Showing papers on "Supercontinuum published in 2003"
TL;DR: Broadband noise on supercontinuum spectra generated in microstructure fiber is shown to lead to amplitude fluctuations as large as 50% for certain input laser pulse parameters, finding good quantitative agreement over a range of input-pulse energies and chirp values.
Abstract: Broadband noise on supercontinuum spectra generated in microstructure fiber is shown to lead to amplitude fluctuations as large as 50% for certain input laser pulse parameters. We study this noise using both experimental measurements and numerical simulations with a generalized stochastic nonlinear Schrodinger equation, finding good quantitative agreement over a range of input-pulse energies and chirp values. This noise is shown to arise from nonlinear amplification of two quantum noise inputs: the input-pulse shot noise and the spontaneous Raman scattering down the fiber.
377 citations
TL;DR: In this article, it was shown that the high spatio-temporal localization of the light field in the filament, which enables the supercontinuum generation, is sustained due to the dynamic transformation of light field on the whole transverse scale of the beam, including its edges.
Abstract: We present experimental and theoretical results on white-light generation in the filamentation of a high-power femtosecond laser pulse in water and atmospheric air. We have shown that the high spatio-temporal localization of the light field in the filament, which enables the supercontinuum generation, is sustained due to the dynamic transformation of the light field on the whole transverse scale of the beam, including its edges. We found that the sources of the supercontinuum blue wing are in the rings, surrounding the filament, as well as at the back of the pulse, where shock-wave formation enhanced by self-steepening takes place. We report on the first observation and demonstration of the interference of the supercontinuum spectral components arising in the course of multiple filamentation in a terawatt laser pulse. We demonstrate that the conversion efficiency of an initially narrow laser pulse spectrum into the supercontinuum depends on the length of the filament with high intensity gradients and can be increased by introducing an initial chirp.
246 citations
TL;DR: Generation of 3.8-fs pulses with energies of up to 15 microJ from a supercontinuum produced in two cascaded hollow fibers is demonstrated through a closed-loop combination of a spatial light modulator for adaptive pulse compression and spectral-phase interferometry for direct electric-field reconstruction (SPIDER) measurements as feedback signal.
Abstract: We demonstrate generation of 3.8-fs pulses with energies of up to 15 μJ from a supercontinuum produced in two cascaded hollow fibers. Ultrabroadband dispersion compensation was achieved through a closed-loop combination of a spatial light modulator for adaptive pulse compression and spectral-phase interferometry for direct electric-field reconstruction (SPIDER) measurements as feedback signal.
226 citations
TL;DR: The generation of an octave-spanning supercontinuum inside a short piece of a highly nonlinear fiber inside a stretched pulse amplifier and self-referencing detection of the carrier-envelope phase evolution with an f-to-2f interferometer is demonstrated.
Abstract: We present an improved design of an amplified Er:fiber laser system for the generation of intense femtosecond pulses. By properly controlling the influence of optical nonlinearities inside a stretched pulse amplifier, the spectrum is broadened to over 100 nm. The pulses are recompressed to 65 fs. A linearly polarized output of 110 mW is obtained at 67 MHz repetition rate. As a first application, we report the generation of an octave-spanning supercontinuum inside a short piece of a highly nonlinear fiber. Self-referencing detection of the carrier-envelope phase evolution with an f-to-2f interferometer is demonstrated.
191 citations
TL;DR: In this paper, the competition between femtosecond laser pulse induced optical breakdown and filamentation in condensed matter is studied both experimentally and numerically using water as an example, and the coexistence of filamentation and breakdown is observed under tight focusing conditions.
Abstract: The competition between femtosecond laser pulse induced optical breakdown and femtosecond laser pulse filamentation in condensed matter is studied both experimentally and numerically using water as an example. The coexistence of filamentation and breakdown is observed under tight focusing conditions. The development of the filamentation process from the creation of a single filament to the formation of many filaments at higher pulse energy is characterized systematically. In addition, strong deflection and modulation of the supercontinuum is observed. They manifest themselves at the beginning of the filamentation process, near the highly disordered plasma created by optical breakdown at the geometrical focus.
178 citations
TL;DR: An all-fiber supercontinuum source based on a passively mode-locked erbium fiber laser and a small-effective-area, germanium-doped silica fiber is presented, generating more than an octave of bandwidth.
