Photonic crystal fiber (PCF) structures with do-octagonal geometry have been studied. These do-octagonal PCF structure have smaller circular holes arranged in rhombic fashion at its centre. Moreover, these small holes are doped with materials like butanol, ethanol, methanol and propanol. Do-octagonal PCF structures doped with methanol and air filled structure report very high birefringence. Ultra flattened zero dispersion has been achieved by all the simulated structures. Besides, low confinement loss and large nonlinearity have also been reported. Numerical simulation for supercontinuum generation has been performed. Supercontinuum spectra obtained for peak power 1 kW, 2 kW, 5 kW and 10 kW are 650 nm, 950 nm, 1450 nm and 2050 nm respectively.

The study reports on the design and performance of two air‐filled and two partial ethanol‐filled photonic crystal fiber (PCF) structures with a tetra core for supercontinuum generation. The PCFs are nonlinear with ultra‐flattened zero dispersion. Holes with smaller areas are used to create a tetra‐core PCF structure. Ethanol is filled in the holes of smaller area while the larger holes of cladding region are air‐filled. Optical properties including dispersion, effective mode area, confinement loss, normalized frequency, and nonlinear coefficient of the designed PCF structures are investigated via full vector finite difference time domain (FDTD) method. A PCF structure with lead silicate as wafer exhibits significantly better results than a PCF structure with silica as wafer. However, both structures report dispersion at a telecommunication wavelength corresponding to 1.55 μm. Furthermore, the PCF structure with lead silicate as wafer exhibits a very high nonlinear coefficient corresponding to 1375 W−1 km−1 at the same wavelength. This scheme can be used for optical communication systems and in optical devices by exploiting the principle of nonlinearity.

We report the experimental generation of a broadband and flat mid-infrared supercontinuum in a silicongermanium-on-silicon two-stage waveguide. Our particular design combines a short and narrow waveguide section for efficient supercontinuum generation, and an inverse tapered section that promotes the generation of two spectrally shifted dispersive waves along the propagation direction, leading to an overall broader and flatter supercontinuum. The experimentally generated supercontinuum extended from 2.4 to 5.5 µm, only limited by the long wavelength detection limit of our spectrum analyzer. Numerical simulations predict that the supercontinuum actually extends to 7.8 µm. We exploit the enhanced flatness of our supercontinuum for a proof-of-principle demonstration of freespace multi-species gas spectroscopy of water vapor and carbon dioxide.

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