Showing papers on "Supercontinuum published in 2013"
TL;DR: In this article, the effect of the fiber geometry on the spectral resolution and bandwidth was investigated, and the additional limitation on the bandwidth imposed by speckle contrast reduction when measuring dense spectra.
Abstract: A standard multimode optical fiber can be used as a general purpose spectrometer after calibrating the wavelength dependent speckle patterns produced by interference between the guided modes of the fiber. A transmission matrix was used to store the calibration data and a robust algorithm was developed to reconstruct an arbitrary input spectrum in the presence of experimental noise. We demonstrate that a 20 meter long fiber can resolve two laser lines separated by only 8 pm. At the other extreme, we show that a 2 centimeter long fiber can measure a broadband continuous spectrum generated from a supercontinuum source. We investigate the effect of the fiber geometry on the spectral resolution and bandwidth, and also discuss the additional limitation on the bandwidth imposed by speckle contrast reduction when measuring dense spectra. Finally, we demonstrate a method to reduce the spectrum reconstruction error and increase the bandwidth by separately imaging the speckle patterns of orthogonal polarizations. The multimode fiber spectrometer is compact, lightweight, low cost, and provides high resolution with low loss.
203 citations
TL;DR: This work investigates the effect of the fiber geometry on the spectral resolution and bandwidth, and discusses the additional limitation on the bandwidth imposed by speckle contrast reduction when measuring dense spectra.
Abstract: A standard multimode optical fiber can be used as a general purpose spectrometer after calibrating the wavelength dependent speckle patterns produced by interference between the guided modes of the fiber. A transmission matrix was used to store the calibration data and a robust algorithm was developed to reconstruct an arbitrary input spectrum in the presence of experimental noise. We demonstrate that a 20 meter long fiber can resolve two laser lines separated by only 8 pm. At the other extreme, we show that a 2 centimeter long fiber can measure a broadband continuous spectrum generated from a supercontinuum source. We investigate the effect of the fiber geometry on the spectral resolution and bandwidth, and also discuss the additional limitation on the bandwidth imposed by speckle contrast reduction when measuring dense spectra. Finally, we demonstrate a method to reduce the spectrum reconstruction error and increase the bandwidth by separately imaging the speckle patterns of orthogonal polarizations. The multimode fiber spectrometer is compact, lightweight, low cost, and provides high resolution with low loss.
187 citations
TL;DR: A passively mode-locked vertical external cavity surface emitting laser (VECSEL) producing 400 fs pulses with 4.35 kW peak power is reported.
Abstract: We report a passively mode-locked vertical external cavity surface emitting laser (VECSEL) producing 400 fs pulses with 4.35 kW peak power. The average output power was 3.3 W and the VECSEL had a repetition rate of 1.67 GHz at a center wavelength of 1013 nm. A near-antiresonant, substrate-removed, 10 quantum well (QW) gain structure designed to enable femtosecond pulse operation is used. A SESAM which uses fast carrier recombination at the semiconductor surface and the optical Stark effect enables passive mode-locking. When 1 W of the VECSEL output is launched into a 2 m long photonic crystal fiber (PCF) with a 2.2 µm core, a supercontinuum spanning 175 nm, with average power 0.5 W is produced.
146 citations
TL;DR: The similarities between gain- Switched and Q-switching techniques that will provide tools for the design and optimization of the gain-switched fiber lasers are illustrated and analyzed.
Abstract: We briefly review the development of gain-switched rare-earth-doped fiber lasers and their applications in wavelength conversion to mid-IR, supercontinuum generation, and medicine in recent years. We illustrate the similarities between gain-switching and Q-switching techniques that will provide tools for the design and optimization of the gain-switched fiber lasers. From the nature of the gain-switched fiber lasers, benefits of this kind of lasers to 2-μm region and in-band-pumped (two-level system) laser systems are obvious. Advantages of in-band-pumped 2-μm lasers are discussed and analyzed with a simple numerical simulation in terms of Tm-doped fiber lasers. We also propose the key factors in the development of the gain-switched fiber lasers and predict the future tendency.
