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

通过在1.5 nm波长的多量子井分布反馈激光器上施加负电反馈，使其光谱线宽减小到250赫兹。利用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的相干性和稳频性能的改善。研制了一种用于产生中频信号的光频梳发生器。即利用安装在法布里-珀罗腔中的电光调制器对主光进行调制，实现了4太赫兹频段的调制边带；用1.5um波长的半导体激光和1.0um波长的YAG光分别照射到310ﾟC的LiNbate晶体上，产生了两个激光器之间的求和信号。其波长和功率分别为0.63um和0.7uW。通过将该信号与频率稳定的Hi-Ne激光混频，实现了光学锁相。将相位误差方差减小到…利用上述结果，实现了利用He-Ne激光器的主频标和波长为1.5 nm的窄线宽半导体激光器的副频标之间的频率链。此外，还研制了光学频率梳发生器，用于连接二次频率标准和被测激光器。测频精度为1×10~(-10)~10~(-10)，保证了光学测频的最高精度。作为目前光学测频系统的应用，提出了一种以0.65微米波长的钙谱线为频率标准，以9台半导体激光器为从振的0.6~1.3微米的频率链。对该系统的倍频和和频进行了实验研究。较少

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