Search

We reviewed the tellurite glass purification studies performed over the last 20 years, in particular dealing with the mid‐infrared (mid‐IR) transmission performances. Best results are obtained under rich O2 atmosphere with platinum crucibles although Gibbs energy calculations show that other crucibles material are possible such as gold or alumina. From the point of view of the thermodynamics of involved oxidation reactions only, we identified the suitable conditions based on Gibbs energy calculations to be a synthesis temperature set above 900 K and a O2 pressure around 105 Pa. The performances of the different purification techniques were also compared. Finally, we analyzed the tellurite fibers recently optimized for mid‐IR which present low attenuation up to 4 µm allowing supercontinuum generation up to 5 µm. [ABSTRACT FROM AUTHOR]

Highlights: [•] Fabrication of low-OH content and low-loss tellurite optical fibers. [•] Incorporation of fluoride ions makes tellurite fibers transparent up to 4μm. [•] 2000nm bandwidth supercontinuum in suspended core microstructured tellurite fiber. [Copyright &y& Elsevier]

We present both a theoretical description and experimental observation of the nonlinear mutual interactions between a pair of copropagative breathers in the framework of the focusing one-dimensional nonlinear Schrödinger equation. As a general case, we show that the resulting bound state of breathers exhibits moleculelike behavior with quasiperiodic oscillatory dynamics (i.e., internal coherent interactions and pulsations), while for commensurate conditions the molecule oscillations become exactly periodic. Our theoretical model is confirmed by an experimental observation of shaped moleculelike breather light waves propagating in a nearly conservative optical fiber system. Our work sheds new light on the existence of localized wave structures and recurrence dynamics beyond the multisoliton complexes. [ABSTRACT FROM AUTHOR]

We present a simultaneous study of the phase properties of rational breather waves generated in a water wave tank and in an optical fiber platform, namely, the Peregrine soliton and related second-order solution. Our analysis of experimental wave measurements makes use of standard demodulation and filtering techniques in hydrodynamics and more complex phase retrieval techniques in optics to quantitatively confirm analytical and numerical predictions. We clearly highlight a characteristic phase shift that is a multiple of π between the central pulsed part and the continuous background of rational breathers at their maximum compression. Moreover, we reveal a large longitudinal phase shift across the point of maximum compression. [ABSTRACT FROM AUTHOR]

The data recorded in optical fiber and in hydrodynamic experiments reported the pioneering observation of nonlinear waves with spatiotemporal localization similar to the Peregrine soliton are examined by using nonlinear spectral analysis. Our approach is based on the integrable nature of the one-dimensional focusing nonlinear Schrödinger equation (1D-NLSE) that governs at leading order the propagation of the optical and hydrodynamic waves in the two experiments. Nonlinear spectral analysis provides certain spectral portraits of the analyzed structures that are composed of bands lying in the complex plane. The spectral portraits can be interpreted within the framework of the so-called finite gap theory (or periodic inverse scattering transform). In particular, the number N of bands composing the nonlinear spectrum determines the genus g=N-1 of the solution that can be viewed as a measure of complexity of the space-time evolution of the considered solution. Within this setting the ideal, rational Peregrine soliton represents a special, degenerate genus 2 solution. While the fitting procedures previously employed show that the experimentally observed structures are quite well approximated by the Peregrine solitons, nonlinear spectral analysis of the breathers observed both in the optical fiber and in the water tank experiments reveals that they exhibit spectral portraits associated with more general, genus 4 finite-gap NLSE solutions. Moreover, the nonlinear spectral analysis shows that the nonlinear spectrum of the breathers observed in the experiments slowly changes with the propagation distance, thus confirming the influence of unavoidable perturbative higher-order effects or dissipation in the experiments. [ABSTRACT FROM AUTHOR]

