Showing papers on "Supercontinuum published in 2006"

Supercontinuum generation in photonic crystal fiber

Abstract: A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

Zero-dispersion wavelength decreasing photonic crystal fibers for ultraviolet-extended supercontinuum generation

Abstract: We report the fabrication of photonic crystal fibers with a continuously-decreasing zero-dispersion wavelength along their length. These tapered fibers are designed to extend the generation of supercontinuum spectra from the visible into the ultraviolet. We report on their performance when pumped with both nanosecond and picosecond sources at 1.064 microm. The supercontinuum spectra have a spectral width (measured at the 10 dB points) extending from 0.372 microm to beyond 1.75 microm. In an optimal configuration a flat (3 dB) spectrum from 395 to 850 nm, with a minimum spectral power density of 2 mW/nm was achieved, with a total continuum output power of 3.5 W. We believe that the shortest wavelengths were generated by cascaded four-wave mixing: the continuous decrease of the zero dispersion wavelength along the fiber length enables the phase-matching condition to be satisfied for a wide range of wavelengths into the ultraviolet, while simultaneously increasing the nonlinear coefficient of the fiber.

Mid-infrared supercontinuum generation to 4.5 μm in ZBLAN fluoride fibers by nanosecond diode pumping

Abstract: A mid-infrared supercontinuum (SC) is generated in ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF...) fluoride fibers from amplified nanosecond laser diode pulses with a continuous spectrum from approximately 0.8 microm to beyond 4.5 microm. The SC has an average power of approximately 23 mW, a pump-to-SC power conversion efficiency exceeding 50%, and a spectral power density of approximately -20 dBm/nm over a large fraction of the spectrum. The SC generation is initiated by the breakup of nanosecond laser diode pulses into femtosecond pulses through modulation instability, and the spectrum is then broadened primarily through fiber nonlinearities in approximately 2-7 m lengths of ZBLAN fiber. The SC long-wavelength edge is consistent with the intrinsic ZBLAN material absorption.

Self-phase-modulation in submicron silicon-on-insulator photonic wires

Abstract: We measure the transmission of ps-pulses through silicon-on-insulator submicron waveguides for excitation wavelengths between 1400 and 1650 nm and peak powers covering four orders of magnitude. Self-phase-modulation induced spectral broadening is found to be significant at coupled peak powers of even a few tens of mW. The nonlinear-index coefficient, extracted from the experimental data, is estimated as n(2) ~ 5*10(-18) m(2)/W at 1500 nm. The experimental results show good agreement with model calculations that take into account nonlinear phase shift, first- and second order dispersion, mode confinement, frequency dispersion of n(2), and dynamics of two-photon-absorption-generated free carriers. Comparison with theory indicates that an observed twofold increase of spectral broadening between 1400 and 1650 nm can be assigned to the dispersion of n(2) as well as first order- rather than second-order dispersion effects. The analysis of pulse broadening, spectral shift and transmission saturation allows estimating a power threshold for nonlinearity-induced signal impairment in nanophotonic devices.

Ultra-high-speed optical coherence tomography with a stretched pulse supercontinuum source.

Abstract: We introduce a new high-speed Fourier-domain optical coherence tomography (FD-OCT) scheme based on a stretched pulse supercontinuum source. A wide-band short pulse of a supercontinuum source of which output spectrum spanned a wavelength range from 1,200 nm to 1,550 nm was stretched to a long pulse of 70-ns duration by using a dispersive fiber due to the group-velocity dispersion, and it was used directly as frequency-swept light for FD-OCT. The OCT spectral interferogram was acquired in the time domain and converted into the spectral domain by the pre-calibrated time-to-wavelength relation. Using this stretched-pulse OCT (SP-OCT) scheme, we have demonstrated an ultrahigh-speed axial-line scanning rate of 5 MHz. The axial resolution of 8 microm was achieved without re-calibration of the sweep characteristic owing to the passive nature of the frequency-sweeping mechanism.

Supercontinuum generation system for optical coherence tomography based on tapered photonic crystal fibre

Abstract: We report smooth and broad continuum generation using a compact femtosecond Ti:Sapphire laser as a pump source and a tapered photonic crystal fibre as a nonlinear element. Spectral output is optimized for use in optical coherence tomography, providing a maximum longitudinal resolution of 1.5 microm in free space at 809 nm centre wavelength without use of additional spectral filtering.

