Showing papers on "Supercontinuum published in 2004"
TL;DR: Photonic crystal fibres exhibiting endlessly single-mode operation and dispersion zero in the range 1040 to 1100 nm are demonstrated.
Abstract: Photonic crystal fibres exhibiting endlessly single-mode operation and dispersion zero in the range 1040 to 1100 nm are demonstrated. A sub-ns pump source at 1064 nm generates a parametric output at 732 nm with an efficiency of 35%, or parametric gain of 55 dB at 1315 nm. A broad, flat supercontinuum extending from 500 nm to beyond 1750 nm is also demonstrated using the same pump source.
507 citations
TL;DR: This work combines confocal microscopy using supercontinuum laser illumination and an interferometric detection technique to identify single nanoparticles of diameter below 10 nm and records the plasmon resonance of a single nanoparticle.
Abstract: We combine confocal microscopy using supercontinuum laser illumination and an interferometric detection technique to identify single nanoparticles of diameter below 10 nm. Spectral analysis of the signal allows us to record the plasmon resonance of a single nanoparticle. Our results hold great promise for fundamental studies of the optical properties of single metal clusters and for their use in biophysical applications.
505 citations
TL;DR: Submicron-diameter tapered fibres and photonic crystal fibre cores, both of which are silica-air waveguides with low dispersion at 532 nm, were made using a conventional tapering process to generate a single-mode supercontinuum broad enough to fill the visible spectrum without spreading far beyond it.
Abstract: Submicron-diameter tapered fibres and photonic crystal fibre cores, both of which are silica-air waveguides with low dispersion at 532 nm, were made using a conventional tapering process. In just cm of either waveguide, ns pulses from a low-power 532-nm microchip laser generated a single-mode supercontinuum broad enough to fill the visible spectrum without spreading far beyond it.
466 citations
TL;DR: A phase-locked frequency comb in the near infrared is demonstrated with a mode-locked, erbium-doped, fiber laser whose output is amplified and spectrally broadened in dispersion-flattened, highly nonlinear optical fiber to span from 1100 to >2200 nm.
Abstract: A phase-locked frequency comb in the near infrared is demonstrated with a mode-locked, erbium-doped, fiber laser whose output is amplified and spectrally broadened in dispersion-flattened, highly nonlinear optical fiber to span from 1100 to >2200 nm. The supercontinuum output comprises a frequency comb with a spacing set by the laser repetition rate and an offset by the carrier-envelope offset frequency, which is detected with the standard f-to-2f heterodyne technique. The comb spacing and offset frequency are phase locked to a stable rf signal with a fiber stretcher in the laser cavity and by control of the pump laser power, respectively. This infrared comb permits frequency metrology experiments in the near infrared in a compact, fiber-laser-based system.
384 citations
TL;DR: The supercontinuum generation in a highly nonlinear photonic crystal fiber with two closely lying zero dispersion wavelengths is demonstrated, which has high spectral density and is extremely independent of the input pulse over a wide range of input pulse parameters.
Abstract: We demonstrate supercontinuum generation in a highly nonlinear photonic crystal fiber with two closely lying zero dispersion wavelengths. The special dispersion of the fiber has a profound influence on the supercontinuum which is generated through self-phase modulation and phasematched four-wave mixing and not soliton fission as in the initial photonic crystal fibers. The supercontinuum has high spectral density and is extremely independent of the input pulse over a wide range of input pulse parameters. Simulations show that the supercontinuum can be compressed to ultrashort pulses.
305 citations
TL;DR: By combining simulation and experiments, the generation mechanism of the visible peak is explored and it is demonstrated that the blue peak is generated only when the input pulse is so strongly compressed that the short-wavelength tail of the spectrum includes the wavelength predicted for the dispersive wave.
Abstract: We study the nonlinear propagation of femtosecond pulses in the anomalous dispersion region of microstructured fibers, where soliton fission mechanisms play an important role. The experiment shows that the output spectrum contains, besides the infrared supercontinuum, a narrow-band 430-nm peak, carrying about one fourth of the input energy. By combining simulation and experiments, we explore the generation mechanism of the visible peak and describe its properties. The simulation demonstrates that the blue peak is generated only when the input pulse is so strongly compressed that the short-wavelength tail of the spectrum includes the wavelength predicted for the dispersive wave. In agreement with simulation, intensity-autocorrelation measurements show that the duration of the blue pulse is in the picosecond time range, and that, by increasing the input intensity, satellite pulses of lower intensity are generated.