The modulation instability (MI) is responsible for the disintegration of a regular nonlinear wave train and can lead to strong localizations in the form of rogue waves. This mechanism has been studied in a variety of nonlinear dispersive media, such as hydrodynamics, optics, plasma, mechanical systems, electric transmission lines, and Bose-Einstein condensates, while its impact on applied sciences is steadily growing. It is well-known that the classical MI dynamics can be triggered when a pair of small-amplitude sidebands are excited within a particular frequency range around the main peak frequency. That is, a three-wave system, consisting of the carrier wave together with a pair of unstable sidebands, is usually adopted to initiate the wave focusing process in a numerical or laboratory experiment. Breather solutions of the nonlinear Schrödinger equation (NLSE) revealed that MI can generate much more complex localized structures, beyond the three-wave system initialization approach or by means of a continuous spectrum. In this work, we report an experimental study for deep-water surface gravity waves asserting that a MI process can be triggered by a single unstable sideband only, and thus, initialized from a two-wave process when including the contribution of the peak frequency. The experimental data are validated against fully nonlinear hydrodynamic numerical wave tank simulations and show very good agreement. The long-term evolution of such unstable wave trains shows a distinct shift in the recurrent Fermi-Pasta-Ulam-Tsingou focusing cycles, which are captured by the NLSE and fully nonlinear hydrodynamic simulations with some distinctions., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

We present theoretical and experimental evidence of high-gain far-detuned nonlinear frequency conversion, extending towards both the visible and the mid-infrared, in a few-mode graded-index silica fiber pumped at 1.064  μ m , and more specifically achieving gains of hundreds of dB per meter below 0.65  μ m and beyond 3.5  μ m . Interestingly, our findings highlight the potential of graded-index fibers for enabling high-gain wavelength conversion into the strong-loss spectral region of silica. Such advancements require an accurate interpretation of intramodal and intermodal four-wave mixing processes., (© 2024. The Author(s).)

We investigate the spectral phase characteristics of dual-pumped Kerr frequency combs generated in a bichromatic Brillouin fiber laser architecture with normal dispersion, producing square-like pulse profiles. Using a pulse shaper, we measure the relative phase between the pump Stokes and adjacent lines, revealing a symmetric phase relationship. Our results highlight good phase coherence of the comb. By manipulating spectral amplitudes and phases, we demonstrate the transformation into various optical waveforms. The stability of our low-noise frequency comb ensures reliable performance in practical settings.

We conduct numerical and experimental investigations on Kerr comb generation in a nonlinear and non-reciprocal fiber cavity by leveraging both stimulated Brillouin backscattering and cascaded four-wave mixing. By engineering the net cavity dispersion to be either normal or anomalous, we enable the formation of diverse patterns and localized structures in the cavity field. The comb's properties depend crucially on the mismatch between the frequency spacing of the bichromatic pump and the free spectral range of the Brillouin laser cavity in both cases. Particularly, in the anomalous regime, adjusting this parameter yields coherent, stable frequency combs in the modulation instability regime. This allows control and expansion of the spectral bandwidth up to 2 THz in normal dispersion and to 6 THz under anomalous net dispersion. This versatile and easily reconfigurable method holds potential for applications in high-speed communications and microwave synthesis.

We report on the experimental development of short-tapered chalcogenide-glass rods for mid-infrared supercontinuum generation. Multi-octave spectral broadening of femtosecond laser pulses is demonstrated from 1.6 to 15.6 µm in a 5-cm-long tapered Ge 20 Se 70 Te 10 rod with a waist diameter of 25 µm. Despite the multimode nature of the optical waveguide used, this work clearly shows the potential of such simple post-processed rods for advancing fiber SC sources with infrared glasses, thereby unlocking new possibilities in terms of coupling efficiency, spectral coverage, and output power.

We experimentally demonstrate a stabilized single-frequency Brillouin fiber laser operating at 1.06 µm by means of a passive highly nonlinear fiber (HNLF) ring cavity combined with a phase-locking loop scheme. The stimulated Brillouin scattering efficiency is first investigated in distinct single-mode germanosilicate core fibers with increasing G e O 2 content. The most suitable fiber, namely, 21 mol.% G e O 2 core fiber, is used as the Brillouin gain medium in the laser cavity made with a 15-m-long segment. A Stokes lasing threshold of 140 mW is reported. We also show significant linewidth narrowing (below 1 kHz) as well as frequency noise reduction compared to that of the initial pump in our mode-hop free Brillouin fiber laser.

