Search

We demonstrate the design, production, characterization and application of two dispersive complementary mirror pairs compensating second- and third-order dispersion, respectively. Both mirror pairs operate in the spectral range from 1.2-3.2µm. This is an unprecedented bandwidth of over 1.4 octaves which can drive further improvements in Cr:ZnS, Cr:ZnSe and other laser systems with a central wavelength around 2µm. The first pair provides a constant group delay dispersion of −100fs2, while the second one enables the compensation of the third-order dispersion that is introduced by a TiO2 crystal.

A third-order dispersion compensating mirror pair was designed, produced and characterized. It covers the spectral range from 1.2-3.2µm. This is shown by the application in a Cr:ZnS laser system.

We present generation of 7.5-fs pulses at 2.3 µm driven by a carrier-envelope-phase-stabilized diode-pumped Cr:ZnS oscillator. The single-cycle waveforms exhibit exceptional stability with a residual phase jitter of 8.6 mrad (0.2 Hz − 11.4 MHz).

Diode-pumped Cr:ZnS oscillators have emerged as precursors for single-cycle infrared pulse generation with excellent noise performance. Here we demonstrate a Cr:ZnS amplifier with direct diode-pumping to boost the output of an ultrafast Cr:ZnS oscillator with minimum added intensity noise. Seeded with a 0.66-W pulse train at 50-MHz repetition rate and 2.4 µm center wavelength, the amplifier provides over 2.2 W of 35-fs pulses. Due to the low-noise performance of the laser pump diodes in the relevant frequency range, the amplifier output achieves a root mean square (RMS) intensity noise level of only 0.03% in the 10 Hz–1 MHz frequency range and a long-term power stability of 0.13% RMS over one hour. The diode-pumped amplifier reported here is a promising driving source for nonlinear compression to the single- or sub-cycle regime, as well as for the generation of bright, multi-octave-spanning mid-infrared pulses for ultra-sensitive vibrational spectroscopy.

The technique of intra-pulse difference frequency generation (IDFG) is highly sought after for delivering broadband mid-infrared (MIR) radiation (2.5-20 µm) in a robust single-beam geometry [1] . Featuring intrinsic carrier-envelope phase stabilization, the few-cycle output pulses can be directly used for numerous emerging time-domain and frequency comb applications [2] , [3] . However, a complex chain of amplification, pulse compression and parametric conversion stages is typically required to drive IDFG in an efficient manner. Here, we report a novel and powerful directly diode-pumped Cr:ZnS oscillator to generate a multi-octave-spanning MIR spectrum.

Carrier-envelope-phase stable, multi-octave-spanning light sources enable novel types of spectroscopy techniques with unprecedented high sensitivity and dynamic range [1] , [2] . They are thus highly sought after, especially in the mid-infrared molecular finger-print region. Cr:ZnS lasers — capable of directly emitting sub-30 fs pulses at a central wavelength around 2.4 µm and at multi-Watt-level of average power [3] , [4] — are the ideal front-end for generating such spectral coverage [5] . These lasers have predominantly been pumped using rare-earth-doped fiber lasers, which often exhibit intensity noise in the kHz range arising from relaxation oscillations. The subsequent transfer of such noise to the Cr:ZnS output in turn affects the signal-to-noise ratio for downstream spectroscopy applications. This can be alleviated by pumping the Cr:ZnS lasers with the direct output of diode lasers, which can also be more cost effective. To this end, we have recently demonstrated a directly diode-pumped femtosecond Cr:ZnS oscillator [6] . To further enhance the available power and widen its possible applications, we report here the first demonstration of a directly diode-pumped Cr:ZnS amplifier, to the best of our knowledge.

We demonstrate for the first time the generation of octave-spanning mid-infrared using a BGSe nonlinear crystal. A Cr:ZnS laser system delivering 28-fs pulses at a central wavelength of 2.4 µm is used as the pump source, which drives the intra-pulse difference frequency generation inside the BGSe crystal. As a result, a coherent broadband mid-infrared continuum spanning from 6 to 18 µm has been obtained. It shows that the BGSe crystal is a promising material for broadband, few-cycle mid-infrared generation via frequency down conversion with femtosecond pump sources.

