Showing papers on "Supercontinuum published in 2008"
TL;DR: In this paper, the fundamental and second-harmonic fields of an ultrafast laser in any one of a number of materials can be used to generate radiation at terahertz frequencies.
Abstract: Frequency mixing the fundamental-and second-harmonic fields of an ultrafast laser in any one of a number of materials can generate radiation at terahertz frequencies. A better understanding of this process leads to a brighter source of light at these very useful wavelengths.
669 citations
TL;DR: Broad bandwidth, mid-IR supercontinuum generation using a sub-cm (8 mm) length of highly nonlinear tellurite microstructured photonic crystal fiber, comparable or in excess of previously reported spectra for other nonlinear glass fiber formulations despite the significantly shorter fiber length is reported.
Abstract: We report broad bandwidth, mid-IR supercontinuum generation using a sub-cm (8 mm) length of highly nonlinear tellurite microstructured photonic crystal fiber (PCF). We pump the fiber at telecommunication wavelengths by using 1550 nm, 100 fs pulses of energy E=1.9 nJ. When coupled in the PCF, these pulses result in a supercontinuum (SC) bandwidth of 4080 nm extending from 789 to 4870 nm measured at 20 dBm below the peak spectral power. This bandwidth is comparable or in excess of previously reported spectra for other nonlinear glass fiber formulations despite the significantly shorter fiber length. In addition, besides offering a convenient pump wavelength, short fiber lengths enable smoother SC spectra, lower dispersion, and reduced material absorption at longer wavelengths making the use of this PCF particularly interesting.
443 citations
TL;DR: A novel optical switch to control the high-order harmonic generation process so that single attosecond pulses can be generated with multiple-cycle pulses and a unique dependence of the harmonic spectra on the carrier-envelope phase of the laser fields is discovered.
Abstract: We demonstrated a novel optical switch to control the high-order harmonic generation process so that single attosecond pulses can be generated with multiple-cycle pulses. The technique combines two powerful optical gating methods: polarization gating and two-color gating. An extreme ultraviolet supercontinuum supporting 130 as was generated with neon gas using 9 fs laser pulses. We discovered a unique dependence of the harmonic spectra on the carrier-envelope phase of the laser fields, which repeats every 2 pi radians.
386 citations
TL;DR: It is demonstrated that rogue wave generation can be enhanced by an order of magnitude through a small modulation across the input pulse envelope and effectively suppressed through the use of a sliding frequency filter.
Abstract: We present a numerical study of the evolution dynamics of “optical rogue waves”, statistically-rare extreme red-shifted soliton pulses arising from supercontinuum generation in photonic crystal fiber [D. R. Solli et al. Nature 450, 1054–1058 (2007)]. Our specific aim is to use nonlinear Schrodinger equation simulations to identify ways in which the rogue wave dynamics can be actively controlled, and we demonstrate that rogue wave generation can be enhanced by an order of magnitude through a small modulation across the input pulse envelope and effectively suppressed through the use of a sliding frequency filter.
296 citations
TL;DR: High nonlinearity in a highly nonlinear arsenic selenide chalcogenide nanowire with tailored dispersion enables low-threshold soliton fission leading to large spectral broadening at a dramatically reduced peak power of several watts, corresponding to picojoule energy.
Abstract: We demonstrate low-threshold supercontinuum generated in a highly nonlinear arsenic selenide chalcogenide nanowire with tailored dispersion. The tapered submicrometer chalcogenide fiber exhibits an ultrahigh nonlinearity, n2~1.1×10−17m2/W and an effective mode area of 0.48 μm2, yielding an effective nonlinearity of γ~93.4W/m, which is over 80,000 times larger than standard silica single-mode fiber at a wavelength of ~1550nm. This high nonlinearity, in conjunction with the engineered anomalous dispersion, enables low-threshold soliton fission leading to large spectral broadening at a dramatically reduced peak power of several watts, corresponding to picojoule energy.
289 citations
TL;DR: It is demonstrated that rogue waves provide a powerful tool to actively control a nonlinear system with minimal effort, and an optically switchable, ultrastable, and bright supercontinuum with greatly enhanced coherence is produced.
Abstract: We demonstrate that rogue waves provide a powerful tool to actively control a nonlinear system with minimal effort. Specifically, optical rogue waves---rare, bright flashes of broadband light arising in subthreshold supercontinuum generation---are initiated by an exceedingly weak stimulus. Using this effect, we produce an optically switchable, ultrastable, and bright supercontinuum with greatly enhanced coherence.
