High-power Supercontinuum Research Articles

Kilowatt-level supercontinuum generation employing a homemade taper-shaped ytterbium-doped fiber amplifier.

A simple generation method of high-power supercontinuum (SC) based on a homemade long ytterbium-doped taper fiber (T-YDF) amplifier has been demonstrated experimentally and analyzed in this work. The power and spectra of the obtained SC are made adjustable by changing the seed pulse repetition rates. Under a 7.5 MHz seed pulse repetition rate, a SC output is obtained with a spectral range of 1000 nm-1650 nm, maximum output power of 1066 W, and conversion efficiency of 75.7%. The core/clad diameters of the homemade T-YDF are ∼20/400 µm and ∼30/600 µm at the input and output ends, respectively, and the total length is 25 m. Such a long taper fiber can further enhance the properties of the SC while ensuring high power and good beam quality. To the best of the authors' knowledge, this is the first report of directly generating a high average power SC based on the T-YDF amplifier, which provides a proof-of-concept experiment to achieve a high average power SC source and greatly improves the potential application value of the SC source.

Tailoring the visible light band of Watt-level SCs pumped via picosecond pulse with different Raman extent

We investigate the supercontinuum (SC) tailoring property by varying the transmission fiber length after the master oscillator power amplifier system. The conversion efficiency of the visible light band is effectively enhanced via tailoring the Raman extent of the injected 30 ps pulse into the nonlinear photonic crystal fiber (PCF). Experimentally, a 3.6 W all-fiber SC spanning from 414 nm to over 1750 nm (@20 dB) is accomplished by using a high duty cycle domestic PCF through precisely controlling the extent of Raman effect. The proposed method is instructive for the further realization of high power SC with an enhanced spectral intensity in the visible light band.

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.

High-power supercontinuum lasers with a flat blue spectrum through pump modulation: a numerical study.

We numerically investigate high-power, modulational instability-based supercontinuum sources. Such sources have spectra that reach the infrared material absorption edge and as a result the spectrum has a strong narrow blue peak (dispersive wave group velocity matched to solitons at the infrared loss edge) followed by a significant dip in the neighboring longer-wavelength region. In a wide range of applications one prefers a broader and more flat blue part within a certain minimum and maximum power spectral density. From the perspective of fiber degradation it would be desirable to achieve this at reduced pump peak powers. We show that it is possible to improve the flatness by more than a factor of 3 by modulating the input peak power, although this comes at the expense of slightly higher relative intensity noise. Specifically, we consider a standard 6.6 W, 80 MHz supercontinuum source with a 455 nm blue edge, which uses 7 ps pump pulses. We then modulate its peak power to generate a pump pulse train having two and three different sub-pulses.

714 W all-fiber supercontinuum generation from an ytterbium-doped fiber amplifier

An all-fiber supercontinuum (SC) source with record average output power of 714 W and spectrum ranging from 690 nm to 2350 nm is demonstrated. The method of SC generation from an ytterbium-doped fiber amplifier is used to achieve the high-power SC output. The source also exhibits a flat spectrum ranging from 1050 nm to 2095 nm at the −10 dB level. The parameters that influence the output power and spectrum of SC, including the pulse width of the seed laser and the passive fiber length in the last stage fiber amplifier, are analyzed in detail. To the best of our knowledge, the output power of SC in this work is the highest power that has been publicly reported. The scheme has the advantage of good robustness, which also has the potential to further increase the SC output power to the kilowatt level.

Simple method for high average power supercontinuum generation based on Raman mode locking in a quasi-CW fiber laser oscillator.

