Triangular Lattice Photonic Crystal Fiber Research Articles

Refractive Index Sensing Simulations of CsPbBr3 Quantum Dots/Gold Bilayer Coated Triangular-Lattice Photonic Crystal Fibers

With the incorporation of noble metal materials, photonic crystal fibers (PCFs) could be performed as an effective platform for refractive index sensing of the filling analytes. Furthermore, by coating functional dielectric layers upon the metal surfaces, the resonance energy transfer is modulated from the core mode of the PCFs towards the surface plasmon resonance mode of the metals, and the sensing performance could be boosted. Here, considering that the exciton-plasmon coupling is efficient between perovskite quantum dots (QDs) and gold, a kind of CsPbBr3 QDs/Au bilayer coated triangular-lattice PCFs has been simulated numerically as the refractive index sensors. With the optimization of the QDs and gold layer thicknesses, together with the variation of the central hole size of the PCFs, in the refractive index (RI) region of 1.26 to 1.34, a rather narrow full width at half maximum (FWHM) of the loss spectra was achieved as 13.74nm when the central hole size was 1.28 µm and the highest figure of merit was 63.79RIU (the central hole size was 1.53 µm). This work demonstrates that the analyte identification accuracy was enhanced by FWHM narrowing of the loss spectra; in addition, taking the abundance of the material choice of perovskite QDs into consideration, more analytes could be detected effectively. Moreover, by adopting asymmetric structures, the sensitivity of the PCFs based refractive index sensors could be further improved.

Simulation of fiber fuse phenomenon in photonic crystal fibers

The unsteady-state thermal conduction process in several photonic crystal fibers (PCFs) was studied theoretically by the explicit finite-difference method using the thermochemical SiOx production model. The threshold power Pth for fiber fuse propagation in these PCFs was one order of magnitude higher than that for conventional single-mode optical fibers (SMFs). These results agreed with the experimental results. Pth of the triangular-lattice PCF was 69 W, and the resistance of this PCF to high-power irradiation was superior to that of SMF. The threshold power density for the honeycomb-structure PCF and/or triangular-lattice PCF was about 45 times larger than that of conventional SMFs.

A squeezed photonic crystal fiber for residual dispersion compensation with high birefringence over S+C+L+U wavelength bands

A squeezed triangular lattice photonic crystal fiber (PCF) composed of elliptical air holes is presented in this paper. Full vector finite element method (FEM) is used to investigate the guiding property. By adjusting the size of air holes in cladding, the fiber offers a flat negative dispersion of -1343.46 ± 6.74 ps/(nm.km) over the wavelength bands of S+C+L+U. The birefringence can be on the order of 10−2 which reaches up to 3.72×10−2 at the wavelength of 1.55μm. The proposed PCF may show some important applications in residual dispersion compensation and polarization maintaining fibers.

Calculation of effective mode field area of photonic crystal fiber with digital image processing algorithm

Photonic crystal fiber as a new type of optical fiber has been extensively applied because of its unique properties. The effective mode area of optical fiber is an important parameter, which has a great influence on the performance of optical fiber. In this study, digital image processing algorithm was used for preprocessing to improve the accuracy of calculation of mode field area. Then the effective mode field area of optical fiber was calculated using Matlab based Gauss fitting method. Take single-mode fiber G.652 as an example, the effective mode field area was calculated using the traditional algorithm and digital image processing algorithm respectively. It was found that the results obtained using digital image processing algorithm were within the allowed error range, suggesting the effectiveness of the algorithm. Then the calculation of the effective mode area of the triangular lattice photonic crystal fiber further verified the reliability of the algorithm.

Designing high-performance fiber laser based on ring structured PCF host

The tight modal confinement property with circularly symmetric fundamental mode-field pattern of a ring structured photonic crystal fiber (PCF) is utilized to improve the laser threshold and output characteristics of existing fiber lasers. We perform a detailed study of continuous-wave lasing characteristics in such erbium-doped fiber host by varying associated geometrical and optical parameters towards achieving a high performance and short length fiber laser. A finite difference mode-convergence analysis is implemented to determine the required modal properties of the guiding host, which is then used to solve standard propagation rate equations. The laser properties of the structure considered is compared with equivalent regular triangular-lattice photonic crystal fiber illustrating a significant improvement in the characteristics of fiber lasers reported so far.