287 citations
TL;DR: This implementation of STED microscopy avoids elaborate preparations of laser pulses and conveniently provides multicolor imaging and affords reduced photobleaching rates by allowing the fluorophore to relax from excitable metastable dark states involved in photodegradation.
Abstract: We report on a straightforward yet powerful implementation of stimulated emission depletion (STED) fluorescence microscopy providing subdiffraction resolution in the far-field. Utilizing the same supercontinuum pulsed laser source both for excitation and STED, this implementation of STED microscopy avoids elaborate preparations of laser pulses and conveniently provides multicolor imaging. Operating at pulse repetition rates around 1 MHz, it also affords reduced photobleaching rates by allowing the fluorophore to relax from excitable metastable dark states involved in photodegradation. The imaging of dense nanoparticles and of the microtubular network of mammalian cells evidences a spatial resolution of 30–50 nm in the focal plane, i.e. by a factor of 8–9 beyond the diffraction barrier.
280 citations
TL;DR: This work demonstrates supercontinuum generation in a highly nonlinear As(2)S(3) chalcogenide planar waveguide which is dispersion engineered to have anomalous dispersion at near-infrared wavelengths.
Abstract: We demonstrate supercontinuum generation in a highly nonlinear As2S3 chalcogenide planar waveguide which is dispersion engineered to have anomalous dispersion at near-infrared wavelengths. This waveguide is 60 mm long with a cross-section of 2 µm by 870 nm, resulting in a nonlinear parameter of 10/W/m and a dispersion of +29 ps/nm/km. Using pulses with a width of 610 fs and peak power of 68 W, we generate supercontinuum with a 30 dB bandwidth of 750 nm, in good agreement with theory.
275 citations
TL;DR: In this paper, the authors demonstrate stimulated emission depletion (STED) microscopy implemented in a laser scanning confocal microscope using excitation light derived from supercontinuum generation in a microstructured optical fiber.
Abstract: We demonstrate stimulated emission depletion (STED) microscopy implemented in a laser scanning confocal microscope using excitation light derived from supercontinuum generation in a microstructured optical fiber. Images with resolution improvement beyond the far-field diffraction limit in both the lateral and axial directions were acquired by scanning overlapped excitation and depletion beams in two dimensions using the flying spot scanner of a commercially available laser scanning confocal microscope. The spatial properties of the depletion beam were controlled holographically using a programmable spatial light modulator, which can rapidly change between different STED imaging modes and also compensate for aberrations in the optical path. STED fluorescence lifetime imaging microscopy is demonstrated through the use of time-correlated single photon counting.
230 citations
TL;DR: In this paper, the authors focus on the use of supercontinuum sources to construct novel instrumentation for chemical sensing and provide an outlook and a summary of where and how the field may develop over coming years.
Abstract: The advent of compact, high brightness supercontinuum radiation sources employing solid core photonic crystal fibres is beginning to make an impact across the field of applied spectroscopy research In this article we focus on the use of supercontinuum sources to construct novel instrumentation for chemical sensing A brief overview is given on the mechanisms of supercontinuum generation in solid core photonic crystal fibres, and then we review recent, and present new, results from our own research We present examples on gas phase sensing applications, permitting wide bandwidth molecular spectra to be gathered at ultrahigh speed Furthermore we demonstrate the design and construction of a wide bandwidth microscope for wavelength flexible hyperspectral confocal imaging We conclude with an outlook and a summary of where and how we think the field may develop over coming years
208 citations
TL;DR: This work demonstrates continuous wave supercontinuum generation extending to the visible spectral region by pumping photonic crystal fibers at 1.07 microm with a 400 W single mode, continuous wave, ytterbium fiber laser.
Abstract: We demonstrate continuous wave supercontinuum generation extending to the visible spectral region by pumping photonic crystal fibers at 1.07 microm with a 400 W single mode, continuous wave, ytterbium fiber laser. The continuum spans over 1300 nm with average powers up to 50 W and spectral power densities over 50 mW/nm. Numerical modeling and understanding of the physical mechanisms has led us to identify the dominant contribution to the short wavelength extension to be trapping and scattering of dispersive waves by high energy solitons.
TL;DR: In this article, visibly white supercontinuum generation in photonic crystal fibers using a sub ns pump source at 1064 nm was reported, and the spectra extend from below 400 nm to 2450 nm, some 50 nm further into the blue than previously reported spectra.
Abstract: We report on visibly white supercontinuum generation in photonic crystal fibers using a sub ns pump source at 1064 nm. The spectra extend from below 400 nm to 2450 nm, some 50 nm further into the blue than previously reported spectra. The extra bandwidth which is achieved by a simple modification to the fiber structure gives a higher apparent color temperature and a truly "white" visual appearance. The mechanism for the generation of the deeper blue to ultraviolet frequencies is outlined and our modified fiber is compared with fibers which have been conventionally used for supercontinuum generation.