A simple generation method for a supercontinuum (SC) based on Raman mode locking (RML) in a quasi-continuous wave (QCW) fiber laser oscillator is demonstrated experimentally and analyzed in this paper. The power of the SC is adjustable by changing the pump repetition rate and duty cycle. Under the pump repetition rate of 1 kHz and duty cycle of 11.5%, an SC output with a spectral range of 1000-1500 nm is obtained at a maximum output power of 791 W. The RML is fully analyzed in terms of the spectral and temporal dynamics. RML plays a major role in this process and further enriches the generation of the SC. To the best of the authors' knowledge, this is the first report on directly generating a high and adjustable average power SC using a large-mode-area (LMA)-based oscillator, which provides a proof-of-concept experiment for achieving a high average power SC source and greatly improves the potential application value of the SC source.

Kilowatt-Level Supercontinuum Generation in Random Raman Fiber Laser Oscillator With Full-Open Cavity

High-power supercontinuum (SC) sources are important for remote sensing, homeland defense, and scientific research. Despite recent advances in power scaling of the SC generation in optical fibers, the power record of SC fiber laser sources is still much lower than conventional high-power fiber lasers. Here we demonstrate a method for kilowatt-level SC generation based on the random Raman fiber laser (RRFL) with a full-open cavity. Theoretically, a model including cascaded Raman effect, modulation instability, and Rayleigh scattering is established to qualitatively highlight the dynamics of the kilowatt-level SC generation. Experimentally, injecting the amplified ytterbium-doped fiber laser and Raman fiber laser into the RRFL oscillator formed by a piece of long passive fiber, 3-kW-level SC spanning from 925 to 1862 nm is achieved. The experimental results suggest that the full-open-cavity RRFL is a promising approach for kilowatt-level SC generation and the theoretical model demonstrates the importance of Rayleigh backscattering during the SC generation.

Generation of high-power multiple-octave supercontinuum from fan-out periodically poled lithium niobate

We report on high-power supercontinuum (SC) generation using a fan-out periodically poled lithium niobite (PPLN) with controllable chirp rate. Ultra-broadband parametric down-conversion processes are fulfilled by chirped quasi-phase matching. Simultaneously, the high intensity pump pulses naturally ignite various cubic nonlinear processes, such as self-phase modulation (SPM) and cross-phase modulation (XPM), which synergically act with the quadratic nonlinear process, to generate high-power multi-octave SC spanning from 650 to 3900 nm.

Recent Development of Mid-Infrared Supercontinuum Generation in Fluoroindate Glass Fibers

Supercontinuum (SC) generation that leads to the emission of broadband radiation has been extensively studied. In particular, SC sources encompassing the wavelength range of 2–5 μm have attracted considerable interest in the last decade, and a continuous increase in the output power and spectrum width has been observed. To enable broadband and high-power SC generation, suitable nonlinear media combined with appropriate pump sources must be used, maintaining the output as spectrally flat. This paper briefly reviews the current state-of-the-art SC sources restricted to those based on fluoroindate fibers, including systems pumped with femtosecond, picosecond, and nanosecond pulses. First, the concept of SC generation in optical fibers is briefly presented. This is followed by an examination of indium fluoride optical fibers, with an emphasis on their material and waveguide properties. Furthermore, the advances in SC generation in fluoroindate fibers, including the latest results on high-power (Watt-level) continuum generation adopting different pump schemes, are also explored. A record time-averaged output power of 11.8 W with a spectrum spanning from ~1.9 to 4.9 µm has been demonstrated, which is certainly not the power limit of this technology. Finally, potential future directions of research are discussed at the end of this paper.

Tunable Ultraviolet Second Harmonics Generation Pumped by Supercontinuum Laser

This paper presents the first systematic study on second harmonics generation based on a supercontinuum source. We analyzed the effect of the supercontinuum beam diameter and the crystal length to generate second harmonics. The walk-off effect on the second harmonics was also investigated; the efficiency was limited by the walk-off, and the beam of the second harmonic was out of shape. A tunable ultraviolet in the range of 285340 nm is obtained with the pump of a visible supercontinuum, which is generated by a laser with an all-fiber device. The results provide a theoretical basis for the improvement of the second harmonic power and optimization of the crystal and beam diameters. A potentially tunable ultraviolet with a power exceeding 10 mW can be obtained by a high-power supercontinuum pump.

