Nonlinear Photonic Crystal Fiber Research Articles

Nonlinear dynamics of relative intensity noise transfer at fiber amplification and supercontinuum generation

Supercontinuum sources via femtosecond pumping in highly nonlinear photonic crystal fibers considerably impact scientific research and industrial applications. Herein, we investigate the complex transfer function of relative intensity noise in a broadband fiber supercontinuum source generated using an ytterbium-doped mode-locked laser. A designed intensity noise was artificially added to the system through the introduction of weak sinusoidal intensity modulation to the seed pulses. Owing to the influence of nonlinear gain dynamics and soliton dynamics during power amplification and spectral broadening, the transfer functions exhibit unique frequency and wavelength dependencies. Systematic measurements indicate that the seed transfer functions exhibit the characteristics of damped high-pass filters and saturate at low Fourier frequencies within the fiber amplifier. Moreover, supercontinuum broadening induces a nonlinear transformation of fluctuations, resulting in considerable amplification and negative correlation within the dispersion wave and soliton self-frequency shift regions. Clarifying the mechanism and bandwidth of this system is imperative to achieving low-noise supercontinuum generation because they provide insights into the nonlinear laser dynamics associated with broadband spectral broadening and noise transformation.

Tailored Dispersion and Nonlinear Effects in Flint Glass Honeycomb PCF for Optical Communication

This paper describes a highly nonlinear flint glass-based honeycomb photonic crystal fiber (FGH-PCF) with a wavelength of 1550 nm. The PCF’s distinctive honeycomb lattice structure, combined with the nonlinear capabilities of flint glass, enables a wide range of nonlinear optical applications. To adjust the PCF's dispersion and nonlinear effects, numerical simulations and optimization approaches were used. To achieve maximum performance, fabrication procedures were carefully regulated. Dispersion values of −436.6 ps/(nm.km) for x polarization and −448.1 ps/(nm.km) for y polarization were verified by experimental characterization. The PCF displayed low confinement losses of 2.289 dB/cm (x polarization) and 4.935 dB/cm (y polarization), as well as birefringence of 2.202×10-3. The PCF measured 558.8 and 547.9 W-1 km-1 for x and y polarization, respectively, indicating a high nonlinear coefficient. The highly nonlinear FGH-PCF shows promising potential for nonlinear optical applications such as four-wave mixing, supercontinuum generation, frequency conversion, and parametric amplification. This research paves the way for compact and efficient nonlinear devices in modern optical communication systems and other cutting-edge technologies.

Highly nonlinear tellurite photonic crystal fiber for supercontinuum generation: Design and quantitative performance analysis

This research study proposes a unique photonic crystal fiber (PCF) consisting of a solid core and a hexa-spiral shape, using tellurite as the background material. The proposed PCF exhibits numerous significant optical guiding properties, such as nonlinearity, dispersion, effective index, effective mode area, etc. Simulated findings from COMSOL Multiphysics v5.5 confirm that the PCF can achieve high nonlinearity and zero-dispersion at 1650 nm. The base material is tellurite, which has a significant nonlinear refractive index (RI) of 5.11 × 10−19 m2 W−1. The resultant wave has a bandwidth of 562.65 nm when pumped at a wavelength of 1650 nm. Additionally, a continuum can be produced by pumping at 1500 and 1550 nm. The designed PCF can generate a broad spectrum of supercontinuum with a pulse duration of 200 fs and 10 kW input power. Here is also performed measurements and inspections on the impact of higher-order Taylor series dispersion coefficients, pulse width, input power, etc. The proposed PCF has many potential applications, including nonlinear optics, high dispersion characteristics, infinitely single-mode fibers, high wattage beam transmission, particle trapping, and sensing. To address these applications, here is used COMSOL Multiphysics to generate data, such as propagation constants, attenuations, effective area, and fields, which were used by Optisystem. To the best of our knowledge, this is the first investigation to verify the performance of our designed PCF in Optisystem, for modeling signal transmission for supercontinuum generation and Raman shift.

Rhombus-shaped, M-shaped- solitons, 2D-lumps vector and tunneling in perturbed Gerdjikov–Ivanov equation with fourth-order dispersion: Modulation instability and global bifurcation

The Perturbed Gerdjikov–Ivanov Equation (PGIE) describes optical solitons in nonlinear fiber optics and photonic crystal fibers. It was currently studied in the literature. Here, we consider a new complex field equation, the PGIE with fourth-order dispersion. The exact solutions of the aforementioned equation are obtained by implementing the unified method. These solutions are evaluated numerically and they are shown in graphs. Our objectives, here, are to inspect the onset of self- steepening and self-phase modulation and investigate the structures of solitons produced. It is found that these phenomena are launched for high values of the relevant coefficients, and they may be overlapped. Multiple solitons shapes are observed; M-shaped solitons, rhombus shapes, solitons with tunneling, 2D-lumps vector, and solitons- cascade. Further, the analysis of modulation instability (MI) and global bifurcation are carried out. It is established that the MI triggers when the coefficient of Raman scattering exceeds a critical value. It is worth mentioning that two kinds of bifurcations can be studied, namely local and global bifurcations. Here, we are concerned with studying global bifurcation. This is based on constructing the phase portrait via Hamiltonian function.

