Tunable diffraction and self-defocusing in liquid-filled photonic crystal fibers

Abstract

We suggest and demonstrate a novel platform for the study of tunable nonlinear light propagation in two-dimensional discrete systems, based on photonic crystal fibers filled with high index nonlinear liquids. Using the infiltrated cladding region of a photonic crystal fiber as a nonlinear waveguide array, we experimentally demonstrate highly tunable beam diffraction and thermal self-defocusing, and realize a compact all-optical power limiter based on a tunable nonlinear response.

Tunability of discrete diffraction in photonic liquid crystal fibres

“…Regu− larity of a periodic structure (i.e., the lack of defects in the photonic lattice) is opposite to typical PCFs (with solid core, not representing fully periodic structures). However, even if it has been demonstrated that for the large enough solid−core microstructured fibres they can be considered as a periodic matrix without structural defects [11], we have decided to use a hollow−core fibre in order to study discrete phenom− ena in analogous conditions as it has been performed in uni− form two−dimensional waveguide arrays [19,24]. Specifi− cally, in our case, by use of capillary forces and/or high pressure, the air holes of PCF have been infiltrated with LCs whose refractive indices are higher than that of silica for whole range of temperatures and wavelengths used in expe− rimental conditions.…”

“…The second one, a photonic bandgap (PBG) mechanism, allows for the light (from the particular spectral range) to be guided in the region of lower refractive index (e.g., in the air−core). On the other hand, PCF can also be considered as a two−dimensional photonic lattice (with pe− riodic modulation of refractive index in two dimensions), thus allowing (in specific cases) for a discrete light propagation (typical for waveguide arrays/photonic lattices as described below) [10][11][12].…”

“…Propagation properties of PCFs can be dynamically changed (including switching between different guiding mechanisms) by introducing gaseous, liquid or solid media into the air−channels [1,[11][12][13][14][15][16][17]. This simple idea has been found to be very useful while broadening the applicability of PCFs.…”

“…Recently, the concept of discrete light propagation in 2D periodic systems has been also transferred to the fluid−filled microstructured fibre devices, thus opening the gate to a new field of optics, namely the optofluidics. In this way, completely [11][12] and selec− tively [34][35][36] fluid−infiltrated PCFs have been adopted to the needs of discrete optics. The main reason for their appli− cation is the well−established fabrication process which allows for structural regularity to be easily accomplished.…”

“…More− over, application of the liquids with particular properties allows for observation of nonlinear effects. In particular, it has been shown that for a standard PCF infiltrated with a high index nonlinear liquid and by employing its thermal nonli− nearity it is possible to obtain a beam self−defocusing at high optical powers [11]. Moreover, spatial solitons in optofluidic systems formed by selectively fluid−filled PCFs and relying on the ultrafast Kerr nonlinearity of highly nonlinear liquids have been demonstrated [36].…”