Lou Xiutao, Yuan Ziyue, Dong Yongkang
Opt Express. 2019 Apr 29;27(9):13160-13171. doi: 10.1364/OE.27.013160.
Spectroscopic gas analysis for monitoring transient events in fast processes requires high spectrum acquisition rate with low uncertainty; however, so far high-speed spectroscopic gas detection with sufficient spectral resolution and spectral span is still challenging. Here, we propose an innovative method based on optical linear chirp chain (OLCC) for rapid acquisition of high-resolution gas spectra with a rate up to the order of MHz with 100% duty cycle, spectral resolution at 10-MHz level and spectral span > 20 GHz. The OLCC is generated by high-speed optical modulation driven by a digital arbitrary waveform generator in combination with a four-wave-mixing process, exhibiting a highly linear frequency chirp (linearity error of ~10) and low level of residual amplitude modulation (<1%). An image denoising method based on nonlocal means algorithm is exploited to reduce the high-frequency noise while guaranteeing the response time and spectral resolution. We demonstrate this method by monitoring a fast charging process of acetylene gas into a vacuumized gas cell, clearly unfolding gas pressure oscillations at μs time scale. Our proposed OLCC-based spectroscopic method opens up prospects for the development of high-speed spectrometers and optical sensors.
用于监测快速过程中瞬态事件的光谱气体分析需要高光谱采集速率且不确定性低；然而，到目前为止，实现具有足够光谱分辨率和光谱范围的高速光谱气体检测仍然具有挑战性。在此，我们提出一种基于光学线性啁啾链（OLCC）的创新方法，用于以高达兆赫兹量级的速率快速采集高分辨率气体光谱，占空比为100%，光谱分辨率达到10兆赫兹水平，光谱范围>20吉赫兹。OLCC由数字任意波形发生器驱动的高速光调制结合四波混频过程产生，呈现出高度线性的频率啁啾（线性误差约为10）和低水平的残余幅度调制（<1%）。利用基于非局部均值算法的图像去噪方法来降低高频噪声，同时保证响应时间和光谱分辨率。我们通过监测乙炔气体快速充入真空气室的过程来演示该方法，清晰地展现了微秒时间尺度上的气体压力振荡。我们提出的基于OLCC的光谱方法为高速光谱仪和光学传感器的发展开辟了前景。
