title: Absolute group refractive index measurement of air by dispersive interferometry using frequency comb.
abstract: The absolute group refractive index of air at 1563 nm is measured by dispersive interferometry, and a combined uncertainty of 1.2 × 10(-8) is achieved. The group refractive index of air is calculated from the dispersive interferograms of the two beams passing through the inner and outer regions of a vacuum cell by fast-Fourier-transform. Experimental results show that the discrepancies between our method and modified Edlén equation are less than 3.43 × 10(-8) and 4.4 × 10(-8) for short-term and long-term experiments, respectively. The interferogram update rate is 15 ms, which makes it suitable for application of real-time monitoring. Furthermore, it is promising to improve the measurement uncertainty to 3.0 × 10(-9) by changing the material of the vacuum cell and measuring its length more accurately through optical interferometry.
authors.forename: L J
authors.initials: LJ
authors.lastname: Yang
authors.forename: H Y
authors.initials: HY
authors.lastname: Zhang
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.forename: H Y
authors.initials: HY
authors.lastname: Wei