Thin-disk technology uniquely enables the simultaneous scaling of both average and peak powers, while maintaining an excellent beam profile. It has been widely adopted in the 1-μm region, not only for continuous wave lasers but also for pulsed oscillators and amplifiers. However, the development of 2-μm thin-disk lasers is still at a very early stage, with passive mode locking having been demonstrated only recently. Here, we describe in detail a new femtosecond Ho:YAG thin-disk oscillator and recent power-scaling experiments that resulted in an average power of up to 25 W—the highest average power of any mode-locked oscillator in the 2-μm region. The future directions toward even higher average and peak power thin-disk oscillators are also discussed.

Dual-comb spectroscopy (DCS) normally operates with two independent, relatively low power and actively synchronized laser sources. This hinders the wide adoption for practical implementations and frequency conversion into deep UV and VUV spectral ranges. Here, we report a fully passive, high power dual-comb laser based on thin-disk technology and its application to direct frequency comb spectroscopy. The peak power (1.2 MW) and the average power (15 W) of our Yb:YAG thin-disk dual-comb system are more than one-order-of-magnitude higher than in any previous systems. The scheme allows easy adjustment of the repetition frequency difference during operation. Both combs share all cavity components which leads to an excellent mutual stability. A time-domain signal recorded over 10 ms without any active stabilization was sufficient to resolve individual comb lines after Fourier transformation.

We report a Kerr-lens mode-locked Cr:ZnS oscillator directly pumped by two laser diodes, providing 34 fs pulses with 800 mW average power at 2.4 pm. This low-noise affordable femtosecond laser facilitates numerous emerging mid-infrared applications.

Lasers based on Cr$^{2+}$-doped II-VI material, often known as the Ti:Sapphire of the mid-infrared, can directly provide few-cycle pulses with super-octave-spanning spectra, and serve as efficient drivers for generating broadband mid-infrared radiation. It is expected that the wider adoption of this technology benefits from more compact and cost-effective embodiments. Here, we report the first directly diode-pumped, Kerr-lens mode-locked Cr$^{2+}$-doped II-VI oscillator pumped by a single InP diode, providing average powers of over 500 mW and pulse durations of 45 fs - shorter than six optical cycles at 2.4 $\mu$m. These correspond to a sixty-fold increase in peak power compared to the previous diode-pumped record, and are at similar levels with respect to more mature fiber-pumped oscillators. The diode-pumped femtosecond oscillator presented here constitutes a key step towards a more accessible alternative to synchrotron-like infrared radiation, and is expected to accelerate research in laser spectroscopy and ultrafast infrared optics., Comment: 8 pages, 5 figures

We present a mid-infrared (MIR) source based on intra-pulse difference-frequency generation under the random quasi-phase-matching condition. The scheme enables the use of non-birefringent materials whose crystal orientations are not perfectly and periodically poled, widening the choice of media for nonlinear frequency conversion. With a 2 μm driving source based on a Ho:YAG thin-disk laser, together with a polycrystalline ZnSe element, an octave-spanning MIR continuum (2.7–20 μm) was generated. At over 20 mW, the average power is comparable to regular phase-matching in birefringent crystals. A 1 μm laser system based on a Yb:YAG thin-disk laser was also tested as a driving source in this scheme. The new approach provides a simplified way for generating coherent MIR radiation with an ultrabroad bandwidth at reasonable efficiency.