136 citations
TL;DR: The supercontinuum (SC) generation in a suspended-core As(2)S(3) chalcogenide microstructured optical fiber (MOF) is demonstrated and the generalized nonlinear Schrödinger equation agrees well with the experiment.
Abstract: We demonstrate the supercontinuum (SC) generation in a suspended-core As2S3 chalcogenide microstructured optical fiber (MOF) The variation of SC is investigated by changing the fiber length, pump peak power and pump wavelength In the case of long fibers (20 and 40 cm), the SC ranges are discontinuous and stop at the wavelengths shorter than 3500 nm, due to the absorption of fiber In the case of short fibers (13 and 24 cm), the SC ranges are continuous and can extend to the wavelengths longer than 4 μm The SC broadening is observed when the pump peak power increases from 024 to 132 kW at 2500 nm The SC range increases with the pump wavelength changing from 2200 to 2600 nm, corresponding to the dispersion of As2S3 MOF from the normal to anomalous region The SC generation is simulated by the generalized nonlinear Schrodinger equation The simulation includes the SC difference between 13 and 24 cm long fiber by 2500 nm pumping, the variation of SC with pump peak power in 24 cm long fiber, and the variation of SC with pump wavelength in 13 cm long fiber The simulation agrees well with the experiment
134 citations
TL;DR: Theoretical simulations indicate that the physical mechanism of SC generation is due to nonlinear effects in fibers, and the cascaded Raman scattering is responsible for significant spectral broadening in the longer wavelength regions whereas the Kerr effect results in smoothing of SC generated spectrum.
Abstract: We report generation of broadband supercontinuum (SC) by noise-like pulses (NLPs) with a central wavelength of 1070 nm propagating through a long piece of standard single-mode fibers (~100 meters) in normal dispersion region far from the zero-dispersion point. Theoretical simulations indicate that the physical mechanism of SC generation is due to nonlinear effects in fibers. The cascaded Raman scattering is responsible for significant spectral broadening in the longer wavelength regions whereas the Kerr effect results in smoothing of SC generated spectrum. The SC exhibits low threshold (43 nJ) and a flat spectrum over 1050-1250 nm.
134 citations
TL;DR: Nonlinear fiber optics and femtosecond laser development are the focus of this review, because they can be integrated into a low-cost portable biophotonics source platform, enabling new applications such as point-of-care coherent optical biomedical imaging.
Abstract: Biophotonics and nonlinear fiber optics have traditionally been two independent fields. Since the discovery of fiber-based supercontinuum generation in 1999, biophotonics applications employing incoherent light have experienced a large impact from nonlinear fiber optics, primarily because of the access to a wide range of wavelengths and a uniform spatial profile afforded by fiber supercontinuum. However, biophotonics applications employing coherent light have not benefited from the most well-known techniques of supercontinuum generation for reasons such as poor coherence (or high noise), insufficient controllability, and inadequate portability. Fortunately, a few key techniques involving nonlinear fiber optics and femtosecond laser development have emerged to overcome these critical limitations. Despite their relative independence, these techniques are the focus of this review, because they can be integrated into a low-cost portable biophotonics source platform. This platform can be shared across many different areas of research in biophotonics, enabling new applications such as point-of-care coherent optical biomedical imaging.
115 citations
TL;DR: A 10-GHz ultra-broadband flat-topped optical frequency comb (> 3.64-THz or 28 nm bandwidth with ~365 spectral lines within 3.5-dB power variation) covering the entire C-band is presented.
