Continuously tunable devices based on electrical control of dual-frequency liquid crystal filled photonic bandgap fibers

Abstract

We present an electrically controlled photonic bandgap fiber device obtained by infiltrating the air holes of a photonic crystal fiber (PCF) with a dual-frequency liquid crystal (LC) with pre-tilted molecules. Compared to previously demonstrated devices of this kind, the main new feature of this one is its continuous tunability due to the fact that the used LC does not exhibit reverse tilt domain defects and threshold effects. Furthermore, the dual-frequency features of the LC enables electrical control of the spectral position of the bandgaps towards both shorter and longer wavelengths in the same device. We investigate the dynamics of this device and demonstrate a birefringence controller based on this principle.

Frequency tunability of solid-core photonic crystal fibers filled with nanoparticle-doped liquid crystals

“…The capillary was sandwiched between two glass plates covered with transparent indium-tin-oxide (ITO); two unfilled capillaries were used as spacers and a few drops of a UV-curable polymer on the electrodes made sure that the filled capillary did not move while under study. Polarized optical microscopy is a standard procedure used in order to investigate the alignment of liquid crystals [9][10][11][12][13]; by increasing the amplitude of the applied ac field, the liquid crystal realigns and a change of color can be observed through the microscope. For planar aligned liquid crystals, their molecules move only if the amplitude of the voltage is above a certain threshold, called the Frederiks transition [29].…”

“…If typical index-guiding PCFs are infiltrated with liquid crystals, they start guiding light by the bandgap effect, since liquid crystals have refractive indices higher than that of silica. Based on liquid crystal filled PCFs (LCPCF), devices which can be thermally, electrically or optically tuned, have been demonstrated [9][10][11][12][13][14][15][16][17][18][19][20]. Among these, we find, for example, devices for tuning, scrambling and controlling the polarization [11,19] tunable Gaussian filters for Optical Coherence Tomography (OCT) [14], tunable electrically and mechanically induced gratings [15], tunable notch filters [16], devices with tunable birefringence [18] and devices for single-polarization and high-birefringence guidance [20].…”

Analysis on Transition between Index- and Bandgap-guided Modes in Photonic Crystal Fiber

“…All-solid photonic bandgap fiber (ASPBGF) is a type of bandgap-guiding PCF. This has been made of high refractive index material (HRIM) inserts embedded in a PCF preform or filled into PCF afterwards [8][9][10][11][12][13][14]. Unusual dispersive properties have been also observed in the fiber, so the ASPBGFs were often applied to femtosecond laser and amplifier developments [15][16][17].…”

Comparison of Different Liquid Crystal Materials under Planar and Homeotropic Boundary Conditions in Capillaries

“…PCFs infiltrated with liquid crystals (LCs) create photonic liquid crystal fibers (PLCFs), that can be used as dynamically tuned photonic devices or sensors for various quantities [4][5][6][7][8][9][10][11]. Principle of operation of PLCF devices is based on change in propagation light properties induced by a change in LC molecules orientation.…”