Supercontinuum Generation Research Articles

Low-noise supercontinuum generation in chiral all-normal dispersion photonic crystal fibers.

We present the advantages of supercontinuum generation in chiral, therefore circularly birefringent, all-normal dispersion fibers. Due to the absence of nonlinear power transfer between the polarization eigenstates of the fiber, chiral all-normal dispersion fibers do not exhibit any polarization instabilities and thus are an ideal platform for a low-noise supercontinuum generation. By pumping a chiral all-normal dispersion fiber at 802 nm, we obtained an octave-spanning, robustly circularly polarized supercontinuum with a low noise.

Supercontinuum Generation in Dispersion Engineered Highly Doped Silica Glass Waveguides

AbstractThe effect of a lower index oxide layer inclusion within a highly doped silica glass slot waveguide is investigated for optimized supercontinuum generation at telecom wavelengths. By controlling the thickness of the oxide slot, it is demonstrated that one can engineer the waveguide dispersion profile in order to obtain supercontinua with vastly different spectral broadening dynamics and bandwidths. Using this approach, a waveguide with a low and flat dispersion profile of less than 43 across a wavelength range spanning over 1000 nm is designed and fabricated. It is shown that, when pumped at the telecom C‐band, a supercontinuum that spans over 1.5 octaves can be generated from 817 to 2183 nm. The numerical simulations, whose parameters are derived from the measured waveguide dimension and material indices, exhibit good agreement with experimental measurements, where one can observe both a qualitative and quantitative match in the supercontinuum overall spectrum and specific features (e.g., soliton and dispersive wave locations). This study represents an important step forward in the control and manipulation of dispersive and nonlinear dynamics in highly doped silica glass waveguides, paving the way toward advanced on‐chip broadband light manipulation.

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.

Modulation instability induced supercontinuum generation in Barium Zinc Borate glass doped with Praseodymium based photonic crystal fiber

Modulation instability induced supercontinuum generation in Barium Zinc Borate glass doped with Praseodymium based photonic crystal fiber

A new type of supercontinuum generation in hexagonal lattice C6H6-core PCF with broadband and low-power pump

Most of the spectral bandwidths of previous publications are still limited by high input powers making them economically less than ideal. By using a benzene core (C6H6) photonic crystal fiber (PCF) as a new supercontinuum (SC) light source, it is possible to achieve a very large spectral broadening with hundreds of times lower peak power. Due to the change in the diameter of air holes in the first ring near the core, near-zero flattened dispersion, high nonlinearity and small attenuation can be achieved for spectral broadening. The structural geometries of two C6H6-PCFs are optimized to generate wide SC at low input energy. The SC spectrum produced in 1[Formula: see text]cm long of all dispersion fiber extends from a part of visible light to the near-infrared range at 1.3[Formula: see text][Formula: see text]m wavelength and a small pulse energy of 18[Formula: see text]pJ (or 450[Formula: see text]W of electrical input). The second PCF shows wide soliton-induced SC from 0.8 to 4.2[Formula: see text][Formula: see text]m with 71[Formula: see text]pJ pulse energy (or input power approximately 790[Formula: see text]W) at 1.5[Formula: see text][Formula: see text]m wavelength within a fiber of 12[Formula: see text]cm. The proposed structures have the potential to become a new class of microstructured optical fibers for low-cost, broad-spectrum SC generation.

Supercontinuum Generation from Airy-Gaussian Pulses in Photonic Crystal Fiber with Three Zero-Dispersion Points

The supercontinuum generation and manipulation of Airy-Gaussian pulses in a photonic crystal fiber with three zero-dispersion points are studied using the split-step Fourier method. Firstly, the spectral evolution of Airy-Gaussian pulses in four photonic crystal fibers with different barrier widths was discussed, and the optimal fiber was determined after considering the factors of width and flatness. By analyzing the mechanism of supercontinuum generation in photonic crystal fibers with single, double and three zero-dispersion points, it is found that the photonic crystal fiber with three zero-dispersion points have a larger spectral width due to the component of tunneling solitons. Then, the effects of four characteristic parameters (truncation factor a, distribution factor χ0, initial chirp C and central wavelength λ) on forming the supercontinuum spectrum of Airy-Gaussian pulses are analyzed in detail. The results show that the spectral width and energy intensity of the dispersive wave and tunneling soliton generation can be well controlled by adjusting the barrier width and initial parameters of the pulse. These research results provide a theoretical basis for generating and manipulating high-power mid-infrared supercontinuum sources.