A highly birefringent and compact nonlinear photonic crystal fiber for next-generation optical fiber applications: design and investigation

A highly birefringent and compact nonlinear photonic crystal fiber for next-generation optical fiber applications: design and investigation

High birefringence and near‐zero dispersion control of nonlinear photonic crystal fibers with a double‐cladded coaxial core

AbstractOptical propagation characteristics of high birefringence (HB), near‐zero chromatic dispersion, and small effective mode area are first investigated along with simultaneously effective controllability for the new double‐cladded coaxial core photonic crystal fibers with the breakthrough air‐hole defects at the middle‐top, middle‐bottom, right‐top, and left‐bottom, as pairs, which enable the adaptation of novel systematic approach for design goals in the inner first hexagonal cladding layer. Compared with results (around 3.2 × 10−4) of well‐known HB optical fibers, superior performance for preserving the lightwave polarization state by about three times higher HB levels has been achieved with additive advantages of fabrication from only pure fused silica material and broadly unlimited stable single‐mode operation.

High birefringence and nonlinearity photonic crystal fiber

High birefringence and nonlinearity photonic crystal fiber

High birefringence and nonlinear photonic crystal fiber with two zero-dispersion wavelengths

High birefringence and nonlinear photonic crystal fiber with two zero-dispersion wavelengths

A nonlinear ZBLAN-based photonic crystal fiber with ultra-high birefringence and flattened dispersion in short-wavelength infrared region

In this paper, a high nonlinear ZBLAN-based photonic crystal fiber (PCF) with ultra-high birefringence and flattened dispersion is numerically proposed in short-wavelength infrared region based on finite element method. Eight elliptical-hole arrays are arranged surrounding the fiber core to separate x-polarized and y-polarized fundamental modes. The birefringence can reach to an excellent level of 4.46 × 10−2 at wavelength 2.5 µm and interestingly shows a hopping phenomenon as the ellipticity increases from 2.2 to 3.1. In addition, the design also exhibits a single-mode propagation, short beat length (< 0.12 µm), high nonlinear coefficient 131 W−1·km−1, low confinement loss 10−9 dB/m and flattened dispersion with a maximum fluctuation 50 ps·km−1nm−1 in wavelength range from 1.5 µm to 2.5 µm. The effect of the structure parameters (air hole diameter, lattice constant and ellipticity of elliptical holes) on the optical properties is symmetrically investigated. This ZBLAN-based PCF has great potential in the nonlinear applications of fiber laser and supercontinuum generation in infrared region.

Design, fabrication and characterization of nonlinear photonic crystal fibers for sources of correlated photon pairs

In this work, a series of silica glass photonic crystal fibers (PCFs) were designed through implementation of a numerical method [1] based on an experimental model that allows the calculation of chromatic dispersion from two structural parameters of the PCFs. Then, the PCFs were fabricated by stretching a structured preform using a calculated preliminary design. Some characterization techniques were implemented with the aim to find the PCF structural and optical properties. Finally, the developed PCFs were used for supercontinuum generation.

Delineation of profoundly birefringent nonlinear photonic crystal fiber in terahertz frequency regime

Abstract The photonic aspects of semiconducting hexagon-shaped photonic crystal fiber including effective mode area, effective mode index, dispersion, and confinement loss, have already been investigated. The finite element method has been used to compute the maximum distribution of the studied photonic crystal fiber by COMSOL software. The linear modifications from both the effective mode index and an effective mode area have been investigated. Dispersion and confinement loss are examined in terms of air hole ring number and wavelength. For every wavelength, the effective-index model implies that the studied fiber can indeed be single mode. Even though its practical single-mode range inside the opacity aperture of silica appears large, it is eventually confined by a bend-loss edge at both brief &amp; medium wavelengths. Moreover, the reported fiber offers minimal confinement loss of almost 10−8 dB/cm, birefringence 0.0012, and dispersion around 10−11 ps/km nm.