ASE suppression in Er3+ doped dual-core triangular lattice photonic crystal fibers (PCFs) for narrowband and broadband dispersion compensation for communication wavelength

In this article, silica based triangular lattice PCF has been investigated toward both narrowband and broadband dispersion compensation for application in the communication wavelength. A dual core structure is obtained by introducing two different air-hole diameters in the cladding of the PCF. Dependence of individual structural parameters toward high negative dispersion (both narrowband and broadband) has been investigated in details with multipole mode based solver. The numerical investigation exhibits narrowband of very large negative dispersion of −37,300ps/nm/km around the wavelength of 1550nm. Present investigation also reports broadband dispersion values varying from −800ps/nm/km to −2600ps/nm/km over a 200nm wavelength (1400–1600nm) range, and kappa values near 300nm, which matches well with standard single mode fiber. Using the principle of power transfer from the inner core to the outer core after the coupling wavelength, we have investigated possible design of ASE suppressed amplifier in which wavelengths after the coupling wavelength cannot be amplified as most of the power tunnel to the outer core, where doped ion does not exist.

Broadband high birefringence and low dispersion terahertz photonic crystal fiber

We propose a novel type of triangular lattice terahertz photonic crystal fiber with high birefringence and low dispersion in a wide spectrum range. The proposed structures have circular and elliptical air holes in the cladding. Properties of birefringence, confinement loss, and group velocity dispersion have been studied by using full-vector finite-element methods. Through adjusting the structural parameters of the photonic crystal fiber, birefringence up to 10−3 could be achieved in the frequency range of 0.1–5 THz. Moreover, group velocity dispersion curve in this frequency range is flat and the values are nearly zero. Therefore, it can be used to transmit broadband THz pulses with the polarization maintained.

Near-elliptic Core Triangular-lattice and Square-lattice PCFs: A Comparison of Birefringence, Cut-off and GVD Characteristics Towards Fiber Device Application

In this work, we report detailed numerical analysis of the near-elliptic core index-guiding triangular-lattice and square-lattice photonic crystal fiber (PCFs); where we numerically characterize the birefringence, single mode, cut-off behavior and group velocity dispersion and effective area properties. By varying geometry and examining the modal field profile we find that for the same relative values of <TEX>$d/{\Lambda}$</TEX>, triangular-lattice PCFs show higher birefringence whereas the square-lattice PCFs show a wider range of single-mode operation. Square-lattice PCF was found to be endlessly single-mode for higher air-filling fraction (<TEX>$d/{\Lambda}$</TEX>). Dispersion comparison between the two structures reveal that we need smaller lengths of triangular-lattice PCF for dispersion compensation whereas PCFs with square-lattice with nearer relative dispersion slope (RDS) can better compensate the broadband dispersion. Square-lattice PCFs show zero dispersion wavelength (ZDW) red-shifted, making it preferable for mid-IR supercontinuum generation (SCG) with highly non-linear chalcogenide material. Square-lattice PCFs show higher dispersion slope that leads to compression of the broadband, thus accumulating more power in the pulse. On the other hand, triangular-lattice PCF with flat dispersion profile can generate broader SCG. Square-lattice PCF with low Group Velocity Dispersion (GVD) at the anomalous dispersion corresponds to higher dispersion length (<TEX>$L_D$</TEX>) and higher degree of solitonic interaction. The effective area of square-lattice PCF is always greater than its triangular-lattice counterpart making it better suited for high power applications. We have also performed a comparison of the dispersion properties of between the symmetric-core and asymmetric-core triangular-lattice PCF. While we need smaller length of symmetric-core PCF for dispersion compensation, broadband dispersion compensation can be performed with asymmetric-core PCF. Mid-Infrared (IR) SCG can be better performed with asymmetric core PCF with compressed and high power pulse, while wider range of SCG can be performed with symmetric core PCF. Thus, this study will be extremely useful for designing/realizing fiber towards a custom application around these characteristics.