Higher harmonics and supercontinuum generated from the Kerr response time in different states of matter from a universal electromagnetic model

There is a need for a universal model to describe higher harmonic generation (HHG) in different states of matter. Based on an electromagnetic model (EM), the generation of odd higher harmonic (HHG) and supercontinuum (SC) from intense fs and ps pulses for visible, NIR, and MIR lasers is simulated based on the parameters from experimental observation. HHG and SC depend critically on the different Kerr material response times τ from the ultrafast on the order of 100 as for electronic cloud distortion to fast ~ 10 fs from plasma and molecular redistribution and to the slower picoseconds rotational and vibrational molecular processes. The number of odd HHG generated is shown to depend critically on the fastest Kerr response time on the order of ~ 1 fs from electronic self-phase modulation (ESPM). In this study, different states of matter from noble gas Argon to condensed matter ZnO and LBG are simulated showing the dependence on the Kerr response time to produce HHG for various applications in Physics, Chemistry, Biology, and Engineering. The EM model is universal to produce HHG and SC in different states of matter.

Distinguishing the nonlinear propagation regimes of vortex femtosecond pulses in fused silica by evaluating the broadened spectrum.

The nonlinear propagation dynamics of vortex femtosecond laser pulses in optical media is a topic with significant importance in various fields, such as nonlinear optics, micromachining, light bullet generation, vortex air lasing, air waveguide and supercontinuum generation. However, how to distinguish the various regimes of nonlinear propagation of vortex femtosecond pulses remains challenging. This study presents a simple method for distinguishing the regimes of nonlinear propagation of femtosecond pulses in fused silica by evaluating the broadening of the laser spectrum as the input pulse power gradually increases. The linear, self-focusing and mature filamentation regimes for Gaussian and vortex femtosecond pulses in fused silica are distinguished. The critical powers for self-focusing and mature filamentation of both types of laser pulses are obtained. Our work provides a rapid and convenient method for distinguishing different regimes of nonlinear propagation and determining the critical powers for self-focusing and mature filamentation of Gaussian and structured laser pulses in optical media.

Mid-infrared supercontinuum generation of orbital angular momentum modes based on ring-core As2S3 photonic crystal fiber

In this paper, a wide supercontinuum of multi-order orbital angular momentum (OAM) modes is generated theoretically in the mid-infrared region based on a ring-core As2S3-based photonic crystal fiber (PCF). This PCF supports six OAM modes with two orders and exhibits an ultra-high effective refractive index difference of 10-2 between the vortex modes. After customizing the nonlinear coefficient and dispersion, all the supported OAM modes can be used for wide-band supercontinuum (>3100 nm) generation at low input pulse power of 1000 W. In particular, the supercontinuum of OAM1,1 mode covers a wavelength range from 2860 nm to 6120 nm at −40 dB level. This work has great potentials in the OAM-based mid-infrared source in optical communication and sensor systems.

Enhanced spectral broadening via the optical rogue wave stimulated by spectral sinusoidal phase

We numerically investigate the extended spectral broadening via a spectral sinusoidal phase-modulated Gaussian pulse. The modulated pulse can create two predominant solitons that collide with each other to form a rogue wave (RW), resulting in an RW-induced dispersive wave emission. This leads to a further spectral broadening beyond the soliton-induced dispersive wave and can be manipulated by tuning the phase modulation parameters. Before the appearance of RW, the modulated pulse-propagation scenario is governed by the optical Newton’s cradles and the optical event horizons. These complex dynamics reveal a new method for controlling the RW generation as well as spectral broadening at relatively low power levels. Our results have potential implications for controllable excitation of RWs and broadband supercontinuum generation.

Optical heating-induced spectral tuning of supercontinuum generation in liquid core fibers using multiwall carbon nanotubes.

In this work, we demonstrate the optical heating modulation of soliton-based supercontinuum generation through the employment of multi-walled carbon nanotubes (MW-CNTs) acting as fast and efficient heat generators. By utilizing highly dispersion-sensitive liquid-core fibers in combination with MW-CNTs coated to the outer wall of the fiber, spectral tuning of dispersive waves with response times below one second via exploiting the strong thermo-optic response of the core liquid was achieved. Local illumination of the MW-CNTs coated fiber at selected points allowed modulation of the waveguide dispersion, thus controlling the soliton fission process. Experimentally, a spectral shift of the two dispersive waves towards the region of anomalous dispersion was observed at increasing temperatures. The presented tuning concept shows great potential in the context of nonlinear photonics, as complex and dynamically reconfigurable dispersion profiles can be generated by using structured light fields. This allows investigating nonlinear frequency conversion processes under unconventional conditions, and realizing nonlinear light sources that are reconfigurable quickly.

