mid-IR Supercontinuum Generation Research Articles

Nonlinear compression of mid-infrared supercontinuum generation in dispersion-engineered As2S5 chalcogenide ridge waveguide

We numerically demonstrated nonlinear compression of mid-infrared (mid-IR) supercontinuum (SC) generation in As2S5 chalcogenide glass (ChG) ridge waveguides, achieving a small dispersion value at the pump wavelength of 2.5 µm by adjusting the waveguide width (normal dispersions of -10.547 ps.nm−1.km−1 and the anomalous dispersions of +5.314 ps.nm−1.km−1). These waveguides were designed using the negative slope of the dispersions with the negative third-order dispersion, which are applied to generate the nonlinear compression of SC generation. Using a 50-fs pulse with the peak power of 2000 W, the two waveguides could compress the maximum pulse peak power of 6900 W (> 3.4 octaves) and 6360 W (> 3.1 octaves) and generate the widest SC spectra, spanning from 1.20 µm to 12.96 µm and from 1.25 µm to >13 µm with only short waveguides 0.85 mm and 1 mm long, respectively. The key process behind SC formation in such ChG waveguides is related to self-phase modulation, four-wave mixing, and nonlinear compression. This particular design is effective, and ChG waveguides can generate high peak power and the widest spectra of SC generation. Moreover, the waveguides are also relatively flexible in design, which is concerned with optical design and engineering, and micro-optical devices. As the ultra-wideband mid-IR SC source, high pulse peak power, very short waveguides, and low-energy pulses (<1 pJ) are important for on-chip mid-IR SC sources, the proposed work would offer the greatest benefits in practical application.

Cascade picosecond optical parametric amplification for generating radiation in the 2.1 [formula omitted

The paper demonstrates the experimental implementation of a broadband picosecond radiation source with a wavelength of 2.0−2.2μm based on a cascade parametric amplifier. To do this, in the first cascade, as a result of parametric luminescence in the MgO:PPLN fan-out crystal, pumped by Nd:YAG laser pulses (90 ps, 10 Hz), radiation with a wavelength of 2.1μm and a pulse energy of ∼185 μJ at a pump energy of 6.5 mJ was generated. To increase the output radiation energy to a level of ∼840 μJ, a second parametric amplification cascade based on two KTiOPO4 crystals with a walk-off angle compensation was used. The results of numerical simulation of the spatial and energy characteristics of the radiation being generated are in good agreement with the experimental results. The developed picosecond 2.1μm radiation source is designed to be used for mid-IR range supercontinuum generation in non-oxide crystals.

Mid-IR supercontinuum generation using a slab with D-shaped/semi-ellipse core waveguide at 4μm

In the present article, we designed a D-shaped optical waveguide for supercontinuum generation. The designed waveguide consists of a slab with a D-shape core (or semi-ellipse) made of As2Se3 which is sandwiched between top and bottom claddings made of GeAsS chalcogenide glass. Pulse confinement, transmission loss, and nonlinear parameters are taken to be in consideration while optimizing the waveguide parameters. In this work, we have numerically calculated the effect of waveguide parameters on dispersion. In addition, we have studied the effect of the D-shaped parameter ‘b’ on the supercontinuum spectrum. For b = 1.9 μm, the proposed waveguide achieves a broad-band supercontinuum spanning from 1.9 μm to 24.5 μm by pumping 50 fs pulse duration sech pulses at the central wavelength of 4 μm, with a peak power of 5 kW. Apart from this, we have also evaluated the supercontinuum spectra with 1 kW, and 2 kW peak powers. The designed waveguide in this paper is easy to fabricate because of its semi-ellipse core shape. From the numerical results, it is pointed out that the proposed waveguide should be useful in the generation of supercontinuum sources, telecommunications, and spectroscopy in the mid-infrared region.

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.

Mid-infrared supercontinuum source and evanescent wave spectroscopy based on multiple tapered sections of a singleoptical chalcogenide glass rod

Mid-infrared supercontinuum sources are particularly important for identifying and characterizing molecules and materials through spectroscopy, thus enabling key applications. We here demonstrate the possibility of combining both mid-IR supercontinuum generation and evanescent wave spectroscopy in a single chalcogenide fiber device by means of heat-and-draw processes to manage linear and nonlinear wave-guiding properties.