Abstract: We present an all-fiber supercontinuum source based on a passively mode-locked erbium fiber laser and a small-effective-area, germanium-doped silica fiber. The parallels between this system and the continuum generated in microstructured fibers with 800-nm pulses are discussed, and the role of dispersion is investigated experimentally. We construct a hybrid fiber by fusion splicing lengths of different-dispersion fiber together, generating more than an octave of bandwidth.
176 citations
TL;DR: In this paper, the effect of varying the dispersion on the pulsed continuum and noise effects in the continuous-wave continuum has been investigated using a nonlinear Schrodinger-equation model.
Abstract: Supercontinuum generation in a highly nonlinear, dispersion-shifted fiber at 1550 nm is discussed. Spectrum generation under both pulsed and continuous-wave conditions is considered. With a few meters of highly nonlinear, dispersion-shifted fiber and a femtosecond erbium fiber laser, an octave-spanning supercontinuum is demonstrated. Kilometer lengths of nonlinear fiber pumped by a continuous-wave Raman fiber laser are shown to generate a continuum with a bandwidth greater than 247 nm. A nonlinear Schrodinger-equation model is used to investigate the effect of varying the dispersion on the pulsed continuum and noise effects in the continuous-wave continuum.
159 citations
TL;DR: In this paper, the authors present experimental results on supercontinuum generation in a highly birefringent microstructured fiber and investigate the impact of pump wavelength and pulse duration on the continuum and use the results to generate an ultrabroadband continuum.
Abstract: We present experimental results on supercontinuum generation in a highly birefringent microstructured fiber We show that such a fiber offers clear advantages for continuum generation over weakly birefringent fibers In particular, the polarization is preserved along the fiber for all the spectral components Furthermore, the two eigenpolarizations exhibit different dispersion characteristics, which provide a convenient way of tuning the properties of the generated continuum We investigate the impact of the pump wavelength and pulse duration on the continuum and use the results to generate an ultrabroadband continuum extending from 400 to 1750 nm
150 citations
TL;DR: A comparison of experimental results with numerical simulations suggests that the primary source of coherence degradation is the technical noise-induced fluctuations in the injected peak power.
Abstract: The phase coherence of supercontinuum generation in microstructure fiber is quantified by performing a Young’s type interference experiment between independently generated supercontinua from two separate fiber segments. Analysis of the resulting interferogram yields the wavelength dependence of the magnitude of the mutual degree of coherence, and a comparison of experimental results with numerical simulations suggests that the primary source of coherence degradation is the technical noise-induced fluctuations in the injected peak power.
148 citations
TL;DR: This work quantifies the noise amplification factor and its dependence on the supercontinuum wavelength and on the energy and duration of the input pulse.
Abstract: Supercontinua generated by femtosecond pulses launched in microstructure fiber can exhibit significant low-frequency (<1-MHz) amplitude noise on the output pulse train. We show that this low-frequency noise is an amplified version of the amplitude noise that is already present on the input laser pulse train. Through both experimental measurements and numerical simulations, we quantify the noise amplification factor and its dependence on the supercontinuum wavelength and on the energy and duration of the input pulse. Interestingly, the dependence differs significantly from that of the broadband white-noise component, which arises from amplification of the input laser shot noise.
140 citations
TL;DR: In this paper, the nonlinear propagation of ultrashort pulses in a microstructured fiber is experimentally investigated, and the output spectrum is made of a broad infrared supercontinuum coexisting with a sharp and very intense blue peak that takes up to 24% of the input power.
Abstract: The nonlinear propagation of ultrashort pulses in a microstructured fiber is experimentally investigated. By working around 800 nm, in the anomalous dispersion region, clear evidence of pulse break-up and soliton propagation is obtained. This is consistent with the recently suggested mechanism of spectral broadening based upon the fission of higher order solitons into red-shifted fundamental solitons and blue-shifted dispersion waves. When 190-fs pulses at high input intensities are used, the output spectrum is made of a broad infrared supercontinuum coexisting with a sharp and very intense blue peak that takes up to 24% of the input power. We tentatively propose an explanation of this effect by invoking pulse-trapping phenomena controlled by the group-velocity matching of infrared and visible pulses.