Abstract: The generation of high-repetition-rate optical frequency combs with an ultra-broad, coherent and smooth spectrum is important for many applications in optical communications, radio-frequency photonics and optical arbitrary waveform generation. Usually, nonlinear broadening techniques of comb-based sources do not provide the required flatness over the whole available bandwidth. Here we present a 10-GHz ultra-broadband flat-topped optical frequency comb (> 3.64-THz or 28 nm bandwidth with ~365 spectral lines within 3.5-dB power variation) covering the entire C-band. The key enabling point is the development of a pre-shaping-free directly generated Gaussian comb-based 10-GHz pulse train to seed a highly nonlinear fiber with normal dispersion profile. The combination of the temporal characteristics of the seed pulses with the nonlinear device allows the pulses to enter into the optical wave-breaking regime, thus achieving a smooth flat-topped comb spectral envelope. To further illustrate the high spectral coherence of the comb, we demonstrate high-quality pedestal-free short pulse compression to the transform-limited duration.
105 citations
TL;DR: Efficient generation of a broad-band mid-infrared supercontinuum spectrum is reported in an arsenic trisulphide waveguide embedded in silica, designed to transform the incident light adiabatically into the fundamental mode of a 2-mm-long uniform section 1 µm in diameter.
Abstract: Efficient generation of a broad-band mid-infrared supercontinuum spectrum is reported in an arsenic trisulphide waveguide embedded in silica. A chalcogenide "nano-spike", designed to transform the incident light adiabatically into the fundamental mode of a 2-mm-long uniform section 1 μm in diameter, is used to achieve high launch efficiencies. The nano-spike is fully encapsulated in a fused silica cladding, protecting it from the environment. Nano-spikes provide a convenient means of launching light into sub-wavelength scale waveguides. Ultrashort (65 fs, repetition rate 100 MHz) pulses at wavelength 2 μm, delivered from a Tm-doped fiber laser, are launched with an efficiency ~12% into the subwavelength chalcogenide waveguide. Soliton fission and dispersive wave generation along the uniform section result in spectral broadening out to almost 4 μm for launched energies of only 18 pJ. The spectrum generated will have immediate uses in metrology and infrared spectroscopy.
101 citations
TL;DR: A supercontinuum laser based double integrating sphere setup in combination with an unscattered transmittance measurement setup was developed and carefully validated for optical characterization of turbid samples in the 500-2250 nm wavelength range.
Abstract: A supercontinuum laser based double integrating sphere setup in combination with an unscattered transmittance measurement setup was developed and carefully validated for optical characterization of turbid samples in the 500-2250 nm wavelength range. A set of 57 liquid optical phantoms, covering a wide range of absorption and scattering properties, were prepared and measured at two sample thicknesses. The estimated bulk optical properties matched well for both thicknesses, and with theory and literature, without significant crosstalk between absorption and scattering. Equations were derived for the bulk scattering properties μ(s), μ(s)' and g of Intralipid® 20% which can be used to calculate the bulk scattering properties of intralipid-dilutions in the 500-2250 nm range.
97 citations
TL;DR: It is demonstrated a novel method of mid-infrared (mid-IR) supercontinuum (SC) generation with the use of a 2 µm gain-switched self-mode-locked thulium-doped fiber laser, the first report on such an approach to generate a mid-IR SC in optical fibers.
Abstract: We demonstrate a novel method of mid-infrared (mid-IR) supercontinuum (SC) generation with the use of a 2 µm gain-switched self-mode-locked thulium-doped fiber laser. SC radiation ranging from ~1.9 to 3.8 µm wavelength, generated in a single-mode ZBLAN fiber with a zero-dispersion wavelength (ZDW) shifted to ~1.9 µm, is reported. An average output power of 0.74 W with 0.27 W at wavelengths longer than 2.4 µm was measured. It is, to the best of our knowledge, the first report on such an approach to generate a mid-IR SC in optical fibers.
TL;DR: The first demonstration of mid-IR supercontinuum generation directly pumped with picosecond pulses from a Thulium fiber-amplified gain-switched laser diode at 2 µm is presented, which offers high stability, power-scaling capability to the 10 W regime, and demonstrates an attractive route towards relatively inexpensive, versatile and practical sources of high power broadband mid-ir radiation.