Over-1000-channel ultradense WDM transmission with supercontinuum multicarrier source

Abstract: In this paper, ultradense wavelength-division multiplexing (WDM) transmission technologies are discussed, and a field demonstration of over-1000-channel ultradense WDM transmission is reported. The generation of an ultradense WDM signal using a supercontinuum multicarrier source that generates more than 1000 carriers and uniform precise channel spacing of 6.25 GHz is presented. The influence of four-wave-mixing generated in the transmission fiber and the requirements placed on the WDM multiplexer and demultiplexer is described. An over-1000-channel ultradense WDM transmission experiment is reported. A 1046 /spl times/ 2.67-Gbit/s 6.25-GHz-spaced ultradense WDM signal is successfully transmitted over 126 km of field-installed fibers in the test bed of JGN II.

Nonlinear properties of chalcogenide glass fibers

Abstract: Chalcogenide glasses have demonstrated high third-order Kerr (Χ (3) ) nonlinearities up to 1000x higher than silica glass which make them attractive for applications such as nonlinear switching, optical regeneration, Raman amplification, parametric amplification, and supercontinuum generation. Poling of chalcogenide glasses to induce an effective second order (Χ (2) ) nonlinearity has also been demonstrated and opens the possibility for the use of poled glass waveguides for applications such as frequency conversion or electro-optic modulation. Stimulated Brillouin scattering (SBS) has also been investigated in As 2 S 3 and As 2 Se 3 single-mode fibers. The threshold intensity for the stimulated Brillouin scattering process was measured and used to estimate the Brillouin gain coefficient. Preliminary results indicate record high values for the figure of merit and theoretical gain, compared to silica, which bodes well for slow-light based applications in chalcogenide fibers.

Let there be white light: supercontinuum generation by ultrashort laser pulses

Abstract: Three centuries after Newton's experiments on the decomposition of white light into its spectral components and the synthesis of white light from various colors, nonlinear-optical transformations of ultrashort laser pulses have made it possible to produce an artificial white light with unique spectral properties, controlled time duration, and a high spectral brightness. Owing to its broad and continuous spectrum, such radiation is called supercontinuum. The laser generation of white light is an interesting physical phenomenon and the relevant technology is gaining in practical implications — it offers novel solutions for optical communications and control of ultrashort laser pulses, helps to achieve an unprecedented precision in optical metrology, serves to probe the atmosphere of the Earth, and suggests new strategies for the creation of compact multiplex light sources for nonlinear spectroscopy, microscopy, and laser biomedicine. Here, we provide a review of physical mechanisms behind the laser generation of white light, examine its applications, and discuss the methods of generation of broadband radiation with controlled spectral, temporal, and phase parameters.

Theoretical design of a liquid-core photonic crystal fiber for supercontinuum generation.

Abstract: We have numerically studied a hollow-core photonic crystal fiber, with its core filled with highly nonlinear liquids such as carbon disulfide and nitrobenzene Calculations show that the fiber has an extremely high nonlinear parameter γ on the order of 24/W/m at 155 μm The group velocity dispersion of this fiber exhibits an anomalous region in the near-infrared, and its zero-dispersion wavelength is around 155 μm This leads to potentially significant improvements and a large bandwidth in supercontinuum generation The spectral properties of the supercontinuum generation in liquid-core photonic crystal fibers are simulated by solving the generalized nonlinear Schrodinger equation The results demonstrate that the liquid-core PCF is capable to generate dramatically broadened supercontinua in a range from 700 nm to more than 2500 nm when pumping at 155 μm with subpicosecond pulses

High-nonlinearity dispersion-shifted lead-silicate holey fibers for efficient 1-μm pumped supercontinuum generation