TL;DR: In this article, the femto and picosecond pulses delivered by the amplifier are coupled into two different photonic crystal fibers and obtained the highest output power of 5 W with a spectrum ranging from below 500 nm up to above 1800 nm.
TL;DR: The generation of symmetrical supercontinuum of over 40 nm in the 1.55 m region is demonstrated by injecting 1562 nm, 2.2 ps, 40 GHz optical pulses into a 200 m-long, dispersion-flattened polarization-maintaining photonic crystal fiber.
Abstract: We demonstrate the generation of symmetrical supercontinuum of over 40 nm in the 1.55 m region (1540 - 1580 nm) by injecting 1562 nm, 2.2 ps, 40 GHz optical pulses into a 200 m-long, dispersion-flattened polarization-maintaining photonic crystal fiber. The chromatic dispersion and dispersion slope of the fiber at 1.55 m are -0.23 ps/km/nm and 0.01 ps/km/nm2, respectively. This is the first report of 1.55 m band supercontinuum generation in a dispersion-flattened and polarization-maintaining photonic crystal fiber.
TL;DR: It is shown by detailed spectral analysis that this supercontinuum originates from a preliminary four-wave mixing process with multimode phase matching and subsequent double-cascade stimulated Raman scattering and is transversely single mode as a result of Raman-induced mode competition.
Abstract: We report the experimental generation, simply by use of a subnanosecond microchip laser at 532 nm and a conventional dispersion-shifted fiber, of a supercontinuum that spans more than 1100 nm. We show by detailed spectral analysis that this supercontinuum originates from a preliminary four-wave mixing process with multimode phase matching and subsequent double-cascade stimulated Raman scattering and is transversely single mode as a result of Raman-induced mode competition. This technique is believed to be the simplest configuration that allows one to generate a stable supercontinuum.
TL;DR: In contrast to the standard scenario, where arrest of self-focusing collapse by multiphoton absorption and plasma defocusing are viewed as imposing a limit to supercontinuum broadening, it is shown that linear chromatic dispersion also plays a major role.
Abstract: Based on simulations of femtosecond pulse propagation in water we elucidate the physical factors that limit the attainable spectral extent of supercontinuum generation in bulk media. In contrast to the standard scenario, where arrest of self-focusing collapse by multiphoton absorption and plasma defocusing are viewed as imposing a limit to supercontinuum broadening, we show that linear chromatic dispersion also plays a major role. This insight provides an intuitive explanation of the observed band gap dependence of the attainable supercontinuum generation in condensed media.
TL;DR: In this paper, the supercontinuum generated by the terawatt femtosecond laser of the Teramobile system was used for the first time in the near-infrared.
Abstract: Lidar signals were obtained for the first time in the near-infrared using the supercontinuum generated by the terawatt femtosecond laser of the Teramobile system. A signal up to 4 km in altitude, in the band 1–1.7 μm, was collected using a 2 m astronomical telescope. We observed a 10-fold enhancement of the infrared signal backscattered from the atmosphere compared with that expected using a previously measured laboratory spectrum. This suggests a more efficient frequency conversion into the infrared (typically 7% into the 1–1.5 μm band) under long-distance propagation conditions.
TL;DR: In this article, the relative intensity noise as a function of wavelength across the supercontinuum is measured over a wide range of input pulse parameters, and experimental results and simulations are shown to be in good quantitative agreement.
Abstract: Broadband supercontinuum spectra are generated in a microstructured fiber using femtosecond laser pulses. Noise properties of these spectra are studied through experiments and numerical simulations based on a generalized stochastic nonlinear Schrodinger equation. In particular, the relative intensity noise as a function of wavelength across the supercontinuum is measured over a wide range of input pulse parameters, and experimental results and simulations are shown to be in good quantitative agreement. For certain input pulse parameters, amplitude fluctuations as large as 50% are observed. The simulations clarify that the intensity noise on the supercontinuum arises from the amplification of two noise inputs during propagation – quantum-limited shot noise on the input pulse, and spontaneous Raman scattering in the fiber. The amplification factor is a sensitive function of the input pulse parameters. Short input pulses are critical for the generation of very broad supercontinua with low noise.