Design of a broadband dispersion compensated ultra-high nonlinear photonic crystal fiber

A photonic crystal fiber (PCF) with four circular rings of air holes expanded toward the cladding region is proposed. Four circular tiny air hole rings have been used between the air holes in a regular circular PCF to achieve low dispersion and confinement loss. Additionally, the core region is perforated with a rectangular-shaped hole filled with an extremely nonlinear material, gallium phosphide, to achieve the desired level of nonlinearity. We achieved extremely high nonlinearity and birefringence values of 4.6104 W−1 km−1 and 0.078 at the 1.55 µm telecommunication window by doing so. Further, we observed the structure with varying pitch (Ʌ) values and found a significant reduction in dispersion and confinement loss, as well as a decrease in effective material loss. Thus, at 1.55 µm, an ultra-high negative dispersion of − 8000 ps/nm km is achieved, particularly with Ʌ = 1.8 µm, along with extremely low confinement and material losses of 10–9 dB/km and 0.017 cm−1, respectively. Similarly, other critical parameters such as the power fraction, numerical aperture, and effective area have been examined. Hence, owing to these enhanced optical properties, the proposed PCF is capable of effectively compensating for dispersion, generating supercontinuum, and maintaining polarization.

All-optical 2R regenerator based on similariton-induced spectral broadening

We numerically investigated an all-optical high-bit-rate 2R-regenerator based on similariton-induced spectral broadening of the optical signal spectrum. The proposed configuration incorporates two cascaded regeneration stages. Active and passive generation of similariton pulses in a highly nonlinear photonic crystal fiber and a comb-like dispersion decreasing fiber are used for the first and the second stages, respectively. The study of the static behavior of the regenerator linking the design to their nonlinear power transfer functions reveals the operating conditions under which the regenerator is able to reduce amplitude noise and improve the signal extinction ratio. Furthermore, the potential of the proposed configuration is evaluated to regenerate an optical signal at 40 Gbit / s, and the 2R-regenerator is then assessed in a long recirculating fiber loop to investigate its cascadibility. The ability of the 2R-regenerator to enable operating at high-bit rates up to 160 Gbit / s is also investigated. The results demonstrate the high potential of similariton pulses for all-optical 2R-regeneration in future high-speed and long-haul transmission systems.

Investigation on nanocore-centred nonlinear PCF for high nonlinearity and low dispersion

In this paper, a nanocore-centred nonlinear photonic crystal fiber (NCN-PCF) has been projected with control over group velocity dispersion for supercontinuum generation. The NCN-PCF consists of nonlinear cladding with helical structured air hole rings near the core region and hexagonally structured air-hoes at the outer cladding region. The spiral symmetry of helical rings near the core region gives rise to varying refractive indexes over the length of the fiber. The optical properties of the proposed structure have been optimized through parametric analysis in NCN-PCF. By utilizing the finite element method, the proposed NCN-PCF displays a low dispersion between −90.42 and + 116.55 ps/(nm.km), very low effective mode area of 0.0021 μm2, group velocity dispersion of −0.1485 × 10−3 ps2/(nm.km) and birefringence of 1.5 × 10−5. For a wavelength of 1.550 μm, the nonlinearity is found to be between 1.2397 × 109 and 3.5503 × 109 W−1km−1.

All-fiber supercontinuum source operating at 1\xa0\u03bcm with combination of different PCFs

We demonstrate an all-fiber scheme for generating supercontinuum spectrum based on a combination method. The configuration employed a nonlinear photonic crystal fiber for dispersion pre-management, an Yb-doped gain fiber for amplification and a special tapered photonic crystal fiber for supercontinuum generation. This setup allows for the generation of highly coherent supercontinuum with 30-dB bandwidth covering from 800 to 1240 nm as well as dispersive waves at 480 nm and 540 nm. The initial pulses were centered at 1030 nm with average power of 90 mW and repetition rate of 216 MHz. Based on the generated supercontinuum and dispersive waves at 540 nm, an envelope-carrier phase offset frequency with signal to noise ratio up to 37 dB was detected by a standard f-2f interferometer. The high signal to noise ratio shows that the infrared supercontinuum and the dispersive waves were highly coherent. Such a robust supercontinuum source achieved at low energy would promote the application of laser comb in precision measurement.