Intracavity ultra-broad supercontinuum generation from a figure-9 Yb-doped fiber laser

Intracavity supercontinuum generation based on self-Q-switch assisted by stimulated Brillouin scattering is experimentally demonstrated from an all-fiber Ytterbium laser in the form of figure-9 configuration. At 3 W of pump power, a supercontinuum (SC) extending from visible red light to beyond two microns is obtained. Such spectrum has a flatness better than 5 dB in the 1256–2141 nm range and spans more than an octave ∼ 856–2141 nm at − 20 dB level excluding the main peak. The proposed SC laser source comes in a compact, simple, and low-cost design which could find application in areas such as spectroscopy, microscopy, and biomedical imaging.

Structural Analysis of Nano Core PCF With Fused Cladding for Supercontinuum Generation in 6G Networks

AbstractThe Sixth Generation (6G) networks have identified the use of frequency range between 95 GHz and 3 THz with a targeted data rate of 1 Terabytes/second at the access network for holographic video applications. As is demands broadening of spectrum at the core network, this paper proposes a Supercontinuum Generation (SCG) through photonic crystal fiber (PCF) as it provides excellent broadening of the optical spectrum. Discussed in the paper is supercontinuum generation at high pumping power as per the standards specified by the International Telecommunications Union. The proposed PCF is designed with silicon nanocrystal core and the cladding microstructures is arranged in a fusion approach to effectively optimize the optical parameters such as dispersion, nonlinearity, birefringence, group‐velocity dispersion, and confinement loss. The fused cladding comprises of a flower‐cladding assembly in which air‐holes arrangement is inspired from petals in a pleated structure. Such arrangement is shown here to provide high nonlinearity and negative dispersion for high power supercontinuum generation. The novel nanocore assembly with improved structural constraints delivers a non‐linearity of 6.37 × 106 W−1 km−1 and a negative dispersion of −142.1 (ps/nm‐km) at 1,550 nm. Moreover, a supercontinuum spectrum is generated using different pulse widths ranging from 350 to 650 ps with 25 kW pump power for PCF lengths of 10 and 15 mm.

Comprehensive Analysis of Dual Core Photonic Crystal Fibers for Optimizing Optical Properties Towards Highly Coherent Supercontinuum Generation

A systematic study implementing numerical analysis has been presented in this work in order to design a hexagonal lattice dual core photonic crystal fiber (DC-PCF) which will be simple to fabricate but possesses very good values of optical properties for supercontinuum generation (SCG). By utilizing a full vectoral finite element method with perfectly matched boundary conditions, important propagation properties are numerically evaluated and tuned to desired value through the optimization of structural parameters. Finally, it is found that the optimized PCF structure exhibits very low confinement loss, high birefringence, large effective mode area while maintaining negative chromatic dispersion of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 8.3138 ps/km.nm pumping at 1060 nm wavelength. The fiber when excited by a hyperbolic secant pulse having a full-width at half-maximum (FWHM) of 50 fs and a relatively low energy of 4 nJ generates a SC spectrum spanning 600 nm to 1600 nm. The effect of altering the pump power and other parameters on the generated spectra is also explored. Furthermore, the input noise effects on generated SCs have been analyzed through the inclusion of different types of noise. It is found that the generated SC demonstrates excellent coherence property over the entire band extended from visible to the near-IR region and thus it may find applications in lasing, biological imaging, and telecommunication.

Low-threshold supercontinuum generation in a homogeneous bulk material at 76 MHz pulse repetition rate.

We report on high average power, low threshold supercontinuum generation in a homogeneous bulk material at 76 MHz pulse repetition rate with amplified as well as unamplified pulses from a Yb:KGW oscillator. An octave-spanning supercontinuum was produced in undoped potassium gadolinium tungstate (KGW), which demonstrated robust, damage-free long-term performance with a total average pump power of 6.4 W. The supercontinuum generation was unambiguously attested by the distinctive features of the phenomenon: beam filamentation visualized via filament-induced luminescence; conical emission and its characteristic angular distribution captured by angle-resolved spectral measurements; and pulse splitting that produced the sub-pulses with well-behaved phases, as retrieved from the measurements employing a second harmonic frequency-resolved optical gating technique.

Three octave visible to mid-infrared supercontinuum generation seeded by multimode silica fiber pumped at 1064 nm.

Hyperspectral spectroscopy requires light sources with wide spectral ranges from the visible to the mid-infrared. Here, we demonstrate the first fiber-based mid-infrared supercontinuum covering three octaves of frequency by leveraging 1-µm laser technology. The process consists in spectral broadening of a 1064-nm pump toward 0.48-2.5 µm in a graded-index multimode fiber, followed by a fluoro-indate fiber used to reach deeper into the near infrared (4.3 µm). Finally, an arsenic selenide chalcogenide fiber allows us to reach the 6-µm wavelength region, providing a 0.75-6-µm supercontinuum. We illustrate the potential of this light source by recording mid-infrared absorption spectra of organic compounds.