Abstract: We present the first demonstration of mid-IR supercontinuum generation directly pumped with picosecond pulses from a Thulium fiber amplified gain-switched laser diode at 2 µm. We achieve more than two octaves of bandwidth from 750 - 4000 nm in step-index ZBLAN fiber with Watt-level average power and spectral flatness of less than 1.5 dB over a 1300 nm range in the mid-IR from 2450 - 3750 nm. The system offers high stability, power-scaling capability to the 10 W regime, and demonstrates an attractive route towards relatively inexpensive, versatile and practical sources of high power broadband mid-IR radiation.
TL;DR: A method to control the absolute phase of such supercontinuum THz pulses as an essential tool for future field-sensitive investigations is presented.
Abstract: High-field terahertz (THz) single-cycle pulses with 1.5 MV/cm are generated by optical rectification in the stilbazolium salt crystal 4-N,N-dimethylamino-4'-N'-methyl-stilbazolium 2,4,6-trimethylbenzenesulfonate. We show experimentally that the generated THz transient carrying 5 octaves (0.15 to 5.5 THz) undergoes a complex time-frequency evolution when tightly focused, and we present a model based on three independent oscillating dipoles capable to describe this anomalous field evolution. Finally, we present a method to control the absolute phase of such supercontinuum THz pulses as an essential tool for future field-sensitive investigations.
TL;DR: Spatially coherent multicolored optical vector vortex beams were created using a tunable liquid crystal q-plate and a supercontinuum light source for multiplexing for broadband high-speed optical communication, ultradense data networking, and super-resolution microscopy.
Abstract: Spatially coherent multicolored optical vector vortex beams were created using a tunable liquid crystal q-plate and a supercontinuum light source. The feasibility of the q-plate as a tunable spectral filter (switch) was demonstrated, and the polarization topology of the resulting vector vortex beam was mapped. Potential applications include multiplexing for broadband high-speed optical communication, ultradense data networking, and super-resolution microscopy.
TL;DR: A supercontinuum spanning well over an octave of measurable bandwidth from about 1 to 3.7 μm in a 2.1 mm long As₂S₃ fiber taper is reported using the in situ tapering method.
Abstract: We report a supercontinuum spanning well over an octave of measurable bandwidth from about 1 to 3.7 μm in a 2.1 mm long As2S3 fiber taper using the in situ tapering method. A sub-100-fs mode-locked thulium-doped fiber laser system with ∼300 pJ of pulse energy was used as the pump source. Third-harmonic generation was observed and currently limits the pump pulse energy and achievable spectral bandwidth.
Posted Content•
TL;DR: In this paper, the dispersive Fourier transformation was used to measure shot-to-shot spectral instabilities in femtosecond supercontinuum generation, and the results showed the clear advantages of dispersive wave generation for studying spectral noise during supercontinuity generation.
Abstract: We use dispersive Fourier transformation to measure shot-to-shot spectral instabilities in femtosecond supercontinuum generation. We study both the onset phase of supercontinuum generation with distinct dispersive wave generation, as well as a highly-unstable supercontinuum regime spanning an octave in bandwidth. Wavelength correlation maps allow interactions between separated spectral components to be identified, even when such interactions are not apparent in shot-to-shot or average measurements. Experimental results are interpreted using numerical simulations. Our results show the clear advantages of dispersive Fourier transformation for studying spectral noise during supercontinuum generation.
TL;DR: This work uses dispersive Fourier transformation to measure shot-to-shot spectral instabilities in femtosecond supercontinuum generation and studies both the onset phase of supercontinuity generation with distinct dispersive wave generation, as well as a highly-unstablesupercontinuum regime spanning an octave in bandwidth.
