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Ultraviolet-to-millimeter-band supercontinua driven by ultrashort mid-infrared laser pulses
Optica ( IF 10.4 ) Pub Date : 2020-01-03 , DOI: 10.1364/optica.7.000015
A. V. Mitrofanov , D. A. Sidorov-Biryukov , M. M. Nazarov , A. A. Voronin , M. V. Rozhko , A. D. Shutov , S. V. Ryabchuk , E. E. Serebryannikov , A. B. Fedotov , A. M. Zheltikov

Combined optical nonlinearity of bound and free electrons in a fast-ionizing medium driven by ultrashort, mid-infrared (mid-IR) pulses gives rise to a vast variety of ultrafast nonlinear-optical scenarios, producing bright, broadband radiation in spectral ranges as different as ultraviolet (UV) and terahertz (THz). Given its enormous bandwidth, a quantitative experimental analysis of this type of nonlinear response is anything but simple. Here, we confront this challenge by ultrabroadband spectral measurements performed across the spectral range from the UV to the millimeter-wave (MMW) band jointly with beam profile analysis in the THz-to-MMW band and direct time-domain field waveform characterization. As one of the most striking results, the nonlinear response of a fast-ionizing gas driven by a two-color field, consisting of a high-peak-power sub-100-fs mid-IR pulse and its second harmonic, is shown to provide a source of a bright multiband supercontinuum (SC) radiation, whose spectrum spans over about 14 octaves, stretching from below 300 nm all the way beyond 4.3 mm. The MMW-to-THz part of this SC is emitted, as direct measurements show, in the form of half-cycle field waveforms that can be focused to yield a field strength of $ {\approx}{5}\;{\rm MV/cm}$. At least 1.5% of the MMW–THz supercontinuum energy is emitted in the MMW range, giving rise to MMW field strengths up to 100 kV/cm in the beam waist region.

中文翻译:

超短中红外激光脉冲驱动的紫外到毫米带超连续谱

在由超短,中红外(mid-IR)脉冲驱动的快速电离介质中,结合电子和自由电子的光学非线性结合在一起,产生了各种各样的超快速非线性光学场景,在不同光谱范围内产生了明亮的宽带辐射作为紫外线(UV)和太赫兹(THz)。鉴于其巨大的带宽,对这种非线性响应进行定量实验分析绝非易事。在这里,我们通过在从紫外线到毫米波(MMW)波段的光谱范围内进行超宽带光谱测量,以及在THz到MMW波段的光束轮廓分析以及直接时域场波形表征,来面对这一挑战。作为最引人注目的结果之一,是由双色场驱动的快速电离气体的非线性响应,由高峰值功率低于100-fs的中红外脉冲及其二次谐波组成,可以提供明亮的多波段超连续谱(SC)辐射源,其光谱范围跨越约14个八度音阶,从300以下延伸一直超过4.3毫米。直接测量结果表明,该SC的MMW至THz部分以半周期场波形的形式发射,可以集中产生场强为$ {\ approx} {5} \; {\ rm MV / cm} $。在MMW范围内发射至少1.5%的MMW–THz超连续谱能量,从而在束腰区域产生高达100 kV / cm的MMW场强。
更新日期:2020-01-21
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