PCFs (Photonic Crystal Fibers) with ‘T’ – shaped core have been proposed in this paper. ‘T’ –shaped core PCF structures have been analyzed using two different background materials: silica and lead silicate. A total of 3600 rotation at an interval of 900 has been introduced in the design of PCF structures. PCF structures A, B, C and D with rotation of 00, 900, 1800 and 2700 have silica as wafer. Similarly PCF structures E, F, G and H with similar rotation have lead silicate as background material. Numerical investigations shows structures ‘D’, ‘F’, ‘G’ and ‘H’ to have anomalous dispersion. PCF structures ‘F’, ‘G’, and ‘H’ have reported birefringence of the order of 10-2. Besides, other PCF structures report birefringence of the order of 10-3. Ultra low confinement loss has been observed in all the investigated PCF structures. Moreover, splice loss observed by the structure is very low. Large mode area has been shown by all the designed PCF structures.

This paper outlines a measurement method of properties of microstructured optical fibers that are useful in sensing applications. Experimental studies of produced photonic-crystal fibers allow for a better understanding of the principles of energy coupling in photonic-crystal fibers. For that purpose, fibers with different filling factors and lattice constants were produced. The measurements demonstrated the influence of the fiber geometry on the coupling level of light between the cores. For a distance between the cores of 15 μm, a very low level (below 2%) of energy coupling was obtained. For a distance of 13 μm, the level of energy transfer to neighboring cores on the order of 2-4% was achieved for a filling factor of 0.29. The elimination of the energycoupling phenomenon between the cores was achieved by duplicating the filling factor of the fiber. The coupling level was as high as 22% in the case of fibers with a distance between the cores of 8.5 μm. Our results can be used for microstructured-fiber sensing applications and for transmission-channel switching in liquid-crystal multi-core photonic fibers.

The aim of this work was to induce permanent birefringence both in typical liquid crystal cells and photonic crystal fibers (PCFs) by photo-polymerization. For this purpose three different liquid crystalline materials, namely E7, 5CB, and 6CHBT were combined with a mixture of RM257 monomer and a UV sensitive initiator with the percentage weight less than 10%. Due to the photo-polymerization process it was possible to achieve polymer-stabilized liquid crystal orientation inside LC cells and micro-sized cylindrical glass tubes. In particular, periodic change in spatial molecular orientation was achieved by selective photo-polymerization. Successful results obtained in these simple geometries allowed for the experimental procedure to be repeated in PCFs leading to locally-induced permanent birefringence in PCFs.

This work suggests a brand-new 1*4 two-dimensional demultiplexer design based on multicore photonic crystal fiber. Numerical models show that the optical signals can be separated in a photonic crystal fiber construction using optical signals with wavelengths of 0.85, 1.1, 1.19, and 1.35 μm injected on the center core and separated into four cores. The innovative design switches different air-hole positions using pure silica layers throughout the length of the fiber to regulate the direction of light transmission between layers.
Wavelength demultiplexers are essential parts of optical systemic communications. They serve as a data distributor and can use a single input to produce multiple outputs. The background material is frequently natural silica, and air holes can be found anywhere throughout the length of the fiber as the low-index components.
The simulation results showed that after a 6 mm light propagation, the four-channel demux can start to demultiplex.

All normal dispersion (ANDi) and highly nonlinear chalcogenide glass photonic crystal fiber (PCF) is proposed and numerically investigated for a broad, coherent and ultra-flat mid-infrared supercontinuum generation. The proposed PCF consists of a solid core made of Ga₈Sb₃₂S₆₀ glass surrounded by seven rings of air holes arranged in a triangular lattice. We show by employing the finite difference frequency domain (FDFD) method that the Ga₈Sb₃₂S₆₀ PCF dispersion properties can be engineered by carefully adjusting the air holes diameter in the cladding region and ANDi regime is achieved over the entire range of wavelengths with a zero chromatic dispersion around 4.5 μm. Moreover, we demonstrate that injecting 50 fs width and 20 kW peak power laser pulses (corresponding to a pulse energy of 1.06 nJ) at a pump wavelength of 4.5 μm into a 1 cm long ANDi Ga₈Sb₃₂S₆₀ PCF generates a broad, flat-top and perfectly coherent SC spectrum extending from 1.65 μm to 9.24 μm at the 20 dB spectral flatness. These results make the proposed Ga₈Sb₃₂S₆₀ PCF an excellent candidate for various important mid-infrared region applications including mid-infrared spectroscopy, medical imaging, optical coherence tomography and materials characterization.