Abstract: We use dispersive Fourier transformation to measure shot-to-shot spectral instabilities in femtosecond supercontinuum generation. We study both the onset phase of supercontinuum generation with distinct dispersive wave generation, as well as a highly-unstable supercontinuum regime spanning an octave in bandwidth. Wavelength correlation maps allow interactions between separated spectral components to be identified, even when such interactions are not apparent in shot-to-shot or average measurements. Experimental results are interpreted using numerical simulations. Our results show the clear advantages of dispersive Fourier transformation for studying spectral noise during supercontinuum generation.
TL;DR: In this paper, a 2D Fourier transform spectroscopy was conducted in a shaper-assisted collinear setup comprising fully tunable UV pulse pairs and supercontinuum probe spanning 250-720 nm.
Abstract: Experimental realizations of two-dimensional (2D) electronic spectroscopy in the ultraviolet (UV) must so far contend with a limited bandwidth in both the excitation and particularly the probe frequency. The pump bandwidth is at best 1500 cm−1 (full width at half maximum) at a fixed wavelength of 267 nm or 400 cm−1 for tunable pulses. The use of a replica of the pump pulse as a probe limits the observation of photochemical processes to the excitation region and makes the disentanglement of overlapping signal contributions difficult. We show that 2D Fourier transform spectroscopy can be conducted in a shaper-assisted collinear setup comprising fully tunable UV pulse pairs and supercontinuum probe spanning 250–720 nm. The pump pulses are broadened up to a useable spectral coverage of 2000 cm−1 (25 nm at 316 nm) by self-phase modulation in bulk CaF2 and compressed to 18 fs. By referencing the white light probe and eliminating pump stray light contributions, high signal-to-noise ratios even for weak probe intensities are achieved. Data acquisition times as short as 4 min for a selected population time allow the rapid recording of 2D spectra for photolabile biological samples even with the employed 1 kHz laser system. The potential of the setup is demonstrated on two representative molecules: pyrene and 2,2-diphenyl-5,6-benzo(2H)chromene. Well-resolved cross-peaks are observed and the excitation energy dependence of the relaxation processes is revealed.
15 Oct 2013
TL;DR: In this article, the authors used a tellurite-based dispersion managed nonlinear fiber and an all-fiber based short pulse (20 ps) single mode pump source to generate a high power, single mode beam with extremely wide (1μm-5μm) and simultaneous wavelength coverage.
Abstract: Mid-infrared sources are a key enabling technology for various applications such as remote chemical sensing, defense communications and countermeasures, and bio-photonic diagnostics and therapeutics. Conventional mid-IR sources include optical parametric amplifiers, quantum cascade lasers, synchrotron and free electron lasers. An all-fiber approach to generate a high power, single mode beam with extremely wide (1μm-5μm) and simultaneous wavelength coverage has significant advantages in terms of reliability (no moving parts or alignment), room temperature operation, size, weight, and power efficiency. Here, we report single mode, high power extended wavelength coverage (1μm to 5μm) supercontinuum generation using a tellurite-based dispersion managed nonlinear fiber and an all-fiber based short pulse (20 ps), single mode pump source. We have developed this mid IR supercontinuum source based on highly purified solid-core tellurite glass fibers that are waveguide engineered for dispersion-zero matching with Tm-doped pulsed fiber laser pumps. The conversion efficiency from 1922nm pump to mid IR (2μm-5μm) supercontinuum is greater than 30%, and approaching 60% for the full spectrum. We have achieved > 1.2W covering from 1μm to 5μm with 2W of pump. In particular, the wavelength region above 4μm has been difficult to cover with supercontinuum sources based on ZBLAN or chalcogenide fibers. In contrast to that, our nonlinear tellurite fibers have a wider transparency window free of unwanted absorption, and are highly suited for extending the long wavelength emission above 4μm. We achieve spectral power density at 4.1μm already exceeding 0.2mW/nm and with potential for higher by scaling of pump power.
