Multiple Zero Dispersion Wavelengths Research Articles

Design and analysis of a hexagonal circular photonic crystal fibre with ultra-high negative dispersion and low confinement loss

This paper proposes a Hexagonal Circular Photonic Crystal Fiber (HC-PCF) with uniform tiny air holes around the core, obtaining ultra-high negative dispersion, high Birefringence and low confinement loss. The modal properties of the HC-PCF are investigated using the full-vectorial-Finite Element Method (FEM) with a perfectly matched layer as the boundary condition. The numerical investigations show ultra-high negative dispersion of −25503 ps/nm.km, a birefringence of 1.36×10-2, a nonlinearity of 38.34w-1km-1 and a confinement loss of 4.95×10-3 dB km-1 at the wavelength of 1550 nm. Moreover, the proposed HC-PCF exhibits a high negative dispersion and multiple Zero Dispersion within the 800 to 2000 nm wavelengths range. Specifically, the high negative dispersion, low optical Confinement Loss, and multiple Zero Dispersion Wavelengths (ZDW) give the proposed HC-PCF high Power Spectral Density (PSD). These characteristics make the proposed fibre suitable for long-range telecommunication networks and optical sensing.

Design and Theoretical Analysis of Highly Negative Dispersion-Compensating Photonic Crystal Fibers with Multiple Zero-Dispersion Wavelengths

This paper presents a highly negative dispersion-compensating photonic crystal fiber (DC-PCF) with multiple zero dispersion wavelengths (ZDWs) within the telecommunication bands. The multiple ZDWs of the PCF may lead to high spectral densities than those of other PCFs with few ZDWs. The full-vectorial finite element method with a perfectly matched layer (PML) is used to investigate the optical properties of the PCFs. The numerical analysis shows that the proposed PCF, i.e., PCF (b), exhibits multiple ZDWS and also achieves a high negative chromatic dispersion of −15089.0 ps/nm·km at 1.55 μ m wavelength, with the multiple ZDWs occurring within the range from 0.8 to 2.0 μ m range. Other optical properties such as the confinement loss of 0.059 dB/km, the birefringence of 4.11 × 10 − 1 , the nonlinearity of 18.92 W − 1 k m − 1 , and a normalized frequency of 2.633 was also achieved at 1.55 μ m wavelength. These characteristics make the PCF suitable for high-speed, long-distance optical communication systems, optical sensing, soliton pulse transmission, and polarization-maintaining applications.

Design and modeling of the nonlinear properties of octagonal lattice Ge20Sb5Se75 photonic crystal fibers

Most silica photonic crystal fibers have limited spectral broadening in the infrared region, making them less than ideal in terms of technological applications. In this work, we propose a new Ge20Sb5Se75 chalcogenide octagonal photonic crystal fiber that provides diverse dispersions with all-normal and anomalous regimes and multiple zero-dispersion wavelengths. The nonlinear properties are investigated over a wide wavelength range up to 14 µm by numerically solving Maxwell's wave equations using Lumerical Mode Solutions software. The full-vector finite-difference eigenmode method minimizes the losses so that low confinement losses in the short-wavelength region of 1 − 6 µm are found and nonlinear coefficients as high as thousands of W−1.km−1 are achieved. Three fibers with an all-normal dispersion profile and anomalous dispersion with one or three zero dispersion wavelengths are proposed for supercontinuum generation. The fibers provide small dispersion values of −0.88, 0.08, and 1.646 ps/(nm.km) at suitable pump wavelengths. Furthermore, the very small confinement loss of approximately 10−5 to 10−11 dB/m is the outstanding advantage of these optical fibers. A broadband spectrum with low input power is expected as a result of the proposed fiber-based supercontinuum generation.

Tunable all-optical AND logic gates via four-wave mixing based on graphene-on-silicon slot microring resonators

We propose a novel graphene-on-silicon organic hybrid slot microring resonator (GSHMIR) for tunable all-optical logic gates, which could offer broadband ultra-flattened dispersion with multiple zero-dispersion wavelengths (ZDWs) and high nonlinearity coefficient of 1.67 × 104 W−1m−1. Further investigations on temporal evolution dynamics for all-optical logic function suggest that the third-order dispersion will induce the temporal drift and tail oscillation of output pulses. The tunable all-optical AND logic function over the wavelength range from 1536 nm to 1569 nm could be obtained for 40 Gb/s signals with the conversion efficiency as high as −6.4 dB. These results are essential for all-optical wavelength division multiplexer (WDM) technology of future integrated optoelectronic systems, as well as providing a novel architecture for on-chip optical communications.