TL;DR: In this paper, the nonlinear propagation of femtosecond pulses and supercontinuum generation in photonic crystal fibers made from glasses with high nonlinear refractive indices are theoretically investigated without the use of the slowly varying envelope approximation.
Abstract: The nonlinear propagation of femtosecond pulses and supercontinuum generation in photonic crystal fibers made from glasses with high nonlinear refractive indices are theoretically investigated without the use of the slowly varying envelope approximation. For specifically designed photonic crystal fibers with two zero-dispersion wavelengths, we predict supercontinuum generation due to nonsolitonic radiation emitted by the solitons on the shorter- and on the longer-wavelength sides. The physical mechanism and the peculiarities of such radiation on both spectral sides are studied and explained by the specific phase-matching relations between the solitons and their associated radiation.
TL;DR: In this paper, the authors describe a process of nonlinear generation of very high-order UV modes by pumping such fibers with 100 fs Ti:sapphire pulses through a mechanism distinct from supercontinuum generation.
Abstract: Cobweb microstructured optical fibers are often strongly multimode in the visible and near infrared regions. This may lead to a number of intermodally phase-matched nonlinear processes. Here we describe a process of nonlinear generation of very high-order UV modes by pumping such fibers with 100 fs Ti:sapphire pulses. Wavelengths as short as 260 nm are generated through a mechanism distinct from supercontinuum generation.
TL;DR: In this paper, the onset of supercontinuum generation in a photonic crystal fiber is investigated experimentally and numerically as a function of pump wavelength and intensity with 100-fs pulses Soliton formation is found to be the determining factor in the initial step.
Abstract: The onset of supercontinuum generation in a photonic crystal fiber is investigated experimentally and numerically as a function of pump wavelength and intensity with 100-fs pulses Soliton formation is found to be the determining factor in the initial step The formation and behavior of a blueshifted, nonsolitonic component, emitted as the soliton evolves towards the stable regime, is investigated and the role of phase matching through higher-order dispersion is highlighted Good agreement between experiments and simulations is obtained
TL;DR: The temporal and spectral profiles of supercontinuum radiation generated from a photonic crystal fiber are evaluated with a polarization-gate frequency-resolved optical gating technique and a stimulated Raman signal of cyclohexane is observed as an induced absorption signal with an instantaneous response.
Abstract: The temporal and spectral profiles of supercontinuum radiation generated from a photonic crystal fiber are evaluated with a polarization-gate frequency-resolved optical gating technique. The supercontinuum is then applied to coherent inverse Raman spectroscopy. A stimulated Raman signal of cyclohexane is observed as an induced absorption signal with an instantaneous response. The Raman signal has a peak at a slight negative delay time, which is explained by perturbed Raman-induced coherence.
TL;DR: In this article, a supercontinuum, nearly flat spectrum covering the S, C and L transmission bands defined by the International Telecommunication Union is obtained by pumping a conventional nonzero dispersion-shifted fiber with a continuous-wave Raman fiber laser tuned to the region of small anomalous dispersion.
TL;DR: In this article, a combination of a passively mode-locked Nd:YVO 4 pump laser with 10 ps pump pulse duration at 1064 nm and a dispersion-adapted air-silica microstructured fiber generates supercontinuum radiation with an average power of 2.4 W in a spectral range from 700 to 1600 nm.
TL;DR: In this article, a theoretical study of supercontinuum generation in photonic crystal fiber and its application to pulse compression is presented, where the evolution of the spectrum can be divided into three stages: initial broadening below a certain threshold propagation distance, dramatic broadening to a super-continuum at a threshold distance, and saturation of the spectral width on propagation.
Abstract: A theoretical study of supercontinuum generation in photonic crystal fiber and its application to pulse compression is presented. The evolution of the spectrum can be divided into three stages: initial broadening below a certain threshold propagation distance, dramatic broadening to a supercontinuum at a threshold distance, and, finally, saturation of the spectral width on propagation. It is found that the group delay and group-delay dispersion of the supercontinum are sensitive to the input pulse peak power after further propagation at the third stage. Fluctuations from the input pulse are amplified and translated into fluctuations and time shift of the compressed pulses. There exists an optimum compressed distance at which compressed pulses with negligible fluctuation and time shift can be obtained.
