Accurate displacement-measuring interferometer with wide range using an I-2 frequency-stabilized laser diode based on sinusoidal frequency modulation

作者：Thanh Tung Vu; Higuchi Masato; Aketagawa Masato^*

来源：Measurement Science and Technology, 2016, 27(10): 105201.

DOI：10.1088/0957-0233/27/10/105201

• frequency modulation
• frequency stabilization
• laser diode
• hyperfine spectrum
• saturated absorption
• displacement measurement

We propose the use of the sinusoidal frequency modulation technique to improve both the frequency stability of an external cavity laser diode (ECLD) and the measurement accuracy and range of a displacement-measuring interferometer. The frequency of the ECLD was modulated at 300 kHz by modulating the injection current, and it was locked to the b(21) hyperfine component of the transition 6-3, P(33), I-127(2) (633 nm) by the null method. A relative frequency stability of 6.5 x 10(-11) was achieved at 100 s sampling time. The stabilized ECLD was then utilized as a light source for an unbalanced Michelson interferometer. In the interferometer, the displacement and direction of the target mirror can be determined using a Lissajous diagram based on two consecutive and quadrant-phase harmonics of the interference signal. Generally, the measurement range of the interferometer by the proposed method is limited by the modulation index and the signal-to-noise ratio of the harmonics. To overcome this drawback, suitable consecutive harmonic pairs were selected for the specific measurement ranges to measure the displacement. The displacements determined in the specific ranges by the proposed method were compared with those observed by a commercial capacitive sensor. From the comparison, the proposed method has high precision to determine the displacement. The measurement range was also extended up to 10 m by selecting a suitable modulation index and suitable consecutive pairs of harmonics.

• 出版日期2016-10