Abstract: This paper reports on the recent progress in the design and fabrication of high-nonlinearity lead-silicate holey fibers (HFs). First, the fabrication of a fiber designed to offer close to the maximum possible nonlinearity per unit length in this glass type is described. A value of γ = 1860 W -1 . km -1 at a wavelength of 1.55 μm is achieved, which is believed to be a record for any fiber at this wavelength. Second, the design and fabrication of a fiber with a slightly reduced nonlinearity but with dispersion-shifted characteristics tailored to enhance broadband supercontinuum (SC) generation when pumped at a wavelength of 1.06 μm-a wavelength readily generated using Yb-doped fiber lasers-are described. SC generation spanning more than 1000 nm is observed for modest pulse energies of ∼ 100 pJ using a short length of this fiber. Finally, the results of numerical simulations of the SC process in the proposed fibers are presented, which are in good agreement with the experimental observations and highlight the importance of accurate control of the zero-dispersion wavelength (ZDW) when optimizing such fibers for SC performance.

High-nonlinearity dispersion-shifted lead-silicate holey fibers for efficient 1-/spl mu/m pumped supercontinuum generation

Abstract: This paper reports on the recent progress in the design and fabrication of high-nonlinearity lead-silicate holey fibers (HFs). First, the fabrication of a fiber designed to offer close to the maximum possible nonlinearity per unit length in this glass type is described. A value of /spl gamma/=1860 W/sup -1//spl middot/km/sup -1/ at a wavelength of 1.55 /spl mu/m is achieved, which is believed to be a record for any fiber at this wavelength. Second, the design and fabrication of a fiber with a slightly reduced nonlinearity but with dispersion-shifted characteristics tailored to enhance broadband supercontinuum (SC) generation when pumped at a wavelength of 1.06 /spl mu/m-a wavelength readily generated using Yb-doped fiber lasers-are described. SC generation spanning more than 1000 nm is observed for modest pulse energies of /spl sim/ 100 pJ using a short length of this fiber. Finally, the results of numerical simulations of the SC process in the proposed fibers are presented, which are in good agreement with the experimental observations and highlight the importance of accurate control of the zero-dispersion wavelength (ZDW) when optimizing such fibers for SC performance.

Soliton collision and Raman gain regimes in continuous-wave pumped supercontinuum generation.

Abstract: We numerically investigate supercontinuum generation using continuous-wave pumping. It is found that energy transfer during collision of solitons plays an important role. The relative influence of Raman gain on spectral broadening is shown to depend on the width of the calculation time window. Our results indicate that increasing the spectral linewidth of the pump can decrease the supercontinuum spectral width. Using a fiber with smaller dispersion at the pump wavelength reduces the required fiber length by decreasing the temporal width of the solitons formed from modulation instability. This also reduces the sensitivity to the pump spectral linewidth.

Wavelength-division-multiplexed Millimeter-waveband radio-on-fiber system using a supercontinuum light source

Abstract: We propose to use a supercontinuum (SC) for a low-phase-noise multiwavelength light source in wavelength-division-multiplexing (WDM) millimeter-waveband (mm-waveband) radio-on-fiber (RoF) systems. We demonstrate the generation of low-phase-noise 60-GHz-band RoF signal. We also demonstrate the generation of two-channel WDM 60-GHz-band RoF signals and the transmission of the signals over a 25-km standard single-mode fiber (SMF) using photonic upconversion. The single multiwavelength light source can be shared with a number of users and simplifies the system configuration, which would allow the realization of high-reliability as well as low-cost RoF systems. Finally, the RoF network capacity with a single SC light source is estimated to be over 10 000 channels when the spectrum of the SC light source is fully utilized.

Fragmentation of colloidal nanoparticles by femtosecond laser-induced supercontinuum generation

Abstract: A femtosecond laser-based method to control the size characteristics of gold colloidal nanoparticles is reported. The method uses the supercontinuum generation produced through a strong nonlinear-optical interaction of the femtosecond radiation with a liquid to fragment relatively large colloids and reduce their agglomeration. The fragmented species then recoalesce to form smaller, less dispersed, and much more stable nanoparticles in the solution. The size of the nanoparticles after the treatment is independent of the initial characteristics of colloids, but depends strongly on laser parameters and on the presence of chemically active species in the solution.

