Supplementary document for Ultraviolet-to-millimeter-band supercontinua driven by ultrashort mid-infrared laser pulses - 4226713.pdf (original) (raw)
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Multi-octave supercontinuum generation from mid-infrared filamentation in a bulk crystal
Nature Communications, 2012
In supercontinuum generation, various propagation effects combine to produce a dramatic spectral broadening of intense ultrashort optical pulses. With a host of applications, supercontinuum sources are often required to possess a range of properties such as spectral coverage from the ultraviolet across the visible and into the infrared, shot-to-shot repeatability, high spectral energy density and an absence of complicated pulse splitting. Here we present an all-in-one solution, the first supercontinuum in a bulk homogeneous material extending from 450 nm into the mid-infrared. The spectrum spans 3.3 octaves and carries high spectral energy density (2 pJ nm − 1 -10 nJ nm − 1 ), and the generation process has high shot-to-shot reproducibility and preserves the carrier-to-envelope phase. Our method, based on filamentation of femtosecond mid-infrared pulses in the anomalous dispersion regime, allows for compact new supercontinuum sources.
Extending the supercontinuum spectrum down to 200 nm with few-cycle pulses
New Journal of Physics, 2006
By focusing 805 nm pulses of low energy (0.2-1 mJ) into atmospheric-pressure argon, a supercontinuum is generated with a shortwavelength cutoff of 640, 250 and 210 nm for initial pulse durations of 45, 10 and 6 fs, respectively. It is shown numerically that the large shift of the UV cutoff and many features of the spectrum are caused by terms beyond the slowly-varyingenvelope approximation (SVEA). Their effect on pulse compression and filament length is also discussed.
Spectral extent and pulse shape of the supercontinuum for ultrashort laser pulse
IEEE Journal of Quantum Electronics, 1986
The pulse shape and the generated supercontinuum spectral distribution associated with the propagation of an ultrashort intense pulse in a cubic (@') nonlinear medium are obtained by solving the electromagnetic field wave equation using the method of multiple scales. New forms for the set of quasi-linear partial differential equations describing the system, pulse distortion, and the spectral extent of the supercontinuum are the focus of this paper. S I. INTRODUCTION UPERCONTINUUM generation is the production of nearly white continuous spectrum by propagating picosecond and subpicosecond laser pulses through nonlinear media. Alfano and Shapiro [ l ] were the first to experimentally observe this phenomenon more than 15 years ago. They and others [2] used this superbroadening as a means to produce ultrashort pulses in the spectral range from ultraviolet to infrared. The shape, fine structure, and extent of the spectrum produced are functions of the nonlinear index of refraction of the medium, the shape, wavelength, duration, intensity, and phase modulation of the pump laser pulse, and the interaction length of the pulse in the medium. Typically, the observed broadened spectrum consists of larger frequency extent towards the blue than the red by factors of approximately two, a feature commonly referred to as spectral asymmetry. This coherent and ultrafast superbroad frequency band has been mainly used as a spectral tool for time-resolved absorption spectroscopy [3], [4] and nonlinear optical effects [3], [5]. Recently, new uses in engineering applications [6], such as ranging, 3-D imaging, atmospheric remote sensing, and optical fiber characterization, have been proposed. The supercontinuum was explained either as a result of self-phase modulation (SPM) following self-focusing and optical breakdown [7] or as a result of a four-wave parametric process [8]. The asymmetry in the Stokes and anti-Stokes regions was attributed to contributions from plasmas and/or the time response of the nonlinear index of refraction. Recent experiments [9] suggest, however, that the supercontinuum can be observed in experimental conditions where self-focusing and optical breakdown are ab-Manuscript received April 10, 1985.
JETP Letters, 2008
Nonlinear-optical spatiotemporal transformation of high-intensity ultrashort field waveforms in ionizing gases gives rise to the generation of radiation with a broad continuous spectrum . This phenomenon, known as white-light, or supercontinuum, generation suggests interesting options for the remote sensing of the atmosphere [8], the creation of novel broadband light sources , and the development of new strategies for the generation of ultrashort pulses with a stabilized carrier-envelope phase . Supercontinuum generation by few-cycle light pulses is accompanied by intriguing nonlinear-optical effects and reveals unique spatiotemporal dynamics of broadband optical signals .