130 W continuous-wave supercontinuum generation within a random Raman fiber laser

We have demonstrated a 134 W, octave-spanning, continuous-wave (CW) supercontinuum (SC), which is generated within a random Raman fiber laser (RRFL) pumped by Ytterbium (Yb) fiber sources. A piece of 600-m long standard telecom fiber with a zero-dispersion wavelength (ZDW) around 1.3 μm was used to provide Raman gain and random distributed feedback for the RRFL. High power SC is excited when the wavelength of the cascade RRFL reaches the ZDW. 20-dB spectrum ranging from 852 nm to 2055 nm is achieved with an average power spectral density over 111 mW/nm. To the best of our knowledge, this is the highest power of CW SC source ever reported. Moreover, two different 1064 nm Yb-doped fiber sources were used as pumps, which are seeded with a normal oscillator and amplified spontaneous emission, respectively. The difference of the SC generated by the two pump sources are compared in detail, including spectrum, efficiency, and relative intensity noise.

High-power broadband supercontinuum generation through a simple narrow-bandwidth FBGs-based fiber laser cavity

The generation of supercontinuum (SC) often requires ultrashort pulsed lasers with high peak power and gain media with large nonlinear coefficients, such as a long piece of fiber or photonic crystal fiber. In this Letter, we propose and demonstrate that high-power SC can be generated through a simple narrow-bandwidth fiber Bragg gratings (FBGs)-based laser cavity without any modulation, based on the mechanism of intense nonlinear effects induced by the inherent self-pulsation generated inside the cavity. In the experiment, an ∼80 W SC laser with the spectrum range from <600 nm to 1600 nm was achieved. To the best of our knowledge, this is the first report about SC generation through a simple fiber laser cavity. This work enriches the research content of SC and provides a cost-effective method for high-power SC lasers.

Progress on High-Power Supercontinuum Laser Sources at 3-5 μm

Progress on High-Power Supercontinuum Laser Sources at 3-5 μm

High power supercontinuum generation by dual-color femtosecond laser pulses in fused silica

High power supercontinuum (SC) is generated by focusing 800 nm and 400 nm femtosecond laser pulses in fused silica with a microlens array. It is found that the spectrum of the SC is getting broader compared with the case of a single laser pulse, and the spectral energy density between the two fundamental laser wavelengths is getting significantly higher by optimizing the phase matching angle of the BBO. It exceeds μJ/nm over 490 nm range which is from 380 nm to 870 nm, overcoming the disadvantage of relative lower power in the ranges far from the fundamental wavelength.

730 mW, 2-8 μm supercontinuum generation and the precise estimation of multi-pulse spectral evolution in the soft-glass fibers cascaded nonlinear system

We experimentally demonstrate the 2-8 μm high-power supercontinuum generation and theoretically propose a statistical method for precise estimation of the multi-pulse spectral evolution in the ZBLAN and As2S3 fiber cascaded all-fiber structured nonlinear system. In the experiment, with the aid of the ultra-low loss fusion splice technology, high-efficiency fiber butt-coupling technology and precise thermal management technology, we obtained a record-breaking supercontinuum source with a spectrum spanning from 2 μm to 8 μm at a power of 730 mW. Considering the strong pulse splitting and soliton fission effects in fibers, to precisely estimate the multi-pulse spectral evolution in this system, we, for the first time, built a multi-pulse pump model with the Pearson product-moment correlation coefficient method based multi-pulse selection mechanism. In combination with the existing approaches and some new programmatic work, finally, we verified that the simulation results are in good agreement with the experimental one.