The Supercontinuum Laser Source: Fundamentals with Updated References

Abstract: Alfano's The Supercontinuum Laser Source 2/e Contents New Preface 1989 Edition Preface Contributors Part I: Fundamentals Chapter 1 Theory of Self Phase Modulation and Spectral Boradening Y.R. Shen and Guo-Zhen Yang Chapter 2 Supercontinuum Generation and Condensed Matter Q.Z. Wang, P.P. Ho, and R.R. Alfano Chapter 3 Ultrashort Pulse Propagation in Nonlinear Dispersive Fibers Govind P. Agrawal Chapter 4 Cross-Phase Modulation: A New Technique for Controlling the Spectral, Temporal, and Spatial Properties of Ultrashort Pulses P.L. Baldeck, P.P. Ho, and R.R. Alfano Chapter 5 Simple Models of Self-Phase and Induced-Phase Modulation Jamal T. Manassah Chapter 6 Self-steepening of Optical Pulses B.R. Suydam Chapter 7 Self-focusing and Continuum Generation in Gases Paul B. Corkum and Claude Rolland Chapter 8 Utilization of UV and IR Supercontinua in Gas-Phase Subpicosecond Kinetic Spectroscopy J.H. Glownia, J. Misewich, and P.P. Sorokin Chapter 9 Applications of Supercontinuum: Present and Future R.Dorsinville, P.P. Ho, Jamal T. Manassah, and R.R. Alfano Chapter 10 Pulse Compression in Single-Mode Fibers-Picoseconds to Femtoseconds A.M. Johnson and C.V. Shank Index Part II: New Developments Chapter 11 Coherence Properties of the Supercontinuum Source I. Zeylikovich and R.R. Alfano Chapter 12 Supercontinuum Generation in Materials (Solids, Liquids, Gases, Air) Summary Updated References Chapter 13 Supercontinuum generation in microstructure fiber Summary UpdatedReferences Chapter 14 Supercontinuum in wavelength division multiplex telecommunication Summary Updated References Chapter 15 Femtosecond Pump - Supercontinuum Probe for Applications in Semiconductors, Biology and Chemistry Summary Updated References Chapter 16 Supercontinuum in optical coherence tomography Summary Updated References Chapter 17 Supercontinuum in fs carrier-envelope phase stabilization Summary Updated References Chapter 18 Supercontinuum in ultrafast pulse compression Summary Updated References Chapter 19 Supercontinuum in time and frequency metrology Summary Updated References Chapter 20 Supercontinuum in Atmospheric Science Summary Updated References Chapter 21 Coherence of the Supercontinuum Summary Updated References

Four-wave mixing of solitons with radiation and quasi-nondispersive wave packets at the short-wavelength edge of a supercontinuum

Abstract: We apply the recently developed theory of frequency generation by mixing of solitons and dispersive waves [Phys. Rev. E 72, 016619 (2005)] to explain the observed formation, quasi-trapping and frequency shift of the spectral peaks at the blue edge of supercontinua generated in silica-core photonic crystal fibers.

Supercontinuum generation in submicrometer diameter silica fibers.

Abstract: Silica nanowires provide strong mode confinement in a cylindrical silica-core/air-cladding geometry and serve a model system for studying nonlinear propagation of short optical pulses inside fibers. We report on the fiber diameter dependence of the supercontinuum generated by femtosecond laser pulses in silica fiber tapers with average diameters in the range of 200 nm to 1200 nm. We observe a strong diameter-dependence of the spectral broadening, which can be attributed to the fiber's diameter-dependent dispersion and nonlinearity. The short interaction length (less than 20 mm) and the low energy threshold for supercontinuum generation (about 1 nJ) make tapered fibers with diameters between 400 nm and 800 nm an ideal source of coherent white-light source in nanophotonics.

Numerical aperture dependence of damage and supercontinuum generation from femtosecond laser pulses in bulk fused silica

Abstract: Competing nonlinear optical effects are involved in the interaction of femtosecond laser pulses with transparent dielectrics: supercontinuum generation and multiphoton-induced bulk damage. We measured the threshold energy for supercontinuum generation and bulk damage in fused silica using numerical apertures (NAs) ranging from 0.01 to 0.65. The threshold for supercontinuum generation exhibits a minimum near 0.05NA and increases quickly above 0.1 NA. For NAs greater than 0.25, we observe no supercontinuum generation. The extent of the blue broadening of the supercontinuum spectrum decreases significantly as the NA is increased from 0.01 to 0.08, showing that weak focusing is important for generating the broadest supercontinuum spectrum. Using a light-scattering technique to detect the onset of bulk damage, we confirmed bulk damage at all NAs studied. At a high NA, the damage threshold is well below the critical power for self-focusing.