TL;DR: A novel method for supercontinuum generation in an optical fiber based on two-color pumping with a delay and a group velocity matching that exhibits extraordinary coherence properties, enabling the temporal compression of octave bandwidth into a short pulse.
Abstract: We demonstrate a novel method for supercontinuum generation in an optical fiber based on two-color pumping with a delay and a group velocity matching. The scheme relies on the enhanced cross-phase-modulation at an intensity induced refractive index barrier between a dispersive wave and a soliton. The generation mechanism neither incorporates soliton fission nor a modulation instability and therefore exhibits extraordinary coherence properties, enabling the temporal compression of octave bandwidth into a short pulse. Moreover, the properties of the supercontinuum are adjustable over a wide range in the frequency domain by suitable choice of the dispersive wave.
TL;DR: An integrated dual-modal photoacoustic and optical coherence tomography (PA-OCT) system using a single near-infrared supercontinuum laser source to simultaneously provide both optical absorption and scattering contrasts is developed.
Abstract: We developed an integrated dual-modal photoacoustic and optical coherence tomography (PA-OCT) system using a single near-infrared supercontinuum laser source to simultaneously provide both optical absorption and scattering contrasts. A pulsed broadband supercontinuum source was generated by a pulsed Nd:YAG laser and a photonic-crystal fiber. When we imaged two colored hairs, the black hair was visible in both PA and OCT images, whereas the white hair was only mapped in the OCT image. The single laser source will potentially allow us to implement relatively simple, cheap, and compact dual-modal PA-OCT systems, which are key criteria for fast clinical translation and commercialization.
TL;DR: A high-power, picosecond, thulium-doped, all-fiber master oscillator power amplifier with average power of 120.4 W and the first demonstration of average power exceeding 100 W from an ultrashort pulse laser at 2 μm wavelength is demonstrated.
Abstract: We demonstrate a high-power, picosecond, thulium-doped, all-fiber master oscillator power amplifier with average power of 120.4 W. The compact fiber oscillator is carefully designed with high repetition rate for the purpose of overcoming the detrimental effects of fiber nonlinearity in the later fiber amplifiers. The pulse duration of 16 ps at 333.75 MHz repetition rate results in a peak power of 22.5 kW in the final fiber power amplifier. To the best of our knowledge, this is the first demonstration of average power exceeding 100 W from an ultrashort pulse laser at 2 μm wavelength. On the other hand, by decreasing the fiber oscillator repetition rate and pulse duration for enhancing the fiber nonlinearity effects, we also demonstrate a high-power supercontinuum source with average power of 36 W from 1.95 μm to beyond 2.4 μm in the final fiber power amplifier.
TL;DR: Simulation results show that, when a W-type tellurite fiber with a zero dispersion wavelength (ZDW) of 2.7 µm is pumped at 2.78 μm, the power proportion of the SC laser beyond 3 µm can exceed 40% and the attainable SC output power of the proposed solid-cladding telluite fiber is one order of magnitude higher than that of existing microstructured tellurites.
Abstract: High power mid-infrared (mid-IR) supercontinuum (SC) laser sources in the 3-12 µm region are of great interest for a variety of applications in many fields. Although various mid-IR SC laser sources have been proposed and investigated experimentally and theoretically in the past several years, power scaling of mid-IR SC lasers beyond 3 μm with infrared edges extending beyond 7 μm are still challenges because the wavelengths of most previously used pump sources are below 2 μm. These problems can be solved with the recent development of mode-locked fiber lasers at 3 μm. In this paper, high power mid-IR SC laser sources based on dispersion engineered tellurite and chalcogenide fibers and pumped by ultrafast lasers at 3 µm are proposed and investigated. Our simulation results show that, when a W-type tellurite fiber with a zero dispersion wavelength (ZDW) of 2.7 µm is pumped at 2.78 μm, the power proportion of the SC laser beyond 3 µm can exceed 40% and the attainable SC output power of the proposed solid-cladding tellurite fiber is one order of magnitude higher than that of existing microstructured tellurite fibers. Our calculation also predicts that a very promising super-broadband mid-IR SC fiber laser source covering two atmospheric windows and molecules' "fingerprint" region can be obtained with a microstructured As2Se3 chalcogenide fiber pumped at 2.78 μm.