Geometric definition of the V-parameter in photonic crystal fibers

We propose a general geometric definition of the V-parameter in photonic crystal fibers (PCF). We argue that the fundamental modal field in both square-lattice and triangular-lattice PCFs can be approached by certain proper assemblies of the fundamental mode in a one-dimensional planar waveguide. This observation suggests a geometric definition of the effective core radius and the single-mode regime of V≤π/2 in various PCFs. The numerical results imply that the suggestion is valid for all of the one-rod, seven-rod, 19-rod, and 37-rod core triangular-lattice PCFs and the one-rod, nine-rod, and 25-rod core square-lattice PCFs.

Investigation of structural dependence of host erbium-doped triangular-lattice PCF on lasing properties and design of high performance laser

A detailed study is presented on the lasing properties of an erbium-doped photonic crystal fiber (PCF) laser. The effects of the host PCF’s structure and laser parameters on continuous-wave laser emission are analyzed by considering the confinement and overlap of pump and signal fields in the gain medium for varying values of pitch, hole diameter, and doping radius. For analysis, we used a finite-difference mode-calculation algorithm devised with standard population and propagation rate-equation solver. Our analysis, applied to an experimentally realized PCF laser, reproduces the observed/reported data, thereby showing the efficacy of our analysis. Finally, a fiber geometry to realize a laser with threshold as low as 6 mW using a short fiber length of 0.52 m is prescribed. The aim of the design is to greatly reduce splice loss with standard single-mode SM28/G.652 fiber while maintaining the optimum performance. These results are new in PCF laser research and should be useful in realizing high performance PCF-based laser devices.

Dependence of birefringence on elliptical-hole orientation in photonic crystal fibers

In this paper, the dependence of birefringence on the orientation of elliptical holes in triangular-lattice elliptical-hole photonic crystal fibers (PCFs) is investigated numerically. A resonant enhancement of birefringence between the anisotropic lattice arrangement and oriented elliptical holes is observed, and the birefringence varies periodically with the ellipticalhole orientation. When the major axes of adjacent elliptical holes are parallel, the birefringence approaches the maximum. Based on the numeric analysis, a novel highly birefringent PCF is proposed, and the maximum modal birefringence of 0.086 is achieved.

Design of Broadband Dispersion Compensating Photonic Crystal Fiber

This paper presents a triangular-lattice photonic crystal fiber for broadband dispersion compensation. The finite element method with perfectly matched absorbing layers boundary condition is used to investigate the guiding properties. The designed dispersion compensating fiber shows that it is possible to obtain a larger negative dispersion coefficient of ?360 ps/(nm.km) at 1.55 ?m, better dispersion slope compensation, better compensation ratio in the entire telecommunication (1460-1640 nm) band by using a modest number of design parameters and very simple cladding design.

The Numerical Calculation on the Effective Area of Photonic Crystal Fiber Using FEM

The effective areas of triangular lattice photonic crystal fiber (PCF) are analyzed using the finite element method (FEM) both for single-rod and three-rod core PCF. While keeping the normalized wavelength constant, the effective areas of PCF increase with increasing wavelength, it also decrease with increasing ratio of hole diameter over the hole pitch. We also compared the effective area of single-rod core and three-rod core PCF. We find that the effective area of three-rod core PCF is larger than that of single-rod core PCF as the normalized wavelength is small.

Tailoring Of Flattened Dispersion In Triangular-Lattice Photonic Crystal Fiber

The interest of researchers and engineers in several laboratories, since the1980s, has been attracted by the ability to structure materials on the scale of the optical wavelength, a fraction of micrometers or less, in order to develop new optical medium, known as photonic crystals . Photonic crystals rely on a regular morphological microstructure of air-holes, incorporated into the material, which radically alters its optical properties. In Photonic Crystal Fiber (PCF) it is possible to realize flat dispersion over a wide wavelength range that cannot be realized with a conventional singlemode fiber. In PCFs, the dispersion can be controlled and tailored with unprecedented freedom. In fact, due to the high refractive index difference between silica and air, and to the flexibility of changing airhole sizes and patterns, the waveguide contribution to the dispersion parameter can be significantly changed, thus obtaining unusual position of the zero dispersion wavelength, as well as particular values of the dispersion curve slope. In particular, by manipulating the air- hole radius or the lattice period of the micro structured cladding, it is possible to control the zero-dispersion wavelength, which can be tuned over a very wide range, or the dispersion curves, which can be engineered to be ultra flattened. In this paper the geometric parameters of triangular PCF have been properly changed to optimize the dispersion compensation over a wide wavelength range.

