Nadia H Rafat

In this study, the design and characterization of a photonic crystal fiber (PCF) as a light source for a mid-infrared supercontinuum generation (SCG) is presented. This PCF is based on a highly nonlinear chalcogenide $${\text{As}}_{40}{\text{Se}}_{60}$$background material with a hexagonal structure arrangement of air-holes rings. The PCF parameters such as the chromatic dispersion (D), the effective refractive index ($${n}_{eff}$$) and the nonlinear coefficient (γ) have been investigated. We study the stimulated SCG in two types of dispersion regimes: anomalous and all-normal dispersion (ANDi). We initiate the study by sending a 28.4 fs wide optical pulse with a peak power of 10 kW and a central wavelength of 2.8 µm through a 2 cm long PCF. In the anomalous dispersion, we demonstrate the generation of coherent and broadband SCG spectrum spanning the wavelength region from 1.6 to 7.8 µm. While, in the ANDi regime we demonstrate the generation of a broad, ultra-flat-top and highly coherent SCG spectrum extending from 2 to 4 µm at 6 dB spectral flatness. Thus, we achieve ultra-flat SCG spectrum source with a bandwidth as wide as 2400 nm within only 2 cm propagation length of the proposed PCF. This spectrum range is very suitable for variety of applications in mid-infrared region such as optical metrology, frequency comb generation, and optical coherence tomography (OCT). Results further demonstrate that with an applied pump power of 15 kW through the ANDi regime, a flat spectral bandwidth of 380 nm (wavelengths ranging from 1260 to 1640 nm) at just 3 dB spectral flatness is achieved. This band covers the five-telecommunication optical bands O-, E-, S-, C- and L-bands that comply with ITU-T-compliant wavelengths for wavelength division multiplexing (WDM) applications like coarse WDM (CWDM) and dense WDM (DWDM).

In this study, we propose a new design based on photonic crystal fibers (PCFs) for broadband dispersion compensation in telecommunication networks. The proposed design has a hexagonal structure arrangement of air-holes rings of different diameters between the silica core and the cladding. The PCF properties like effective area, nonlinearity, dispersion slope, confinement loss, and birefringence are reported and discussed. For the best performance we present three designs A, B and C. Simulation results show that the three designs cover the six-telecommunication optical bands O-, E-, S-, C-, L- and U- bands (wavelengths ranging from 1260 to 1675 nm). Design A achieves a large negative dispersion value of about − 1716 ps/(nm.km) with relative dispersion slope equals to that of conventional single-mode optical fibers (SMFs) of about 0.0036 nm−1, which makes it very suitable for long-haul DWDM transmission systems. With a little modification in the core, designs B and C achieve much higher confinement ability and achieve a very large birefringence value for polarization mode dispersion and sensing applications. Design C is engineered to have exact opposite dispersion of SMF with zero dispersion at the wavelength 1310 nm, which makes it a promising design in CWDM transmission system. The numerical values have been investigated using the full vector finite element method.