Phase retardation measurement of an arbitrary wave plate based on magneto-optical modulating and residue detecting of the base frequency component of the signal.

Wave plates (WPs) are key components in optical polarization systems whose phase retardations should be measured accurately. The key point of most light extinction methods focuses on how to precisely judge the system's extinction state and then confirm corresponding angle positions of the optical components. Usually the extinction state of a measurement system is judged by detecting residue of outgoing light intensity.

Humidity coefficient correction in the calculation equations of air refractive index by He-Ne laser based on phase step interferometry.

The refractive index of air (RIA) is an important parameter in precision measurement. The revisions to Edlen's equations by Boensch and Potulski [Metrologia 35, 133 (1998)] are mostly used to calculate the RIA at present. Since the humidity correction coefficients in the formulas were performed with four wavelengths of a Cd(114) lamp (644.

Measurement of air refractive index fluctuation based on interferometry with two different reference cavity lengths.

A measurement method based on interferometry with two different reference cavity lengths is presented and applied in air refractive index measurement in which the two cavity lengths and a laser wavelength are combined to generate two wavelength equivalents of cavity. Corresponding calculation equations are derived, and the optical path configuration is designed, which is inspired by the traditional synthetic wavelength method. Theoretical analyses indicate that the measurement uncertainty of the determined index of refraction is about 2.

Measurement of air refractive index based on surface plasmon resonance and phase detection.

A method for refractive index of air measurement is presented based on surface plasmon resonance (SPR) and phase detection using a dual-frequency laser interferometer. Theoretical analyses indicate that the phase-difference variation of the measurement signal versus the reference signal is linear with refractive index of air (RIA) fluctuation, and the calculation formula of RIA is derived. The structure design of the self-adaptive SPR sensor greatly reduces the measurement error resulting from the incident angle shift and improves the sensitivity.