Ever shorter, more broadband and higher peak power laser sources at high repetition rates are in strong demand, as they can benefit researches such as nonlinear spectroscopy. The all-bulk spectral broadening approach, arranged for example as a multi-pass cell, has seen rapid development recently. The scheme involves self-phase modulation (SPM) and compression of high-power laser pulses, either emitted from MOPA-type systems [1] or oscillator devices [2]. In contrast to waveguides, the separation of nonlinear and dispersive elements allows extensive control over the net dispersion, making it particularly interesting for the realizing of different nonlinear effects, such as soliton Raman self-frequency shift (SRSFS) effect. In comparison to the symmetric broadening of SPM, SRSFS can generate a power-tunable, asymmetric red-shift [3]. This technique has frequently been applied in optical fibers at a nJ-level of pulse energy. Here we present, to the best of our knowledge, the first implementation of this process to high-energy (>1 μJ) pulses in a Herriott-type multi-pass cell (HC).

Coherent mid-infrared (MIR) light has a plethora of important applications ranging from life-science to industrial processes. Simultaneous coverage of this region will enable the parallel detection of various chemicals and enhance the specificity of their detection [1]. One of the most popular broadband infrared generation methods is nonlinear down-conversion from the near-infrared. An effective conversion can be achieved by using phase-matching and quasi-phase-matching in birefringent crystals and crystals with periodically poled structure respectively. Random quasi-phase-matching (RQPM) in poly-crystals is an alternative method that has recently shown great promise [2,3], which results in a gradual growth of the generated signal linear to the propagation length. Compared to generic phase-matching schemes, RQPM offers an unparalleled phase-matching bandwidth that is insensitive to incident angle. In addition, unlike single-crystals, poly-crystals can easily be grown into larger dimensions to enable longer interaction lengths. Here we describe the generation of octave-spanning MIR continuum at over 20 mW of average power based on RQPM driven by a Ho:YAG thin-disk oscillator at 2.1 μm [4]. To the best of our knowledge, this is the first time RQPM has been implemented for intra-pulse difference-frequency generation (DFG). A 1 μm laser system based on a Yb:YAG thin-disk oscillator [5] was also tested as the driving source in this scheme.

Waveform-stable, pulsed laser sources have enabled both time-domain and frequency-domain precision metrology, through real-time measurement of electric-field-driven light-matter interactions on their native femto- and attosecond time scales, and by harnessing the frequency-comb nature of high-repetition-rate pulse trains. Particular interest has been shown in these sources for use in infrared (IR) molecular fingerprinting [1,2], offering increased sensitivity and specificity compared to traditional, thermal-source-based Fourier-transform spectroscopy, for applications such as biomedical spectroscopy or trace-chemical sensing. Here, we present a compact, 50-MHz source of high-power, waveform-stable IR pulses. Driven by a 2μm based fiber chirped pulse amplifier (FCPA), three parallel nonlinear fiber channels are used to cover the spectral range of 1.4 to 20 μm.

Advanced broadband dispersive multilayer optical components have become key elements in modern laser systems [1]. Along with well-known dispersive mirrors operating effectively in the systems based on Ti:Sa lasers (∼800 nm) and near-infrared Yb:YAG lasers (∼1030 nm), the dispersive optics technology is being used in 2-μm laser systems based on Thulium- and Holmium[2]. Further development of the technology based on 2.4 μm Cr:ZnS-lasers will extend laser output to 3.2 μm [3,4]. Availability of dispersive optics covering the spectral range from 2 to 3.2 μm is demanded for this promising technology. Until now, the best achievements in this direction was a 1/3-octave dispersive mirror operating in the range 2.2–2.7 μm with the group delay dispersion of −200 fs2 and a high-reflector compensating the third-order dispersion of −3000 fs3[5]. In the present work, a large progress in the development of dispersive optics for 2–4 μm region is reported. The novel 2/3-octave dispersive elements achieve reflectance exceeding 99.6% and group delay values of (−200 fs2) in the entire range from 2 to 3.2 μm. The advanced feature is a very small degradation of reflectance in the OH absorption wavelength range between 2.7 μm and 2.9 μm. Exploitation of typical thin-film materials such as Ta 2 O 5 /SiO 2 and Nb 2 O 5 /SiO 2 do not provide the refractive index ratios, which are large not enough to achieve both high reflectance and desired phase properties. Also, the use of thin-film materials typical for the visible-near-infrared ranges does not allow achieving negative group delay dispersion values required for the development of Cr:ZnS oscillator because of very high oscillations in group delay dispersion. In the present work, the thin-film materials Si and SiO 2 providing a high ratio of the refractive index values of 2.3 are used for the first time for the design and production of dispersive elements in the infrared spectral range 2–3.2 μm.

