The miniaturized femtosecond laser in near infrared-II region is the core equipment of three-photon microscopy. In this paper, we design a compact and robust illumination source that emits dual-color linearly polarized light for three-photon microscopy. Based on an all-polarization-maintaining passive mode-locked fiber laser, we shift the center wavelength of the pulses to the 1.7μm band utilizing cascade Raman effect, thereby generate dual-wavelength pulses. To enhance clarity, the two wavelengths are separated through the graded-index multimode fiber. Then we obtain the dual-pulse sequences with 1639.4nm and 1683.7nm wavelengths, 920fs pulse duration, and 23.75MHz pulse repetition rate. The average power of the signal is 53.64mW, corresponding to a single pulse energy of 2.25nJ. This illumination source can be further amplified and compressed for three-photon fluorescence imaging, especially dual-color three-photon fluorescence imaging, making it an ideal option for biomedical applications.

光学参量过程是产生压缩光的关键环节，为了提高实验中光学参量振荡腔的稳定性，必须将激光与光学参量振荡腔进行模式匹配，并用锁定技术稳定光学参量振荡腔。理论分析了模式匹配效率对压缩度和偏频锁定技术精度的影响。经过模式匹配之后，在实验上实现了光学参量振荡腔的锁定，并对锁定后的光学参量振荡腔进行了稳定性测量。理论与实验结果表明：模式匹配效果越好，压缩光的压缩度和偏频技术的锁定精度越高；在较好的模式匹配条件下，光学参量振荡腔的腔长锁定精度为7.35 nm，稳定时间可达2 h以上，能够满足对压缩态光场的探测需要。