Relative intensity noise (RIN) inherent in fiber lasers poses a serious obstacle to their use in pump–probe spectroscopy and imaging. RIN can be removed through an analog balanced detector, or, as we have previously shown, software adaptive noise cancellation (ANC) on digitized signals. One major drawback to software ANC is the added time required for digitizing and post-processing. In this article, we describe a design for ANC on a field-programmable gate array (FPGA), making use of high-level synthesis tools and fixed-point arithmetic to achieve real-time laser RIN suppression at 25 MHz sample rates. Unlike the software-ANC approach, the FPGA-ANC device can serve as a dedicated drop-in denoiser, placed between the detectors and a commercial lock-in amplifier. We demonstrate its application to transient absorption spectroscopy and microscopy, lowering the noise floor to ∼17 dB above the shot noise limit. Furthermore, we demonstrate a dramatic improvement in data acquisition time from ∼6 h to ∼5 min in a real-time imaging scenario.

中文翻译：

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DR-RINS：用于泵浦光谱和显微镜的数字实时相对强度噪声抑制器

光纤激光器固有的相对强度噪声（RIN）严重限制了它们在泵浦探针光谱学和成像中的使用。RIN可以通过模拟平衡检测器消除，或者如我们先前所示，通过数字信号的软件自适应噪声消除（ANC）消除。软件ANC的一个主要缺点是数字化和后处理需要增加时间。在本文中，我们描述了一种在现场可编程门阵列（FPGA）上用于ANC的设计，该设计利用高级综合工具和定点算法在25 MHz采样率下实现实时激光RIN抑制。与软件ANC方法不同，FPGA-ANC器件可以用作专用的插入式降噪器，放置在检测器和商用锁定放大器之间。我们展示了其在瞬态吸收光谱法和显微镜中的应用，将本底噪声降低到散粒噪声限制以上约〜17 dB。此外，在实时成像场景中，我们证明了数据采集时间从约6小时到约5分钟有了显着改善。