Zero Dispersion Research Articles

Supercontinuum generation in Ga‐Sb‐S chalcogenide‐based PCF using optofluidic approach

AbstractWe report the design and theoretical study of a Ga‐Sb‐S chalcogenide glass‐based photonic crystal fiber (PCF) structure for mid‐infrared supercontinuum generation. The proposed design is engineered by adjusting the diameter of air holes in the cladding region and pitch, giving us control over the dispersion characteristics of the fiber. The optimized structure design offers the Zero Dispersion Wavelength of 5.2 μm. When pumped with 50 fs secant hyperbolic pulses of peak power 4.9 kW, for a fiber of length 8 mm at pump wavelength of 5 μm, the proposed structure design produces an ultra‐broadband supercontinuum spectrum spanning 1.5–14 μm. Proposed PCF design should be helpful in, biomedical imaging, supercontinuum sources, biosesning, and optical coherence tomography.

Numerical Analysis of Optical Properties Using Octagonal Shaped Ge15As15Se17Te53 Chalcogenide Photonic Crystal Fiber

A novel Ge15As15Se17Te53 chalcogenide-based photonic crystal fiber with an octagonal cladding was designed which exhibits low confinement loss and high nonlinearity. The dispersion properties were investigated over a wide wavelength range of up to 11 µm. Based on preliminary simulation results, three fibers with suitable characteristic quantities are proposed for supercontinuum generation. Among these fibers, fiber #F1 (Ʌ = 3.1 µm, d/Ʌ = 0.3) exhibits all-normal dispersion with a small value of −0.374 ps/[nm.km]. At the same time, the highest nonlinear coefficient of 2876.861 W−1.km−1 at the pump wavelength of 5.45 µm is also found. The #F2 fiber (Ʌ= 4.5 µm, d/Ʌ = 0.3) has anomalous flat dispersion with one zero dispersion wavelength. This fiber has the smallest dispersion and lowest confinement loss values of 0.281 ps/[nm.km] and 1.360×10−9 at 5.7 µm pump wavelength, respectively. With the anomalous dispersion, #F3 fiber (Ʌ = 3.5 µm, d/Ʌ = 0.3) offers a small effective mode area of 20.892 µm2 and a low confinement loss of 4.974×10−8 dB/m at 5.25 µm wavelength. The proposed fibers can be a low peak power, broadband supercontinuum source, suitable for application fields such as optical communication and biomedical sensors.

Mixed integer programming with kriging surrogate model technique for dispersion control of photonic crystal fibers

In this paper, mixed integer nonlinear programming (MINLP) optimization algorithm integrated with kriging surrogate-model is newly formulated to optimize the dispersion characteristics of photonic crystal fibers (PCFs). The MINLP is linked with full vectorial finite difference method (FVFDM) to optimize the modal properties of the PCFs. Through the optimization process, the design parameters can take real and/or integer values. The integer values can be used to selectively fill the PCF air holes to control its dispersion characteristics. However, the other optimization techniques deal with real design parameters where the PCF can be optimized using none or predefined infiltrated air holes. The MINLP algorithm is used to obtain an ultra-flat zero dispersion over a broadband of wavelength range from 1.25 to 1.6 μm using silica PCF selectively infiltrated with Ethanol material. To show the superiority of the proposed algorithm, nematic liquid crystal selectively infiltrated PCFs are also designed with high negative flat dispersion over wide range of wavelengths from 1.25 to 1.6 μm for the quasi transverse magnetic (TM) and the quasi transverse electric (TE) modes. Such designs have negative flat dispersions of − 163 ± 0.9 and − 170 ± 1.2 ps/Km nm, respectively over the studied wavelength range. Therefore, the MINLP algorithms could be used efficiently for the design and optimization of selectively filled photonic devices.

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.

Ultra-high birefringence mid-infrared Ge20Sb15Se65 chalcogenide glass photonic crystal fiber with low confinement loss

This study introduces a Ge20Sb15Se65 chalcogenide-glass-based photonic crystal fiber (PCF) with high birefringence and nonlinearity and ultra-low confinement loss, in which two elliptical air holes are added in the core. The propagation properties of the proposed PCF are investigated in mid-infrared range (3.0–5.0 μm) using the finite element method (FEM). Simulation results indicate that optimizing structural parameters can increase the birefringence and nonlinear coefficient to a maximum of 3.16 × 10−1 and 5937 W−1km−1 (in y-polarization mode), respectively, a significantly low confinement loss reach 10−14 dB m−1 at 3.0 μm wavelength, there can obtain one zero dispersion wavelength in the study band, and the designed structure can be fabricated using available technology. The designed PCF will have promising application in mid-infrared fiber fields, optical communication, super-continuum generation, precision, and nonlinear optics.