Dispersion engineered mid-IR supercontinuum generation using multi-core silicon-rich nitride photonic integrated waveguide

The multi-core silicon-rich nitride photonic integrated waveguide is presented here to numerically model the spanning of supercontinuum generation in the mid-IR region beyond the 4 μm wavelength range by engineering the dispersion profile such that maximum phase-matching can be achieved. Tunable dispersive wave generation has been observed in a long mid-IR region up to 5.2 μm wavelength by the variation of gap spacing between the cores. This unique geometry enables a higher phase matching from 1.2 μm to 2.6 μm wavelength range resulting in the flat dispersion profile in the near-IR region by coupling the fundamental mode in narrow waveguide core to the higher-order mode in wide waveguide core that gives rise to anomalous GVD which plays an essential role in compensating chromatic dispersion in the mid-IR region.

Mid-IR supercontinuum generation initiated by two-cascade stimulated Raman scattering in D2-filled revolver fibre

We report a numerical study of coherent mid-IR supercontinuum generation at wavelengths above 2.4 μm, initiated by two-cascade stimulated Raman scattering in a deuterium-filled revolver fibre pumped by positively chirped picosecond pulses at a wavelength of 1.03 μm. It is shown that the highest efficiency of conversion to the second Stokes is ensured by fibre lengths at which the spectrum is strongly broadened by Kerr nonlinear effects. A range of optimal parameters (deuterium pressure, fibre length, pulse energy, and pulse duration) is found that ensure quantum efficiency at a level of 50 % and a mid-IR supercontinuum width above 1000 nm. The coherence properties of the supercontinuum are shown to be determined by the pulse duration, the magnitude of the pulse chirp, and dispersion characteristics in each transmission band of the fibre. We demonstrate the feasibility of generating a single compressed mid-IR pulse of 20-fs duration with an energy of 1.9 μJ.

Chalcogenide Glass Microfibers for Mid-Infrared Optics

With diameters close to the wavelength of the guided light, optical microfibers (MFs) can guide light with tight optical confinement, strong evanescent fields and manageable waveguide dispersion and have been widely investigated in the past decades for a variety of applications. Compared to silica MFs, which are ideal for working in visible and near-infrared regions, chalcogenide glass (ChG) MFs are promising for mid-infrared (mid-IR) optics, owing to their easy fabrication, broad-band transparency and high nonlinearity, and have been attracting increasing attention in applications ranging from near-field coupling and molecular sensing to nonlinear optics. Here, we review this emerging field, mainly based on its progress in the last decade. Starting from the high-temperature taper drawing technique for MF fabrication, we introduce basic mid-IR waveguiding properties of typical ChG MFs made of As2S3 and As2Se3. Then, we focus on ChG-MF-based passive optical devices, including optical couplers, resonators and gratings and active and nonlinear applications of ChG MFs for mid-IR Raman lasers, frequency combs and supercontinuum (SC) generation. MF-based spectroscopy and chemical/biological sensors are also introduced. Finally, we conclude the review with a brief summary and an outlook on future challenges and opportunities of ChG MFs.

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.

Exploiting higher-order mode dispersion of bend M-type chalcogenide fiber in mid-IR supercontinuum generation

Abstract We propose and numerically demonstrate chalcogenide based bend M-type fiber for mid-IR supercontinuum (SC) generation through higher order mode (HOM) of LP02. In order to achieve this, we comprise two glass materials such as As2Se3 in core and Ge10As23.4Se66.6 in cladding. M-type index fiber has a special property that the HOM of LP02 is confined into the core region with help of high index ring. The mode field distribution of the proposed fiber is numerically calculated by a finite element method. By optimizing structural dimensions in each bending case, we realize a zero dispersion wavelength, double zero dispersion wavelength effective area and power fraction in core. The simulation results shows the flat anomalous dispersion in the wavelength range of 2.1–2.6µm and 2.5–6.5µm for the core radius 4 and 10 µm, respectively at bending case of 1, 3, and 5 cm. which is important for employing the mature fiber laser technology at mid-IR regions.