Broadband coherent infrared radiation has numerous applications in chemical, biological and material science. In particular, the spectral region spanning 2–20 μιη is highly sought after for chemical identification [1]. Recently, intra-pulse difference-frequency generation based on 2 μm lasers has emerged as a promising technique for robustly generating broadband coherent mid-infrared radiation [2–5]. It can also provide few-cycle pulses [6] with intrinsic carrier-envelope phase stabilization—critical for time domain and frequency comb applications. Here we present a table-top IDFG system that can simultaneously cover most of the spectral region of interest at hundred-mW-level average power.

Solid-state lasers based on Cr2+-doped II-VI materials have proven to be reliable sources for generating few-cycle pulses in the mid-infrared (2–3 μm) spectral range [1–3], making them highly attractive for spectroscopic applications [1]. Er:fiber and Tm:fiber lasers are currently the pump sources of choice for building high-power Cr:ZnS/ZnSe oscillators. However, they involve high initial costs and usually result in strong intensity noise features in the kHz-frequency range [2]. Recent improvements in output power of laser diodes, which have intrinsically lower intensity noise, render direct diode-pumping of Cr:ZnS/ZnSe lasers a viable alternative to common fiber-based schemes. Here, we report the first time that diode-pumping was applied to a Kerr-lens mode-locked oscillator with a Cr2+-doped II-VI gain material.

Femtosecond light sources in the 3–5 μm region are highly sought after for numerous applications. While they can be generated by using nonlinear effects in optical fibers, the efficiencies and effectiveness of frequency conversion can be significantly enhanced by using ultrashort driving pulses. Here, we report on a few-cycle Cr:ZnS oscillator driving low-order soliton dynamics in soft-glass fibers. By selecting appropriate parameters, sub-two-cycle pulses or broad supercontinua spanning over 1.7 octaves from 1.6 to 5.1 μm can be generated at average power levels exceeding 300 mW. In the same setting, Raman-induced soliton self-frequency shifting has been exploited to generate sub-100-fs pulses continuously tunable from 2.3 to 3.85 μm with a conversion efficiency of ∼50%. These results demonstrate the vast potential of using Cr:ZnS or Cr:ZnSe lasers for powerful mid-infrared generation.

Dispersive mirrors operating in a broadband infrared spectral range are reported for the first time. The mirrors are based on Si/SiO

Dispersive mirrors operating in a broadband infrared spectral range are reported for the first time. The mirrors are based on Si/SiO2 thin-film materials. The coatings exhibit reflectance exceeding 99.6% in the spectral range from 2 to 3.2 µm and provide a group delay dispersion of -100 fs2 and -200 fs2 in this range. The fabricated mirrors are expected to be key elements of Cr:ZnS/Cr:ZnSe femtosecond lasers and amplifiers. The mirrors open a new avenue in the development of ultrafast dispersive optics operating in the infrared spectral range.

We report Si/SiO2 mirrors operating in the spectral range 2-3.2 um. The coatings exhibit reflectance exceeding 99.6% and provide group delay dispersion of (-100 fs2) and (-200 fs2.) The mirrors are key elements of Cr:ZnS/Cr:ZnSe femtosecond lasers and oscillators.

We report a 2-octave mid-infrared continuum simultaneously spanning from 500 cm-1 to 2250 cm-1 at 24 mW of average power. It is based on difference frequency generation driven by a newly developed femtosecond Ho:YAG thin-disk oscillator.

