Realization of a highly accurate optical frequency measurement system by novel frequency chain

在1.5 μ m波长的多量子阱分布反馈激光器上施加负反馈，使其光谱线宽减小到250 Hz。将该激光器作为感染锁定系统的主激光器，实现了高功率激光器相干性的提高和频率的稳定。研制了一种用于产生中频信号的光频梳发生器。也就是说，通过使用安装在法布里-珀罗腔中的电光调制器调制主激光器来实现超过4THz频率跨度的调制边带。通过将1.5 μ m波长的半导体激光和1.0 μ m波长的YAG激光照射到310 μ C的钛酸锂晶体，产生这些激光之间的和频信号。其波长和功率分别为0.63 μ m和0.7 μ W。通过将该信号与稳频的Hi-Ne激光混合，实现了光学相位锁定。相位误差方差减小到 ...更多信息 s低至0.05弧度^[2]，由此证实了稳定的零差光学相位锁定，利用上述结果，实现了由He-Ne激光器构成的主频标和由1.5 μ m窄线宽半导体激光器构成的次频标之间的频率链。此外，还研制了光频梳发生器，用于连接二级频标和待测激光器。作为<-10>现有光学测频系统的应用，提出了一种以0.65 μ m钙谱线为频标，以9个半导体激光器为从振荡器的0.6 ~ 1.3 μ m波长的新型频率链。对该系统进行了二次谐波和和频产生实验。少

By applying a negative electrical feedhack to a multi-quantum well distributed feedback laser at 1.5 um wavelength, its spectral linewidth was reduced to 250 Hz. By using this laser as the master laser for an infection locking system, improvement of coherence and frequency stabilization of a high power laser was realized. An optical frequency comb generator was developed to generate an intermediate frequency signal. That is, modulation sidebands over 4 THz frequency span was realized by modulating the master laser by using an electro-optical modulator installed in a Fabry-Perot cavity.By irradiating a 1.5 um-wavelength semiconductor laser light and 1.0 um-wavelength YAG laser light to a lithium niobate crystal of 310ﾟC, a sumfrequency signal between these lasers was generated. Its wavelength and power were 0.63 um and 0.7 uW, respectively. An optical phase locking was realized by mixing this signal with a frequency-stabilized Hi-Ne laser light. The phase error variance was reduced to a … More s low as 0.05 radian^2, from which a stable homodyne optical phase socking was confirmed.By the results obtained above, a frequency chain for frequency measurement system was realized between the primary frequency standard using a He-Ne laser and the secondary frequency standard using a narrow-linewidth semiconductor laser of 1.5 um-wavelengh. Furthermore, optical frequency comb generator was developed to connect the secondary frequency standard and the laser under measurement. The accuracy of frequency measurement was estimated to be as high as 1 x 10^<-10>, by which the optical frequency measurement with the highest accuracy was confirmed.As an application of the present optical frequency measurement system, a novel frequency chain for the wavelength of 0.6 - 1.3 um was proposed by using a calcium spectral line at 0.65 um-wavelength as the frequency standard and nine semiconductor lasers as slave oscillator. Experiments on the second harmonic and sum-frequency generations for this system were carried out. Less