Showing papers on "Supercontinuum published in 2011"

Coherent octave spanning near-infrared and visible supercontinuum generation in all-normal dispersion photonic crystal fibers.

Abstract: We present the first detailed demonstrations of octave-spanning SC generation in all-normal dispersion photonic crystal fibers (ANDi PCF) in the visible and near-infrared spectral regions. The resulting spectral profiles are extremely flat without significant fine structure and with excellent stability and coherence properties. The key benefit of SC generation in ANDi PCF is the conservation of a single ultrashort pulse in the time domain with smooth and recompressible phase distribution. For the first time we confirm the exceptional temporal properties of the generated SC pulses experimentally and demonstrate their applicability in ultrafast transient absorption spectroscopy. The experimental results are in excellent agreement with numerical simulations, which are used to illustrate the SC generation dynamics by self-phase modulation and optical wave breaking. To our knowledge, we present the broadest spectra generated in the normal dispersion regime of an optical fiber.

Coherent supercontinuum generation in photonic crystal fiber with all-normal group velocity dispersion.

Abstract: We demonstrate supercontinuum generation in a photonic crystal fiber with all-normal group velocity dispersion. Pumping a short section of this fiber with compressed pulses from a compact amplified fiber laser generates a 200 nm bandwidth continuum with typical self-phase-modulation characteristics. We demonstrate that the supercontinuum is compressible to a duration of 26 fs. It therefore has a high degree of coherence between all the frequency components, and is a single pulse in the time domain. A smooth, flat spectrum spanning 800 nm is achieved using a longer piece of fiber.

Bright spatially coherent wavelength-tunable deep-UV laser source using an Ar-filled photonic crystal fiber.

Abstract: We report on the spectral broadening of ~1 μJ 30 fs pulses propagating in an Ar-filled hollow-core photonic crystal fiber. In contrast with supercontinuum generation in a solid-core photonic crystal fiber, the absence of Raman and unique pressure-controlled dispersion results in efficient emission of dispersive waves in the deep-UV region. The UV light emerges in the single-lobed fundamental mode and is tunable from 200 to 320 nm by varying the pulse energy and gas pressure. The setup is extremely simple, involving <1 m of a gas-filled photonic crystal fiber, and the UV signal is stable and bright, with experimental IR to deep-UV conversion efficiencies as high as 8%. The source is of immediate interest in applications demanding high spatial coherence, such as laser lithography or confocal microscopy.

Nonlinear fiber optics: its history and recent progress [Invited]

Abstract: This review begins with an historical introduction to the field of nonlinear fiber optics and then focuses on the propagation of short optical pulses inside optical fibers. The underlying nonlinear Schrodinger equation is used to discuss the nonlinear phenomenon of self-phase modulation that leads to the formation of solitons in the presence of anomalous dispersion. Recent work on supercontinuum generation is reviewed with emphasis on the important nonlinear processes, such as the fission of higher-order solitons and intrapulse Raman scattering. Applications of fiber-based supercontinuum sources are also discussed in diverse areas ranging from biomedical imaging to frequency metrology. The last part describes applications resulting from nonlinear phenomena, such as cross-phase modulation, stimulated Raman scattering, and four-wave mixing.

Mid-infrared to telecom-band supercontinuum generation in highly nonlinear silicon-on-insulator wire waveguides

Abstract: We demonstrate the generation of a supercontinuum in a 2 cm long silicon wire by pumping the wire with mid-infrared picosecond pulses in the anomalous dispersion regime. The supercontinuum extends from 1535 nm up to 2525 nm for a coupled peak power of 12.7 W. It is shown that the supercontinuum originates primarily from the amplification of background noise. A detailed analysis of the spectral components which are generated through phase-matched processes is applied to extract the group velocity dispersion and fourth-order dispersion coefficient of the silicon wire waveguide.