Ultra-high birefringence with tuneable double zero chromatic dispersion-PCF: a theoretical analysis

This work presents photonic crystal fibres made up of four hexagonal shape of four rings. Four structures have been designed and configured. The structures show improvement in optical properties consecutively to achieve the optimum configuration. The full vectorial finite-element method is adopted for this work. COMSOL Multiphysics is used for the simulation. The results show a birefringence of 1.308 × 10−2 at 1.55 µm and tuneable double zero dispersion at wavelengths of 0.99 µm and 1.8 µm for x-polarisation mode. Also, the chromatic dispersion of − 24.062 ps/km nm and nonlinear coefficient of 30.32 W−1 km−1 are obtained at a telecommunication wavelength of 1.55 µm. The proposed photonic crystal fibre can be beneficial in nonlinear and supercontinuum applications since photonic crystal fibres of double zero dispersion demonstrate higher power spectral densities than single zero dispersion.

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.

Dispersive waves generation in photonic crystal fibers: The role on supercontinuum generation and rogue waves manipulation

Based on photonic crystal fiber, the generation and behavior of dispersive waves in optical fiber system are presented. The individual soliton induced dispersive waves and collision-induced dispersive waves generation are introduced and compared, and the ways of dispersion wave generation are also given in terms of pumping conditions and fiber properties. The dispersion slope affects soliton trapping of dispersive waves and the role of soliton trapping of dispersive waves on supercontinuum is different in photonic crystal fibers with different zero dispersion wavelengths. From the point of view of the number of zero dispersion wavelength, we reveal the effect of dispersive waves on supercontinuum generation and the relationship between dispersive wave and zero dispersion wavelength. Rogue waves induced by dispersive waves are also discussed and how to control rogue waves by using dispersive waves is shown.

High power ytterbium rod-type fiber laser delivering tunable picosecond pulses.

We designed an all-normal dispersion ytterbium rod-type fiber laser oscillator delivering picosecond pulses which are continuously tunable both in central wavelength and pulse duration. This system delivers self-mode-locked pulses with an average power up to 25 W. At a repetition rate of 78 MHz, it yields picosecond laser pulses, of which the central wavelength and pulse duration can be tuned between 1010 nm - 1060 nm and 4.5 ps - 1.8 ps, respectively. The tunability is obtained by adjusting the position and the width of a slit which acts as a spectral bandwidth filter, placed close to the center of a 4f-folded zero dispersion line inserted in the laser cavity. This oscillator delivers nearly Fourier limited pulses with at most a 1.2 time-bandwidth product. A numerical model accounts well for the behavior of this all-normal dispersion fiber oscillator.

Optimizing optical properties by core geometry variation of chalcogenide tellurite based photonic crystal fiber

We propose an approach based on core geometry variation in designing photonic crystal fiber (PCF) to optimize different optical properties. To investigate those properties of the nobly designed geometrically varied core PCF, Finite element method (FEM) is adopted. The nonlinearity, scattering loss, confinement loss, dispersion profile, numerical aperture, dissemination of power in different portions and effective modal area of the designed waveguide are thoroughly analyzed. The proposed structure with circular core numerically shows unprecedented confinement loss of the order of 10−10 (2.22 × 10−10 dB/m to be precise) with nonlinearity of 51000 W−1km−1 and scattering loss of 1. 2 × 10−12 dB/km. Zero dispersion is also obtained at 1500 nm. The fiber is then used for supercontinuum generation and obtained bandwidth of about 3500 nm at – 40 dB along 2 mm of fiber length. It is anticipated that the proposed PCF could be useful in spectroscopy and biomedical imaging as well.