TL;DR: Prior to spectral super-broadening, third-harmonic generation, which occurs in the condition of large phase and group velocity mismatch and consists of free and driven components, is observed.
Abstract: We report on the generation of ultrabroadband supercontinuum (SC) by filamentation of two optical-cycle, carrier-envelope phase-stable pulses at 2 μm in fused silica, sapphire, CaF2 and YAG. The SC spectra extend from 450 nm to more than 2500 nm, and their particular shapes depend on dispersive properties of the materials. Prior to spectral super-broadening, we observe third-harmonic generation, which occurs in the condition of large phase and group velocity mismatch and consists of free and driven components. A double-peaked third-harmonic structure coexists with the SC pulse as demonstrated by the numerical simulations and verified experimentally. The SC pulses have stable carrier envelope phase with short-term rms fluctuations of ∼ 300 mrad, as simultaneously measured in YAG crystal by f-2f and f-3f interferometry, where the latter makes use of intrinsic third-harmonic generation.
TL;DR: In this article, the authors presented a numerical model with which they have obtained excellent quantitative agreement with two recent experiments in the femtosecond regime, and they have been able to correctly predict both the observed pulse duration and the output power for the first time.
Abstract: Optically pumped vertical-external-cavity surface-emitting lasers (OP-VECSELs), passively modelocked with a semiconductor saturable absorber mirror (SESAM), have generated the highest average output power from any sub-picosecond semiconductor laser. Many applications, including frequency comb synthesis and coherent supercontinuum generation, require pulses in the sub-300-fs regime. A quantitative understanding of the pulse formation mechanism is required in order to reach this regime while maintaining stable, high-average-power performance. We present a numerical model with which we have obtained excellent quantitative agreement with two recent experiments in the femtosecond regime, and we have been able to correctly predict both the observed pulse duration and the output power for the first time. Our numerical model not only confirms the soliton-like pulse formation in the femtosecond regime, but also allows us to develop several clear guidelines to scale the performance toward shorter pulses and higher average output power. In particular, we show that a key VECSEL design parameter is a high gain saturation fluence. By optimizing this parameter, 200-fs pulses with an average output power of more than 1 W should be possible.
TL;DR: In this paper, the authors theoretically investigate high-order harmonic generation in a spatially inhomogeneous field with mid-infrared driving wavelength and few-cycle duration, and they show that this spatiotemporally synthesized electric field is powerful to control the quantum path; as a result an ultra-broadband supercontinuum with bandwidth over 300 eV can be obtained successfully.
Abstract: We theoretically investigate high-order harmonic generation in a spatially inhomogeneous field with mid-infrared driving wavelength and few-cycle duration. It is found that this spatiotemporally synthesized electric field is powerful to control the quantum path; as a result an ultra-broadband supercontinuum with bandwidth over 300 eV can be obtained successfully. Important characteristics of the attosecond pulse generation, including temporal envelope, harmonic chirp and carrier–envelope phase (CEP) dependence are further discussed. The results show that close-to-Fourier-limit 27 as isolated pulses are straightforwardly filtered from the supercontinuum. Moreover, such short isolated attosecond pulses can be supported by nearly all the CEPs of the laser electric field. This would open a way to obtain broadband isolated attosecond pulses with no need of CEP stabilization of the laser field.
TL;DR: In this article, an average output power of 2.37 W in a spectral band of?(1.75?2.7) was achieved by a single-mode Tm-doped fiber amplifier.
