Transmission and Detection Analysis of Time-Stretched CARS Signal

相干反斯托克斯拉曼散射(Coherent Anti-Stokes Raman Spectroscopy, CARS)是一种非侵入、无标记的光学检测技术，广泛用于生物成像和化学分析。时间拉伸方法可展宽CARS信号，提高光谱采集速度。然而，光纤长度影响信号的功率衰减和时域展宽，探测端的上升沿和噪声也影响信噪比和光谱分辨率。因此，优化光纤长度和探测系统的时间响应特性至关重要。本研究首先测得了二甲基亚砜的CARS光谱，然后采用数值模拟的方法，分析了CARS信号在不同光纤长度下的功率衰减、展宽及色散引起的延时变化，并结合雪崩光电二极管响应特性，模拟了非共振背景和噪声对信噪比的影响。成功模拟得到了时间拉伸后的CARS信号，并进一步分析了上升沿与光纤长度对光谱分辨率的影响。研究结果表明，光纤长度与非共振背景噪声强度及探测系统的时间响应特性均显著影响CARS的信号质量和探测精度。本研究为CARS信号的光纤传输优化及高性能探测系统设计提供了理论支持。Coherent Anti-Stokes Raman Spectroscopy (CARS) is a non-invasive and label-free optical detection technique widely utilized in biological imaging and chemical analysis. The time-stretching approach can broaden CARS signals, enhancing spectral acquisition speed. However, the optical fiber length affects signal power attenuation and temporal broadening, while the detector’s rise time and noise influence the signal-to-noise ratio (SNR) and spectral resolution. Therefore, optimizing the fiber length and the temporal response characteristics of the detection system is crucial. In this study, the CARS spectrum of dimethyl sulfoxide (DMSO) was first obtained. A numerical simulation was then conducted to analyze the power attenuation, broadening, and dispersion-induced delay variation of CARS signals at different fiber lengths. Furthermore, the response characteristics of the avalanche photodiode (APD) were incorporated to simulate the influence of the non-resonant background and noise on the SNR. The time-stretched CARS signal was successfully simulated, and the effects of the detector rise time and fiber length on the spectral resolution were further examined. The results demonstrate that fiber length, non-resonant background noise intensity, and the temporal response characteristics of the detection system significantly impact CARS signal quality and detection accuracy. This study provides theoretical support for optimizing optical fiber transmission of CARS signals and designing high-performance detection systems.