The broadband dispersive mirror based on Si/SiO2 thin-film materials and providing group delay dispersion of -200 fs2 in the spectral range from 2 to 3.2 µm have been successfully developed and produced for the first time. The mirrors open a new avenue in the development of ultrafast optics operating in the infrared spectral range and push forward the ultrafast mid-infrared technology.

A simplified scheme of broadband mid-infrared generation is presented, where the intra-pulse difference-frequency-generation (IDFG) process is cascaded in a single pass. Driven by a Cr:ZnS laser, the system provides ultra-broadband coverage with femtosecond pulse durations.

High power ultrafast laser sources at 2 μm are highly desirable as primary sources in many fields such as mid-IR generation, remote sensing, Lidar systems, and medical use. Ho:YAG is an excellent gain crystal for such kind of sources due to its low quantum defect, good crystal quality and broad emission bandwidth. To date, Ho:YAG has been utilized in q-switched and actively mode-locked systems [1, 2]. Very recently passive mode locking has also been demonstrated using semiconductor saturable absorber mirrors (SESAMs) [3, 4]. However, the output power and pulse duration were limited to only several hundred milliwatts and few picoseconds, respectively. Since the invention of thin disk technology, great progress has been made in power and energy scaling of thin disk lasers mode-locked by both SESAM and Kerr-lens mode locking (KLM) [5, 6]. However, KLM shows great advantages compared to SESAM mode-locking in generating shorter pulses with high power due to its fast response time, broad bandwidth operation and higher damage threshold. Here we present a KLM Ho:YAG thin disk oscillator working at 2.1 μm for the first time. It delivers 220 fs pulses with average power up to 20 W, which is, to the best of our knowledge, the shortest pulse duration ever obtained in a Ho:YAG oscillator and highest average power of any mode locked ultrafast oscillator in 2 μm range.

High peak power, few cycle pulses at 2 um are highly sought after for their ability to generate ultrabroad, passively CEP stabilized continua in the mid-infrared (IR) [1] using highly nonlinear non-oxide crystals, which promises numerous applications in physics, environmental and life sciences. Recently, a Kerr-lens mode-locked Ho:YAG thin disk (based on TRUMPF technology) oscillator has directly generated high power femtosecond pulses at 2.1 micron [2], and the output can be further compressed for applications requiring few-cycle pulses. Soliton self-compression is an elegant scheme that can deliver such pulses directly from the fiber, and has previously been applied to pulse compression of a Yb:YAG thin-disk oscillator [3] and to ∼2 micron fiber sources [4,5]. Here we demonstrate the compression of 260 fs pulses down to 15 fs using a silica glass fiber, delivering, to the best of our knowledge, the shortest pulses from any holmium or thulium-based laser system.

We report a challenging design, fabrication and post-production characterization problem of a dispersive mirror supporting the spectral range from 2000 nm to 2200 nm and providing a group delay dispersion of -1000 fssup2/sup. The absolute reflectance in the working range is over 99.95%. The reported mirror is a critical element for Tm and Ho based lasers and paves the way for the development of ultrafast 2 µm lasers with sub-100 fs pulse duration.

We present a source of brilliant mid-infrared radiation, seamlessly covering the wavelength range between 1.33 and 18 μm (7500–555 cm−1) with three channels, employing broadband nonlinear conversion processes driven by the output of a thulium-fiber laser system. The high-average-power femtosecond frontend delivers a 50 MHz train of 250 fs pulses spectrally centered at 1.96 μm. The three parallel channels employ soliton self-compression in a fused-silica fiber, supercontinuum generation in a ZBLAN fiber, and difference-frequency generation in GaSe driven by soliton self-compressed pulses. The total output enables spectral coverage from 1.33 to 2.4 μm, from 2.4 to 5.2 μm, and from 5.2 to 18 μm with 4.5 W, 0.22 W and 0.5 W, respectively. This spatially coherent source with a footprint of less than 4 m2 exceeds the brilliance of 3rd-generation synchrotrons by more than three orders of magnitude over 90% of the bandwidth.

