Photonic Quasi-crystal Fiber Research Articles

Analysis and optimization of a dual-core dispersion compensation fiber based on a 12-fold photonic quasicrystal structure.

In this paper, a dual-concentric-core photonic quasicrystal fiber (DCC-PQF) with a 12-fold symmetric structure has been designed to compensate for dispersion effects. To this end, a new design based on modifying the positions of the nearest air holes to the central core has been proposed for dispersion compensation, in which ultra-high negative dispersion of about -44,000 ps/(nm·km) at 1.55μm can be estimated. In addition, by optimizing structural parameters, high negative dispersion for the proposed DCC-PQF has been predicted, approximately -12,000 ps/(nm·km) at around 1.55μm, with an FWHM about 42nm in the wavelength ranges between 1529 and 1571nm, which entirely covers the C telecommunication band. Furthermore, a dispersion relation dependency on hole-to-hole spacing, first ring air hole diameters, as well as diameter of the air holes in the outer core and its position, has been investigated and discussed in detail.

Design of a photonic quasi-crystal fiber for the generation of few cycle laser pulses

In this work, we design a novel, index guiding, silica core photonic quasi-crystal fiber (PQF) of 6, 8 and 10-folds for a wide range of operating wavelengths from 0.6 to 3μm. Further, we explore the various optical properties, namely, birefringence, dispersion, and nonlinearity for all the folds. Of all the folds, 10-fold PQF provides a low dispersion of −2.4765ps2km−1, a high nonlinearity of 22W−1km−1, admissible level of a less birefringence of 3.8×10−5 and confinement loss of 0.30446dB/cm at 1.06μm. These optical properties form the crucial requirements for the generation of few cycle laser pulses. Besides, we calculate the quality factor (Q) of the fundamental mode for all the folds and report a maximum quality factor of 0.9961 for the 10-fold PQF at 1.06μm wavelength.

A highly nonlinear photonic quasi-crystal fiber with low confinement loss and flattened dispersion

We proposed a novel photonic quasi-crystal fiber with near-zero flattened dispersion, highly nonlinear coefficient, and low confinement loss by using the dual concentric core structure. By optimizing the structure parameter, the proposed photonic quasi-crystal fiber can achieve a nonlinear coefficient larger than 33W−1km−1 and near-zero flatten dispersion of 0±3.4ps/nm/km with a near-zero dispersion slope of 8.5×10−3ps/nm2/km at the wavelength of 1550nm. Near-zero flattened dispersion and low confinement loss in the ultralow order of 10−7dB/m are simultaneously obtained in the wavelength range from 1373 to 1627nm. Furthermore, two zero dispersion wavelengths can be achieved in a wide wavelength ranger from 1373 to 1725nm. From the point of view of practical fabrication, the influence of deviation of each air hole diameter within 3% of imperfections on dispersion, nonlinearity, and is discussed to verify the robustness of our design.

Highly birefringent ZBLAN photonic quasi-crystal fiber with four circular air holes in the core

A highly birefringent ZBLAN photonic quasi-crystal fiber with a rectangular array of four relatively small circular air holes in the core region is proposed. Through optimizing fiber structure parameters using a full-vector finite-element method combined with perfectly matched layers boundary condition, its birefringence is up to 2.88×10−2 and the confinement losses of both polarized modes are less than 4.95×10−4dB/m at 2μm. To our knowledge, this is the first simulation study showing that a birefringence can be achieved with the order of 10−2 by all-circular-hole PQFs around 2μm.

Designing photonic quasi-crystal fibers of various folds: onto optimization of efficiency and bandwidth of second harmonic generation.

We design photonic quasi-crystal fibers (PQFs) of six-, eight-, ten-, and twelve-folds for determining the optimized efficiency as well as the bandwidth of second harmonic generation (SHG). We report a maximum SHG relative efficiency of 941.36% W⁻¹ cm⁻² for a twelve-fold PQF of 2 μm pitch. The detailed numerical results reveal that, while the relative efficiency increases appreciably, the phase-matching bandwidth increases marginally, as and when the number of folds increases. As the primary interest of this work is to enhance the relative efficiency, we focus our analysis with a twelve-fold PQF for which the efficiency turns a maximum. In line with the practical feasibility of poling, we keep the pitch at 7 μm and report an optimized relative efficiency and phase-matching bandwidth as 95.28% W⁻¹ cm⁻² and 50.51 nm.cm, respectively.