TL;DR: This work reports the first use of a supercontinuum radiation source for broadband trace gas detection using a cavity enhanced absorption technique, and demonstrates that a conceptually simple and robust instrument is capable of highly sensitive broadband absorption measurements.
Abstract: Supercontinuum radiation sources are attractive for spectroscopic applications owing to their broad wavelength coverage, which enables spectral signatures of multiple species to be detected simultaneously. Here we report the first use of a supercontinuum radiation source for broadband trace gas detection using a cavity enhanced absorption technique. Spectra were recorded at bandwidths of up to 100 nm, encompassing multiple absorption bands of H2O, O2 and O2-O2. The same instrument was also used to make quantitative measurements of NO2 and NO3. For NO3 a detection limit of 3 parts-per-trillion in 2 s was achieved, which corresponds to an effective 3σ sensitivity of 2.4×10-9 cm-1Hz-1/2. Our results demonstrate that a conceptually simple and robust instrument is capable of highly sensitive broadband absorption measurements.
TL;DR: A 29 W CW supercontinuum spanning from 1.06 to 1.67 microm is generated in a short length of PCF with two zero dispersion wavelengths, which enables the continuum to expand beyond the water loss at 1.4 microm.
Abstract: A 29 W CW supercontinuum spanning from 1.06 to 1.67 µm is generated in a short length of PCF with two zero dispersion wavelengths. The continuum has the highest spectral power density, greater than 50 mW/nm up to 1.4 µm, reported to date. The use of a short length of PCF enables the continuum to expand beyond the water loss at 1.4 µm. The dynamics of the continuum evolution are studied experimentally and numerically with close attention given to the effects of the water loss and the second zero dispersion wavelength.
TL;DR: In this article, numerical simulations are used to study how fiber supercontinuum generation seeded by picosecond pulses can be actively controlled through the use of input pulse modulation, and the results are discussed in terms of the nonlinear propagation dynamics and pump depletion.
Abstract: Numerical simulations are used to study how fiber supercontinuum generation seeded by picosecond pulses can be actively controlled through the use of input pulse modulation. By carrying out multiple simulations in the presence of noise, we show how tailored supercontinuum Spectra with increased bandwidth and improved stability can be generated using an input envelope modulation of appropriate frequency and depth. The results are discussed in terms of the non-linear propagation dynamics and pump depletion.
31 Jan 2008
TL;DR: Spectral broadening of more than 350 nm upon propagation of ultrashort pulses in a 4.7-mm-long silicon-photonic-wire waveguide is observed.
Abstract: We observe spectral broadening of more than 350 nm upon propagation of ultrashort pulses in a 4.7-mm-long silicon-photonic-wire waveguide. The output spectral characteristics are shown to be consistent, in part, with higher-order soliton radiative effects.
04 May 2008
TL;DR: The bandwidth of the supercontinuum generated in uniform fibers pumped at 1064 nm is described, and the spectra extend to ~400 nm, some 50 nm deeper into the blue than previously with the same pump source.
Abstract: We describe how to extend the bandwidth of the supercontinuum generated in uniform fibers pumped at 1064 nm. The spectra extend to ~400 nm, some 50 nm deeper into the blue than previously with the same pump source.
TL;DR: It is shown that longer driving pulses can be applied to confine the efficient recollision of electron wave packet to half an optical cycle, and an attosecond pulse can be straightforwardly obtained just by filtering different range of the spectrum.
Abstract: We propose a method to generate broadband supercontinuum with a modulated polarization gating in the multi-cycle regime. The polarization gating at 1600 nm is employed to intensify the ellipticity dependence of high harmonic signal, and the adding second harmonic (SH) field is used for modulating ionization ratio between the driving field half-cycles. It is shown that longer driving pulses (6 optical cycles, 32.4 fs) can be applied to confine the efficient recollision of electron wave packet to half an optical cycle. The produced bandwidth of the extreme ultraviolet (XUV) supercontinuum is about 280 eV, corresponding to a fourier-transform-limited pulse of 10 as. In addition, an attosecond pulse of about 100 as with tunable wavelength can be straightforwardly obtained just by filtering different range of the spectrum.
TL;DR: This work investigates dynamic localization in curved femtosecond laser written waveguide arrays by monitoring fluorescence of color centers induced during the fs writing process and launching white light supercontinuum into the arrays.