Supercontinuum generation from ~19 to 45 μmin ZBLAN fiber with high average power generation beyond 38 μm using a thulium-doped fiber amplifier

Abstract: A mid-IR supercontinuum (SC) fiber laser based on a thulium-doped fiber amplifier (TDFA) is demonstrated. A continuous spectrum extending from ∼1.9 to 4.5 μm is generated with ∼0.7 W time-average power in wavelengths beyond 3.8 μm. The laser outputs a total average power of up to ∼2.6 W from ∼8.5 m length of ZrF4─BaF2─LaF3─AlF3─NaF (ZBLAN) fiber, with an optical conversion efficiency of ∼9% from the TDFA pump to the mid-IR SC. Optimal efficiency in generating wavelengths beyond 3.8 μm is achieved by reducing the losses in the TDFA stage and optimizing the ZBLAN fiber length. We demonstrate a novel (to our knowledge) approach of generating modulation instability-initiated SC starting from 1.55 μm by splitting the spectral shifting process into two steps. In the first step, amplified approximately nanosecond-long 1.55 μm laser diode pulses with ∼2.5 kW peak power generate a SC extending beyond 2.1 μm in ∼25 m length of standard single-mode fiber (SMF). The ∼2 μm wavelength components at the standard SMF output are amplified in a TDFA and coupled into ZBLAN fiber leading to mid-IR SC generation. Up to ∼270 nm SC long wavelength edge extension and ∼2.5× higher optical conversion efficiency to wavelengths beyond 3.8 μm are achieved by switching an Er:Yb-based power amplifier stage with a TDFA. The laser also demonstrates scalability in the average output power with respect to the pulse repetition rate and the amplifier pump power. Numerical simulations are performed by solving the generalized nonlinear Schrodinger equation, which show the long wavelength edge of the SC to be limited by the loss in ZBLAN.

Supercontinuum generation in chalcogenide-silica step-index fibers

Abstract: We explore the use of a highly nonlinear chalcogenide-silica waveguide for supercontinuum generation in the near infrared. The structure was fabricated by a pressure-assisted melt-filling of a silica capillary fiber (1.6 µm bore diameter) with Ga4Ge21Sb10S65 glass. It was designed to have zero group velocity dispersion (for HE11 core mode) at 1550 nm. Pumping a 1 cm length with 60 fs pulses from an erbium-doped fiber laser results in the generation of octave-spanning supercontinuum light for pulse energies of only 60 pJ. Good agreement is obtained between the experimental results and theoretical predictions based on numerical solutions of the generalized nonlinear Schrodinger equation. The pressure-assisted melt-filling approach makes it possible to realize highly nonlinear devices with unusual combinations of materials. For example, we show numerically that a 1 cm long As2S3:silica step-index fiber with a core diameter of 1 µm, pumped by 60 fs pulses at 1550 nm, would generate a broadband supercontinuum out to 4 µm.

Supercontinuum generation with femtosecond self-healing Airy pulses.

Abstract: We report experiments and numerical simulations on supercontinuum generation with femtosecond Airy pulses in a highly nonlinear optical fiber. The ability of the Airy waveform to regenerate its dominant intensity peak results in the generation of distinct spectral features. Airy pulses and other self-healing temporal waveforms may be useful for the generation of spectra with desired properties.

Supercontinuum generation in quasi-phase-matched LiNbO3 waveguide pumped by a Tm-doped fiber laser system.

Abstract: We demonstrate self-referencing of a Tm-doped fiber oscillator–amplifier system by performing octave-spanning supercontinuum generation in a periodically poled lithium niobate waveguide. We model the supercontinuum generation numerically and show good agreement with the experiment.

High quality sub-two cycle pulses from compression of supercontinuum generated in all-normal dispersion photonic crystal fiber

Abstract: We demonstrate nonlinear pulse compression based on recently introduced highly coherent broadband supercontinuum (SC) generation in all-normal dispersion photonic crystal fiber (ANDi PCF). The special temporal properties of the octave-spanning SC spectra generated with 15 fs, 1.7 nJ pulses from a Ti:Sapphire oscillator in a 1.7 mm fiber piece allow the compression to 5.0 fs high quality pulses by linear chirp compensation with a compact chirped mirror compressor. This is the shortest pulse duration achieved to date from the external recompression of SC pulses generated in PCF. Numerical simulations in excellent agreement with the experimental results are used to discuss the scalability of the concept to the single-cycle regime employing active phase shaping. We show that previously reported limits to few-cycle pulse generation from compression of SC spectra generated in conventional PCF possessing one or more zero dispersion wavelengths do not apply for ANDi PCF.

Octave spanning supercontinuum in an As 2 S 3 taper using ultra-low pump pulse energy

Abstract: An octave spanning spectrum is generated in an As 2 S 3 taper via 77 pJ pulses from an ultrafast fiber laser. Chirp compensation allows the octave to be generated directly from the un-amplified laser output.