285 citations
TL;DR: Rayleigh scattering spectra were obtained from individual single-walled carbon nanotubes with the use of a laser-generated visible and near-infrared supercontinuum and the results correlated with Raman scattering data on individual tubes.
Abstract: Rayleigh scattering spectra were obtained from individual single-walled carbon nanotubes with the use of a laser-generated visible and near-infrared supercontinuum. This diagnostic method is noninvasive and general for nanoscale objects. The approach permits clear identification of excited states in arbitrary metallic and semiconducting nanotubes. We analyzed spectral lineshapes in relation to the role of excitonic effects and correlated the results with Raman scattering data on individual tubes. The nanotube structure remained the same over distances of tens of micrometers. Small nanotube bundles retained distinct Rayleigh spectroscopic signatures of their component nanotubes, thus allowing the probing of nanotube-nanotube interactions.
249 citations
TL;DR: It is shown through numerical results that the novel microstructured optical fiber with small normal group-velocity dispersion and nearly zero dispersion slope offers the possibility of efficient supercontinuum generation in the telecommunication window using a few ps pulses.
Abstract: We propose a new structure of highly nonlinear dispersion-flattened (HNDF) photonic crystal fiber (PCF) with nonlinear coefficient as large as 30 W(-1)km(-1) at 1.55 microm designed by varying the diameters of the air-hole rings along the fiber radius. This innovative HNDF-PCF has a unique effective-index profile that can offer not only a large nonlinear coefficient but also flat dispersion slope and low leakage losses. It is shown through numerical results that the novel microstructured optical fiber with small normal group-velocity dispersion and nearly zero dispersion slope offers the possibility of efficient supercontinuum generation in the telecommunication window using a few ps pulses.
227 citations
TL;DR: It is determined that waveguides with asymmetrical cross sections provide the maximum possible nonlinearity, although only a small improvement over the symmetric case, and that for a specified waveguide shape the largest non linearity occurs for nearly the same core area in all cases.
Abstract: We investigate strong light confinement in high core-cladding index contrast waveguides with dimensions comparable to and smaller than the wavelength of incident light. We consider oval and rectangular cross sections and demonstrate that an optimal core size exists that maximizes the effective nonlinearity. We also determine that waveguides with asymmetrical cross sections provide the maximum possible nonlinearity, although only a small improvement over the symmetric case. Furthermore, we find that for a specified waveguide shape the largest nonlinearity occurs for nearly the same core area in all cases. Calculations of the dispersion for the optimal-size waveguide at a particular wavelength indicate that the group-velocity dispersion is normal. Ultimately, such designs could be used to develop low-power all-optical devices and to produce waveguides for ultra-low threshold nonlinear frequency generation such as supercontinuum generation.
222 citations
TL;DR: It is demonstrated that the simultaneous excitation of the microstuctured fiber in its normal and anomalous dispersion regimes using the fundamental and second harmonic signals of a passively Q-switched microchip laser leads to a homogeneous supercontinuum in the visible range.
Abstract: We report on the experimental demonstration of a white-light supercontinuum generation in normally dispersive singlemode air-silica microstructured fiber. We demonstrate that the simultaneous excitation of the microstuctured fiber in its normal and anomalous dispersion regimes using the fundamental and second harmonic signals of a passively Q-switched microchip laser leads to a homogeneous supercontinuum in the visible range. This pumping scheme allows the suppression of the cascaded Raman effect predominance in favor of an efficient spectrum broadening induced by parametric phenomena. A flat supercontinuum extended from 400 to 700 nm is achieved.
202 citations
TL;DR: In this article, a single attosecond pulse with a time-dependent ellipticity was generated by gating high-order harmonic emission with fields whose ellipticity varies rapidly with time.
Abstract: It is proposed that single attosecond pulses be generated by gating high-order harmonic emission with fields whose ellipticity varies rapidly with time. The laser pulse with a time-dependent ellipticity is created from two 5-fs laser pulses centered at 750 nm and separated by 5 fs. One of the laser pulses is left-circularly polarized and the other is right-circularly polarized. Numerical simulations show that when neon atoms are driven by such laser pulses, the generated high-order harmonic spectrum in the 25th to the 85th orders are a supercontinuum that corresponds to single attosecond pulses. A simple analytical expression is derived for estimating the high-harmonic radiation time.
TL;DR: The effects of cross-phase modulation between the solitons and dispersive waves present in a supercontinuum generated in microstructured fibers by sub-30 fs pulses are investigated.