Spectrally smooth supercontinuum from 350 nm to 3 mu m in sub-centimeter lengths of soft-glass photonic crystal fibers.

Abstract: The conversion of light fields in photonic crystal fibers (PCFs) capitalizes on the dramatic enhancement of several optical nonlinearities. We present here spectrally smooth, highly broadband supercontinuum radiation in a short piece of high-nonlinearity soft-glass PCF. This supercontinuum spans several optical octaves, with a spectral range extending from 350 nm to beyond 3000 nm. The selection of an appropriate propagation-length determines the spectral quality of the supercontinuum generated. Experimentally, we clearly identify two regimes of nonlinear pulse transformation: when the fiber length is much shorter than the dispersion length, soliton propagation is not important and a symmetric supercontinuum spectrum arises from almost pure self-phase modulation. For longer fiber lengths the supercontinuum is formed by the breakup of multiple Raman-shifting solitons. In both regions very broad supercontinuum radiation is produced.

3D laser microfabrication: principles and applications

Abstract: List of Contributors. 1 Introduction (Hiroaki Misawa and Saulius Juodkazis). 2 Laser-Matter Interaction Confined Inside the Bulk of a Transparent Solid (Eugene Gamaly, Barry Luther-Davies and Andrei Rode). 2.1 Introduction. 2.2 Laser-matter Interactions: Basic Processes and Governing Equations. 2.3 Nondestructive Interaction: Laser-induced Phase Transitions. 2.4 Laser-Solid Interaction at High Intensity. 2.5 Multiple-pulse Interaction: Energy Accumulation. 2.6 Conclusions. 3 Spherical Aberration and its Compensation for High Numerical Aperture Objectives (Min Gu and Guangyong Zhou). 3.1 Three-dimensional Indensity Point-spread Function in the Second Medium. 3.2 Spherical Aberration Compensation by a Tube-length Change. 3.3 Effects of Refractive Indices Mismatch-induced Spherical Aberration on 3D Optical Data Storage. 3.4 Effects of Refractive Index Mismatch Induced Spherical Aberration on the Laser Trapping Force. 3.5 Summary. 4 The Measurement of Ultrashort Light Pulses in Microfabrication Applications (Xun Gu, Selcuk Akturk, Aparna Shreenath, Qiang Cao, and Rick Trebino). 4.1 Introduction. 4.2 Alternatives to FROG. 4.3 FROG and Cross-correlation FROG. 4.4 Dithered-crystal XFROG for Measuring Ultracomplex Supercontinuum Pulses. 4.5 OPAXFROG for Measuring Ultraweak Broadband Emission. 4.6 Extremely Simple FROG Device. 4.7 Other Progress. 4.8 Conclusions. 5 Nonlinear Optics (John Buck and Rick Trebino). 5.1 Linear versus Nonlinear Optics. 5.2 Nonlinear-optical Effects. 5.3 Some General Observations about Nonlinear Optics. 5.4 The Mathematics of Nonlinear Optics. 5.5 Phase-matching. 5.6 Phase-matching Bandwidth. 5.7 Nonlinear-optical Strengths. 6 Filamentation versus Optical Breakdown in Bulk Transparent Media (Eugenijus Gaiz&acaron uskas). 6.1 Introduction. 6.2 Conical Waves: Tilted Pulses, Bessel Beams and X-type Waves. 6.3 Dynamics of Short-pulse Splitting in Nonlinear Media with Normal Dispersion: Effects of Nonlinear Losses. 6.4 On the Physics of Self-channeling: Beam Reconstruction from Conial Waves. 6.5 Multi-filaments and Multi-focuses. 6.6 Filamentation Induced by Conical Wavepacket. 6.7 Conclusion. 7 Photophysics and Photochemistry of Ultrafast Laser Materials Processing (Richard F. Haglund, Jr.). 7.1 Introduction and Motivation. 7.2 Ultrafast Laser Materials Interactions: Electronic Excitation. 7.3 Ultrafast Laser-materials Interaction: Vibrational Excitation. 7.4 Photochemistry in Femtosecond Laser-materials Interactions. 7.5 Photomechanical Effects at Femtosecond Timescales. 7.6 Pulsed Laser Deposition. 7.7 Future Trends in Ultrafast Laser Micromachining. 7.8 Summary and Conclusions. 8 Formation of Sub-wavelength Periodic Structures Inside Transparent Materials (Peter G. Kazansky). 