Optics letters, 2015
We experimentally and numerically investigate the spectral and temporal structure of mid-infrared (mid-IR) filaments in bulk dielectrics with normal and anomalous group velocity dispersion (GVD) pumped by a 2.1 μm optical parametric chirped-pulse amplifier (OPCPA). The formation of stable and robust filaments with several microjoules of pulse energy is observed. We demonstrate a supercontinuum that spans more than three octaves from ZnS in the normal GVD regime and self-compression of the mid-IR pulse to sub-two-cycle duration in CaF<sub>2</sub> in the anomalous GVD regime. The experimental observations quantitatively agree well with the numerical simulations based on a three-dimensional nonlinear wave equation that reveals the detailed spatio-temporal dynamics of mid-IR filaments in dielectrics.
Control of near-infrared supercontinuum bandwidth by adjusting pump pulse duration
Optics Express, 2012
We experimentally and numerically investigated the impact of input pump pulse duration on the near-infrared bandwidth of supercontinuum generation in a photonic crystal fiber. We continuously stretched the temporal duration of the input pump laser (centered at 1030 nm) pulses from 500 fs up to 10 ps, while keeping fixed the pump peak power. We observed that the long-wavelength edge of the supercontinuum spectrum is increased by 200 nm as the pump pulse duration grows from 500 fs to 10 ps. We provide a quantitative fit of the experimental results by means of numerical simulations. Moreover, we have explained the observed spectral broadening enhancement induced by pump pulse energy by developing an approximate yet fully analytical model for soliton energy exchange through a series of collisions in the presence of stimulated Raman scattering.
Ultrashort pulse generation in the mid-IR
Progress in Quantum Electronics, 2015
Recent developments in laser sources operating in the mid-IR (3-8 µm), have been motivated by the numerous possibilities for both fundamental and applied research. One example is the ability to unambiguously detect pollutants and carcinogens due to the much larger oscillator strengths of their absorption features in the mid-IR spectral region compared with the visible. Broadband sources are of particular interest for spectroscopic applications since they remove the need for arduous scanning or several lasers and allow simultaneous use of multiple absorption features thus increasing the confidence level of detection. In addition, sources capable of producing ultrashort and intense mid-IR radiation are gaining relevance in attoscience and strong-field physics due to wavelength scaling of re-collision based processes. In this paper we review the state-of-the-art in sources of coherent, pulsed mid-IR radiation. First we discuss semiconductor based sources which are compact and turnkey, but typically do not yield short pulse duration. Mid-IR laser gain material based approaches will be discussed, either for direct broadband mid-IR lasers or as narrowband pump lasers for parametric amplification in nonlinear crystals. The main part will focus on mid-IR generation and amplification based on parametric frequency conversion, enabling highest mid-IR peak power pulses. Lastly we close with an overview of nonlinear post-compression techniques, for decreasing pulse duration to the sub-2-optical-cycle regime.
Visible-to-near-infrared octave spanning supercontinuum generation in
2015
The generation of an octave spanning supercontinuum covering 488-978 nm (at −30 dB) is demonstrated for the first time on-chip. This result is achieved by dispersion engineering a 1-cm-long Si 3 N 4 waveguide and pumping it with an 100-fs Ti:Sapphire laser emitting at 795 nm. This work offers a bright broadband source for biophotonic applications and frequency metrology.
Influencing supercontinuum generation by phase distorting an ultrashort laser pulse
Optics Letters, 2015
We show that the spectral distribution of the supercontinuum (SC) generated in barium fluoride is amenable to alteration simply by controlling the second-and third-order phase distortion of incident femtosecond-duration pulses. The second-and third-order phase distortions are controlled by an acoustic-optic programmable dispersive filter (AOPDF). The spectral extent on the blue side of the SC is influenced by independently varying the phase distortion of an ultrashort laser pulse.
Applied Optics, 2015
A dispersion-varying tapered planar waveguide is designed to generate supercontinuum efficiently in the midinfrared region. The rib waveguide of lead-silicate glass on silica is 1.8 cm long, consisting of a segment with longitudinally increasing etch depth. The mechanism involves nonlinear soliton dynamics. The dispersion profile is shifted along the propagation distance, leading to continuous modification of the phase-matching condition for dispersive wave (DW) emission and enhancement of energy transfer efficiency between solitons and DWs. With low input pulse energy of 45 pJ, simulation demonstrates the generation of both broadband and flat near-octave spectrum spanning 1.3-2.5 μm at the −20 dB level.