Multioctave, 3-18 μm sub-two-cycle supercontinua from self-compressing, self-focusing soliton transients in a solid (original) (raw)
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Optical Materials Express, 2013
We discuss a novel method for generating octave-spanning supercontinua and few-cycle pulses in the important mid-IR wavelength range. The technique relies on strongly phase-mismatched cascaded second-harmonic generation (SHG) in mid-IR nonlinear frequency conversion crystals. Importantly we here investigate the so-called noncritical SHG case, where no phase matching can be achieved but as a compensation the largest quadratic nonlinearities are exploited. A self-defocusing temporal soliton can be excited if the cascading nonlinearity is larger than the competing material self-focusing nonlinearity, and we define a suitable figure of merit to screen a wide range of mid-IR dielectric and semiconductor materials with large effective second-order nonlinearities d eff . The best candidates have simultaneously a large bandgap and a large d eff . We show selected realistic numerical examples using one of the promising crystals: in one case soliton pulse compression from 50 fs to 15 fs (1.5 cycles) at 3.0 µm is achieved, and at the same time a 3-cycle dispersive wave at 5.0 µm is formed that can be isolated using a long-pass filter. In another example we show that extremely broadband supercontinua can form spanning the near-IR to the end of the mid-IR (nearly 4 octaves).
2020
This document provides supplementary information to "Ultraviolet-to-millimeter-band supercontinua driven by ultrashort mid-infrared laser pulses," https://doi.org/10.1364/OPTICA.7.000015, offering an expanded description of the methods and models used in our work to analyze and understand UV-to-mm-band supercontinua driven by ultrashort, high-peak-power mid-infrared laser pulses. Technical details of the analysis of phase-matching effects in multidecade supercontinuum generation by mid-infrared laser pulses are also provided.
Optics Letters, 2006
We present a soliton effect pulse compression technique that uses self-defocusing cascaded-quadratic nonlinearities, with no fundamental limit to its scalability to high pulse energies and the capability of generating few-cycle pulses with only a frequency-doubling crystal. The conditions for which group-velocity mismatch causes an acceptable perturbation to soliton compression are analyzed and underlie optimization of the compressor. Calculations predict compression to near-single-cycle durations, with compression ratios as high as 100. Initial experiments closely agree with calculations, demonstrating compression to durations under three optical cycles ͑12 fs͒ and generation of 600 nm bandwidths.
Soliton filtering from a supercontinuum: a tunable femtosecond pulse source
Journal of Physics: Conference Series, 2011
In this article we report experimental results related with the generation of a supercontinuum in a microstructured fiber, from which the soliton with the longest wavelength is filtered out of the continuum and is used to construct a tunable ultrashort pulses source by varying the pump power. Pulses of an 80 fs duration (FWHM) from a Ti:sapphire oscillator were input into a 2 m long fiber to generate the continuum. The duration of the solitons at the fiber output was preserved by using a zero dispersion filtering system, which selected the longest wavelength soliton, while avoiding temporal spreading of the solitons. We present a complete characterization of the filtered pulses that are continuously tunable in the 850-1100 nm range. We also show that the experimental results have a qualitative agreement with theory. An important property of the proposed near-infrared pulsed source is that the soliton pulse energies obtained after filtering are large enough for applications in nonlinear microscopy.
Self-compression to sub-3-cycle duration of mid-infrared optical pulses in dielectrics
2013
The generation of few-cycle pulses with controlled waveforms in the mid-infrared spectral region is a longstanding challenge but is expected, to enable a new generation of high-field physics experiments, uncovering intricate physical phenomena. Successful generation of such optical pulses is limited by the tremendous spectral widthexceeding 1000 nmrequired to withstand fewcycle pulses in the mid-IR correlated with the need to tightly control the spectral phase over such a broad bandwidth. Here, we present the first demonstration of sub-3 cycle optical pulses at 3.1 m central wavelength using for the first time self-compression in the anomalous dispersion regime in bulk material. The pulses emerging from this compact and efficient self-compression setup could be focused to intensities exceeding 10 14 W/cm 2 , a suitable range for high field physics experiments. Our experimental findings are corroborated by numerical simulations using a 3D nonlinear propagation code, therefore providing theoretical insight on the processes involved.
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.
Journal of the Optical Society of America B, 2013
We investigate numerically the supercontinuum generation (SCG) phenomenon, using femtosecond pulses in the subnanoscale of energies through the generalized nonlinear Schrödinger equation that includes non-Kerr terms. Our results with 50 fs pulses in the anomalous dispersion regime show that, in comparison to the single cubic Kerr nonlinearity (CKN) case, the cooperative nonlinearities improve the spectral broadening, while the competing ones compress the spectral SCG bandwidth. Surprisingly, with the reduction of the pulse width, the cooperative nonlinearities induce a spectral compression while the competing ones keep the SCG bandwidth nearly constant from the input to the output of the considered waveguide. The increase of both the energy and the nonlinearity confirms this feature, showing that spectral compression is also obtained in the single CKN case, but less than in the case of cooperative nonlinearities.
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.
Optics Communications, 2010
We study the supercontinuum process in optical fibers numerically for a variety of dispersion profiles to investigate how a specific dispersion profile controls the emission of dispersive waves. We conclude that the number of zero-dispersion points in the dispersion profile of a fiber is an excellent predictor of the dispersive-wave peaks when it is pumped with femtosecond pulses in the anomalous dispersion regime. Our study reveals that two or more such peaks can form on the same side of the input wavelength in specially designed and practically achievable dispersion profiles. We show that dispersive waves are emitted even in the case of normal dispersion where soliton fission does not occur. We suggest that a phenomenon related to soliton spectral tunneling is responsible for this radiation. Distinct dispersive peaks may also appear when an optical pulse, launched in the normal dispersion region, later begins to propagate in the anomalous dispersion regime because of its spectral broadening. Several dispersion profiles are numerically employed to show how the soliton fission process creates non-solitonic radiation even under normal dispersion pumping. A time-domain picture clearly shows this radiation when the conventional phase matching condition is satisfied. We also propose a realistic photonic crystal fiber with a dispersion profile that supports dispersivewave generation in the normal-dispersion region. Our study should prove useful for experiments designed to control the generation of blue light by launching femtosecond pulses into optical fibers.