Highly Nonlinear Photonic Crystal Fiber Research Articles

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.

Generation of Visible to Near-infrared Supercontinuum in Highly-nonlinear Photonic Crystal Fiber

Generation of Visible to Near-infrared Supercontinuum in Highly-nonlinear Photonic Crystal Fiber

Continuously spacing-tunable multi-wavelength single-frequency fiber laser based on cascaded four-wave mixing at 1.06 μm

A continuously spacing-tunable multi-wavelength single-frequency fiber laser (MW-SFFL) at 1.06 μm is investigated based on cascaded four-wave mixing (CFWM) in a high-nonlinearity photonic crystal fiber (HN-PCF). By using two separate wavelength-tunable continuous-wave (CW) SFFLs for pumping the HN-PCF, the MW-SFFL with up to ten stable wavelengths is generated under a total pump power of 890 mW. Furthermore, when the wavelength and the power of pump lasers are appropriately manipulated, the wavelength spaces of the MW-SFFL can be tuned freely within 166 pm and the numbers of wavelengths can be controlled to 4, 6, 8, and 10, respectively. To our knowledge, it is demonstrated for the first time that the MW-SFFL based on CFWM at 1.0 μm band are directly excited by CW SFFLs.

Verification of All-Optical Regeneration with Hybrid Modulation and with On-Off Keying Modulation with Return to Zero and Non-Return to Zero Coding

In this work we study the non-linear effects through the analysis of the operating results of three alloptical 3R regeneration (re-amplifying, re-shaping and re-timing) under the effects of cross-phase modulation (XPM) and four-wave mixing (FWM), being a system with hybrid modulation and two other communication systems with modulation on-off keying (OOK) with return to zero (RZ) and non-return to zero (NRZ) coding. The main part of the 3R regeneration system proposed here is a Mach-Zehnder interferometer (MZI) composed of an acousto optical filter (AOF) and a highly nonlinear photonic crystal fiber (HNL-PCF), so the system proposed here was named 3R-MZIAOF regenerator. The comparison of the system results occurred through the variation of the input power variation from -10 dBm to 10 dBm for the link length of 121.3 km and transmission rate 10 Gbps. The results showed that the regeneration 3R scheme OOK-NRZ with AOF presented excellent values of bit error rate (BER) equal to 10-21 and quality factor (Q-Factor) equal to 9.4, when compared to a system with OOK-NRZ 3R regeneration and hybrid modulation.

Numerical Study on Supercontinuum Generation in an Active Highly Nonlinear Photonic Crystal Fiber With Anomalous Dispersion

We numerically study supercontinuum (SC) generation (SCG) in a rare-earth-doped highly nonlinear photonic crystal fiber (HNL-PCF) with anomalous dispersion (AD) in the sub-picosecond pulse regime. We develop a semi-classical numerical model based on the generalized Ginzburg-Landau equation in order to take account of ultrafast interactions between gain ions and ultra-broadband SC radiation encompassing sub-100-femtosecond solitons. Based on the numerical model, we analyze SCG characteristics of an active HNL-PCF in comparison with a passive-type counterpart, unveiling novel optical gain effects in a highly nonlinear optical fiber with AD. We rigorously investigate gain-induced soliton dynamics, such as soliton-cascade-like behaviors, soliton-quasi-soliton collisions, and phase-matched dispersive wave generation, which eventually contributes to enhancement of energy scaling of SC radiation without incurring considerable degradation of its spectral flatness. We also verify that such superior performance characteristics of an active HNL-PCF make it suitable for the use as a boost amplifier for SC radiation. We think that the findings from this study will incite other subsequent studies on unveiling detailed nonlinear pulse dynamics in various gain-embedded nonlinear optical media.

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.

900 nm waveband four wave mixing generation in highly nonlinear photonic crystal fiber

We demonstrate, for the first time to the best of our knowledge, four wave mixing (FWM) process in a 900 nm wavelength region. A 54 m highly nonlinear photonic crystal fiber (HN-PCF) is used as nonlinear medium, and continuous wave laser diodes at near 975 nm are selected as pump sources. By simultaneously injecting two pump sources into the HN-PCF, FWM is observed with wavelength spacing of 0.4 nm and 2 nm, respectively. Compared with FWM in conventional highly nonlinear fibers, HN-PCF one possesses much higher conversion efficiency. These FWMs introduce an opportunity to extend the wavelength coverage of fiber lasers and amplifiers in 900 nm waveband, and also indicate that HN-PCFs can have great potential for FWM applications towards short wavelength regions.