Investigation of a novel all-solid large-mode-area photonic quasi-crystal fiber

Large-mode-area single-mode fibers play an important role in the field of high power lasers, high power delivery, and high sensitivity sensor. A novel all-solid large-mode-area single-mode photonic quasi-crystal fiber with extremely low loss is proposed. This kind of fiber contains a hexagonal quasi-crystal array of slightly fluorine-doped silica rods in a silica background. Its structure and properties are simulated numerically in virtue of finite element method. Effects of variation of d/Λ, or Λ on fiber loss and effective mode-area properties are investigated. Numerical results demonstrate that an effective mode-area of 5197 μm2, low confinement loss of 10-5 dB/km for fundamental mode and high confinement loss of 100 dB/km of second-order mode at a wavelength of 1064 nm. Numerical simulations show that this fiber can operate effectively in single-mode and remove the conflict between large-mode-area and low loss. Moreover, the bending loss for a bending radius of 10 cm is as low as 0.01 dB/m. This fiber can increase the thermal damage threshold of the PQF, decrease the coupling loss and simplify the fabrication process. The design of new fibers is highly meaningful for the development of high power delivery, fiber lasers, and fiber amplifiers.

Highly birefringent ZrF4-BaF2-LaF3-AlF3-NaF photonic quasi-crystal fiber with twin grapefruits holes

A novel design of highly birefringent photonic quasi-crystal fiber based on ZrF4-BaF2-LaF3-AlF3-NaF glass with twin grapefruit air holes near the core and twofold symmetry is proposed. The basic unit is composed of one square and its neighboring regular triangle. Using the finite element method, the birefringence and confinement loss are investigated simultaneously by changing the pitch of air holes and sizes of air holes. Numerical results show that the fiber maintains single mode operation in a wide wavelength range from 1.8 μm to 2.2 μm, and the birefringence is on the order of 10-2, two orders of magnitude larger than that of the conventional polarization-maintaining fibers, which is largest (around 2 μm) ever reported to our knowledge and the same order of magnitude as that obtained by fiber using elliptic air holes But this designed fiber is easy to fabricate compared with the fibers using elliptic air holes.

Design of a highly nonlinear twin bow-tie polymer photonic quasi-crystal fiber with high birefringence

A twin bow-tie polymer-based photonic quasi-crystal fiber with high birefringence, high nonlinearity and low dispersion as well as maintaining single mode operation is presented in the wavelength range 1.8–2.2μm. Through optimizing fiber structure parameter using a full-vector finite-element method combined with perfectly matched layers boundary condition, the birefringence is as high as 2.43×10−3, the nonlinearity is as high as 118W−1km−1, and the dispersion is only 25ps/nm/km at 2μm with the holes pitch of 3.3μm. From the point of fabrication, the influences of deviation of each air hole diameter are discussed to verify the robustness of the photonic quasi-crystal fiber designed.

Exploring a photonic quasi-crystal fiber for enhancing the efficiency of second harmonic generation: Modeling and analysis

In this paper, we explore the possibility of using a new type of microstructured optical fiber called photonic quasi-crystal fiber (PQF) for enhancing the efficiency of second harmonic generation (SHG). We model a six-fold, index guided, silica core PQF with a relative air hole diameter ranging from 0.1–0.5. We compute the various factors related to SHG, namely, phase mismatch factor, wave-vector mismatch, coherence length, quasi-phase matching length and overlap area. Of the various factors, we focus more on the role of wave-vector mismatch and overlap area as these parameters are highly sensitive to the variations in the geometrical arrangement of air holes in the cladding. Further, these parameters are required to be as minimum as possible for enhancing the efficiency of SHG. We find that the wave-vector mismatch factor does decrease for higher values of pitch and for lower values of relative air hole diameter. However, the overlap area increases for higher values of pitch and for lower values of relative air hole diameter. Therefore, we optimize the hitherto mentioned parameters such that the wave-vector mismatch is 0.145μm−1 and the overlap area is 3.48μm2. With these values, we demonstrate a relative efficiency of 62.96%W−1cm−2 with the proposed PQF.

S+C+L波段色散斜率补偿光子准晶体光纤

针对光纤通信中的色散补偿,尤其是密集波分复用系统的多信道同时补偿的需求,提出了一种用于宽带色散斜率补偿的光子准晶体光纤.该光纤结构包层空气孔为准晶体排列,并且在纤芯引入了中心缺陷.通过对光纤特性的数值分析表明,在1 460-1 625 nm的光通信波段,该结构光纤的相对色散斜率为0.004 4-0.002 9 nm^-1,相对色散斜率与标准单模光纤近似相等,且负色散值达-2 476 ps·nm^-1·km^-1.对标准单模光纤进行色散补偿后,在S＋C＋L波段色散值为（-0.5-0）ps·nm^-1·km^-1.该光纤可用于对当前光纤通信系统进行宽带色散补偿,实现多信道同时补偿,简化结构,并降低补偿成本.

Supermode analysis of seven-core photonic quasi-crystal fibers

We design custom-shaped modes for a sixfold symmetric photonic quasi-crystal fiber (PQF), an optical fiber with a sixfold symmetric quasi-periodic array of air holes in the cladding region. The supermodes of the PQF are calculated by the finite element method, and the coupling of an in-phase supermode for the quasi-periodic optical fiber is numerically optimized to obtain identical values. The optimization is guaranteed by the selection of appropriate PQF design parameters. The eigenvalue equation associated with a seven-core PQF is derived from a coupled mode equation. We realize mode shaping and provide the far-field distribution mode of PQFs. The results are beneficial for the structural design and uniform distribution of the in-phase supermodes of PQFs.

