基于Er光纤laser的倍频程中红外频率梳及差频产生
Mid-infrared frequency comb spanning an octave based on an Er fiber laser and difference-frequency generation
摘要：
我们描述了一个相干的中红外连续光源与700 cm-1的可用带宽，很容易在600 - 2500 cm-1（4 - 17 \mum），从而覆盖了大部分的红外“指纹”分子振动区域内调谐。它是基于非线性频率转换的GaSe使用一个紧凑的商业100 fs脉冲Er光纤激光系统提供两个放大的近红外光束，其中一个扩大了非线性光纤。所得到的1 mW准连续功率的准直中红外连续光束表示具有零载波包络相位的相干红外频率梳，包含约500，000个模式，这些模式是40 MHz的脉冲重复率的精确倍数。该光束的衍射极限性能使远距离光谱探测以及经典和超分辨近场显微镜的最大可聚焦性成为可能。应用程序也预见在瞬态化学现象的研究，甚至在超快泵探测规模，并在高分辨率气体光谱，例如呼吸分析。
英文摘要：
We describe a coherent mid-infrared continuum source with 700 cm-1 usable bandwidth, readily tuned within 600 - 2500 cm-1 (4 - 17 \mum) and thus covering much of the infrared "fingerprint" molecular vibration region. It is based on nonlinear frequency conversion in GaSe using a compact commercial 100-fs-pulsed Er fiber laser system providing two amplified near-infrared beams, one of them broadened by a nonlinear optical fiber. The resulting collimated mid-infrared continuum beam of 1 mW quasi-cw power represents a coherent infrared frequency comb with zero carrier-envelope phase, containing about 500,000 modes that are exact multiples of the pulse repetition rate of 40 MHz. The beam's diffraction-limited performance enables long-distance spectroscopic probing as well as maximal focusability for classical and ultraresolving near-field microscopies. Applications are foreseen also in studies of transient chemical phenomena even at ultrafast pump-probe scale, and in high-resolution gas spectroscopy for e.g. breath analysis.
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