Abstract: We investigate the effects of cross-phase modulation between the solitons and dispersive waves present in a supercontinuum generated in microstructured fibers by sub-30 fs pulses. Cross-phase modulation is shown to have a crucial importance as it extends the supercontinuum towards shorter wavelengths. The experimental observations are confirmed through numerical simulations.
TL;DR: Wideband of 1180-2100 nm, flatly broadened supercontinuum (SC) generation using highly nonlinear hybrid fibers and femtosecond fiber laser is presented.
Abstract: We present wideband of 1180-2100 nm, flatly broadened supercontinuum (SC) generation using highly nonlinear hybrid fibers and femtosecond fiber laser. Stable and smooth spectra without fine structure are demonstrated. The hybrid fibers are constructed by fusion splicing fibers with different properties. The SC spectra can be properly controlled by the optimal design of the hybrid fiber based on the numerical analysis. The generated SC pulse shows the low relative intensity noise (RIN).
TL;DR: It is demonstrated that with highly nonlinear dispersion shifted fiber (HNLF) fusion spliced directly to the amplifier output, the system generates a supercontinuum spectrum that spans more than an octave, with an average power 400 mW.
Abstract: We present a source of high power femtosecond pulses at 1550 nm with compressed pulses at the end of a single mode fiber (SMF) pigtail. The system generates 34 femtosecond pulses at a repetition rate of 46 MHz, with average powers greater than 400 mW. The pulses are generated in a passively modelocked, erbium-doped fiber laser, and amplified in a short, erbium-doped fiber amplifier. The output of the fiber amplifier consists of highly chirped picosecond pulses. These picosecond pulses are then compressed in standard single mode fiber. While the compressed pulses in the SMF pigtail do show a low pedestal that could be avoided with the use of bulk-optic compression, the desire to compress the pulses in SMF is motivated by the ability to splice the single mode fiber to a nonlinear fiber, for continuum generation applications. We demonstrate that with highly nonlinear dispersion shifted fiber (HNLF) fusion spliced directly to the amplifier output, we generate a supercontinuum spectrum that spans more than an octave, with an average power 400 mW. Such a high power, all-fiber supercontinuum source has many important applications including frequency metrology and bio-medical imaging.
TL;DR: Enhancement of the bandwidth of supercontinuum generated in microstructured fibers with a tailored dispersion profile is demonstrated experimentally and the underlying physics behind the broad continuum formation is discussed and analyzed in detail.
Abstract: Enhancement of the bandwidth of supercontinuum generated in microstructured fibers with a tailored dispersion profile is demonstrated experimentally. The fibers are designed to have two zero-dispersion wavelengths separated by more than 700 nm, which results in an amplification of two dispersive waves at visible and infrared wavelengths. The underlying physics behind the broad continuum formation is discussed and analyzed in detail. The experimental observations are confirmed through numerical simulations.
TL;DR: A novel chromatic confocal microscope system using supercontinuum white light generated from a photonic crystal fiber with effective depth scanning range of 7 microm and corresponding depth resolution to be less than 1 microm is reported.
Abstract: We report on a novel chromatic confocal microscope system using supercontinuum white light generated from a photonic crystal fiber. The chromatic aberration of a pair of singlet lenses is employed to focus the different spectral components of the supercontinuum at different depth levels. An effective depth scanning range of 7 μm is demonstrated. The corresponding depth resolution is measured to be less than 1 μm (FWHM).
TL;DR: Broadband asymmetric spectral broadening is reported experimentally and found in fairly good agreement with a numerical Schrödinger simulation including a phase-diffusion model for the partially coherent beam.
Abstract: The nonlinear propagation of a partially coherent continuous-wave laser beam in single-mode optical fibers is investigated both theoretically and experimentally, with a special attention to the zero-dispersion wavelength region where modulation instability is expected. Broadband asymmetric spectral broadening is reported experimentally and found in fairly good agreement with a numerical Schrodinger simulation including a phase-diffusion model for the partially coherent beam. This model shows in addition that the underlying spectral broadening mechanism relies not only on modulation instability but also on the generation of high-order soliton-like pulses and dispersive waves. The coherence degradation which results from these ultrafast phenomena is confirmed by autocorrelation measurement.
TL;DR: High-power supercontinua are demonstrated in highly nonlinear, dispersion-shifted fibers with a continuous-wave Raman fiber laser and the effect on continuum generation of parametric four-wave mixing coupled with the higher-order dispersion properties of the fiber is investigated.