准光子晶体光纤的色散特性

准光子晶体光纤的色散特性

Large Pitch Photonic Quasi-Crystal Fiber Amplifier

We design an ytterbium-doped large pitch photonic quasi-crystal fiber (PQF) for amplifying high-energy ultrashort laser pulses. The proposed fiber exhibits unique properties such as very large mode area (4660 μm2), less attenuation (0.42 dB/km), high overlapping factor (0.55 for the fundamental mode), and low bending loss. These properties help amplify with high-average power ultrashort pulses with less distortion and high efficiency. To meet these requirements, we design a fiber with optimum gain filtering as well as loss filtering. From the numerical simulation of the analytical model, we confirm that the large pitch PQF plays an indispensable role in amplifying high-energy ultrashort pulses.

High Normal Dispersion and Large Mode Area Photonic Quasi-Crystal Fiber Stretcher

We propose a fiber stretcher for stretching the high-energy ultrashort pulses which require high dispersion and large mode area to secure high stretching ratio and for ensuring distortionless pulses. In this line, we suggest a novel design of photonic quasi-crystal fiber (PQF) to achieve the desired high normal group velocity dispersion (GVD) of 1000 ps2/km at 1.06 μm and inner core effective mode area as 35 μm2 . These unique properties have been exploited to achieve a high stretching ratio (>; 105 ) as well as less nonlinearity, which, in turn, results in a distortionless fiber stretcher for an Yb-doped high-energy ultrafast fiber laser system based on chirped pulse amplification.

A Novel Photonic Quasicrystal Fiber with Broadband Large Negative Dispersion

A broadband highly dispersive fiber based on a dual-concentric-core photonic quasicrystal fiber (PQF) is designed for chromatic dispersion compensation. The fiber is composed of pure silica background and air-holes without doping. The fundamental supermode has a large negative dispersion value of about −9600 ps·nm−1·km−1 over an optical communication band around 1550 nm and a full width at half maximum (FWHM) of 40 nm. By adjusting the structural parameters, a dispersion of −2250 ps·nm−1·km−1 around 1550 nm with the FWHM exceeding 280 nm is obtained and the dispersion-bandwidth product can reach 630 GHz−1·km−1, which is the highest value of dispersion-bandwidth product from pure silica fibers reported so far.

Air Guiding With Photonic Quasi-Crystal Fiber

We present and analyze a novel hollow-core photonic quasi-crystal fiber (HC-PQF) constructed with 12-fold quasi-periodic structure. The quasi-periodic cladding is shown in this letter to be able to guide light in a large-size hollow core. This HC-PQF provides two photonic bandgaps in the ?/? < 1 region, thus two spectral windows of low loss guidance can be achieved. The behavior of guided modes that depends on the size of the defect core is studied, and the dispersion and confinement loss are also investigated. This research gives a physical insight into the propagation mechanism in HC-PQF and is crucial for future transmission applications.

Validity of the V parameter for photonic quasi-crystal fibers

We have investigated the validity of the V parameter to identify the single-mode operation regime for photonic quasi-crystal fibers. Our results show that the V parameter can be considered only for smoothly changing fibers. On the other hand, for fibers showing isolated high refractive regions around the core, only a mode area analysis can allow the estimation of the threshold for the single-mode operation regime. Finally, these findings can be generalized to any kind of optical fiber.

Dispersion properties of dual-core photonic-quasicrystal fiber

We propose a photonic quasi-crystal fiber with a dual-core structure. The circular-like outer core caused by the quasi-periodic arrangement gives rise to an interesting dispersion property that is different from that of a photonic crystal fiber with a dual-core structure. The absolute value of negative dispersion for the dual-core photonic quasi-crystal fiber increases as the distance between the nearest holes increases, while the absolute value of negative dispersion for the dual-core photonic crystal fiber decreases. The dispersion property can be useful in reducing the coupling loss between the compensating dispersion fiber and a conventional single mode fiber.

改进的八重准光子晶体光纤的色散特性研究

改进的八重准光子晶体光纤的色散特性研究

Novel optical properties of six-fold symmetric photonic quasicrystal fibers

We have investigated optical properties of an optical fiber having a six-fold symmetric quasiperiodic array of air holes in cladding, a six-fold symmetric photonic quasicrystal fiber. The photonic quasicrystal fiber exhibits larger cutoff ratio for endlessly single mode operation than that of a triangular photonic crystal fiber having six-fold symmetry and almost zero ultra-flattened chromatic dispersion, 0+/-0.05 ps/km/nm, in the range of wavelength from 1490 to 1680 nm. The dispersion value is much less than those of the proposed dispersion flattened PCFs.