Description

The hollow core microstructured optical fibers (HC MOFs) are a special kind of optical fibers which confine the light inside a hollow core surrounded by a microstructured cladding. The key advantage of HC MOFs is that the radiation propagates mostly in the air core and optical damage threshold is raised. Hollow core photonic crystal fibers (HC PCFs) can guide the light by virtue of a photonic band gap or due to an inhibited coupling between the air core modes and the cladding modes. Recently, a new type of HC MOFs with an alternating curvature of the core - cladding boundary and simplified cladding has been proposed. Such construction of the core - cladding boundary led to complication of boundary conditions for electromagnetic fields in the air core. It is clear that HC MOFs with an alternating curvature of core cladding boundary have no 1D or 2D photonic crystals in the cladding and the mechanism of light localization in their air cores is different from the ones in other types of HC MOFs. The new waveguide mechanism allows to strengthen the light localization in the air core and transmit the light in the spectral range, where material loss of the silica glass is very high. It was demonstrated experimentally that light can be transmitted in mid IR at wavelength of 8 microns, where material loss of silica glass is about 1000000 dB/m. Nevertheless, hollow core photonic crystal fiber fabricated from high - purity synthetic silica, with a wide operating bandwidth between 3.1 and 3.7 µm, was also reported. Analyses and comparison of the waveguide properties of different kinds of HC MOFs is very important point for the theory of HC MOFs. This is one of the main problem which will be cleared up in this Topic. Moreover, HC MOFs have very interesting optical properties which can be used for many important applications, for example, in the field of gas based nonlinear optics. Resonant behavior of the bending loss, very flat dispersion curves are examples of such interesting optical properties in the case of HC MOFs with an alternating curvature of the core - cladding boundary. HC MOFs can have potential very important applications in industry, medicine, sensing, telecommunications etc. This is the second very important problem which will be considered in this Topic. The third problem which will be considered in this Topic is a fabrication process of HC MOFs of different types which are made of different kinds of glasses.