Supercontinuum generation in quasi-phasematched waveguides

Abstract: We numerically investigate supercontinuum generation in quasi-phase-matched waveguides using a single-envelope approach to capture second and third order nonlinear processes involved in the generation of octave-spanning spectra. Simulations are shown to agree with experimental results in reverse-proton-exchanged lithium-niobate waveguides. The competition between χ((2)) and χ((3)) self phase modulation effects is discussed. Chirped quasi-phasematched gratings and stimulated Raman scattering are shown to enhance spectral broadening, and the pulse dynamics involved in the broadening processes are explained.

Design of all-normal dispersion microstructured optical fibers for pulse-preserving supercontinuum generation

Abstract: Recently, the generation of coherent, octave-spanning, and recompressible supercontinuum (SC) light has been demonstrated in optical fibers with all-normal group velocity dispersion (GVD) behavior by femtosecond pumping. In the normal dispersion regime, soliton dynamics are suppressed and the SC generation process is mainly due to self-phase modulation and optical wave breaking. This makes such white light sources suitable for time-resolved applications. The broadest spectra can be obtained when the pump wavelength equals the wavelength of maximum all-normal GVD. Therefore each available pump wavelength requires a specifically designed optical fiber with suitable GVD to unfold its full power. We investigate the possibilities to shift the all-normal maximum dispersion wavelength in microstructured optical fibers from the near infra red (NIR) to the ultra violet (UV). In general, a submicron guiding fiber core surrounded by a holey region is required to overcome the material dispersion of silica. Photonic crystal fibers (PCFs) with a hexagonal array of holes as well as suspended core fibers are simulated for this purpose over a wide field of parameters. The PCFs are varied concerning their air hole diameter and pitch and the suspended core fibers are varied concerning the number of supporting walls and the wall width. We show that these two fiber types complement each other well in their possible wavelength regions for all-normal GVD. While the PCFs are suitable for obtaining a maximum all-normal GVD in the NIR, suspended core fibers are well applicable in the visible wavelength range.

Observations of four types of pulses in a fiber laser with large net-normal dispersion

Abstract: Four different types of pulses are experimentally obtained in one erbium-doped all-fiber laser with large net-normal dispersion. The proposed laser can deliver the rectangular-spectrum (RS), Gaussian-spectrum (GS), broadband-spectrum (BS), and noise-like pulses by appropriately adjusting the polarization states. These kinds of pulses have distinctly different characteristics. The RS pulses can easily be compressed to femtosecond level whereas the pulse energy is restricted by the trend of multi-pulse shaping with excessive pump. The GS and BS pulses always maintain the single-pulse operation with much higher pulse-energy and accumulate much more chirp. After launching the pulses into the photonic-crystal fiber, the supercontinuum can be generated with the bandwidth of >700 nm by the BS pulses and of ~400 nm by the GS pulses, whereas it can hardly be generated by the RS pulses. The physical mechanisms behind the continuum generation are qualitatively investigated relating to different operating regimes. This work could help to a deeper insight of the normal-dispersion pulses.

Complete characterization of supercontinuum coherence

Abstract: Using second-order coherence theory of nonstationary light we examine in detail the coherence properties of supercontinuum radiation generated in nonlinear fibers. We show that the supercontinuum c ...

Ultrabroadband coherent supercontinuum frequency comb

Abstract: We present detailed studies of the coherence properties of an ultrabroadband supercontinuum, enabled by a comprehensive approach involving continuous-wave laser sources to independently probe both the amplitude and phase noise quadratures across the entire spectrum. The continuum coherently spans more than 1.5 octaves, supporting Hz-level comparison of ultrastable lasers at 698 nm and 1.54 $\ensuremath{\mu}$m. We present a complete numerical simulation of the accumulated comb coherence in the limit of many pulses, in contrast to the single-pulse level, with systematic experimental verification. The experiment and numerical simulations reveal the presence of quantum-seeded broadband amplitude noise without phase coherence degradation, including the discovery of a dependence of the supercontinuum coherence on the fiber fractional Raman gain.

