Nonlinear Photonic Crystal Fiber Research Articles

Quantum random numbers from a fiber-optic photon-pair source

We demonstrate a fiber-optic source of random numbers in which random-number generation (RNG) is implemented via an inherently quantum process—detection of correlated photon pairs produced by spontaneous four-wave mixing (FWM) inside an optical fiber. The detection times of individual photon pairs, generated in our RNG scheme via phase-matched FWM in a highly nonlinear photonic-crystal fiber with a suitable dispersion profile, are converted into megabit-size binary sequences, serving as strings of random numbers. The randomness of these bit strings is verified by the National Institute of Standards and Technology Statistical Test Suite. We identify FWM regimes in which mode-locked short-pulse laser sources can provide a high peak power needed to drive photon-pair generation in optical fibers without an excessive loss of randomness due to unwanted patterns in the RNG photon-pair output.

Chalcogenide–Tellurite Composite Photonic Crystal Fiber: Extreme Non-Linearity Meets Large Birefringence

In this paper, we propose a novel design of a photonic crystal fiber (PCF) with tellurite-cladding, three rings of air-holes and elliptical concentration of As2S3 in the fiber core. The combined effect of tight mode confinement (an effective mode area of nearly 0.6 µm2), large non-linear refractive index of As2S3 and significant variation between the effective modal index values of the two orthogonal states of the fundamental guided mode leads to extreme non-linear coefficient and birefringence values, all achieved at the zero dispersion wavelength (ZDW) of 1550 nm. The corresponding birefringence and non-linear coefficient (7 × 10−3 and 28 W−1 m−1, respectively) are more than three orders of magnitude larger than that of the regular silica-based highly non-linear PCFs. In addition, we numerically demonstrate that by modifying the core and air-hole dimensions one can easily control the dispersion curve and tune the ZDW of the proposed fiber to any excitation wavelength ranging from near-infrared to short-wave-infrared, including optical telecommunication windows close to 1550 nm. The superior characteristics of the proposed elliptical-core composite PCF including extreme non-linearity, nearly-zero confinement loss (2.47 × 10−12 dB/cm), the ability to maintain polarization of light, and tunable ZDW can open the door to new possibilities in non-linear optics, optical telecommunications, optical signal processing, and sensing devices.

Supercontinuum generation in helically twisted photonic crystal fibers with a solid core

We present a numerical study of the effective mode dispersion characteristics modification of nonlinear photonic crystal fibers by their twisting effects. A photonic crystal fiber based on fused silica glass, with eight rings of air holes ordered in a hexagonal lattice, is proposed. The guiding properties in terms of dispersion, confinement loss, and mode area of the fundamental mode are studied numerically. As a result, although reducing the helix period makes dispersion less flat, the bandwidth of the ultra-flat dispersion region increases. In addition, changing the helix period can move the dispersion from an anomalous to a normal region. The influence of the helix period on the supercontinuum generation of the fiber was demonstrated.

Michelson interferometer system with acoustic optic filter and fiber Bragg grating for reduction of four-wave mixing

In this paper a simplified design and efficient of a Michelson Interferometer (MI) system is presented, capable of reducing the Four-Wave Mixing (FWM) effects, using fiber Bragg grating and acoustic optic filter (FBG and AOF) with the aid of a highly non-linear photonic crystal fiber (HNL-PCF). The analysis of the MI system based in FBG and AOF was performed according to the effect of fiber length and input power by performance metrics: Optical Spectrum, maximum Quality factor (max. Q-factor), minimum bit error rate (min. BER), eye height, optical signal-to-noise ratio (OSNR) and timing jitter. The numerical simulation results showed that the MI system with FBG and AOF maintained a good signal performance, with Q-factor equal to 33.3 even after 100 km of single mode fiber (SMF) and with downstream signal power by up to 10 dBm.