Numerical simulation and experimental investigation of photonic bandgap photonic crystal fibers with interstitial holes

AbstractThe photonic bandgaps and modal properties of triangular lattice photonic bandgap photonic crystal fibers (PBG‐PCFs) with interstitial holes are analyzed by the full‐vector plane‐wave expansion method. We analyzed the influence of the air holes array triangular lattice cladding and the interstitial holes on the photonic bandgaps and calculated the spectrum range of photonic bandgaps. We found that the PBG‐PCFs with interstitial holes have a fundamental bandgap and a secondary bandgap. The transmission spectrum of PBG‐PCFs is measured. The results indicate that there are two strong transmission bands in the near‐infrared, but hardly any transmission phenomena in the visible region, which show that there are some bandgaps in near‐infrared wavelength. The results of the experiments are consistent with the numerically simulative results using the full‐vector plane‐wave expansion method. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:233–236, 2012

Designing high performance Er +3-doped fiber amplifier in triangular-lattice photonic crystal fiber host towards higher gain, low splice loss

In order to improve the over-all performance of all-fiber amplifier using Er +3-doped triangular-lattice photonic crystal fiber (PCF), we performed a detailed study on the amplifying characteristics of the PCF host by varying all associated geometrical parameters towards utilizing controllable effective numerical aperture and tight modal confinement. A finite difference (FD) mode convergence analysis is used to determine the modal propagation characteristics of the structure, which is then used to solve a standard propagation and population rate equation. Our results show that a spectral gain of the amplifier as high as 51 dB and that too over a short length ∼2.5 m of the fiber is achievable by optimizing the transverse geometry of the fiber. Aimed at field-deployment of the amplifier as inline component, we calculate the important all-fiber characteristics, namely, beam divergence, bending loss and nonlinearity and then optimize the splicing/coupling loss (resulting from the fundamental mode mismatch only) of this active fiber device. Notably, the splice loss with standard telecom-grade SMF-28 fiber is considerably minimized through an improved mode-matching of the design. These results record a marked improvement in fiber amplifier research in realizing high-performance EDFA-PCF amplifiers.

Guiding Properties of Modified Triangular Lattice Photonic Crystal Fibers

We present guiding properties of modified triangular lattice photonic crystal fibers. The finite difference method under anisotropic perfectly matched layer boundary condition is used to investigate the guiding properties. Dispersion and effective area properties of the proposed fibers are presented for different pitches and air-hole diameters. From the results of simulation, for a small pitch, the effective area of the proposed fibers around 1550 nm telecommunication window is found to be different than that of other fibers reported to date. The dual-slope effective area of the proposed fibers within the telecommunication window may be suitable for designing highly nonlinear fibers for various applications in nonlinear regimes. Moreover, large negative dispersion magnitude and slope are also found near 1550 nm wavelength.

An efficient algorithm for modeling photonic crystal fibers

Combining perfectly matched layer (PML) for the boundary treatment, an efficient compact two-dimensional finite-difference time-domain (2-D FDTD) method was introduced to model photonic crystal fibers (PCF). For photonic crystal fibers, if we assume that the propagation constant along the propagation direction is fixed, three-dimensional hybrid guided modes can be calculated by using only a two-dimensional mesh. The computation time and computer memory would be significantly reduced in this way. The numerical results for a triangular lattice photonic crystal fiber are in very good agreement with those from the other theoretical tool and experiment. We also analyze the modal properties of the PCF with air hole deformation. The results show that modal properties of the PCF with air hole deformation in the inner ring of air holes, especially in the first inner ring of air holes, would be affected more than that with air hole deformation in the outer ring of air holes even in the second inner ring of air holes. The compact 2-D FDTD algorithm shows a potential for improving the fabrication technique of PCF efficiently.

Fabrication of functional microstructured optical fibers through a selective-filling technique

We develop a method for the fabrication of functional microstructured optical fibers (MOFs) by selectively filling the air holes with liquid phase materials, where we utilize the dependence of filling speed on the size of the air holes. As a demonstration, we construct a hybrid MOF by filling the center hollow core of a triangular lattice photonic crystal fiber with dye-doped curable polymer, and experimentally observe the two-photon fluorescence from the hybrid MOF.