Manipulating supercontinuum generation by minute continuous wave

Abstract: We report a simple triggering mechanism that greatly enhances and stabilizes supercontinuum generation by using an extremely weak cw light (~200,000 times weaker than the pump light). Such an active manipulation scheme can be enabled by a wide range of input conditions and circumvents complex techniques such as precise time delay tuning and dedicated feedback control. It thus offers a handy and versatile approach to control and optimize supercontinuum generation, expanding its range of applications, including ultrafast all-optical signal processing, spectroscopy, and imaging. The utility of the present technique for improving signal integrity in chirped pump optical parametric amplification is also demonstrated.

Arrest of self-focusing collapse in femtosecond air filaments: higher order Kerr or plasma defocusing?

Abstract: Experimentally measured conical emission rings on the blue side of the filament supercontinuum of a 800 nm50 fs pulse in air are reproduced in simulations with plasma and the third-order Kerr as the nonlinear terms. This agreement indicates plasma as the dominant mechanism arresting the self-focusing collapse. The higher order Kerr terms with the recently measured coefficients stop the collapse at a lower intensity than the plasma does and lead to the spherical angle-wavelength spectrum without blueshifted rings.

Generation of high quality, 1.3 cycle pulses by active phase control of an octave spanning supercontinuum.

Abstract: Nonlinear pulse compression based on the generation of ultra-broadband supercontinuum (SC) in an all-normal dispersion photonic crystal fiber (ANDi PCF) is demonstrated. The highly coherent and smooth octave-spanning SC spectra are generated using 6 fs, 3 nJ pulses from a Ti:Sapphire oscillator for pumping a 13 mm piece of ANDi PCF. Applying active phase control has enabled the generation of 4.5 fs pulses. Additional spectral amplitude shaping has increased the bandwidth of the SC spectra further leading to nearly transform-limited pulses with a duration of 3.64 fs, which corresponds to only 1.3 optical cycles at a central wavelength of 810 nm. This is the shortest pulse duration achieved via compression of SC spectra generated in PCF to date. Due to the high stability and the smooth spectral intensity and phase distribution of the generated SC, an excellent temporal pulse quality exhibiting a pulse contrast of 14 dB with respect to the pre- and post-pulses is achieved.

On-chip two-octave supercontinuum generation by enhancing self-steepening of optical pulses

Abstract: Dramatic advances in supercontinuum generation have been made recently using photonic crystal fibers, but it is quite challenging to obtain an octave-spanning supercontinuum on a chip, partially because of strong dispersion in high-index-contrast nonlinear integrated waveguides. We show by simulation that extremely flat and low dispersion can be achieved in silicon nitride slot waveguides over a wavelength band of 500 nm. Different from most of previously reported supercontinua that were generated either by higher-order soliton fission in anomalous dispersion regime or by self-phase modulation in normal dispersion regime, a two-octave supercontinuum from 630 to 2650 nm (360 THz in total) can be generated by enhancing self-steepening in pulse propagation in nearly zero dispersion regime, when an optical shock as short as 3 fs is formed.

Stimulated Raman scattering using a single femtosecond oscillator with flexibility for imaging and spectral applications.

Abstract: Stimulated Raman scattering (SRS) is a powerful tool for obtaining background-free chemical information about a material without extrinsic labeling. Background-free spectra are particularly important in the fingerprint region (~800 and 1800 cm(-1)) where peaks are narrow, closely-spaced, and may be in abundance for a particular chemical. We demonstrate a method for obtaining SRS spectra using a single femtosecond laser oscillator. A photonic crystal fiber is used to create a supercontinuum to provide a range of Stokes shifts from ~300 to 3400 cm(-1). This SRS approach provides for collection capabilities that are easily modified between obtaining broadband spectra and single-frequency images.

Micrometer axial resolution OCT for corneal imaging

Abstract: An optical coherence tomography (OCT) for high axial resolution corneal imaging is presented. The system uses 375 nm bandwidth (625 to 1000 nm) from a broadband supercontinuum light source. The system was developed in free space to minimize image quality degradation due to dispersion. A custom-designed spectrometer based on a Czerny Turner configuration was implemented to achieve an imaging depth of 1 mm. Experimentally measured axial resolution was 1.1 μm in corneal tissue and had a good agreement with the theoretically calculated resolution from the envelope of the spectral interference fringes. In vivo imaging was carried out and thin corneal layers such as the tear film and the Bowman’s layer were quantified in normal, keratoconus, and contact lens wearing eyes, indicating the system’s suitability for several ophthalmic applications.

