In pump/probe spectroscopy employing supercontinuum (SC) probe light (Pr), multi-wavelength information is provided at the same time. The SC probe generated by a photonic crystal fiber is advantageous owing to the broad spectrum and synchronized timings of the SC Pr pulse and pump pulse. However, SC light accompanies formidable wavelength dependent noise due to the various contributions of generation mechanisms. We previously developed two noise cancellation methodologies suitable for multiwavelength measurements with SC light, that is, phase detection noise cancellation (PDNC) and time division noise cancellation (TDNC), where the pulse timings for Pr and reference (Rf) are time-shifted and detected by a single photodiode (PD) after passing through the common optical system, providing an identical spectral dispersion to conserve the wavelength-dependent noise correlation. In PDNC, Pr and Rf are discriminated based on the pulse repetition phase, and the Pr is then divided by Rf, whereas in TDNC they are distinguished by the detection time, and Rf is subtracted from Pr. However, a shot noise limited performance with high-power input has yet to be realized. In this study, the deterioration mechanisms for PDNC and TDNC are investigated. The nonlinear effect of the photodetector was found to have a non-negligible impact on the phase noise and intensity noise correlation between Pr and Rf. Adequate decay of the photocurrent of Pr at the detection of the Rf optical pulse is effective for avoiding nonlinearity and maintaining the noise correlation of Pr and Rf for the best noise cancellation. Based on this fact, a near-shot-noise-limited performance is demonstrated by the TDNC, where the Rf optical pulse is incident on the PD after sufficient relaxation of the Pr photocurrent. In addition, the coincidence of the timing of Pr and Rf for the noise subtraction was found to be essential for wideband noise cancellation.

在采用超连续谱（SC）探测光（Pr）的泵浦/探针光谱学中，同时提供多波长信息。由于SC Pr脉冲和泵浦脉冲的光谱范围广且同步，因此由光子晶体光纤产生的SC探针具有优势。然而，由于产生机理的各种贡献，SC光伴随着强大的波长依赖性噪声。我们之前开发了两种适用于用SC光进行多波长测量的噪声消除方法，即相位检测噪声消除（PDNC）和时分噪声消除（TDNC），其中Pr和参考（Rf）的脉冲时序是时移的，在通过通用光学系统后由单个光电二极管（PD）检测到，提供相同的光谱色散以节省与波长相关的噪声相关性。在PDNC中，根据脉冲重复相位来区分Pr和Rf，然后将Pr除以Rf，而在TDNC中，它们将通过检测时间进行区分，并从Pr中减去Rf。然而，尚未实现具有大功率输入的散粒噪声限制的性能。在这项研究中，研究了PDNC和TDNC的劣化机理。发现光电探测器的非线性效应对Pr和Rf之间的相位噪声和强度噪声相关性具有不可忽略的影响。在检测Rf光脉冲时，Pr的光电流的充分衰减对于避免非线性和保持Pr和Rf的噪声相关性以实现最佳噪声消除是有效的。基于这个事实，TDNC证明了近乎噪声限制的性能，其中在充分释放Pr光电流后，Rf光脉冲入射到PD上。另外，发现用于噪声相减的Pr和Rf的定时的一致对于宽带噪声消除是必不可少的。