Absolute optical frequency scanning interferometry for picometer displacement measurement using femtosecond optical combs

在这项研究中，我们进行了以下三个主题，旨在展示皮米干涉测量的新技术。（1）高效率、高功率LD泵浦锁模固体激光器的研制在Yb激光器中，采用220 kW/cm ~ 2的超高泵浦密度，在连续工作区获得了81%的光-光转换效率，在脉冲工作区获得了62%的光-光转换效率。通过在激光腔中插入额外的光学克尔材料，同时实现了高稳定性和高效率。研制了基于聚合物嵌入碳纳米管的可饱和吸收镜锁模Er/Yb：glass激光器。在Er/Yb：glass激光器中获得了迄今为止最短的脉冲宽度（68 fs）。（2）“波长梳“的形成实验观察到展宽的钕玻璃激光梳与可调谐连续激光器之间的频率差拍，具有平坦的本底噪声，信噪比优于40 dB。锁相可调光 关于我们 研制了一种工频发生器。波长参考激光器由锁定在低热膨胀玻璃参考腔中的连续Nd：YAG激光器制成。当梳的模式之一被锁定到参考激光器时，周围模式的波长同时稳定。这样就发展出了一种新的“波长梳”方案。（3）干涉位移测量将可调谐连续激光器锁相到法布里-珀罗腔中进行位移测量，并对稳定性进行了评价。在不使用波长梳的情况下，由于环境空气折射率的变化，观察到在1小时内测量的腔长的10 nm的漂移。另一方面，通过使用波长梳，漂移已被显着抑制到10 pm。最后，其中一个腔镜移动的商业纳米定位工作台。成功地测量了12 μ m的位移，不确定度小于100 μ m。对平台的重复性和非线性进行了评价。少

In this study, we performed the following three topics aiming to demonstrate the new technique for picometer interferometric measurements.(1)Development of highly efficient and high-power LD-pumped mode-locked solid-state lasersWith extremely high pump density of 220 kW/cm2 in Yb laser, optical-to-optical conversion efficiency of 81 % has been achieved in the CW operation regime, and 62 % in the pulse operation regime. By inserting additional optical Kerr material in the laser cavity, high stability and efficiency have been realized simultaneously. Er/Yb : glass laser mode-locked by saturable absorber mirrors based on polymer-embedded carbon nanotubes was developed. The shortest pulse width (68 fs) ever achieved in the Er/Yb:glass laser has been achieved.(2)Development of "wavelength comb"Frequency beat between a spectrally broadened Nd : glass-laser comb and a tunable CW laser was observed with a flat noise-floor and signal-to-noise ratio of better than 40 dB. Phase-locked tunable opt … More ical frequency generator has been developed. Wavelength reference laser was made by a CW Nd:YAG laser locked to a low-thermal-expansion-glass reference cavity. When one of the modes of the comb was locked to the reference laser, wavelengths of the surrounding modes were simultaneously stabilized. In this way, new scheme of "wavelength comb" has been developed.(3)Inteferometric displacement measurementFrequency-tunable CW laser was phase-locked to the Fabry-Perot cavity for displacement measurements and the stability was evaluated. Without the use of wavelength comb, the drift in the measured cavity-length for 10 nm during 1 hour was observed due to the environmental air-refractive-index change. On the other hand, by using the wavelength comb, the drift has been dramatically suppressed down to 10 pm.Finally, one of the cavity mirrors was moved by a commercial nano-positioning stage. Displacement of 12 um was successfully measured with smaller than 100-pm uncertainty. Evaluation of repeatability and nonlinearity of the stage was demonstrated. Less