Abstract: High-power supercontinua are demonstrated in highly nonlinear, dispersion-shifted fibers with a continuous-wave Raman fiber laser. Supercontinuum growth is experimentally studied under different combinations of fiber length and launch power to show output powers as high as 3.2 W and bandwidths greater than 544 nm. Modulation instability (MI) is observed to seed spectral broadening at low launch powers, and the interplay between MI and stimulated Raman scattering plays an important role in the growth of the continuum at high launch powers. The effect on continuum generation of parametric four-wave mixing coupled with the higher-order dispersion properties of the fiber is investigated.
TL;DR: In this article, the authors report the analysis of ultrawideband supercontinuum generation in a highly nonlinear dispersion-shifted fiber, where a >1000-nm-spanning white-light continuum is generated by pumping the femtosecond fiber laser pulse at the extreme vicinity of the zero-dispersion wavelength of the fiber.
Abstract: We report the analysis of ultrawideband supercontinuum generation in a highly nonlinear dispersion-shifted fiber. A >1000-nm-spanning white-light continuum is generated by pumping the femtosecond fiber laser pulse at λ=1.56 μm into the extreme vicinity of the zero-dispersion wavelength of the fiber. The supercontinuum pulses are characterized with the experimentally observed sonogram traces. The numerical calculation based on the nonlinear Schrodinger equation is used to investigate the mechanism of the supercontinuum generation, and these results are in good agreement with experiment. We show that there are two stages with different spectral-broadening processes in the propagation evolution. Self-phase modulation and group-velocity dispersion play an important role in the first spectral broadening. Through an increase the propagation distance, further spectral broadening occurs due to the soliton self-frequency shift and the trapping effect by the redshifted soliton pulse through cross-phase modulation. Additionally, we show that the temporal and spectral interferences between the generated supercontinuum components cause the oscillating fine structure on the temporal waveform and the spectrum.
TL;DR: Using a tapered small-core microstructured fiber with a sub-wavelength diameter core, an octave-spanning supercontinuum with 250 pJ pulses from a femtosecond modelocked Ti:sapphire oscillator is generated.
Abstract: We show that optical waveguides with sub-wavelength transverse dimensions optimize the effective nonlinearity and provide desireable dispersive properties for generating supercontinuum with ultra-low threshold power. Using a tapered small-core microstructured fiber with a sub-wavelength diameter core, we generate an octave-spanning supercontinuum with 250 pJ pulses from a femtosecond modelocked Ti:sapphire oscillator.
TL;DR: In this paper, the authors carried out an experimental study of the mutual spectral coherence of supercontinuum trains generated through a tapered fiber by means of a delayed pulsed method.
Abstract: By means of a delayed pulsed method, we carry out an experimental study of the mutual spectral coherence of supercontinuum trains generated through a tapered fiber. We observe a strong dependence of the spectral coherence on the input wavelength. Analysis of the interferograms shows that this is related to the robustness of different order soliton fission processes. A broadband continuum with 20dB wavelength from 500nm~1300nm with high coherence (mean visibility g12~0.7) is obtained.
TL;DR: In this article, a numerical study of the polarization properties of the broadband supercontinuum (SC) generated in birefringent photonic crystal fibers (PCFs) is presented.
Abstract: We present a numerical study of the polarization properties of the broadband supercontinuum (SC) generated in birefringent photonic crystal fibers (PCFs). The simulations are based on generalized coupled nonlinear Schrodinger equations with quantum noise taken into account. The simulations illustrate the complicated polarization behavior in the SC spectra and show that the pulse-to-pulse polarization state of SC spectra fluctuates because of vector modulation instability. We investigate the polarization stability and uniformity of SC spectra under several simulation conditions and discuss generation of the SC in birefringent PCFs for applications with various polarization requirements.
TL;DR: In this article, a femtosecond time-resolved coherent anti-Stokes Raman scattering (CARS) spectroscopy was demonstrated using a Ti:Sapphire oscillator and a photonic crystal fiber.
Abstract: Femtosecond time-resolved coherent anti-Stokes Raman scattering (CARS) spectroscopy is demonstrated using a Ti:Sapphire oscillator and a photonic crystal fiber. A spectrally dispersed CARS signal of cyclohexane exhibits well-defined beats with a period of 430fs, which agrees well with a frequency difference between the symmetric and antisymmetric CH2-stretching vibrational modes.
TL;DR: The fundamental limits to the compressibility of broadband supercontinuum spectra generated in photonic crystal fiber are examined using numerical simulations based on a stochastic extended nonlinear Schrödinger equation.