Abstract: We investigate dynamic localization in curved femtosecond (fs) laser written waveguide arrays. The light propagation inside the array is directly observed by monitoring fluorescence of color centers induced during the fs writing process. In addition to monochromatic excitation the spectral response of the arrays is investigated by launching white light supercontinuum into the arrays.
TL;DR: The second order nonlinear refractive index n2 of various multicomponent glasses was measured at the wavelength of 1240 nm close to the 1.3-μm fiber transmission window as discussed by the authors.
Abstract: The second order nonlinear refractive index n2 of various multicomponent glasses was measured at the wavelength of 1240 nm close to the 1.3-μm fiber transmission window. With the refractive index covering the range from 1.45 to 2.3, a comparatively broad range of n2 with values from 1.1×10−20 m2/W for boro-silicate based glass NC21 to 4.3×10−19 m2/W for lead–bismuth-gallate based glass PBG08 was measured using the Z-scan method. Considering the broad infrared transmission range of multicomponent glasses, these materials pose a great potential for future applications as photonic crystal fiber sources of infrared supercontinuum.
TL;DR: The supercontinuum generation mechanisms for bulk and waveguide setups are compared and tuning of the zero-dispersion wavelength via waveguide dispersion is theoretically investigated.
Abstract: Supercontinuum generation is demonstrated in a 5-cm-long water-core photonic crystal fiber pumped near water's zero-dispersion wavelength. Up to 500-nm spectral width (evaluated at -20 dB from the peak) is achieved, while spectral widths were over 4 times narrower with a bulk setup at the same wavelength and peak power, and over 3 times narrower if the PCF was pumped away from the zero-dispersion wavelength. The supercontinuum generation mechanisms for bulk and waveguide setups are compared and tuning of the zero-dispersion wavelength via waveguide dispersion is theoretically investigated.
TL;DR: The ultrabroadband subnanosecond supercontinuum has facilitated multiplex coherent anti-Stokes Raman scattering (CARS) microspectroscopy in the spectral range from 1,000 to 3,000 cm(-1) with lateral and depth spatial resolution of 0.9 and 4.6 microm, respectively.
Abstract: Subnanosecond supercontinuum (SC) has been generated by a 1064nm microchip laser combined with a photonic crystal fiber. The ultrabroadband (>2000cm−1) SC has facilitated multiplex coherent anti-Stokes Raman scattering (CARS) microspectroscopy in the spectral range from 1000 to 3000cm−1 with lateral and depth spatial resolution of 0.9 and 4.6μm, respectively. A clear CARS image of a Nicotiana tabacum L. cv. Bright Yellow 2 cell has been obtained with high vibrational contrast.
TL;DR: The experimental demonstration of a visible supercontinuum in the cw pumping regime is reported, generated in the fundamental mode via trapping of dispersive waves by redshifted solitons.
Abstract: We report the experimental demonstration of a visible supercontinuum in the cw pumping regime. A 20 W ytterbium fiber laser at 1.06 μm is used to pump a photonic crystal fiber whose zero-dispersion wavelength decreases along the fiber length. Visible wavelengths are generated in the fundamental mode via trapping of dispersive waves by redshifted solitons.
TL;DR: A flat, polarized and single mode supercontinuum (SC) spanning 450-1750 nm in a highly birefringent photonic crystal fibre pumped by a 1064 nm microchip laser is generated.
Abstract: We generate a flat, polarized and single mode supercontinuum (SC) spanning 450-1750 nm in a highly birefringent photonic crystal fibre (PCF) pumped by a 1064 nm microchip laser. More than 99% of the total power is kept in a single linear polarization. The measured power coupling penalty due to the elliptical core is less than 6% (0.25 dB). As one of its applications, we demonstrate tuneable visible/UV generation in the nonlinear crystal BIBO pumped by this polarized SC source. A tuneable range of 400-525 nm is obtained by critical phase matching in BIBO. We also show the results of visible/UV generation in BIBO pumped by the signal wavelength of polarized four-wave mixing (FWM) in PCF.
TL;DR: Experiments confirm that Octave-spanning spectrum can be easily generated at peak pump power levels as low as approximately 1.5 kW at 1 microm and approximately 1 kW at 800 nm, which effectively enables f ceo stabilization of mode-locked fiber lasers without further amplification.