Mid-infrared supercontinuum generation in dispersion-engineered highly nonlinear chalcogenide photonic crystal fiber

An [Formula: see text]-based chalcogenide highly nonlinear photonic crystal fiber (PCF) with concentric rings consisting of air-holes is proposed to achieve extraordinary flat and small chromatic dispersion in mid-infrared region. This is obtained by design and optimization of the PCF cross-sectional structure. The dispersion variation between ±[Formula: see text]5 ps/(nm[Formula: see text]km) is obtained over 800 nm bandwidth. Both the effective mode area and nonlinear coefficient of the proposed PCF within the whole wavelength range from [Formula: see text] to [Formula: see text] are investigated. Furthermore, the output supercontinuum (SC) optical spectra for different pump wavelengths located at the normal and abnormal dispersion region are investigated, respectively. The results show that the broadest SC with −20 dB spectral width of 1034 nm covering from [Formula: see text] to [Formula: see text] is obtained for the pump wavelength of [Formula: see text] with 100 fs secant hyperbolic pulse of the peak power of 10 kW. Our PCF design offers a low-cost SC source, which can find potential application in mid-infrared photonics.

Broadband quantum light on a fiber-optic platform: from biphotons and heralded single photons to bright squeezed vacuum

Four-wave mixing (FWM) of ultrashort laser pulses in a highly nonlinear photonic-crystal fiber is shown to provide a multimodal source of broadband quantum states of light. In the regime of low pump powers, generation of two-photon states and heralded single photons with a bandwidth up to ≈6 THz is demonstrated within an FWM-sideband tunability range of ≈55 THz. In the modality of heralded single-photon generation, three-detector measurements of the conditional second-order correlation function reveal a strong antibunching in the signal-photon channel, with more than 99.2% of the signal counts identified as truly single-photon states. At high pump powers, two-detector signal-idler correlation function measurements indicate broadband bright squeezed vacuum generation.

Analytic description of pulse frequency self-shift in nonlinear photonic crystal fibers

We analyze the solutions of integro-differential generalized nonlinear Shrödinger equation, which was introduced recently to describe intense optical pulse propagation in gas-filled hollow core photonic crystal fibers. With the help of moment method, we have derived explicit analytic expressions for the evolution of pulse parameters, which allow explaining nonlinear phenomena connected with red and blue frequency self-shift and its saturation. Both soliton and non-soliton propagation regimes were analyzed. Obtained expressions fit well to the numerical solution of the nonlinear wave equation.

Numerical investigation of a broadband coherent supercontinuum generation in Ga8Sb32S60 chalcogenide photonic crystal fiber with all-normal dispersion

All normal dispersion (ANDi) and highly nonlinear chalcogenide glass photonic crystal fiber (PCF) is proposed and numerically investigated for a broad, coherent and ultra-flat mid-infrared supercontinuum generation. The proposed PCF consists of a solid core made of Ga8Sb32S60 glass surrounded by seven rings of air holes arranged in a triangular lattice. We show by employing the finite difference frequency domain (FDFD) method that the Ga8Sb32S60 PCF dispersion properties can be engineered by carefully adjusting the air holes diameter in the cladding region and ANDi regime is achieved over the entire range of wavelengths with a zero chromatic dispersion around 4.5 μm. Moreover, we demonstrate that injecting 50 fs width and 20 kW peak power laser pulses (corresponding to a pulse energy of 1.06 nJ) at a pump wavelength of 4.5 μm into a 1 cm long ANDi Ga8Sb32S60 PCF generates a broad, flat-top and perfectly coherent SC spectrum extending from 1.65 μm to 9.24 μm at the 20 dB spectral flatness. These results make the proposed Ga8Sb32S60 PCF an excellent candidate for various important mid-infrared region applications including mid-infrared spectroscopy, medical imaging, optical coherence tomography and materials characterization.

Degenerate four-wave mixing for measurement of magnetic field using a nanoparticles-doped highly nonlinear photonic crystal fiber.