8.1 Introduction. 8.2 Anomalous Anisotropic Light-scattering in Glass. 8.3 Anisotropic Cherenkov Light-generation in Glass. 8.4 Anisotropic Reflection from Femtosecond-laser Self-organized Nanostructures in Glass. 8.5 Direct Observation of Self-organized Nanostructures in Glass. 8.6 Mechanism of Formation of Self-organized Nanostructures in Glass. 8.7 Self-organized Form Birefringence. 8.8 Conclusion. 9 X-ray Generation from Optical Transparent Materials by Focusing Ultrashort Laser Pulses (Koji Hatanaka and Hiroshi Fukumura). 9.1 Introduction. 9.2 Laser-induced High-energy Photon Emission from Transparent Materials. 9.3 Characteristics of Hard X-ray Emission from Transparent Materials. 9.4 Possible Applications. 9.5 Summary. 10 Femtosecond Laser Microfabrication of Photonic Crystals (Vygantas Mizeikis, Shigeki Matsuo, Saulius Juodkazis, and Hiroaki Misawa). 10.1 Microfabrication of Photonic Crystals by Ultrafast Lasers. 10.2 Photonic Crystals Obtained by Direct Laser Writing. 10.3 Lithography by Multiple-beam Interference. 10.4 Conclusions. 11 Photophysical Processes that Lead to Ablation-free Microfabrication in Glass-ceramic Materials (Frank E. Livingston and Henry Helvajian). 11.1 Introduction. 11.2 Photostructurable Glass-ceramic (PSGC) Materials. 11.3 Laser Processing Photophysics. 11.4 Laser Direct-write Microfabrication. 11.5 Conclusions. 12 Applications of Femtosecond Lasers in 3D Machining (Andreas Ostendorf, Frank Korte, Guenther Kamlage, Ulrich Klug, Juergen Koch, Jesper Serbin, Niko Baersch, Thorsten Bauer, Boris N. Chichkov). 12.1 Machining System. 12.2 Beam Delivery. 12.3 Material Processing. 12.4 Nonlinear Effects for Nano-machining. 12.5 Machining Technology. 12.6 Applications. 13 (Some) Future Trends (Saulius Juodkazis and Hiroaki Misawa). 13.1 General Outlook. 13.2 On the Way to the Future. 13.3 Example: "Shocked" Materials. 13.4 The Future is Here. Index.

Dispersive wave blue-shift in supercontinuum generation.

Abstract: We numerically study dispersive wave emission during femtosecond-pumped supercontinuum generation in photonic crystal fibres. We show that dispersive waves are primarily generated over a short region of high temporal compression. Despite the apparent complexity of the pump pulse in this region, we show that the dynamics of dispersive wave generation are dominated by a single fundamental soliton. However, any straightforward application of the theory that is thought to describe the blue emission, considerably underestimates the frequency shift. We show that in fact the red-shift of the soliton, caused by spectral recoil from the growing dispersive wave, causes an additional blue-shift of the resonant frequency which is in good agreement with full simulations.

Analysis of the interplay between soliton fission and modulation instability in supercontinuum generation

Abstract: We investigate the generation mechanisms for ultra-wide spectra in nonlinear optical fibers. Soliton fission and modulation instability represent fundamental mechanisms for the generation process. The primary origin of the spectral broadening changes with the pump-pulse duration. Soliton fission dominates for low input power and short pulses. Its efficiency for supercontinuum generation and especially the extension to the blue side can be increased by proper design of the dispersion profile. The modulation instability has a strong impact for high input powers and greatly enhances the generation process, but leads to a degradation of the coherence properties. Also for short pulses with durations of 60 fs the modulation instability is present and can hardly be suppressed. The interplay between these two effects leads to various characteristics of the resulting spectra, which are modified by the relative impact of the modulation instability.

