In their comment on Optica 8, 1559 (2021) [CrossRef] , Liang and Vogel performed a theoretical calculation to show that with a 1.1 NA objective and 140 femtosecond (fs) laser pulses with a single pulse energy of 2.2 nJ and 80 MHz repetition rate, the focal point temperature rises 0.3 K and reaches equilibrium after 100 µs in water [Optica 9, 868 (2022) [CrossRef] ]. They suggest that the damage to brain tissue by laser could not be caused by thermal effects but rather by plasma-mediated chemical effects. To quantify the thermal accumulation due to the femtosecond (fs) laser illumination in living animals, we used a thermocouple sensor to measure the temperature change in the vicinity of the laser focus at a depth of 300 µm in the cortex of an adult mouse. Our results show that laser irradiation at 930 nm wavelengths with power ranging from 19 to 300 mW can all lead to a brain tissue temperature rise of more than 0.3 K at 1 s at a distance of 25 µm from the laser focus, and the 300 mW laser can cause a temperature increase of more than 28 K at 6 s. These experimental measurements are significantly higher than theoretically calculated values in the comment. These results suggest that the thermal accumulation effect of focused low-energy pulses from fs laser oscillators could contribute significantly to the collateral damage in the living brain.

中文翻译：

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用精确和有针对性的激光消融在活皮层探测神经元功能：回复

在他们对 Optica 8 , 1559 (2021) [CrossRef]的评论中 ，Liang 和 Vogel 进行了理论计算，表明在 1.1 NA 物镜和 140 飞秒 (fs) 激光脉冲的情况下，单脉冲能量为 2.2 nJ 和 80 MHz 重复速率，焦点温度上升 0.3 K 并在水中 100 µs 后达到平衡 [Optica 9 , 868 (2022) [CrossRef] ]。他们认为激光对脑组织的损伤不是由热效应引起的，而是由等离子体介导的化学作用引起的。为了量化由于飞秒 (fs) 激光照射在活体动物中引起的热积累，我们使用热电偶传感器测量成年小鼠皮层 300 µm 深度处激光焦点附近的温度变化。我们的研究结果表明，在 930 nm 波长、功率范围为 19 至 300 mW 的激光照射下，在距激光焦点 25 µm 的距离处，1 s 时脑组织温度升高超过 0.3 K，而 300 mW激光可以在 6 秒内引起超过 28 K 的温度升高。这些实验测量值明显高于评论中的理论计算值。