Active learning aided four-mode fiber design with equalized zero dispersion for short-reach MDM optical communications

In this work, we demonstrate an active learning method for the optimized design of a few-mode fiber (FMF) with equalized zero dispersion between four modes, which can be used for short-reach mode-division-multiplexed (MDM) optical communication without multi-input-multi-output (MIMO) processing and chromatic dispersion compensation (CDC). To obtain the desired FMF, a multi-parameter design of a complex fiber structure is needed, which is usually very difficult, inaccurate, and time-consuming. The proposed active learning can utilize fewer data than the neural network to achieve improved prediction performance by selecting more valuable data. By balancing zero dispersion, equalized dispersion, and manufacturing feasibility, structure parameters of the four-ring step-index FMF supporting four modes are predicted by the active-learning-based inverse design. The standard deviation of four-mode dispersion of the designed fiber is 0.016. The total dataset is significantly reduced to 400 by using active learning and equalized zero dispersion is obtained. The equalized zero dispersion performance is characterized by using an optical parametric amplification (OPA) modal which is highly sensitive to dispersion. The broad OPA gains with high pump power and low amplification cross talk indicate that the designed FMF has low dispersion near to zero, low nonlinearity, and weak coupling for all four modes, which is highly suitable for high-speed MIMO-less and CDC-less MDM optical communications.

Modeling and comparative analysis of all-class converged-coexistence NG-PON2 network for 5G-IoT-FTTX-services and application

Abstract We presented a concept of converged coexistence (CC) access network and generate, and test model is demonstrated for optimization of channel launch power PTODN in the distribution network which subsequently confirm power budget class of NG-PON2 in this paper. Multiplexing of wavelength and time (TWDM) technology is incorporated for multichannel NG-PON2 configurations for 5G, internet-of-things (IoT) applications, and fiber-to-the-x (FTTX) services. CC NG-PON2 symmetric configuration supporting 2.5 and 10 Gbps channels are analyzed and compared in the sight of channel nonlinear impairments includes Kerr-effect (γ) spanning from self phase modulation (SPM) and cross-phase modulation (CPM), chromatic dispersion (CD), and four wave mixing (FWM) in worst-case scenario. Intensity modulation (IM) technique incorporated before multiplexing the D/S channels by coexisting element (CEx) and coupled to wavelength routed (WR) optical distribution network (ODN). U/S channels are routed using wavelength select (WS) ODN. ODN is implemented using G.652 non zero dispersion shift (NZ-DSF) single-mode (SM) fiber. Multi-channel spectrum envelope propagating in either direction is optimized to PTODN = 3/5/7/9 dBm and 4 dBm, respectively. The theoretical modeling and simulative results confirms the proposed network configuration supports incremental receiver sensitivity (Rxs) as −42.19/−42/−39.75/−37.97 dBm and −35.45/−35.38/−33.45/0.38/−42 dBm for λ1 2.5 Gbps and λ8 10 Gbps TWDM and PtP WDM channels, respectively, for all-class networks supporting splitter configuration ratio of 640 at 50 km mitigating effect of channel nonlinearities like CD, SPM, cross-phase modulation (XPM), and FWM for λ8 10 Gbps channel.

Two-Color Localized Optical Vortices in a Nonlinear Waveguide with Zero Dispersion of the Group Velocity at the Second Harmonics

Using the method of averaged Lagrangian and diffraction approximation, an approximate analytical solution is obtained and analyzed, which describes the propagation of two-color vortex light bullets in a quadratic-nonlinear graded-index waveguide.

Dual pump broadband fiber-optic parametric amplifier based on near-zero dispersion photonic crystal fiber with single zero dispersion wavelength

A broadband fiber-optic parametric amplifier (FOPA) based on near-zero dispersion profile with single zero dispersion wavelength (ZDW) by selective liquid infiltration technique is numerically investigated. Here, the gain and bandwidth for an FOPA incorporating “dual pumping” scheme are thoroughly investigated by varying the fiber length, operating wavelength (central wavelength), and pump power. The structure is engineered in such a way that the dispersion profile is having near-zero dispersion value (negative β2) for a wide wavelength range and small positive β4 around the pump wavelength; thereby, the phase mismatch term remains within the favorable value for a wide wavelength leading to wider FOPA sources. The structure also supports reasonable high nonlinearity and low propagation loss. Our numerical investigation results in an FOPA with optimized bandwidth of around 180 nm close to communication wavelength. Finally, a detailed comparative study of the single pump scheme and dual pump scheme for FOPA/amplifier gain and spectrum bandwidth has been performed for identical fiber parameters. It has been observed that dual pump scheme provides smoother/flatter spectrum (lesser gain fluctuation) around the center of the optimized profile with slightly lesser bandwidth compared to single pump operation. Additionally, it was observed that the dual pump FOPA supports higher pump power thereby enabling higher FOPA unaltered peak gain (3 dB) throughout the bandwidth (the peak and dip of the gain spectrum difference remaining within 3 dB) than that of single pump scheme.