Actively shaped supercontinuum from a photonic crystal fiber for nonlinear coherent microspectroscopy

Abstract: The combination of broadband pulses from a photonic crystal fiber (PCF) pumped by a standard 100 fs oscillator and pulse shaping is successfully employed for coherently controlled nonlinear spectroscopy. The pulse shaper manages not only to compress the PCF supercontinuum in a closed-loop optimization scheme but also to manipulate the phase at the same time for quantum control applications. This approach is demonstrated by single-beam coherent anti-Stokes Raman microspectroscopy and should be, due to its simplicity, well suited for general applications in nonlinear microscopy.

Supercontinuum generation at 1.06µm in holey fibers with dispersion flattened profiles

Abstract: We report the results of a systematic experimental and theoretical study of 1.06 µm pumped supercontinuum generation in a range of holey fibers with different flattened dispersion profiles. Clear differences in terms of the underpinning mechanisms emerge depending on the spacing between the two fiber zero-dispersion wavelengths. By examining the phase matched wavelength range of the corresponding fiber dispersions, one can predict the maximum achievable supercontinuum bandwidth.

In-vivo multi-nonlinear optical imaging of a living cell using a supercontinuum light source generated from a photonic crystal fiber

Abstract: A supercontinuum light source generated with a femtosecond Ti:Sapphire oscillator has been used to obtain both vibrational and two-photon excitation fluorescence (TPEF) images of a living cell simultaneously at different wavelengths. Owing to an ultrabroadband spectral profile of the supercontinuum, multiple vibrational resonances have been detected through coherent anti-Stokes Raman scattering (CARS) process. In addition to the multiplex CARS process, multiple electronic states can be excited due to the broadband electronic two-photon excitation using the supercontinuum, giving rise to a two-photon excitation fluorescence (TPEF) signal. Using a living yeast cell whose nucleus is labeled by green fluorescent protein (GFP), we have succeeded in visualizing organelles such as mitochondria, septum, and nucleus through the CARS and the TPEF processes. The supercontinuum enables us to perform unique multi-nonlinear optical imaging through two different nonlinear optical processes.

High-energy, few-optical-cycle pulses at 1.5 µm with passive carrier-envelope phase stabilization

Abstract: We report on a source of ultrabroadband self-phase-stabilized near-IR pulses by difference-frequency generation of a hollow-fiber broadened supercontinuum followed by two-stage optical parametric amplification We demonstrate energies up to 200 µJ with 15 fs pulse width, making this source suited as a driver for attosecond pulse generation

Dispersion-compensated supercontinuum generation for ultrabroadband multiplex coherent anti-Stokes Raman scattering spectroscopy

Abstract: We have generated a dispersion-compensated picosecond ultrabroadband supercontinuum light source at the sample position without using any additional compensator such as a prism pair or a grating pair. The dispersion-compensated supercontinuum, which is obtained just by optimizing the length of a photonic crystal fiber, has been used as a Stokes laser source for ultrabroadband multiplex coherent anti-Stokes Raman scattering (CARS) spectroscopy. Owing to an optimized temporal overlap between the narrowband pump and the Stokes supercontinuum pulses, a CARS signal has been obtained efficiently with a spectral coverage of more than 2800 cm−1. Furthermore, a vibrationally resonant CARS signal is observed not only when the pump pulse and the Stokes supercontinuum are temporally overlapped but also when the pump pulse follows the supercontinuum. It can be explained by an impulsive excitation of the vibrational coherence by the supercontinuum and a subsequent probe by a narrowband pump pulse. Using the dispersion-compensated supercontinuum, we can perform not only the frequency-domain multiplex CARS but also the time-domain impulsive CARS measurement by controlling the delay time between the narrowband laser and the supercontinuum. Both these techniques can be applied to microspectroscopy in order to obtain the wide spectral range of vibrational resonances and the suppression of the nonresonant background. Copyright © 2006 John Wiley & Sons, Ltd.