Abstract: We have experimentally studied supercontinuum generations in highly nonlinear suspended core silica fibers as alternatives to photonic crystal fibers. Octave-spanning spectrum can be easily generated at peak pump power levels as low as approximately 1.5 kW at 1 microm and approximately 1 kW at 800 nm, which effectively enables f ceo stabilization of mode-locked fiber lasers without further amplification. Experiments also confirm that the blue edge of the supercontinuum undergoes a two-phase growth process, an initial fast growth governed by phase-matched dispersive wave generation and a second slower growth governed by group-velocity-matched cross-phase modulation. We have further experimentally shown that the fundamental solitons generated from the initial fission process can be independent of pump powers and the orders which they are generated. Furthermore, while the fundamental soliton wavelength undergoes continuous red shift by Raman scattering, they continuously lose power to longer wavelength dispersive waves where phase-matching to this long wavelength dispersive wave is allowed and, otherwise, maintain its initial power where phase-matching to long wavelength dispersive wave is not allowed. We also demonstrated that total suppression of dispersive wave generation at short wavelength can be achieved in the absence of dispersion slope at the pump wavelength.
TL;DR: Higher-order-mode excitation experiments are interesting because the anomalous dispersion region is shifted towards smaller wavelengths and because the existence of a cut-off wavelength generates spectral broadening only on the blue side of the pump wavelength.
Abstract: We describe an experiment in which a train of femtosecond pulses is coupled into a photonic crystal fiber (PCF) by means of an offset pumping technique that can selectively excite either the mode LP01 or LP11 or LP21. The PCF presents a wide range of wavelengths in which the fundamental mode experiences normal dispersion, whereas LP11 and LP21 propagate in the anomalous dispersion regime, generating a supercontinuum based on the soliton fission mechanism. We find that the existence of a cut-off wavelength for the higher-order modes makes the spectral broadening asymmetrical. This latter effect is particularly dramatic in the case of the LP21 mode, in which, by using a pump wavelength slightly below cut-off, the spectral broadening occurs only on the blue side of the pump wavelength. Our experimental results are successfully compared to numerical solutions of the nonlinear Schrodinger equation.
TL;DR: In this article, the authors present the experimental study of the nonlinear absorption of gold nanospheres and nanorods in aqueous suspension, using picosecond white-light supercontinuum open-aperture Z-scan.
Abstract: In this work, we present the experimental study of the nonlinear absorption of gold nanospheres and nanorods in aqueous suspension, using picosecond white-light supercontinuum open-aperture Z-scan. We demonstrate a saturable absorption effect in all particle suspensions at low-pulse energy. In the high-pulse energy regime, the apparent reverse-saturable absorption, observed in gold nanorods, was determined to be induced by photodegradation. Using the Lorentzian deconvolution method for the absorption spectra, we explain the variations on nonlinear optical effects and prove that saturable absorption only occurs within the plasmonic bands.
TL;DR: Here, it is demonstrated both numerically and experimentally how the outer four-wave mixing gain peaks can be used to produce a strong amplification peak in a picosecond supercontinuum.
Abstract: In photonic crystal fibers with closely spaced zero dispersion wavelengths it is possible to have two pairs of four-wave mixing (FWM) gain peaks. Here, we demonstrate both numerically and experimentally how the outer four-wave mixing gain peaks can be used to produce a strong amplification peak in a picosecond supercontinuum. The method involves feeding back part of the output light of a SC source and time matching it with the pump light. In this way it is possible to produce a gain of over 20 dB near the FWM gain wavelengths.
TL;DR: In this article, the authors demonstrate the use of photonic crystal fiber to realize a long range dual beam trap that may support multiple wavelengths simultaneously, and develop a dual wavelength conveyor belt for trapped particles and realize the first ever dual beam white light (supercontinuum) trap.
Abstract: The dual beam counterpropagating optical trap has found increased use in studies such as optical stretching, optical binding, Raman spectroscopy, and the trapping of high index particles. In this letter we demonstrate the use of photonic crystal fiber to realize a long range dual beam trap that may support multiple wavelengths simultaneously. We develop a dual wavelength conveyor belt for trapped particles and realize the first ever dual beam white light (supercontinuum) trap. This low coherence light trap permits long range longitudinal optical binding of microparticles in the trap with no deleterious interference effects.
TL;DR: A 1 mum cw-pumped supercontinuum that extends short of the pump wavelength to 0.65 mum is reported, showing that the short-wavelength generation is due to a combination of four-wave mixing and dispersive wave trapping by solitons.
Abstract: We report a 1 μm cw-pumped supercontinuum that extends short of the pump wavelength to 0.65 μm. This is achieved by using a 50 W Yb fiber laser in combination with a photonic crystal fiber with a carefully engineered zero-dispersion wavelength. We show that the short-wavelength generation is due to a combination of four-wave mixing and dispersive wave trapping by solitons. The evolution and limiting factors of the continuum are discussed.