Sub-Doppler resonances in caesium vapours are studied in a laser field produced by counterpropagating two-frequency light beams with mutually orthogonal linear polarisations. The beams are in resonance with optical transitions in the D₁ line, the frequency difference of the field spectral components being equal to the hyperfine ground-state splitting in the Cs atom (∼9.2 GHz). It has already been shown that in this configuration, the hypercontrast effect can be observed for sub-Doppler resonances, which makes this configuration promising for the employment in new-generation miniature optical frequency standards. In the present work, two different two-frequency configurations are compared with each other and with the single-frequency configuration widely used in practice for observing saturated absorption resonances. The parameters of nonlinear resonances are measured at various temperatures of caesium vapours and at different optical field intensities. The results of the investigations performed make it possible to find an optimal two-frequency scheme for exciting nonlinear resonances and to estimate a potential of the scheme for its applications in quantum metrology.

铯蒸气中的亚多普勒共振是在激光场中研究的，该激光场是由具有相互正交线性偏振的双频光束反向传播产生的。_{光束与 D 1}中的光学跃迁共振线，场谱分量的频率差等于 Cs 原子中的超精细基态分裂（~9.2 GHz）。已经表明，在这种配置中，可以观察到亚多普勒共振的超对比度效应，这使得这种配置有望用于新一代微型光学频率标准。在目前的工作中，将两种不同的双频配置相互比较，并与实践中广泛用于观察饱和吸收共振的单频配置进行比较。在铯蒸气的不同温度和不同光场强度下测量非线性共振参数。