Adaptative objects based on shape-memory materials are expected to significantly impact numerous technological sectors including optics and photonics. In this work, we demonstrate the manufacturing of shape-memory optical fibers from the thermal stretching of additively manufactured preforms. First, we show how standard commercially-available thermoplastics can be used to produce long continuously-structured microfilaments with shape-memory abilities. Shape recovery as well as programmability performances of such elongated objects are assessed. Next, we open the way for light-guiding multicomponent fiber architectures that are able to switch from temporary configurations back to user-defined programmed shapes. In particular, we show that distinct designs of fabricated optical fibers can maintain efficient light transmission upon completion of multiple temperature-triggered bending/straightening cycles. Such fibers are also programmed into more complex shapes including coils or near 180 ° curvatures for delivering laser light around obstacles. Finally, a shape-memory exposed-core fiber is employed in fiber evanescent wave spectroscopy experiments to optimize the performance of the sensing scheme. We strongly expect that such actuatable fibers with light-guiding abilities will trigger exciting progress of unprecedented smart devices in the areas of photonics, electronics, or robotics., (© 2023. Springer Nature Limited.)

We report on the experimental and numerical observation of polarization modulation instability (PMI) in a nonlinear fiber Kerr resonator. This phenomenon is phased-matched through the relative phase detuning between the intracavity fields associated with the two principal polarization modes of the cavity. Our experimental investigation is based on a 12 m long fiber ring resonator in which a polarization controller is inserted to finely control the level of intracavity birefringence. Depending on the amount of birefringence, the temporal patterns generated via PMI are found to be either stationary or to exhibit a period-doubled dynamics. The experimental results are in good agreement with numerical simulations based on an Ikeda map for the two orthogonally polarized modes. This Letter provides new insights into the control of modulation instability in multimode Kerr resonators.

Germanosilicate glasses are substantial materials in fiber optic technology that have allowed the control of optical properties such as numerical aperture, photosensitivity, dispersion, nonlinearity, and transparency toward mid-infrared. Here, we investigate stimulated Brillouin scattering in single-mode germanosilicate core fibers with increasing GeO 2 content from 3.6 mol% up to 98 mol%. Our results reveal a wide Brillouin frequency shift tunability over more than 3 GHz with a strong decrease down to 7.7 GHz at high GeO 2 content owing to the low acoustic velocity, while the Brillouin linewidth significantly broadens up to 100 MHz beyond 50 mol% of GeO 2 content. In addition, large Brillouin gain up to 6.5 times larger than in standard silica fibers is also reported by means of a pump-probe experiment.

Simple photonic fiber-based workbenches have been able to emulate well-known nonlinear wave dynamics occurring in deep or shallow water conditions. Here, by investigating the nonlinear reshaping of a flat-top pulse upon propagation in an anomalous dispersive optical fiber, we observe that typical signatures of focusing dam break flows and Peregrine-like breather events can locally coexist in spontaneous pattern formations. The experimental measurements are in good agreement with our numerical predictions.

We demonstrate a polarized all-normal dispersion supercontinuum generated in a birefringent silica microstructured fiber spanning beyond 2.5 µm. To our knowledge, this is the spectra reaching the furthest in mid-infrared ever generated in normal dispersion silica fibers. The generation process was studied experimentally and numerically with 70 fs pump pulses operating at different wavelengths on short propagation distances of 48 mm and 122 mm. The all-normal operation was limited by the zero-dispersion wavelength at 2.56 µm and spectral broadening was stopped by OH absorption peak at 2.72 µm. We identified the asymmetry between propagation in both polarization axes and showed that pumping along a slow fiber axis is beneficial for a higher degree of polarization. Numerical simulations of the generation process conducted by solving the generalized nonlinear Schrödinger equation (NLSE) and coupled NLSEs system showed good agreement with experimental spectra.