Understanding the performance of Abbe-type refractometers with optically absorbing fluids

Abstract

We investigate the use of Abbe-type refractometers with homogeneous absorbing fluids. We derive a simple model based on electromagnetic optics to describe quantitatively the angular distribution of light around the critical angle and report some experimental tests. First, we verify experimentally that the diffusing film near the base of the prism does in fact deliver light that refracts up to the critical angle. Then we compare experimental profiles of refracted light around the critical angle with theoretical profiles, and find very good agreement. Finally, we use the model to analyze some requirements and limitations on using Abbe-type refractometers on absorbing fluids.

Monitoring of temperature-mediated phase transitions of adipose tissue by combined optical coherence tomography and Abbe refractometry

“…Traditionally, to obtain RIs of transparent specimens, the spatial distribution of transmitted light is analyzed. [55][56][57] However, this method cannot be directly used for the measurement of RI of turbid biological tissues with strong scattering and absorption. Thus, in the current study, all the refractometric measurements were performed in the reflection mode.…”

The derivative method of critical-angle refractometry for attenuating media

“…Specular reflection of linearly polarized monochromatic light on an interface is described by the Fresnel equation for the corresponding polarization in terms of the incidence angle and the refractive indices of the media comprising the interface [1,2]. Among other implementations [3,4], a large class of refractometers operates by measuring the specular reflectance of interfaces formed by transparent media with different optical densities for varying incidence angle. The critical angle of total internal reflection (TIR) is located at the inflection point-the derivative maximum-of the resulting reflectance profile, according to the so-called 'derivative method' [5,6].…”

Sensing element for the formation fluid refractometer on the basis of total internal reflection

“…Для измерения показателя преломления жидкостей и газов используются рефрактометры нескольких типов, которые основаны на явлениях интерференции и полного внутреннего отражения [12]. В разработанных моделях интерференционных рефрактометров диапазон измерения показателя преломления n = 1,32-1,56 [13], что сильно ограничивает область применения данных приборов. Метод полного внутреннего отражения (ПВО), на котором построен рефрактометр Аббе, положен в основу большинства промышленных и лабораторных рефрактометров [11,14].…”