Ultra-flat supercontinuum from 1.95 to 2.65 µm in a nanosecond pulsed Thulium-doped fiber laser

Abstract We report on mid-IR supercontinuum generation in an all-silica nanosecond pulsed fiber laser. The laser topology is a master oscillator power amplifier which consists of a two stage Thulium-doped fiber amplifier seeded with a directly modulated semiconductor laser at 1952 nm. The supercontinuum performance is investigated for repetition rate frequencies between 35 kHz and 100 kHz and pulse widths between 6 ns and 21 ns. Supercontinuum average output powers greater than 1.5 W and spectra ranging from 1.95 µm to 2.65 µm are demonstrated.

Deep-UV to Mid-IR Supercontinuum Generation driven by Mid-IR Ultrashort Pulses in a Gas-filled Hollow-core Fiber

Supercontinuum (SC) generation based on ultrashort pulse compression constitutes one of the most promising technologies towards ultra-wide bandwidth, high-brightness, and spatially coherent light sources for applications such as spectroscopy and microscopy. Here, multi-octave SC generation in a gas-filled hollow-core antiresonant fiber (HC-ARF) is reported spanning from 200 nm in the deep ultraviolet (DUV) to 4000 nm in the mid-infrared (mid-IR) having an output energy of 5 μJ. This was obtained by pumping at the center wavelength of the first anti-resonant transmission window (2460 nm) with ~100 fs pulses and an injected pulse energy of ~8 μJ. The mechanism behind the extreme spectral broadening relies upon intense soliton-plasma nonlinear dynamics which leads to efficient soliton self-compression and phase-matched dispersive wave (DW) emission in the DUV region. The strongest DW is observed at 275 nm which corresponds to the calculated phase-matching wavelength of the pump. Furthermore, the effect of changing the pump pulse energy and gas pressure on the nonlinear dynamics and their direct impact on SC generation was investigated. This work represents another step towards gas-filled fiber-based coherent sources, which is set to have a major impact on applications spanning from DUV to mid-IR.

GLS and GLSSe ultrafast laser inscribed waveguides for mid-IR supercontinuum generation

Using the ultrafast laser inscription technique, buried channel waveguides have been fabricated in gallium lanthanum sulfide and gallium lanthanum sulfide selenide glasses to demonstrate the suitability of the materials for supercontinuum generation in the mid-IR. Supercontinuum generation was performed using 100 femtosecond pump pulses with micro-Joule pulse energies and a center wavelength of 4.6 µm, which is in the anomalous dispersion regime for these waveguides. Under such pump conditions, supercontinuum was obtained covering a 25-dB-bandwidth of up to 6.1 um with a long-wavelength edge of 8 µm. To our knowledge, this represents the broadest and the longest-wavelength IR supercontinuum generated from an ultrafast laser inscribed waveguide to date.

Chalcogenide W-type co-axial optical fiber for broadband highly coherent mid-IR supercontinuum generation

A numerical investigation on chalcogenide W-type co-axial optical fiber structures is reported for broadband highly coherent mid-IR supercontinuum generation. The structural parameters of the optical fiber were optimized to achieve small normal dispersion in a broad spectral range of the mid-IR region. The W-type optical fiber structure possesses a flat chromatic dispersion profile with the flatness of the dispersion variation of ±2.45 ps/nm/km within the spectral range of 4.9–12.6 μm. A coherent mid-IR supercontinuum spectrum spanning 2.28 to 15.52 μm at the −40 dB level is obtained using a 4 cm long W-type optical fiber when it pumped by a 200 fs laser pulse with a peak power of 10 kW at 7.0 μm. Broadband coherent mid-infrared supercontinuum sources have potential applications in frequency metrology, nonlinear microscopy, non-destructive testing, optical coherence tomography, and molecular spectroscopy.

Mid-IR supercontinuum generation in a single-mode ZBLAN fiber by erbium-doped fiber laser

We present a compact broadband supercontinuum (SC) generation in a single-mode fluorozirconate ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber pumped by femtosecond pulses from an erbium-doped fiber laser (EDFL). The femtosecond seed pulses are generated through passive mode locking using carbon-nanotubes-based saturable absorber in EDFL ring cavity. An SC spectrum spanning from 1100 to 3200 nm with a spectral flatness of <8 dB has been obtained successfully from a single-mode ZBLAN fiber. A piecewise linear relationship of SC spectrum bandwidth with input pulse power is observed.