Investigation of defective hybrid cladding with silicon nanocrystal PCF for supercontinuum generation

Defective hybrid cladding through a silicon nanocrystal-core-structured photonic crystal fiber intended for high pump power supercontinuum proliferation is discussed in this paper. The cladding comprehends a hybrid approach of a hexagonal air hole in the outer section and a petal-structured air hole in the inner layer with a twisted pattern. Such a procedure with an air hole in the cladding section with a silicon nanocore displays high nonlinearity and negative dispersion at the communication window for varying pulse widths with 20 kW pump power. The impact of structural parameters of the proposed structure on the optical constraints is discussed, namely, dispersion, nonlinearity and group-velocity dispersion for wavelengths ranging from 0.45 µm to 1.85 µm. The proposed structure with optimized structural parameters provides high nonlinearity of about 6.38 × 106 W−1 km−1 with negative dispersion of −70.19 ps (nm km)−1 at 1550 nm.

All-fiber high-power supercontinuum laser source over 3.5 µm based on a germania-core fiber.

In this Letter, a high-power all-fiber mid-infrared (MIR) supercontinuum (SC) laser source based on 9 cm long germania-core fiber (GCF) pumped by a high-power thulium-doped fiber amplifier is presented. As the pump power was set as 60 W, we obtained a 21.34 W broadband SC source extending from 1742 to 3512 nm with a slope efficiency of 32.5%. The 10 dB spectral bandwidth was over 1000 nm, spanning 1.97 to 3.04 µm. Furthermore, the numerical simulation of SC generation in GCF was in good agreement with the experimental results. As far as we know, this is the highest average output power over 3.5 µm in GCF based on a MIR SC laser source.

High-power mid-IR supercontinuum generation in fluoroindate and arsenic sulfide fibers pumped by a broadband 1.9–2.7 μm all-fiber laser source

We report the experimental demonstration of high-power supercontinuum generation in step-index fluoroindate (InF3) and chalcogenide (As2S3) fibers. A home-built fiber-based laser system with a broad spectrum spanning from 1.9 to 2.7 μm and delivering an output average power of 6.15 W was used as the pump source. A time-averaged power of 2.95 W covering the entire 2–5 μm wavelength range is obtained from an InF3 fiber. Cascading the system by adding an As2S3 fiber, the spectrum was extended up to 5.58 μm. Moreover, we present a supercontinuum with an average power of 440 mW and a spectrum extended to 4.17 μm generated by an As2S3 fiber pumped directly by a broadband (2.4–2.7 μm), silica-based laser source centered at 2.55 µm. Combined with a high degree of spectral flatness, the high-output supercontinuum power highlights the potential of the developed sources for use in a wide variety of applications.

Wide-range wavelength and angle resolved light scattering measurement setup.

We present a new version of a light scattering measurement setup, using a high-power supercontinuum laser source, two volume hologram filters, and two low-noise scientific grade cameras. This configuration enables spectral and angle resolved characterization of the light scattered by complex thin-film filters from 400 to 1650 nm. Measurements carried out on specific filters illustrate the performances of the setup.

All-Fiber High Power Supercontinuum Generation by Cascaded Photonic Crystal Fibers Ranging From 370 nm to 2400 nm

104 W supercontinuum (SC) covering 370 nm-2400 nm is reported. High power visible SC is generated by pumping cascaded photonic crystal fibers (PCF) with 1064 nm picosecond pulse. Cascaded PCFs is fabricated by fusion splicing two different PCFs together with a coupling efficiency of 75%. For the purpose of avoiding fiber fuse phenomenon in PCF, the discharge time and intensity of fusion splicer should be precisely controlled. Two components of cascaded PCFs are pumped separately by 1064 nm picosecond pulse for comparing with the impact of cascaded PCFs. As a result of pumping cascaded PCFs, 104 W SC covering 370 nm−2400 nm is generated. Visible spectra (380 nm−780 nm) accounts for 50.4% (52.4 W) by numerical integration. To best of our knowledge, it's the first time that a visible SC with over a hundred watt output and 370 nm short-wave edge is obtained experimentally.