Time-programmable frequency combs enable new measurement paradigms for dual-comb spectroscopy (DCS) that are free of many of the constraints found in traditional DCS. As opposed to fixing the repetition rate offset between combs, free-form DCS uses full control of the temporal offset between the dual-comb pulse trains, thereby enabling user-selectable sampling patterns that optimize resolution, signal-to-noise ratio, species selectivity or acquisition time. Here we show that free-form DCS enables compressive sensing and demonstrate compression factors of up to 155, with an up to 60-fold reduction in acquisition time, while maintaining identical spectral point spacing and comparable signal-to-noise ratio to traditional DCS. We also demonstrate molecular recurrence sampling (an extreme case of compressive sensing) for methane detection at 22× higher sensitivity than traditional DCS at the cost of requiring a priori knowledge of the probed species. Finally, free-form DCS can enable fast species-selective imaging since its radio frequency signal is narrow band, in contrast to traditional DCS, and therefore compatible with limited camera read out rates. We demonstrate imaging of methane plumes across a 128 × 64-pixel focal plane array at a 250 Hz rate. In the future, this flexible free-form approach can enable applications ranging from rapid open-path spectroscopy to nonlinear multidimensional comb-based spectroscopy.

时间可编程频率梳为双梳光谱 (DCS) 提供了新的测量范例，不受传统 DCS 中的许多限制。与固定梳之间的重复率偏移相反，自由形式 DCS 使用双梳脉冲序列之间的时间偏移的完全控制，从而实现用户可选择的采样模式，从而优化分辨率、信噪比、物种选择性或采集时间。在这里，我们展示了自由形式 DCS 可实现压缩传感，并展示了高达 155 的压缩因子，采集时间缩短了 60 倍，同时保持与传统 DCS 相同的谱点间距和可比较的信噪比。我们还展示了用于甲烷检测的分子递归采样（压缩传感的极端情况），其灵敏度比传统 DCS 高 22 倍，但代价是需要对探测物种有先验知识。最后，自由形式 DCS 可以实现快速物种选择性成像，因为与传统 DCS 相比，其射频信号是窄带的，因此与有限的相机读出速率兼容。我们演示了在 128 × 64 像素焦平面阵列上以 250 Hz 速率对甲烷羽流进行成像。未来，这种灵活的自由形式方法可以实现从快速开路光谱到非线性多维梳状光谱的各种应用。