Abstract: The fundamental limits to the compressibility of broadband supercontinuum spectra generated in photonic crystal fiber are examined using numerical simulations based on a stochastic extended nonlinear Schrodinger equation. An ensemble average over multiple simulations performed with random quantum noise on the input pulse and spontaneous Raman noise during propagation allows a quantitative study of the effects of pulse to pulse fluctuations on the ability to obtain few-cycle pulses after compensation of the supercontinuum spectral phase. We study the dependence of the supercontinuum compressibility on the input pulse duration, the photonic crystal fiber length, and the spectral resolution of the pulse compressor employed.
TL;DR: An experimental study of polarization properties of supercontinuum spectra generated in a birefringent photonic crystal fiber is described, validating previous numerical simulations.
Abstract: Besides coherence degradations, supercontinuum spectra generated in birefringent photonic crystal fibers also suffer from polarization fluctuations because of noise in the input pump pulse. This paper describes an experimental study of polarization properties of supercontinuum spectra generated in a birefringent photonic crystal fiber, validating previous numerical simulations.
TL;DR: In this paper, the physical mechanisms behind the enhancement of nonlinear-optical interactions of ultrashort pulses in microstructure and hollow photonic-crystal fibers are analyzed.
Abstract: Microstructure fibers have opened a new phase in nonlinear optics. Due to their unique properties, fibers of this type radically enhance all the basic nonlinear-optical phenomena, offering new strategies for frequency conversion, spectral transformation, and control of ultrashort laser pulses. These fibers allow supercontinuum radiation to be efficiently generated using nano- and subnanojoule femtosecond pulses. Here, we analyze the physical mechanisms behind the enhancement of nonlinear-optical interactions of ultrashort pulses in microstructure and hollow photonic-crystal fibers and discuss applications of microstructure fibers for highly efficient supercontinuum generation and frequency conversion of femtosecond laser pulses.
TL;DR: Numerical simulations show that the supercontinuum bandwidth increases with the linear chirp, and that the coherence ofsupercontinuum improves as frequency chirping increases, and an optimal positive chirP is identified that maximizes the superContinuum bandwidth.
Abstract: Pre-chirp of the input pulse has a significant effect on pulse evolution in a photonic crystal fiber. We present numerical simulations which show that the supercontinuum bandwidth increases with the linear chirp, and that the coherence of supercontinuum improves as frequency chirping increases. An optimal positive chirp is identified that maximizes the supercontinuum bandwidth, corresponding to the formation of only one red-shifting Raman soliton.
TL;DR: It is demonstrated that UV exposure of highly nonlinear, germanosilicate fibers causes a strong change in their chromatic dispersion and can significantly alter the infrared supercontinuum generation in these fibers.
Abstract: We demonstrate that UV exposure of highly nonlinear, germanosilicate fibers causes a strong change in their chromatic dispersion and can significantly alter the infrared supercontinuum generation in these fibers. By varying the level of UV exposure to the fiber, we show that the dispersion zero and the short-wavelength edge of the supercontinuum can be changed by more than 100 nm. A nonlinear Schrodinger equation model of the continuum generation in the nonlinear fiber shows that the short-wavelength behavior of the continuum is primarily controlled by changes in the fiber dispersion caused by the UV-induced change in the refractive index of the fiber core.
TL;DR: This work relates pulse-averaged moments of this electric-field noise to the measured RF spectrum of the frequency comb formed by the supercontinuum, and presents quantitative numerical results for the intrinsic phase and amplitude noise on the frequencyComb resulting from input shot noise.
Abstract: During supercontinuum formation in nonlinear fiber the presence of a noise seed on the input laser pulse can lead to significant excess noise on the generated output supercontinuum electric field. We relate pulse-averaged moments of this electric-field noise to the measured RF spectrum of the frequency comb formed by the supercontinuum. We present quantitative numerical results for the fundamental phase, timing, and amplitude noise on the frequency comb resulting from input quantum noise, including the scaling of the noise with different experimental parameters. This fundamental noise provides a lower limit to the phase stability of frequency combs that originate from microstructure fiber.
TL;DR: It is shown that supercontinuum generation in a tapered fiber is extremely sensitive to the input state of polarization, and multiple vector solitons generated through soliton fission exhibit different states of elliptical polarization while emitting nonsolitonic radiation with complicated polarization features.
Abstract: We investigate the vectorial nature of soliton fission in an isotropic nonlinear medium both theoretically and experimentally. As a specific example, we show that supercontinuum generation in a tapered fiber is extremely sensitive to the input state of polarization. Multiple vector solitons generated through soliton fission exhibit different states of elliptical polarization while emitting nonsolitonic radiation with complicated polarization features. Experiments performed with a tapered fiber agree with our theoretical description.