A myriad of existing and emerging applications could benefit from coherent and broadband mid-infrared (MIR) light. Yet, existing tabletop sources are often complex or sensitive to interferometric optical misalignment. Here we demonstrate a significantly simplified scheme of broadband MIR generation by cascading the intra-pulse difference-frequency generation process in a specific nonlinear crystal. This allows pulses generated directly from mode-locked lasers to be used without further nonlinear temporal compression. The system, together with the driving beam, can provide an ultra-broadband coherent radiation coverage ranging from 2 to 17 μm with femtosecond pulse durations. To the best of our knowledge, this is the first demonstration of cascaded DFG in the MIR range, which brings emerging time-domain spectroscopic techniques closer to real-world applications.

We report the first mode-locked Ho:YAG thin-disk oscillator delivering 220 fs pulses at 20 W average power and 2090 nm central wavelength. The output parameters constitute the highest average power of any mode-locked oscillator around 2 μm.

We report the first mode-locked Ho:YAG thin-disk oscillator delivering 270-fs pulses at 28 W average power and 2090 nm central wavelength. The output parameters constitute the shortest pulse duration and highest average power of any mode-locked oscillator around 2 µm.

We report on the generation of a three-octave-wide supercontinuum extending from the vacuum ultraviolet (VUV) to the near-infrared, spanning at least 113 to 1000 nm (i.e., 11 to 1.2 eV), in He-filled hollow-core kagome-style photonic crystal fiber. Numerical simulations confirm that the main mechanism is a novel and previously undiscovered interaction between dispersive-wave emission and plasma-induced blueshifted soliton recompression around the fiber zero dispersion frequency. The VUV part of the supercontinuum, which modeling shows to be coherent and possess a simple phase structure, has sufficient bandwidth to support single-cycle pulses of 500 attosecond duration. We also demonstrate, in the same system, the generation of narrower-band VUV pulses, through dispersive-wave emission, tunable from 120 to 200 nm with efficiencies exceeding 1% and VUV pulse energies in excess of 50 nJ., Comment: 7 pages, 5 figures

By utilizing the versatile dispersion properties and enhanced nonlinearity of all-silica solid-core photonic crystal fiber, supercontinnum sources extending from below 400 nm up to the near-infrared have been generated (P. St.J. Russell, J. Lightwave Tech. 24, 2006, pp. 4729–4749). The spectral range is usually limited by the transmission properties of the material and alternative ways to extend the achievable wavelengths must be found. One possibility is to use exotic glass such as heavy-metal oxide, chalcogenide or fluoride-based glass. Unfortunately, the viscosity of these glasses rapidly changes with temperature and the suitable range of drawing temperature is considerably reduced compare to silica. Microstructured fibers made of such glasses are therefore extremely challenging to produce. On the other hand, they are ideal candidates for ultra-broad supercontinuum because of their very large transmission window (from ∼200nm to above 7 µm for ZBLAN). We recently successfully drew ZBLAN PCF. We will present here recent results on the generation of ultrabroad supercontinuum is such fibers.

Compression of 250-fs, 1-μJ pulses from a KLM Yb:YAG thin-disk oscillator down to 9.1 fs is demonstrated. A kagomé-PCF with a 36-μm core-diameter is used with a pressure gradient from 0 to 40 bar of krypton. Compression to 22 fs is achieved by 1200 fssup2/supgroup-delay-dispersion provided by chirped mirrors. By coupling the output into a second kagomé-PCF with a pressure gradient from 0 to 25 bar of argon, octave spanning spectral broadening via the soliton-effect is observed at 18-W average output power. Self-compression to 9.1 fs is measured, with compressibility to 5 fs predicted. Also observed is strong emission in the visible via dispersive wave generation, amounting to 4% of the total output power.