High average power, strictly all-fiber supercontinuum source with good beam quality.

Abstract: A 1.05 μm picosecond pulsed fiber master oscillator power amplifier system delivering an average power of over 100 W was used to pump a 5 m long commercially available photonic crystal fiber and a 49.8 W supercontinuum spanning from around 500 nm to above 1700 nm was generated. Strictly single mode operation of the all-fiber supercontinuum source across the whole spectral range was verified through the quantitative measurement of the beam quality.

Self-referenceable frequency comb from a gigahertz diode-pumped solid-state laser

Abstract: We present carrier envelope offset (CEO) frequency detection of a diode-pumped Yb:KGW (ytterbium-doped potassium gadolinium tungstate) laser with a repetition rate of 1 GHz. The SESAM-soliton-modelocked laser delivers 2.2-W average power in 290-fs pulses. This corresponds to a peak power of 6.7 kW and the optical-to-optical efficiency is 38%. With a passive pulse compression the duration is reduced to 100 fs at an average power of 1.1 W. Coherent supercontinuum (SC) generation in a highly nonlinear photonic crystal fiber (PCF) is achieved without additional amplification. Furthermore we have demonstrated that pulse compression towards lower soliton orders of approximately 10 was required for coherent SC generation and CEO detection. Additional numerical simulations further confirm these experimental results.

Single attosecond pulse from terahertz-assisted high-order harmonic generation

Abstract: High-order harmonic generation by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to generate single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse generation from 23 to 93 eV. We demonstrate that phase-matching effects are responsible for the generation of isolated attosecond pulses, even in conditions when single-atom response yields an attosecond pulse train.

Cascaded Raman shifting of high-peak-power nanosecond pulses in As_2S_3 and As_2Se_3 optical fibers

Abstract: We report efficient cascaded Raman scattering of near-IR nanosecond pulses in large-core (65 μm diameter) As2S3 and As2Se3 optical fibers. Raman scattering dominates other spectral broadening mechanisms, such as four-wave mixing, modulation instability, and soliton dynamics, because the fibers have large normal group-velocity dispersion in the spectral range of interest. With ∼2 ns pump pulses at a wavelength of 1.9 μm, four Stokes peaks, all with peak powers greater than 1 kW, have been measured.

Five-order SRSs and supercontinuum generation from a tapered tellurite microstructured fiber with longitudinally varying dispersion

Abstract: We try to obtain stable supercontinuum (SC) generation with broad bandwidth under relative simple pump conditions. We use a 1.3-m-long highly nonlinear tellurite microstructured fiber and pump it by a 15 ps 1064 nm fiber laser. One segment of the fiber is tapered from a core diameter of 3.4 μm to 1.3 μm. For the first time five-order stimulated Raman scatterings (SRSs) are observed for soft glass fibers. SC covering 730-1700 nm is demonstrated with the pump-pulse-energy of several nJ. The mechanisms of SC broadening are mainly SRS, self-phase modulation (SPM) and cross phase modulation (XPM). The tapered segment has two advantages. Firstly it increases the nonlinearity of fiber by several times. Secondly, it acts as a compensation for the dispersion of the untapered segment, and mitigates the walk-off between pump pulse and SRS peaks.

Mid-IR supercontinuum generation in Ho-doped fiber amplifier

Abstract: For the first time to our best knowledge we have used Ho-doped fiber amplifier to get supercontinuum in the mid-IR range using all-fiber scheme. To pump the source Q-switched Er-doped fiber was used. The observed spectrum covers the spectral range from 2000 to 2500 nm with the power variation less than two decades. Average power of 0.4 W and pulse energy of 0.1 mJ was measured.