Visible to Mid-IR Supercontinuum Generation in Cascaded PCF-Germanate Fiber Using Femtosecond Yb-Fiber Pump

Broadband supercontinuum (SC) fiber sources covering the mid-IR range have many significant applications, largely due to their compactness, reliability, and ease of use. However, most of the existing SC fiber sources cannot boast of either high reliability or a wide bandwidth. Thus, supercontinuum sources based on silica fibers are robust, but are not capable of generating SC in the mid-IR range. Sources based on soft glasses (tellurite, chalcogenide, etc.) generate broadband SC in the mid-IR range but are not used commercially, due to the poor mechanical and chemical characteristics of such fibers. In this work, we propose a new approach consisting of cascade generation of a supercontinuum sequentially in a silica photonic crystal fiber (PCF) and a germanate fiber. Using a standard ytterbium chirped-pulse amplification (CPA) laser system for pumping, we have demonstrated a supercontinuum in the range of 450–2950 nm in PCF and germanate fiber firmly connected by a standard fusion splicing technique. Further optimization of the cascade pump will make it possible to create a compact and reliable all-fiber SC source from the visible to mid-IR range.

Broadband supercontinuum generation in hollow-core photonic crystal fibers infiltrated with chloroform

The chloroform-infiltrated square lattice photonic crystal fibers (PCFs) are designed with the difference of the air hole diameters in the cladding to improve chromatic dispersion and nonlinear properties. Based on numerical simulation results, two optimal structures with flat dispersion, high nonlinear coefficient, and small confinement loss are used for supercontinuum (SC) generation. The first fiber has an all-normal dispersion regime, a nonlinear coefficient of 486.355[Formula: see text]W[Formula: see text].km[Formula: see text] generating an SC spectrum of 640.3[Formula: see text]nm within 30 dB levels at a pump wavelength of 0.945[Formula: see text][Formula: see text]m with peak power as low as 1.44[Formula: see text]kW. With anomalous dispersion properties, the second fiber gives a very broad SC spectrum of 1471.8[Formula: see text]nm within 30 dB levels at a 1.4[Formula: see text][Formula: see text]m pumping wavelength with a peak power of 20[Formula: see text]kW. All-fiber SC sources operating with low-power pump lasers can use these fibers to effectively replace glass-core fibers.

Supercontinuum generation in As2S3 chalcogenide waveguide pumped by all-fiber structured dual-femtosecond solitons.

Supercontinuum sources with high compactness are essential for applications such as optical sensing, airborne detection and communication systems. In the past decades, the adoption of bulky optical parametric amplifier to pump various chalcogenide glass waveguides are widely reported for on-chip mid-infrared supercontinuum generation, but this usually leads to a large volume of the whole system, and is not practical. Therefore, integrating advanced femtosecond fiber lasers with optical waveguides using nano-fabrication technology are highly desired. However, the scarcity of compact pump sources and the dispersion-matched high-nonlinearity waveguide in short wavelength regions have hindered the advancement of integrated supercontinuum source performances in the near and mid-infrared region. In this study, we demonstrate a broadband supercontinuum source from As2S3 waveguide pumped by a compact dual-femtosecond solitons pulse source. The laser is completely fiber structured, and its wavelength can be readily tuned from 2 to 2.3 µm using Raman soliton self-frequency shift technology in a Tm3+-doped fiber amplifier. Furthermore, the As2S3 waveguide is designed with controllable dispersion and high nonlinearity for a broadband supercontinuum generation. These results will advance the development of on-chip supercontinuum sources based on chalcogenide waveguides.

NIR to MIR ultra-broadband supercontinuum laser source based on all-silica fibers.

We demonstrated an ultra-broadband supercontinuum (SC) laser source with a wavelength range spanning the near-infrared (NIR) to mid-infrared (MIR) region. The SC spectrum was generated in a very short piece of highly nonlinear silica fiber (HNLF) which has a zero-dispersion wavelength (ZDW) of 1.55 µm. The pump source used has a spectral coverage of 1.5∼2.4 µm which covers the ZDW of HNLF, resulting in a dramatic blue and red shift of the spectrum through strong non-linear effects. As the pump laser pulse launched into HNLF, a SC spectrum with broadband range of 0.92∼2.92 µm and maximum average power of 5.09 W was achieved, which sets record coverage of HNLF-based watts magnitude SC laser sources for now, to the best of the authors' knowledge. The setup consists of silica fiber that can be considered easy-to-implement and with a cost-effectiveness scheme for ultra-broadband SC generation that could be easily applied to optical fiber sensing and spectral imaging technology.