Photonic crystal fibers with high birefringence and multiple zero dispersion wavelengths

Abstract A type of total internal reflection photonic crystal fiber (TIR-PCF) with high birefringence and multiple zero dispersion wavelengths is presented. The optical characteristics are numerically investigated by using the full-vector finite element method. Results show that, by setting the geometrical parameters, the mode birefringence can reach to 2.28 × 10−2 at the wavelength of 1.55 μm, and two zero-dispersion wavelength points appear in the infrared band, one of which emerges near the wavelength of 1.55 μm. It provides a new structure for large birefringence photonic crystal fiber with multiple zero-dispersion wavelengths, and it could be widely used in the fields of fiber polarization control, dispersion management, super-continuum generation and soliton propagation.

Supercontinuum manipulation based on the influence of chirp on soliton spectral tunneling**Project supported by the National Natural Science Foundation of China (Grant Nos. 61275137 and 61571186) and the Natural Science Foundation of Hunan Province, China (Grant No. 2018JJ2061).

The soliton spectral tunneling (SST) effect, as a soliton spectral switching phenomenon, enables a soliton to tunnel through a spectrally limited regime of normal dispersion in the fiber with multiple zero dispersion wavelengths (ZDWs). Since initial chirp can affect the behavior of pulse evolution, we numerically study the influence of chirp on the SST in the process of supercontinuum (SC) occurring in a photonic crystal fiber (PCF) with three ZDWs. The linear chirp is imposed by a phase modulation of input pulse while maintaining a constant pulse duration. Interestingly, it is found that the spectral range and flatness can be flexibly tuned by adjusting the initial chirp value. More specifically, positive chirp facilitates soliton self-frequency shifting (SSFS), making the soliton quickly transfer from one anomalous dispersion regime to another accompanied by the generation of dispersive waves (DWs). In this case, the SST effect further expands the spectral range by enhancing both the red-shift of the fundamental soliton and the blue-shift of DWs, thus generating a broader SC. However, negative chirp suppresses the SST effect, resulting in a smoother SC at the expense of bandwidth. Therefore, the findings in this work provide interesting results relating to the influence of initial chirp on the SST to generate a considerably smoother and broader SC, which is extremely useful in many applications, such as wavelength conversion and SC generation.

Sub-Wavelength Dual Capillaries-Assisted Chalcogenide Optical Fibers: Unusual Modal Properties in Mid-IR (2–5 μm) Spectral Range

In this study, we apply the concept of sub-wavelength light confinement to achieve flat effective mode area ( $A_{{\rm eff}}$ ) characteristics over a wide wavelength range of 1400 nm in nano-sized dual capillary assisted chalcogenide core optical fibers. An unusual spectral behavior of $A_{{\rm eff}}$ is observed where the effective mode area increases, remains constant for a wide bandwidth, decreases and again increases with the increase in wavelength. The spectral region, in which this behavior is observed, can be tuned by varying the structural parameters of the fiber. Additionally, we noticed that the fiber exhibits four zero dispersion wavelengths for a particular polarization which suggests that sub-wavelength light localization can be an alternative solution for the dispersion engineering in order to attain multiple zero dispersion wavelengths. The fabrication tolerance of the dispersion profile has been found to fall within the current fabrication accuracies achievable. We believe that our findings might be useful in different applications such as light-matter interaction and spatial soliton propagation.

Probe-controlled soliton frequency shift in the regime of optical event horizon.

In optical analogy of the event horizon, temporal pulse collision and mutual interactions are mainly between an intense solitary wave (soliton) and a dispersive probe wave. In such a regime, here we numerically investigate the probe-controlled soliton frequency shift as well as the soliton self-compression. In particular, in the dispersion landscape with multiple zero dispersion wavelengths, bi-directional soliton spectral tunneling effects is possible. Moreover, we propose a mid-infrared soliton self-compression to the generation of few-cycle ultrashort pulses, in a bulk of quadratic nonlinear crystals in contrast to optical fibers or cubic nonlinear media, which could contribute to the community with a simple and flexible method to experimental implementations.

Measurement of group velocity dispersion in a solid-core photonic crystal fiber filled with a nematic liquid crystal.

Liquid crystal-filled photonic crystal fibers (PCFs) are promising candidates for electrically tunable integrated photonic devices. In this Letter, we present group velocity measurements on such fibers. A large mode area PCF, LMA8, was infiltrated with the liquid crystal mixture, E7. The measurements were performed with an interferometric setup. The fiber exhibits several spectral transmission windows in the visible wavelength regime that originate from the bandgap guiding mechanism. The dispersion of these windows is very unusual compared to typical fibers. Our measurements show that it can change from -2500 ps km(-1) nm(-1) to +2500 ps km(-1) nm(-1) within a spectral range of only 15 nm. This leads to multiple zero dispersion wavelengths in the visible wavelength range.

