation of the fast fiber core. The results were obtained in regime of high-order soliton propagation and were verified numerically by the coupled generalized nonlinear Schrödinger equations model. The spectral analysis of the radiation transferred to the non-excited core revealed the role of effects such as third order dispersion, soliton compression and spectral dependence of the coupling efficiency. The simulation results provide reasonable agreement with the experimentally observed spectral evolutions in the both fiber cores. Under 1800 nm excitation, narrow band spectral intensity switching was registered with contrast of 23 dB at 10 mm fiber length by changing the excitation pulse energy in sub-nanojoule range.
Possibility of post-fabrication doping of commercial PMMA fibers using well-known solution doping technique is presented. The cladding of 1 mm PMMA fiber is doped with Rhodamine B with the help of methanol-mediated diffusion of the dye molecules into the fiber material. Doping of the fiber core was not possible even at extended doping times. The proposed method represents rather simple and cheap way for preparing custom cladding-doped POFs with high flexibility of dopant choice and fiber length. Produced cladding-doped fibers have potential for various sensing or lighting applications.
Possibility of post-fabrication doping of commercial PMMA fibers using well-known solution doping technique is presented. The cladding of 1 mm PMMA fiber is doped with Rhodamine B with the help of methanol-mediated diffusion of the dye molecules into the fiber material. Doping of the fiber core was not possible even at extended doping times. The proposed method represents rather simple and cheap way for preparing custom cladding-doped POFs with high flexibility of dopant choice and fiber length. Produced cladding-doped fibers have potential for various sensing or lighting applications.
Nonlinear ultrafast switching based on soliton self-trapping in dual-core photonic crystal fibre
(2016)
In this paper, we present a systematic numerical study of a novel ultrafast nonlinear switching
concept based on soliton self-trapping in dual-core (DC) photonic crystal fibre (PCF).
The geometrical parameters of highly-nonlinear (HN) DC microstructure are optimized
with regard to desired linear and nonlinear propagation characteristics. The comparable
magnitude of fibre coupling length and soliton period is identified as a key condition for
presented switching concept. The optimized DC PCF design is subjected to detailed nonlinear
numerical study. Complex temporal-spectral-spatial transformations of 100 fs hyperbolic
secant pulse at 1550 nm in the DC PCF are studied numerically employing a model based on
coupled generalized nonlinear Schrödinger equations solved by a split-step Fourier method.
For the optimized DC structure, mutual interplay of solitonic and coupling processes gives
rise to nonlinear switching of self-trapped soliton. The output channel (fibre core) for the
generated soliton can be controlled via the input pulse energy. For vertical polarization, the
optimal soliton switching with extinction ratio contrast of 32.4 dB at 10.75 mm propagation
distance is achieved. Even better switching contrast of 34.8 dB can be achieved for horizontal
polarization at optimal propagation distance of 10.25 mm. Besides energy-controlled soliton
self-trapping switching, the fibre supports also nonlinear polarization switching with soliton
switching contrast as high as 37.4 dB. The proposed fibre holds a high application potential
allowing efficient ultrafast switching of sub-nanojoule pulses at over-Tb/s data rates requiring
only about 1 cm fibre length.
We describe the fabrication of a polycarbonate (PC) micro-structured polymer optical fiber (mPOF) and the writing of fiber Bragg gratings (FBGs) in it to enable strain and temperature measurements. We demonstrate the photosensitivity of a dopant-free PC fiber by grating inscription using a UV laser. We further show that PC Bragg gratings can be extended up to at least 3% without affecting the initial functionality of the micro-structured fiber. The response of PC FBGs to temperature up to 125°C is also investigated. Polycarbonate has good mechanical properties and its high temperatureresistance might extend the range of application of polymeric FBGs.