Tunable Photonic Crystal Fiber Research Articles

Tunable polarization splitter based on asymmetric dual-core liquid photonic crystal fiber

Tunable photonic crystal fiber polarization splitter is proposed and analyzed. The proposed splitter has a dual asymmetric cores where one core is only filled with a nematic liquid crystal (NLC). The birefringence is also increased between the two polarized modes due to the NLC material which improves the splitting performance. The coupling between the two asymmetric cores occurs at a specific wavelength which can be controlled by the NLC material. Additionally, the splitting between the two polarized modes can be tuned by rotating the NLC molecules using an external electric field. Further, the matching wavelength where the power coupling occurs between the two asymmetric cores can be controlled thermally due to the NLC dependence on the temperature. The analysis of the proposed splitter is carried out using full vectorial finite difference method. The reported polarization splitter has a compact device length of 602 µm at λ = 1.3 μm with high wavelength selectivity. In addition, large bandwidth of 60 nm is obtained with crosstalk lower than − 20 dB which ensures the superiority of the reported device.

Rectangular lattice photonic crystal fiber with simultaneous polarization filtering at communication wavelengths of 1310 nm and 1550 nm

In this study, we developed a tunable photonic crystal fiber (PCF) polarized filter with a gold coating and liquid filling, which was investigated using the full-vector finite-element method. The gold that selectively filled the cladding air holes acted as a defect mode. When light was transmitted into the core, the energy was transferred from the core mode to the defect mode at a given wavelength and a resonance peak was obtained. Numerical results showed that the proposed PCF could be implemented simultaneously for polarization filtering in the communication windows of 1.31 and 1.55 μm. The confinement losses for the y-polarized mode were 251.5 dB/cm for 1.31 μm and 375.3 dB/cm for 1.55 μm. When the fiber length was 90 μm, the corresponding bandwidths were just less than 20 and 70 nm for 1.31 and 1.55 μm, respectively. The bandwidths are the narrowest obtained and they are conducive to applications in integrated systems. We also studied the effects of structural parameters on the resonance performance. The optical fiber structure could be optimized further to obtain better results.

Ultra-high tunable liquid crystal-plasmonic photonic crystal fiber polarization filter

A novel ultra-high tunable photonic crystal fiber (PCF) polarization filter is proposed and analyzed using finite element method. The suggested design has a central hole infiltrated with a nematic liquid crystal (NLC) that offers high tunability with temperature and external electric field. Moreover, the PCF is selectively filled with metal wires into cladding air holes. Results show that the resonance losses and wavelengths are different in x and y polarized directions depending on the rotation angle φ of the NLC. The reported filter of compact device length 0.5 mm can achieve 600 dB / cm resonance losses at φ = 90° for x-polarized mode at communication wavelength of 1300 mm with low losses of 0.00751 dB / cm for y-polarized mode. However, resonance losses of 157.71 dB / cm at φ = 0° can be achieved for y-polarized mode at the same wavelength with low losses of 0.092 dB / cm for x-polarized mode.

Numerical Analysis of Coupling Characteristics of Tunable Photonic Crystal Fiber Coupler for Nonlinear Optical Microscopy

As a kind of significant fiber device, an optical fiber coupler can make the nonlinear optical microscopy more compact and flexible for in vivo imaging. We numerically investigate the coupling efficiencies of side-polished large mode area endlessly single mode photonic crystal fiber coupler over the visible and near infrared wavelength range by using improved fully vectorial effective index method and weak-coupling theory. We find that appropriate combinations of the core distance and the angle between two side-polished fibers can accomplish a large mode area endlessly single mode photonic crystal fiber coupler to simultaneously deliver the near infrared laser for excitation and split the fluorescence for detection.

Design and analysis of thermally tunable liquid crystal filled hybrid photonic crystal fiber coupler

We propose a novel tunable photonic crystal fiber (PCF) coupler scheme, that the light is coupled between a total internal reflection (TIR) guiding core and a photonic bandgap (PBG) guiding core. By introducing the thermo-optic responsive nematic liquid crystals (NLC) into the air holes around the PBG core, the hybrid PCF based coupler exhibits enhanced thermal tunability. The thermo-optical characteristics of the proposed coupler are numerically studied using finite element method (FEM) and beam propagation method (BPM). The proposed design can find promising applications in filtering and sensing devices.

Characterization of tunable photonic crystal fiber directional couplers

We present a tunable photonic crystal fiber (PCF) directional coupler fabricated by a side-polishing method. The PCF directional coupler was modeled as a typical single-mode fiber-based directional coupler and analyzed using the improved effective-index method (IEIM). The characteristics of the PCF directional coupler such as the coupling coefficient and the coupling ratio were measured and found to be in good agreement with those predicted by the theoretical model. The PCF directional coupler exhibited an insertion loss of approximately 2 dB for a 3 dB coupler and was able to tune the coupling ratio between 0% and 100% by tilting the angle of the top side-polished quartz block against the fixed-bottom quartz block.

Efficient, tunable photonic crystal fiber Raman laser

AbstractAn efficient, tunable photonic crystal fiber Raman laser was firstly investigated. At the lasing light of 1126.8 nm, up to 2.7 W of continuous‐wave output power was obtained at the maximum incident pump power of 5.6 W. The corresponding optical conversion efficiency and the slope efficiency were ∼48 and ∼70.9%, respectively. By applying longitudinal tension strain on the fiber Bragg grating, we achieved ∼6.4 nm of the dynamic range with our laser. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 395–397, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22139

Tunable photonic crystal fiber coupler based on a side-polishing technique.

A tunable photonic crystal fiber (PCF) coupler, which couples part of the optical power in one PCF with that in another PCF, has been made by side polishing. We fabricated the PCF coupler by mating two side-polished PCFs. We achieved evanescent field coupling between the core modes of the two PCFs by using side polishing to bring the cores close to each other. By adjusting the mating angle between the two side-polished PCFs we obtained as much as 90% tunability in the coupling ratio. The spectrum of the coupling ratio was almost flat, with small ripples, over a 400-nm wavelength range.