Study on phase-matching of four-wave mixing spectrum in photonic crystal fiber

In the present paper, the four-wave mixing principle of fiber was analyzed, and the high-gain phase-matching conditions were shown. The nonlinear coefficient and dispersion characteristics of photonic crystal fibers were calculated by multipole method. The phase mismatch characteristics of fibers with multiple zero-dispersion wavelengths were analyzed for the first time. The changing rules of phase matching wavelength with the pump wavelength and the pump power were obtained, and the phase matching curves were shown. The characteristics of phase matching wavelengths for different dispersion curves were analyzed. There are four new excitation wavelengths of four-wave mixing spectrum in two zero-dispersion wavelength photonic crystal fiers. Four-wave mixing spectroscopy of photonic crystal fibers with two zero-dispersion wavelengths was obtained in the experi-ent, which is consistent with the theoretical analysis, and verified the reliability of the phase matching theory. The fiber with multiple zero-dispersion wavelengths can create a ricbhphase-matching topology, excite more four-wave mixing wavelengths, ena-ling enhanced control over the spectral locations of the four-wave mixing and resonant-radiation bands emitted by solitons and short pulses. These provide theoretical guidance for photonic crystal fiber wavelength conversion and supercontinoum generation based on four-wave mixing.

Broadband Kerr frequency combs and intracavity soliton dynamics influenced by high-order cavity dispersion.

We numerically investigate the influence of high-order dispersion (HOD) on temporal and spectral characteristics of microresonator-based optical frequency combs. Theoretical analysis based on the moment method associated with numerical simulations are utilized to study the comb evolution dynamics, showing that temporal shifts of steady-state intracavity solitons are induced by high-odd-order dispersion rather than high-even-order dispersion. The role of HOD on comb spectral envelopes is also elucidated through analyzing the intracavity dispersive wave generations. We further demonstrate that the spectral envelope of a broadband optical frequency comb can be engineered by using a cavity dispersion profile with multiple zero dispersion wavelengths.

Photonic crystal fibers with high nonlinearity, large birefringence and multiple zero dispersion-wavelength

A novel kind of total internal reflection photonic crystal fiber (TIR-PCF) with highly nonlinear, large birefringence and multiple zero-dispersion wavelengths is designed. Characteristics such as birefringence, effective mode areas, nonlinearity and dispersion are investigated by finite element method (FEM). Numerical results demonstrate that the birefringence is 2.54×10-2 at the wavelength of 1.55 μm, and high nonlinear coefficients (50.22 W-1·km-1 and 54.61 W-1·km-1 in X, Y polarization directions respectively) are obtained by setting the appropriate structure parameters. In addition, two zero-dispersion wavelength points appear in the infrared band, one of which emerges near the wavelength of 1.55 μm. The design provides a new structure for large birefringence, highly nonlinear and photonic crystal fiber with multiple zero-dispersion wavelengths, and it could be widely used in polarization control, nonlinear optics, dispersion management and super-continuum generation.

Simulation of photonic crystal fiber with three and four zero-dispersion wavelengths

The dispersion characteristics of photonic crystal fibers are computed using the multipole method. Single-mode fiber with three zero-dispersion wavelengths is obtained by properly designing fiber structure parameters. The dispersion characteristics of photonic crystal fiber with a small air hole in the core are analyzed. Fibers with four zero-dispersion wavelengths are designed. The variation rules of zero-dispersion wavelength with fiber structure parameter are found. The locations and spacings of the zero-dispersion wavelengths can be adjusted flexibly in a large wavelength range. Closing to zero and flattened dispersion can be obtained in the fibers with multiple zero-dispersion wavelengths. The multiple zero-dispersion wavelengths can create a rich phase-matching topology, and enable better controlling the spectral locations of the four-wave-mixing and resonant-radiation bands emitted by solitons and short pulses.

Golden spiral photonic crystal fiber: polarization and dispersion properties

A golden spiral photonic crystal fiber (GS-PCF) design is presented in which air holes are arranged in a spiral pattern governed by the golden ratio, where the design has been inspired by the optimal arrangement of seeds found in nature. The birefringence and polarization properties of this fiber are analyzed using a vectorial finite-element method. The fiber that is investigated shows a large modal birefringence peak value of 0.016 at an operating wavelength of 1.55 microm and exhibits highly tuneable dispersion with multiple zero dispersion wavelengths and also large normal dispersion. The GS-PCF design has identical circular air holes that potentially simplify fabrication. In light of its properties, the GS-PCF could have application as a highly birefringent fiber and in nonlinear optics, and moreover the 2D chiral nature of the pattern could yield exotic properties.