Dispersion characteristics of rib-type LiNbO3 photonic wires

Abstract Group velocity dispersion characteristics of rib-type photonic wire(PW) based on LiNbO3 on insulator(LNOI) were studied theoretically. The study focuses on flexibility in dispersion tailoring, zero dispersion, dispersion flatness and zero modal birefringence(ZMB). The results show that the LNOI PW is more flexible in dispersion tailoring than the conventional Ti-diffused LiNbO3 waveguide and Si-on-Insulator (SOI) PW. Zero dispersion at 1.55 μm wavelength can be realized for both TE and TM modes. Zero dispersion wavelength shows definite polarization dependence. It can be tailored by adjusting the rib height. For a TE mode guided in a appropriately designed LNOI PW, zero dispersion can be realized in a broad wavelength range of 1.3–1.7 μm. The TE mode is thus more suitable for dispersion flatness application. The dispersion flatness of the LNOI PW is one order of magnitude better than that of the SOI PW. In contrast, the TM mode is more suitable for dispersion engineering as it shows more significant dispersion feature. ZMB can be realized by adopting an X-cut/Y-propagation scheme. A PW geometry for simultaneous realization of single-mode operation and ZMB is presented.

Ultra-broadband mid-infrared supercontinuum generation in photonic-crystal pillar waveguides pumped at 1.82 μm

In this paper, we theoretically investigate the supercontinuum generation (SCG) spanning from near-infrared (NIR) to mid-infrared utilizing a novel photonic-crystal pillar waveguide (PCPW). The PCPW design and associated dispersion properties have been thoroughly studied and optimized, resulting in a flat and low dispersion profile from 1.67 to 7.31 µm with four zero dispersion wavelengths. Pumped at a relatively shorter NIR wavelength of 1.82 µm, the SCG of optimized PCPW possesses an ultra-broadband spectral broadening from 1 to 10 µm under pump pulses with a low peak power of 2 kW. The proposed PCPW can thus provide an efficient waveguide structure to generate ultra-broadband supercontinuum pumped by shorter wavelength laser sources of less peak power.

Kerr-Raman Optical Frequency Combs in Silica Microsphere Pumped Near Zero Dispersion Wavelength

Optical frequency combs generated in whispering gallery mode microresonators are in high demand for basic science and a large number of applications including telecommunication systems and quantum optics. Here, we study experimentally and theoretically optical frequency comb generation in a silica microsphere with a zero dispersion wavelength near $1.55 μm pumped by a continuous wave laser widely tunable in the C-band. We considered the optical frequency comb generation for a pump wavelength in a normal dispersion region, in a low anomalous dispersion region, and very close to the zero dispersion wavelength. Kerr-assisted and Raman-assisted (Stokes) combs as well as anti-Stokes combs emerging due to the four-wave mixing between the Kerr and Raman combs are attained in experiments. The mechanisms of producing individual peaks of optical frequency combs are verified in numerical simulations. A 270-nm optical frequency comb covering the telecommunication E-, S-, C-, L-, U-bands and further up to $1.7 μm is also demonstrated.

Numerical analysis of photonic crystal fibre with high birefringence and high nonlinearity

Abstract A four-ring microstructure photonic crystal fibre with a descending air hole ring cladding is presented. Numerical analysis of the structure is done using full vectorial finite element method with perfectly matched layer (PML) boundary condition. It is demonstrated that it is possible to achieve at 1.55 µm confinement loss of 2.767 × 10−5 dB/m, birefringence of 0.00346 and a nonlinear co-efficient of 41.77 km−1 W−1. Also, chromatic dispersion realised suggests a tuneable zero dispersion at 0.9–1.1 µm wavelength range.

Exploiting higher-order mode dispersion of bend M-type chalcogenide fiber in mid-IR supercontinuum generation

Abstract We propose and numerically demonstrate chalcogenide based bend M-type fiber for mid-IR supercontinuum (SC) generation through higher order mode (HOM) of LP02. In order to achieve this, we comprise two glass materials such as As2Se3 in core and Ge10As23.4Se66.6 in cladding. M-type index fiber has a special property that the HOM of LP02 is confined into the core region with help of high index ring. The mode field distribution of the proposed fiber is numerically calculated by a finite element method. By optimizing structural dimensions in each bending case, we realize a zero dispersion wavelength, double zero dispersion wavelength effective area and power fraction in core. The simulation results shows the flat anomalous dispersion in the wavelength range of 2.1–2.6µm and 2.5–6.5µm for the core radius 4 and 10 µm, respectively at bending case of 1, 3, and 5 cm. which is important for employing the mature fiber laser technology at mid-IR regions.

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.