A novel magnetic field sensor based on the degenerate four-wave mixing (DFWM) technique is theoretically proposed using a As2S3-core silica-cladding photonic crystal fiber (PCF). In order to enhance the sensitivity, we put forth a novel design of highly nonlinear PCF where the silica cladding is doped with either Au, Ag, or Al metallic nanoparticles. The effect of volume fraction of the nanoparticles within the cladding and the size of nanoparticles are considered as the control parameters in designing the magnetic field PCF sensor to obtain high sensitivity using this novel DFWM scheme. The PCF structure of the proposed sensor is optimized with the proposed pitch of 3μm and air hole diameter of 2.78μm. We consider a pumping pulsed laser light with a wavelength of 2100nm in the mid-IR regime. It has been found that the optimized PCF with Al-SiO2-cladding with small volume fraction and small nanoparticle size possess magnetic field sensitivity values of 2.74 and -0.058 nm/Oe for the Stokes and anti-Stokes gain lines.

高非线性光子晶体光纤中的声光相互作用

高非线性光子晶体光纤中的声光相互作用

Femtosecond Pulse Temporal Overlap Estimation and Adjustment in SSFS-Based CARS System

We present and verify a residual-pump-based temporal overlap estimation method in soliton self-frequency shift-based coherent anti-Stokes Raman scattering system. The residual pump light, output by a highly nonlinear photonic crystal fiber, acts as a crucial link between the pump and Stokes pulses during the temporal overlap estimation. The wavelength-dependent optical delay is estimated to be 0.141 ps/nm when the Stokes wavelength is 900 nm ~1050 nm according to the temporal overlap estimation method. The actual measurement result is 0.138 ps/nm based on the nonresonant signal from a microscope slide, which is very close to the estimated result. In addition, the Raman resonant signals of liquid cyclohexane at 2853 cm -1 , 2923 cm -1 and 2938 cm -1 have also been successfully detected at the predicted optical delays 427.27 ps and 428.17 ps.

高非线性光子晶体光纤中飞秒脉冲压缩(特邀)

高非线性光子晶体光纤中飞秒脉冲压缩(特邀)

Investigation of supercontinuum generated in the cladding of highly nonlinear photonic crystal fiber

We present an experimental and numerical investigation of supercontinuum generation in polarization-maintaining highly nonlinear photonic crystal fiber using subnanosecond pulses of a passively Q-switched neodymium-doped yttrium aluminum garnet microlaser. For analysis of temporal and spectral characteristics, we performed spectrogram measurements using a streak camera. Supercontinuum spectrograms revealed the presence of cladding modes in our photonic crystal fiber and showed that part of the supercontinuum light was actually generated in the cladding modes. Moreover, numerical simulations indicated that distinct cladding modes can exhibit different dispersion, which adds more complexity to supercontinuum generation processes.

Development of highly nonlinear polarization-maintaining fibers with normal dispersion across entire transmission window

A determined polarization state of light is required in nonlinear optics applications related to ultrashort and single-cycle light pulse generation. Such short timescales require up to one full octave of the spectral width of light. A fiber-based, pulse-preserving and linearly polarized supercontinuum can meet these requirements. We report on the development—from linear simulations of the fiber structure, through fabrication of physical fibers to their versatile characterization—of polarization-maintaining, highly nonlinear photonic crystal fibers, intended for femtosecond pumping at a wavelength of 1560 nm. A full octave of linearly polarized light around this wavelength would enable the covering of amplification bandwidths of the three major fiber amplifiers, from ytterbium-doped systems up to thulium- and holmium-doped fiber amplifiers, with a coherent, linearly polarized seed signal. At the same time, an all-normal chromatic dispersion profile over an entire transmission window, and a small dispersion of nonlinearity in the developed fibers, would facilitate use of commercially available femtosecond fiber lasers as pump sources for the developed fibers.

A nonlinear photonic crystal fiber for liquid sensing application with high birefringence and low confinement loss

This paper presents a nonlinear Photonic Crystal Fiber (PCF) based sensor to detect liquid analytes. An extensive analysis has been presented at wide range of wavelength (0.6 μm−1.6 μm) in order to investigate the impact of some design parameters. The numerical investigation has been done using the full vector Finite Element Method (FEM). The proposed model provides an outstanding nonlinear coefficient value with high birefringence, high sensitivity, and low confinement loss. The designed model can be used in sensing and bio-sensing research and their applications.