Dual-cladding high-birefringence and high-nonlinearity photonic crystal fiber with As[formula omitted]S[formula omitted] core

A novel dual-cladding photonic crystal fiber (PCF) with elliptical As2S3 core has been proposed to obtain high-birefringence and high-nonlinearity in PCFs. As2S3 has a high refractive index and a high nonlinear refractive index, as a result, it has a desired application on strengthening birefringence and nonlinearity. Then outer cladding of the PCF contains a hexagonal array of circular air holes. A circular array of circular air holes is introduced near the core as the inner cladding. We find that inner cladding could heighten birefringence and nonlinearity obviously. The simulation results show that the birefringence is as high as 0.307 at a wavelength of 1550 nm, and the nonlinearities of X- and Y-polarized reach 28660 km−1 W−1 and 38080 km−1 W−1 at the same wavelength, respectively.

Numerical Study on the Supercontinuum Generation in an Active Highly Nonlinear Photonic Crystal Fiber With Flattened All-Normal Dispersion

We numerically study the dynamics of supercontinuum generation (SCG) in an ytterbium-doped highly nonlinear photonic crystal fiber (HNL-PCF) with flattened all-normal dispersion (FAND) in the sub-picosecond pulse regime. We discuss the enhancement of the energy spectral density and the recovery of the peak power depletion in the SCG process through the fiber in comparison with the SCG based on a passive-type counterpart. As a unique application of the novel characteristics of the active HNL-PCF with FAND, we also analyze the direct amplification of an SC pulse through it, showing that the incident SC pulse can be amplified by 10 dB without undergoing significant degradations in terms of spectral bandwidth and flatness. Our numerical investigations on the active HNL-PCF with FAND will be helpful for opening up new opportunities for fiber-based SCG technology in the sub-picosecond regime.

Simple open-cavity pulsed Brillouin fiber laser with broadband supercontinuum generation

A simple open-cavity laser is proposed for supercontinuum generation. Broadband supercontinuum covering the wavelength from 630 to 1700 nm with low multimode LD pump power (~ 1.7 W) is demonstrated. Giant nanosecond pulse generation can be realized by pumping a piece of Yb-doped double cladding fiber combined with two pieces of long passive fibers. There are no reflectors or modulators included in this laser. It is confirmed that the process of the passive self-Q-switch is mainly based on the stimulated Brillouin scattering effect. The peak power of the giant nanosecond pulses is high enough to generate supercontinuum with over 1000 nm bandwidth even in standard single-mode fiber, which makes this supercontinuum laser source low-cost and compact. Replacing the standard single-mode fiber with a piece of high nonlinear photonic crystal fiber, broader and flatter supercontinuum can be obtained because of the high nonlinear coefficient and the blue-shift of the zero-dispersion wavelength.

Visible continuum pulses based on enhanced dispersive wave generation for endogenous fluorescence imaging.

In this study, we demonstrate endogenous fluorescence imaging using visible continuum pulses based on 100-fs Ti:sapphire oscillator and a nonlinear photonic crystal fiber. Broadband (500-700 nm) and high-power (150 mW) continuum pulses are generated through enhanced dispersive wave generation by pumping femtosecond pulses at the anomalous dispersion region near zero-dispersion wavelength of high-nonlinear photonic crystal fibers. We also minimize the continuum pulse width by determining the proper fiber length. The visible-wavelength two-photon microscopy produces NADH and tryptophan images of mice tissues simultaneously. Our 500-700 nm continuum pulses support extending nonlinear microscopy to visible wavelength range that is inaccessible to 100-fs Ti:sapphire oscillators and other applications requiring visible laser pulses.

A stable wavelength-spacing-tunable dual-wavelength single-longitudinal-mode fiber ring laser based on a DMD filter

A stable single-longitudinal-mode dual-wavelength( SLM-DW) multiple ring fiber laser with a tunable wavelength spacing was proposed and demonstrated. In the multiple ring cavities,the mode selection is made by the tunable digital micro-mirror device( DMD) filter and two different length passive sub-ring cavities. The DMD filter can select and couple any two wavelengths from the gain spectrum of the erbium-doped fiber( EDF). The SLM lasing is guaranteed by the two sub-ring cavities which serve as a mode filter. The stable and uniform dualwavelength oscillation is obtained by the highly-nonlinear photonic crystal fiber( HN-PCF),which can generate the four-wave-mixing( FWM) effective. By loading different gratings on the DMD filter without any mechanically shift,the tunable wavelength spacing from appropriately 0. 165 nm to 1. 08 nm within a tuning accuracy of 0. 055 nm is achieved at room temperature.