Ge22As20Se58 glass ultrafast laser inscribed waveguides for mid-IR integrated optics

Ultrafast laser inscription has been used to produce channel waveguides in Ge22As20Se58 glass (GASIR-1, Umicore N.V). The mode field diameter and waveguide losses at 2.94 μm were measured along with the waveguide dispersion in the 1 to 4.5 μm range, which is used to estimate the zero-dispersion wavelength. Z-scan measurements of bulk samples have also been performed to determine the nonlinear refractive index. Finally, mid-IR supercontinuum generation has been shown when pumping the waveguides with femtosecond pulses centered at 4.6 μm. Supercontinuum spanning approximately 4 μm from 2.5 to 6.5 μm was measured which, to the best of the authors’ knowledge, represents the broadest and the deepest IR supercontinuum from an ultrafast laser inscribed waveguide to date. This work, combined with the long wavelength transmission of GASIR-1 up to 15 μm, paves the way for realizing further ultrafast laser inscribed waveguide devices in GASIR-1 for mid-IR integrated optics applications.

Tunable Raman gain in mid-IR waveguides

By means of theoretical analysis and numerical simulations, we show a tunable Raman gain which may find applications in a variety of fields, ranging from mid-IR fiber Raman lasers and supercontinuum generation to ultra-wideband slow-light Raman-based devices. In particular, by analyzing the interplay among Raman gain, dispersion, and self-steeping (SE) in a full model of modulation instability (MI) in waveguides, we show that there exists a range of pump powers where the gain spectrum is not only dominated by the Raman contribution, but also, most strikingly, it can be fine-tuned at will. We present analytical and numerical results, in excellent agreement, confirming this observation.

Ultra-Wide mid-IR supercontinuum generation in As2S3 photonic crystal fiber by rods filling technique

In this paper, we study fluid infiltration approach and rod filling technique for dispersion engineering of a photonic crystal fiber (PCF) composed of As2S3-Chalcogenide glass. The numerical results based on finite difference time domain method reveal that when air holes of the innermost ring in a PCF are infiltrated with suitable fluids or filled by glass rods, ultra-flattened near-zero dispersions with high nonlinearities will be achieved over a wide mid-IR wavelength range. The simulations demonstrate that when a 100 fs input optical pulse of 20 kW peak power and central wavelength of 2.5 μm is launched into a 10 mm length of the As2S3 PCF filled by PBG-08 rods, a ripple-free spectral broadening as wide as 9 μm from 1 to 10 μm can be obtained which is used as a suitable source for Mid-IR applications in molecular fingerprint region such as medical diagnosis of diseases, and drug detection.

Solid Tellurite Optical Fiber Based on Stack-and-Draw Method for Mid-Infrared Supercontinuum Generation

Broadband, high-power mid-infrared (mid-IR) sources are critical for many applications. Compared to alternatives such as fluorides and chalcogenides, tellurite fibers are more robust and can handle much higher power. Tellurite fibers also have high nonlinearity and a material zero dispersion close to 2 µm, making them ideal for nonlinear processes pumped by Tm-doped silica fiber lasers. In this work, we have demonstrated solid tellurite fibers fabricated by a stack-and-draw process and investigated their potential for broadband mid-IR supercontinuum generation. We have identified that fibers with low dispersion are beneficial and that low residual hydroxyl (OH) is critical for broadband mid-IR supercontinuum generation in tellurite fibers pumped at ~2 µm.

On the possibility of mid-IR supercontinuum generation in As-Se-Te/As-S core/clad fibers with all-fiber femtosecond pump source

We propose and optimize theoretically a supercontinuum (SC) laser source in the mid-IR based on using As-Se-Te/As-S core/clad step-index fibers and a femtosecond all-fiber laser system at 2μm. Numerically simulated spectra extending from ~1μm to >8μm are demonstrated for pump energy of order 100pJ in a fiber with a core diameter of 2μm. To the best of our knowledge, the possibility of such long-wavelength spectral conversion of pump pulses at the wavelength of 2μm in optical fibers is demonstrated for the first time. The theoretical calculations are performed on the base of real low loss step-index As-Se-Te/As-S glass fibers with various core-clad diameter ratios.