Nonlinear effects in optical fibers

Abstract: Preface. 1 Introduction. References. 2 Electromagnetic Wave Propagation. 2.1 Wave Equation for Linear Media. 2.2 Electromagnetic Waves. 2.3 Energy Density and Flow. 2.4 Phase Velocity and Group Velocity. 2.5 Reflection and Transmission of Waves. 2.6 The Harmonic Oscillator Model. 2.7 The Refractive Index. 2.8 The Limit of Geometrical Optics. Problems. References. 3 Optical Fibers. 3.1 Geometric Optics Description. 3.2 Wave Propagation in Fibers. 3.3 Fiber Attenuation. 3.4 Modulation and Transfer of Information. 3.5 Chromatic Dispersion in Single-Mode Fibers. 3.6 Polarization-Mode Dispersion. Problems. References. 4 The Nonlinear Schrodinger Equation. 4.1 The Nonlinear Polarization. 4.2 The Nonlinear Refractive Index. 4.3 Importance of Nonlinear Effects in Fibers. 4.4 Derivation of the Nonlinear Schrodinger Equation. 4.5 Soliton Solutions. 4.6 Numerical Solution of the NLSE. Problems. References. 5. Nonlinear Phase Modulation. 5.1 Self-Phase Modulation. 5.2 Cross-Phase Modulation. Problems. References. 6. Four-Wave Mixing. 6.1 Wave Mixing. 6.2 Mathematical Description. 6.3 Phase Matching. 6.4 Impact and Control of FWM. 6.5 Fiber Parametric Amplifiers. 6.6 Parametric Oscillators. 6.7 Nonlinear Phase Conjugation with FWM. 6.8 Squeezing and Photo-Pair Sources. Problems. References. 7 Intrachannel Nonlinear Effects. 7.1 Mathematical Description. 7.2 Intrachannel XPM. 7.3 Intrachannel FWM. 7.4 Control of Intrachannels Nonlinear Effects. Problems. References. 8 Soliton Lightwave Systems. 8.1 Soliton Properties. 8.2 Perturbation of Solitons. 8.3 Path-Averaged Solitons. 8.4 Soliton Transmission Control. 8.5 Dissipative Solitons. 8.6 Dispension-Managed Solitons. 8.7 WDM Soliton Systems. Problems. References. 9 Other Applications of Optical Solitons. 9.1 Soliton Fiber Lasers. 9.2 Pulse Compression. 9.3 Fibers Bragg Gratings. Problems. References. 10 Polarization Effects. 10.1 Coupled Nonlinear Schrodinger Equations. 10.2 Nonlinear Phase Shift. 10.3 Solitons in Fibers with Constant Birefringence. 10.4 Solitons in Fibers with Randomly Varying Birefringence. 10.5 PMD-Induced Soliton Pulse Broadening. 10.6 Dispersion-Managed Solitons and PMD. Problems. References. 11 Stimulated Raman Scattering. 11.1 Raman Scattering in the Harmonic Oscillator Model. 11.2 Raman Gain. 11.3 Raman Threshold. 11.4 Impact of Raman Scattering on Communication Systems. 11.5 Raman Amplification. 11.6 Raman Fiber Lasers. Problems. References. 12 Stimulated Brillouin Scattering. 12.1 Light Scattering at Acoustic Waves. 12.2 The Coupled Equations for Stimulated Brillouin Scattering. 12.3 Brillouin Gain and Bandwidth. 12.4 Threshold of Stimulated Brillouin Scattering. 12.5 SBS in Active Fibers. 12.6 Impact of SBS on Communication Systems. 12.7 Fiber Brillouin Amplifiers. 12.8 SBS Slow Light. 12.9 Fiber Brillouin Lasers. Problems. References. 13 Highly Nonlinear and Microstructured Fibers. 13.1 The Nonlinear Parameter in Silica Fibers. 13.2 Microstructured Fibers. 13.3 Non-Silica Fibers. 13.4 Soliton Self-Frequency Shift. 13.5 Four-Wave Mixing. 13.6 Supercontinuum Generation. Problems. References. 14 Optical Signal Processing. 14.1 Nonlinear Sources for WDM Systems. 14.2 Optical Regeneration. 14.3 Optical Pulse Train Generation. 14.4 Wavelength Conversion. 14.5 All-Optical Switching. Problems. References. Index.

Optimum fiber tapers for increasing the power in the blue-edge of a supercontinuum - group-acceleration matching

Abstract: We demonstrate how the gradient of the tapering in a tapered fiber can significantly affect the trapping and blueshift of dispersive waves (DWs) by a soliton. By modeling the propagation of a fundamental 10 fs soliton through tapered fibers with varying gradients, it is shown that the soliton traps and blueshifts an increased fraction of the energy in its DW when the gradient is decreased. This is quantified by the group-acceleration mismatch between the soliton and DW at the entrance of the taper. These findings have direct implications for the achievable power in the blue edge of a supercontinuum generated in a tapered fiber and explain observations of a lack of power in the blue edge.