Abstract: Mid-infrared supercontinuum (SC) generation in a thulium fiber amplifier is reported. The system delivered an average output power of 2.37 W in a spectral band of ?(1.75?2.7)??m which is, to the best of our knowledge, the highest average power of SC generated from a single-mode Tm-doped fiber. For wavelengths longer than 2.4??m, the output power was as high as 0.49?W, constituting almost 21% of the total output power. A 10 dB spectral flatness in the wavelength interval ranging from 1.95 to 2.52??m (570?nm span) with a corresponding (calculated) spectral power density greater than 3?mW?nm?1 is demonstrated. Amplification in both emission bands of Tm3+ ions, as a way to effectively enhance SC generation towards longer wavelengths, is also discussed.
TL;DR: Experimental observation of multi-bound-soliton solutions of the nonlinear Schrödinger equation (NLS) in the context of hydrodynamic surface gravity waves and the universal role that higher-order nonlinear perturbations to the NLS play in supercontinuum generation are reported.
Abstract: We demonstrate experimentally multi-bound-soliton solutions of the Nonlinear Schr\"odinger equation (NLS) in the context of surface gravity waves In particular, the Satsuma-Yajima N-soliton solution with N=2,3,4 is investigated in detail Such solutions, also known as breathers on zero background, lead to periodic self-focussing in the wave group dynamics, and the consequent generation of a steep localized carrier wave underneath the group envelope Our experimental results are compared with predictions from the NLS for low steepness initial conditions where wave-breaking does not occur, with very good agreement We also show the first detailed experimental study of irreversible massive spectral broadening of the water wave spectrum, which we refer to by analogy with optics as the first controlled observation of hydrodynamic supercontinuum a process which is shown to be associated with the fission of the initial multi-soliton bound state into individual fundamental solitons similar to what has been observe in optics
TL;DR: In this paper, a multi-wavelength photoacoustic-nephelometer spectrometer (SC-PNS) was developed for the optical characterization of atmospheric aerosol particles.
Abstract: . A novel multi-wavelength photoacoustic-nephelometer spectrometer (SC-PNS) has been developed for the optical characterization of atmospheric aerosol particles. This instrument integrates a white light supercontinuum laser with photoacoustic and nephelometric spectroscopy to measure aerosol absorption and scattering coefficients at five wavelength bands (centered at 417, 475, 542, 607, and 675 nm). These wavelength bands are selected from the continuous spectrum of the laser (ranging from 400–2200 nm) using a set of optical interference filters. Absorption and scattering measurements on laboratory-generated aerosol samples were performed sequentially at each wavelength band. To test the instrument we measured the wavelength dependence of absorption and scattering coefficients of kerosene soot and common salt aerosols. Results were favorably compared to those obtained with a commercial 3-wavelength photoacoustic and nephelometer instrument demonstrating the utility of the SC light source for studies of aerosol optical properties at selected wavelengths. Here, we discuss instrument design, development, calibration, performance and experimental results.
TL;DR: By using mid-infrared ultrashort laser pulses from an optical parametric amplifier, this work demonstrates generation of a 20 dB spectral flatness supercontinua from 2.7 to 4.7 μm in the fluoroindate fiber, which is twice the spectral broadening compared to a ZBLAN fiber under similar conditions.
Abstract: We report the generation of mid-infrared supercontinua in a step-index fluoroindate-based fiber. The large core of the fluoroindate fiber allows the guiding of multiwatt laser power over a broad spectral range. These fibers exhibit zero dispersion at 1.83 μm, minimal loss of 0.1 dB/m at 3.2 μm up to only 0.8 dB/m at 5 μm. These specifications enable mid-infrared supercontinuum generation and propagation with low loss. By using mid-infrared ultrashort laser pulses from an optical parametric amplifier, we demonstrate generation of a 20 dB spectral flatness supercontinua from 2.7 to 4.7 μm in the fluoroindate fiber, which is twice the spectral broadening compared to a ZBLAN fiber under similar conditions.