Mid-infrared broadband supercontinuum generation in a highly nonlinear rectangular core chalcogenide photonic crystal fiber

Abstract We report the numerical modeling of a highly nonlinear rectangular core Ga-Sb-S chalcogenide photonic crystal fiber for supercontinuum generation in the mid-infrared region. Numerical investigation of linear and nonlinear optical processes has been performed. A finite element method has been employed to study the optical characteristics of confined fundamental mode. Optimization of geometrical parameters i.e., pitch, the diameter of bigger and smaller air-holes has been done in order to achieve small and normal dispersion at the pump wavelength. The proposed design is capable of generating supercontinuum spanning 1–14 µm using a 9 mm long fiber pumped with 90 fs secant hyperbolic pulse of the peak power of 8.19 kW. Such photonic crystal fiber structure in Ga-Sb-S chalcogenide glass is reported the first time and can be proven effective for nonlinear applications of photonic devices.

Simultaneous achievement of highly birefringent and nonlinear photonic crystal fibers with an elliptical tellurite core.

A novel photonic crystal fiber (PCF) with an elliptical tellurite core is proposed to realize high birefringence and high nonlinearity simultaneously as well as low confinement loss at the wavelength of 1.55μm. The guiding properties, such as the birefringence, the nonlinearity, and the confinement loss, have been investigated by using the full vectorial finite element method. The results show that the birefringence and the nonlinear coefficient can be up to 7.57×10-2 and 188.39 W-1 Km-1, respectively, and the confinement loss can be only 10-9 dB/m. The proposed PCF can find potential applications in optical fiber sensing, polarization-maintaining transmission, and super-continuum generation.

Supercontinuum generated high power highly nonlinear photonic crystal fiber for medical and optical communications applications

This paper investigates a supercontinuum generated high power highly nonlinear photonic crystal fiber for medical and optical communication applications. The full vector finite difference method with perfectly matched layer is used as an analysis tool. Numerical simulation results show that it is possible to achieve high nonlinear coefficient, near zero ultra-flattened dispersion, low confinement loss and supercontinuum spectrum with high power. Moreover, numerical results show that short length of the proposed photonic crystal fiber is achieved. The numerical simulation results of supercontinuum generation is conducted by solving the generalized nonlinear Schrödinger equation with the split-step Fourier method. It is observed adequate supercontinuum spectrum that broaden from 960 to 1870 nm by considering center wavelengths of 1.06, 1.31, and 1.55 μm into silica based index guiding photonic crystal fiber. This simulation results prove that the proposed design of a highly nonlinear photonic crystal fiber is a great solution for broad supercontinuum generation with high power.

New optical solitons of space-time conformable fractional perturbed Gerdjikov-Ivanov equation by sine-Gordon equation method

Abstract This paper devotes to conformable fractional space-time perturbed Gerdjikov-Ivanov (GI) equation which appears in nonlinear fiber optics and photonic crystal fibers (PCF). We consider the model with full nonlinearity in order to give a generalized flavor. The sine-Gordon equation approach is carried out to model equation for retrieving the dark, bright, dark-bright, singular and combined singular optical solitons. The constraint conditions are also reported for guaranteeing the existence of these solitons. We also present some graphical simulations of the solutions for better understanding the physical phenomena of the behind the considered model.

Elliptical As2Se3 filled core ultra-high-nonlinearity and polarization-maintaining photonic crystal fiber with double hexagonal lattice cladding

A high birefringence and ultra-high nonlinearity photonic crystal fiber (PCF) is proposed, which is composed of an elliptical As2Se3-doped core and an inner cladding with hexagonal lattice. Optical properties of the PCF are simulated by the full-vector finite element method. The simulation results show that the high birefringence of ∼0.33, ultra-high-nonlinearity coefficient of 300757 W−1km−1 and the low confinement loss can be achieved in the proposed PCF simultaneously at the wavelength of 1.55 μm. Furthermore, by comparison with the other two materials (80PbO•20Ga2O3, As2S3) filled in the core, the As2Se3-doped PCF is found to have the highest birefringence and nonlinearity due to its higher refractive index and nonlinear refractive index. The flattened dispersion feature, as well as the low confinement loss of the proposed PCF structure make it suitable as a wide range of applications, such as the coherent optical communications, polarization-maintaining and nonlinear optics, etc.