METHOD FOR DETERMINING REFRACTION INDEX OF MEDIUM Russian patent published in 2019 - IPC G01N21/41 

FIELD: physics.

SUBSTANCE: invention relates to methods of determining the refractive index of the analyzed medium at different wavelengths of electromagnetic radiation using spontaneous four-wave mixing. Method for determining the refraction index of a medium comprises pumping nanofibre of a given diameter by laser radiation at a wavelength at which a spontaneous four-wave mixing phenomenon is observed, with generation of signal field radiation at output of nanofibre in shorter-wave region of spectrum and radiation of idle field in spectral region, where it is required to determine refraction index. Further, pumping and idle field radiation is suppressed and signaling field radiation is detected. Wavelength of the maximum of the radiation of the signal field is determined and the wavelength of the maximum of the radiation of the idle field is calculated by a mathematical method. Effective refraction index of nanofibre is calculated in vacuum at wave length of maximum of idle field radiation by mathematical method. Further, the method involves pumping of nanofibre of specified diameter placed in the analysed medium by laser radiation. Further, pumping and idle field radiation is suppressed, signal field radiation is detected and wave length of radiation signal maximum is determined. Effective refraction index of the nanofibre is calculated in the analysed medium at the wavelength of the maximum of the idle field radiation by a mathematical method. Further, the refractive index of the surrounding nanofibre of the medium at the wavelength of the maximum of the radiation of the idle field is calculated using a calculation method based on the change in the effective refraction index of the nanofibre at the wavelength of the maximum radiation of the idle field when the nanofibre is placed from the vacuum into the analysed medium.

EFFECT: technical result consists in enabling determination of the refraction index of the medium in a wide range of the spectrum, including in the infrared region, with high accuracy.

1 cl, 2 dwg