The demand for and usage of broadband coherent mid-infrared sources, such as those provided by synchrotron facilities, are growing. Since most organic molecules exhibit characteristic vibrational modes in the wavelength range between 500 and 4000 cm−1, such broadband coherent sources enable micro- or even nano-spectroscopic applications at or below the diffraction limit with a high signal-to-noise ratio1, 2, 3. These techniques have been applied in diverse fields ranging from life sciences, material analysis, and time-resolved spectroscopy. Here we demonstrate a broadband, coherent and intrinsically carrier-envelope-phase-stable source with a spectrum spanning from 500 to 2250 cm−1 (−30 dB) at an average power of 24 mW and a repetition rate of 77 MHz. This performance is enabled by the first mode-locked thin-disk oscillator operating at 2 μm wavelength, providing a tenfold increase in average power over femtosecond oscillators previously demonstrated in this wavelength range4. Multi-octave spectral coverage from this compact and power-scalable system opens up a range of time- and frequency-domain spectroscopic applications.

Continuous-wave Tm:YAG and Ho:YAG thin-disk lasers with maximum optical-to-optical efficiencies of 41% and 58% respectively are presented. Pumped by a 780 nm laser diode, the Tm:YAG laser generated a maximum output power of 24 W. In comparison, the Ho:YAG laser, pumped by a fiber laser at 1908 nm, delivered a maximum output power of 50 W. The reported output powers are, to the best of our knowledge, the highest among all thin-disk lasers emitting at approximate to 2 m, and provide a solid foundation for the further development of next-generation 2 m thin-disk technologies.

We review the state-of-the art in gas-filled hollow-core photonic crystal fiber and its scientific and industrial applications in high-power laser beam delivery, pulse compression and generation of tunable deep and vacuum UV-light. Article not available.

A cross-correlation frequency-resolved optical gating (FROG) concept, potentially suitable for characterizing few or sub-cycle pulses in a single shot, is described in which a counter-propagating transient grating is used as both the gate and the dispersive element in a FROG spectrometer. An all-reflective setup, which can operate over the whole transmission range of the nonlinear medium, within the sensitivity range of the matrix sensor, is also proposed, and proof-of-principle experiments for the ultraviolet and visible-to-near-infrared spectral ranges are reported.

Compression of thin-disk oscillator µJ-level pulses from 250 fs to sub-10 fs using a two-stage gas-filled hollow-core kagome-PCF setup is demonstrated with 18 W average output power. Further compression to sub-5 fs is predicted.

We report two techniques for the efficient generation of tunable ultrafast pulses in the vacuum-ultraviolet, covering at least 117-200 nm, by pumping gas-filled kagome-style photonic crystal fibers with few-µJ, 35 fs, 800 nm laser pulses.

High-harmonic generation driven by 2-fs self-compressed pulses from an argon-filled kagome photonic-crystal fiber is investigated with the 1D atom model. The input carrier-envelope phase strongly modulates the simulated attosecond-pulse emission.

An efficient and tunable 176-550 nm source based on the emission of resonant dispersive radiation from ultrafast solitons at 800 nm is demonstrated in a gas-filled hollow-core photonic crystal fiber (PCF). By careful optimization and appropriate choice of gas, informed by detailed numerical simulations, we show that bright, high quality, localized bands of UV light (relative widths of a few percent) can be generated at all wavelengths across this range. Pulse energies of more than 75 nJ in the deep-UV, with relative bandwidths of ~3%, are generated from pump pulses of a few μJ. Excellent agreement is obtained between numerical and experimental results. The effects of positive and negative axial pressure gradients are also experimentally studied, and the coherence of the deep-UV dispersive wave radiation numerically investigated.

Two schemes for multi-μJ pulse compression in noble-gas-filled hollow-core kagome-PCF are demonstrated and compared. A fiber-plus-chirped-mirror combination compresses 150 fs, 9.5 μJ pulses to 26 fs, and soliton-effect compression produces sub 7 fs pulses.

By combining the anomalous dispersion of hollow-core photonic-crystal-fibres with the Kerr and photo-ionization nonlinearities of a filling gas, many remarkable soliton dynamics can be accessed, including pressure tunable wide-band frequency conversion, and few-cycle pulse compression.