TL;DR: In this article, the authors numerically study supercontinuum generation in photonic crystal fibers pumped with low-power 30-ps pulses close to the zero dispersion wavelength, and show how the efficiency can be significantly improved by designing the dispersion to allow widely separated spectral lines generated by degenerate four-wave mixing directly from the pump to broaden and merge, resulting in a 800nm wide super-continuum.
Abstract: We numerically study supercontinuum generation in photonic crystal fibers pumped with low-power 30-ps pulses close to the zero dispersion wavelength We show how the efficiency is significantly improved by designing the dispersion to allow widely separated spectral lines generated by degenerate four-wave mixing directly from the pump to broaden and merge, resulting in a 800-nm-wide supercontinuum Full-vectorial plane-wave calculations show that a cobweb photonic-crystal-fiber structure can realize the dispersion profiles under consideration The predicted efficient supercontinuum generation is more robust and survives fiber imperfections modeled as random fluctuations of the dispersion coefficients along the fiber
TL;DR: In this paper, the profile of single mode fibers over a flame generates tapered fibers with waist diameters of approximately 1-3 micrometers and waist lengths of up to 90 mm.
Abstract: Drawing single mode fibers over a flame generates tapered fibers with waist diameters of approximately 1–3 micrometers and waist lengths of up to 90 mm. We demonstrate how the profile of such tapered fibers can be determined. We then characterize the white light that is generated in a variety of such fibers, showing its dependence on waist length and waist diameter and demonstrating its dependence on pulse parameters such as pulse duration, spectral position, and pulse power. A comparison with theoretical calculations using a nonlinear Schrodinger equation model including Kerr nonlinearities is given. Furthermore, we show XFROG spectrograms of the pulses propagating through tapered fibers, confirming the model of soliton splitting in the anomalous dispersion regime.
TL;DR: In this article, a change in the spectrum and the energy distribution of the light field of a high-power femtosecond laser pulse is studied numerically in a broad range of its spatial scales.
Abstract: A change in the spectrum and the energy distribution of the light field of a high-power femtosecond laser pulse is studied numerically in a broad range of its spatial scales. It is shown that the effect of filamentation, the generation of a supercontinuum and conical emission, the formation of a ring structure in the distribution of the pulse energy and other effects observed during the propagation of the laser pulse in air are caused by the nonlinear-optical transformation of the light field in the region with dimensions exceeding substantially the transverse size of the filament. The pulse filamentation is accompanied by the redistribution of power in its cross section. The spatio — temporal characteristics of emission calculated for femtosecond laser systems are in quantitative agreement with the experimental data.
Proceedings Article•
06 Jun 2003TL;DR: It is found that the group delay and group-delay dispersion of the supercontinum are sensitive to the input pulse peak power after further propagation at the third stage.
TL;DR: In this article, it was shown that the initial phase modulation of the pulse results in a shift of the beginning of the filament from the output aperture of the laser system and in a significant increase in the filament length.
Abstract: The possibility of controlling the processes of filamentation and generation of a supercontinuum during propagation of a high-power femtosecond laser pulse in air is investigated. Using a numerical simulation, it is shown that the initial phase modulation of the pulse results in a shift of the beginning of the filament from the output aperture of the laser system and in a significant increase in the filament length. The efficiency of the generation of the short-wavelength part of the supercontinuum in a pulse with a negative phase modulation is more than two orders of magnitude higher than for a pulse with a limited spectrum.
TL;DR: An all- fiber diode-pumped Erbium-fiber oscillator-amplifier system as a source for supercontinuum generation in a photonic crystal fiber at 1560 nm observed a more than octave-spanning supercontinuity from 400 nm to beyond 1750 nm.
Abstract: We report an all-fiber diode-pumped Erbium-fiber oscillator-amplifier system as a source for supercontinuum generation in a photonic crystal fiber at 1560 nm. The passively mode-locked oscillator-amplifier system provides linearly polarized output pulses of 60 fs and an average output power of 59 mW at a repetition rate of 59.1 MHz. The laser pulses were launched into an extruded SF6-fiber for generation of an ultra-broadband supercontinuum. The evolution of the supercontinuum as a function of launched pulse energy was investigated. With pulse energies of about 200 pJ we observed a more than octave-spanning supercontinuum from 400 nm to beyond 1750 nm.