提出了一种利用窄线宽激光作为测量光源, 对光学谐振腔自由光谱区、腔内共振激光波长进行精密测量而得到光学谐振腔腔长的方法。对光学谐振腔腔长的测量理论进行了严格推导, 通过理论模拟对测量条件及结果进行了分析讨论。以自行研制的线宽为1.9 Hz、频率不稳定度为1.7×10-14 s-1、中心波长为1550 nm的窄线宽激光作为光源, 对长度约100 mm的光学谐振腔腔长进行了精密测量。对光学谐振腔自由光谱区进行测量, 得到其腔长为0.10024407 m、精度为22 nm; 对光学谐振腔腔内共振激光波长进行测量, 得到其腔长为0.1002440884 m、精度为0.21 nm, 精度相对提高了2个量级。提出的方法有望促进基础物理研究、材料的物理属性精密测量及光纤传感等领域的发展。

A new method for measuring cavity length of optical resonator is proposed by measuring the free spectral range of optical resonator and the intracavity resonance laser wavelength with narrow linewidth lasers as light sources. The measurement theory of optical resonator cavity length is strictly deduced, and the measurement conditions and results are analyzed and discussed by theoretical simulation. An optical resonator with cavity length about 100 mm is measured precisely with the developed narrow linewidth laser as light source, of which the linewidth is 1.9 Hz, the frequency instability is 1.7×10-14 s-1 and the central wavelength is 1550 nm. The free spectral region of the optical resonator is measured, and it is obtained that the cavity length of the optical resonator and the precision are 0.10024407 m and 22 nm, respectively. The intracavity resonance laser wavelength of the optical resonator is measured, and it is obtained that the cavity length of the optical resonator and the precision are 0.1002440884 m and 0.21 nm, respectively. The accuracy is improved by two orders of magnitude. The proposed method is expected to promote the development of basic physics research, physical properties precision measurement of materials, fiber sensing and so on.