A Nonlinear Zblan-Based Photonic Crystal Fiber with Ultra-High Birefringent and Flattened Dispersion in Short-Wavelength Infrared Region

A Nonlinear Zblan-Based Photonic Crystal Fiber with Ultra-High Birefringent and Flattened Dispersion in Short-Wavelength Infrared Region

Highly coherent visible supercontinuum generation in a micrometer-core borosilicate glass photonic crystal fiber

Highly coherent visible supercontinuum (SC) sources are demanded for many applications such as bio-sensing and imaging. Either dispersion management on the fiber or optimizing ultrafast pulsed pump parameters can work for achieving broadband coherent fiber SC. Normally, highly coherent SC with medium bandwidth can be obtained in an all-normal-dispersion (ANDi) nonlinear photonic crystal fiber (PCF), which has normal dispersion for all the wavelengths by tailoring the structure parameters of the microstructured cladding to sub-wavelength scale. Hence, such an ANDi fiber requires a submicron core diameter, and it makes precise fabrication challenging. Instead, using a standard anomalous dispersion pumping scheme and an ultrafast pulsed pump source, broadband SC with a high degree of coherence can also be obtained. In this study, we report broadband visible SC with a high degree of coherence approaching unity in a low-index borosilicate glass air-suspended PCF with a micrometer-core diameter, by the anomalous dispersion pumping scheme. The pulse duration of the 800 nm Ti:sapphire femtosecond laser is 29 fs. The experimental results are in good agreement with the numerical simulations, indicating that ultrashort pump pulses are the primary cause for the high degree of the generated visible SC, while the weak Raman effect of the borosilicate glass host plays a non-negligible but secondary role in the procedure of coherent SC generation.

Single-laser-based simultaneous four-wavelength excitation source for femtosecond two-photon fluorescence microscopy.

Multicolor labeling of biological samples with large volume is required for omic-level of study such as the construction of nervous system connectome. Among the various imaging method, two photon microscope has multiple advantages over traditional single photon microscope for higher resolution and could image large 3D volumes of tissue samples with superior imaging depth. However, the growing number of fluorophores for labeling underlines the urgent need for an ultrafast laser source with the capability of providing simultaneous plural excitation wavelengths for multiple fluorophores. Here, we propose and demonstrate a single-laser-based four-wavelength excitation source for two-photon fluorescence microscopy. Using a sub-100 fs 1,070-nm Yb:fiber laser to pump an ultrashort nonlinear photonic crystal fiber in the low negative dispersion region, we introduced efficient self-phase modulation and acquired a blue-shifted spectrum dual-peaked at 812 and 960 nm with 28.5% wavelength conversion efficiency. By compressing the blue-shift near-IR spectrum to 33 fs to ensure the temporal overlap of the 812 and 960 nm peaks, the so-called sum frequency effect created the third virtual excitation wavelength effectively at 886 nm. Combined with the 1,070 nm laser source as the fourth excitation wavelength, the all-fiber-format four-wavelength excitation source enabled simultaneous four-color two-photon imaging in Brainbow AAV-labeled (TagBFP, mTFP, EYFP, and mCherry) brain samples. With an increased number of excitation wavelengths and improved excitation efficiency than typical commercial femtosecond lasers, our compact four-wavelength excitation approach can provide a versatile, efficient, and easily accessible solution for multiple-color two-photon fluorescence imaging in the field of neuroscience, biomolecular probing, and clinical applications with at least four spectrally-distinct fluorophores.

Supercontinuum generation in near- and mid-infrared spectral region using highly nonlinear silicon-core photonic crystal fiber for sensing applications

In this paper, we design a silicon-core photonic crystal fiber (PCF) composed of MgF2 background material to generate supercontinuum spectra in the near- and mid-infrared wavelength ranges. The linear properties of the PCF, including effective index, group velocity dispersion, loss, and effective area, as well as the nonlinear parameter, are calculated for several core radii. We show that by choosing the PCF's optimal geometric dimensions using the particle swarm optimization algorithm, high flatness and near-zero dispersion profile at the desired wavelength can be achieved. Numerical results reveal that by pumping 50 femtosecond optical pulses with a peak power of 1 kW centered at the wavelength of 2460 nm into the proposed optimized PCF, a spectrum with a spectral bandwidth of 2670 nm in the near- and mid-infrared wavelength ranges at 10-mm long PCF can be generated. Such a broad spectrum has many applications, especially in the production of highly sensitive optical sensors applicable in the medical, security, and petrochemical industries.

Research on four wave mixing performance near communication window and mid infrared region

The four wave mixing (FWM) characteristics of highly nonlinear tellurite photonic crystal fiber are simulated. The material of tellurite fiber is TeO2-Li2O-ZnO-P2O5 (TLZP). It is calculated that there are two zero dispersion points at 1590 nm and 3880 nm in tellurite photonic crystal fiber. The linear phase mismatch, the variation of optical signal gain with fiber length and the pump power are calculated at 1538 nm and 3865 nm respectively. The results show that the fiber has good four wave mixing performance near 1550 nm communication window and mid infrared region.