title: Note: Real-time absolute air refractometer.
abstract: We present a real-time absolute air refractometer benefiting from the synthetic pseudo-wavelength (SPW) method. Based on laser heterodyne interferometry, the SPW method uses three vacuum cells with specific lengths to synthesize a set of synthetic pseudo-wavelengths, by combination of which the refractive index can be determined directly without ambiguity. In addition, owing to the parallel arrangement of the vacuum cells in the optical path, the measured data can be collected simultaneously so that one measurement process can be less than 2 ms. The real-time feature makes it possible for instantaneous compensation for laser interferometers.
authors.affiliation: State Key Lab of Precision Measurement Technology and Instruments, Department of Precision Instruments, Tsinghua University, Beijing 100084, China.
authors.forename: Pei
authors.initials: P
authors.lastname: Huang
authors.affiliation: Department of Electrical and Computer Engineering, University of Arizona, Tucson, Arizona 85721, USA.
authors.forename: Jitao
authors.initials: J
authors.lastname: Zhang
authors.affiliation: State Key Lab of Precision Measurement Technology and Instruments, Department of Precision Instruments, Tsinghua University, Beijing 100084, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.affiliation: State Key Lab of Precision Measurement Technology and Instruments, Department of Precision Instruments, Tsinghua University, Beijing 100084, China.
authors.forename: Haoyun
authors.initials: H
authors.lastname: Wei