Supercontinuum generation in optimized photonic crystal fiber at 1.3 μm for optical coherence tomography

In this paper, we have designed a high nonlinear photonic crystal fiber (HN-PCF) based on square-lattice geometry with the zero dispersion wavelength (ZDW) around 1300 nm. The exploitation of different nonlinear mechanisms in the pulse propagation allows supercontinuum generation, which is used to enhance the axial resolution of the optical coherence tomography (OCT) systems. First mechanism demonstrated is the soliton self-compression, we came up to realize pulse compression of 28.4 fs around 1300 nm by the generation of solitons of different orders to obtain ultrashort pulses of about 4 fs pulses in a PCF length of 66cm, then, we improved the pulse compression until 1.2 fs in a PCF length of 26 cm.The exploitation of the interplay between many nonlinear effects as self-phase modulation, intrapulse Raman scattering and self-steepening as second mechanism allows a generation of supercontinuum with a spectral bandwith of SBW=260 nm. The obtained spectral bandwidth could contribute to enhance the OCwith OCT imaging axial resolution which can be evaluated to 2.8 μm in air, working at 1.3 μm center wavelength which is widely used in several fields.

Optimizational 6-bit all-optical quantization with positive or negative pre-chirp based on photonic crystal fiber

In this paper, we optimize a proposed 6-bit all-optical quantization approach based on soliton self-frequency shift (SSFS) and spectral compression techniques. A 10 m-long high nonlinear photonic crystal fiber (PCF) is still used as an SSFS medium relevant to the power of the sampled optical pulses. Furthermore, a 10 m-long dispersion flattened hybrid cladding hexagonal–octagonal PCF (6/8-PCF) is utilized as a spectral compression medium to realize resolution enhancement after positive or negative pre-chirp process. Simulation results show that the 6-bit quantization is still obtained when a 100 m-long dispersion-increasing fiber (DIF) is replaced by a hybrid cladding 6/8-PCF in spectral compression module.

Optimizational 6-bit all-optical quantization with soliton self-frequency shift and pre-chirp spectral compression techniques based on photonic crystal fiber

In this paper, we optimize a proposed all-optical quantization scheme based on soliton self-frequency shift (SSFS) and pre-chirp spectral compression techniques. A 10m-long high-nonlinear photonic crystal fiber (PCF) is used as an SSFS medium relevant to the power of the sampled optical pulses. Furthermore, a 10m-long dispersion flattened hybrid cladding hexagonal-octagonal PCF (6/8-PCF) is utilized as a spectral compression medium to further enhance the resolution. Simulation results show that 6-bit quantization resolution is still obtained when a 100m-long dispersion-increasing fiber (DIF) is replaced by a 6/8-PCF in spectral compression module.

Synchronous optical sampling with chirped optical pulse based on high nonlinear spiral photonic crystal fiber

We optimize a proposed multicast parametric synchronous sampling scheme. Two segments of 1 cm high nonlinear spiral photonic crystal fiber are utilized as a nonlinear medium in parametric processors. Meanwhile, a segment of 1.8 km dispersion compensation fiber is used to obtain linear chirped sampling pulses instead of a 5 km single-mode fiber. The experimental results show that a 120 GSa∕s equivalent sampling rate, high power of sampling copies, and low variance are obtained. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its

Design of high duty ratio nonlinear photonic crystal fiber with near-zero flattened dispersion after 1.205 μm

The paper presents a high nonlinear photonic crystal fiber (HN-PCF) with highly duty ratio for time-stretch analog-to-digital conversion (TSADC). The simulation results show that a nonlinear of 42.26W−1km−1 and the flattened dispersion of less than 1.0ps/(nmkm) are obtained in more than 495nm waveband (1205–1700nm). Owing to its high nonlinear coefficient and flattened dispersion, the high nonlinear PCF is expected to be suitable for supercontinuum (SC) generation. The numerical simulation results demonstrate that the proposed high duty ratio HN-PCF can generate wideband SC.

Similariton spectrums application for high bit rate WDM communication systems

In this paper, Continuum sources based on similariton spectrums formed in low normal and high nonlinear dispersion photonic crystal fiber (PCF) are generated to achieve high capacity transmission, high channel count, and wavelength division multiplexing multiple access systems (WDM). A wavelength band of 40-nm continuous signal band in the C wavelengths of optical communication window is generated; this continuum allows generating at least 32 channels separated by 100 GHz in ITU-T WDM grid after spectral slicing by optical demultiplexer, where each channel is a pulses train and whose duty cycle relates to the bandwidths of the demultiplexer. Because the continuum is generated while flatness and coherent characteristics are maintained, the peak power variation in the 32 WDM channels is shown to be very small, so that similar powers are transmitted in each channel. Furthermore, because a pulse train of 10 GHz is a signal source, a 10- GHz–based 32-channel -wavelength–division multiplexing is simultaneously generated. These channels are modulated by 27-1 Pseudo Random Binary Sequences (PRBS) signal of the user data. As a result, a 320-Gb/s (32-channel × 10-Gb/s) WDM system is established. To investigate the system performance, Eye-diagrams and Q factors have been calculated. The impact of duty cycle on the system performance is taken into account.